Appendix C No Active Intervention and With Present Management Assessment

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C - i - February 2011

CONTENTS

Page

1 1 1.1 Typical coastal evolution 1 1.1.1 Epoch 1, years 0 – 20 (2025) 1 1.1.2 Epoch 2, years 20 – 50 (2055) 1 1.1.3 Epoch 3, years 50 – 100 (2105) 1 1.2 Unit details – No Active Intervention 2 1.3 Unit details – With Present Management 2

2 WHITSAND BAY TO POINT 4 2.1 Typical coastal evolution 4 2.1.1 Epoch 1, years 0 – 20 (2025) 4 2.1.2 Epoch 2, years 20 – 50 (2055) 4 2.1.3 Epoch 3, years 50 – 100 (2105) 4 2.2 Unit details – No Active Intervention 5 2.3 Unit details – With Present Management 6

3 THE LOOE RIVERS 8 3.1 Typical evolution 8 3.2 Unit details – No Active Intervention 8 3.3 Unit details – With Present Management 9

4 LOOE POINT TO GRIBBIN HEAD 11 4.1 Typical coastal evolution 11 4.1.1 Epoch 1, years 0 – 20 (2025) 11 4.1.2 Epoch 2, years 20 – 50 (2055) 11 4.1.3 Epoch 3, years 50 – 100 (2105) 11 4.2 Unit details – No Active Intervention 12 4.3 Unit details – With Present Management 12

5 GRIBBIN HEAD TO BLACK HEAD 14 5.1 Typical coastal evolution 14 5.1.1 Epoch 1, years 0 – 20 (2025) 14 5.1.2 Epoch 2, years 20 – 50 (2055) 14 5.1.3 Epoch 3, years 50 – 100 (2105) 14 5.2 Unit details – No Active Intervention 15 5.3 Unit details – With Present Management 17

6 BLACK HEAD TO 20 6.1 Typical coastal evolution 20 6.1.1 Epoch 1, years 0 – 20 (2025) 20 6.1.2 Epoch 2, years 20 – 50 (2055) 20 6.1.3 Epoch 3, years 50 – 100 (2105) 20 6.2 Unit details – No Active Intervention 21 6.3 Unit details – With Present Management 22

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C - ii - February 2011

7 DODMAN POINT TO LIZARD POINT 25 7.1 Typical coastal evolution 25 7.1.1 Epoch 1, years 0 – 20 (2025) 25 7.1.2 Epoch 2, years 20 – 50 (2055) 25 7.1.3 Epoch 3, years 50 – 100 (2105) 25 7.2 Unit details – No Active Intervention 26 7.3 Unit details – With Present Management 33

8 42 8.1 Typical evolution 42 8.2 Unit details – No Active Intervention 42 8.3 Unit details – With Present Management 44

9 LIZARD POINT TO PENLEE POINT 48 9.1 Typical coastal evolution 48 9.1.1 Epoch 1, years 0 – 20 (2025) 48 9.1.2 Epoch 2, years 20 – 50 (2055) 48 9.1.3 Epoch 3, years 50 – 100 (2105) 48 9.2 Unit details – No Active Intervention 49 9.3 Unit details – With Present Management 59

10 PENLEE POINT TO LANDS END 70 10.1 Typical coastal evolution 70 10.1.1 Epoch 1, years 0 – 20 (2025) 70 10.1.2 Epoch 2, years 20 – 50 (2055) 70 10.1.3 Epoch 3, years 50 – 100 (2105) 70 10.2 Unit details – No Active Intervention 71 10.3 Unit details – With Present Management 72

11 LANDS END TO ST IVES HEAD 75 11.1 Typical coastal evolution 75 11.1.1 Epoch 1, years 0 – 20 (2025) 75 11.1.2 Epoch 2, years 20 – 50 (2055) 75 11.1.3 Epoch 3, years 50 – 100 (2105) 75 11.2 Unit details – No Active Intervention 76 11.3 Unit details – With Present Management 77

12 CARBIS BAY (ST IVES HEAD TO POINT) 79 12.1 General coastal evolution 79 12.2 Unit details – No Active Intervention 79 12.3 Unit details – With Present Management 82

13 ESTUARY 87 13.1 General estuarial evolution 87 13.2 Unit details – No Active Intervention 87 13.3 Unit details – With Present Management 90

14 GODREVY POINT TO ST AGNES HEAD 93 14.1 Typical coastal evolution 93

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C - iii - February 2011

14.1.1 Epoch 1, years 0 – 20 (2025) 93 14.1.2 Epoch 2, years 20 – 50 (2055) 93 14.1.3 Epoch 3, years 50 – 100 (2105) 93 14.2 Unit details – No Active Intervention 94 14.3 Unit details – With Present Management 95

15 ST AGNES HEAD TO 97 15.1 Typical coastal evolution 97 15.1.1 Epoch 1, years 0 – 20 (2025) 97 15.1.2 Epoch 2, years 20 – 50 (2055) 97 15.1.3 Epoch 3, years 50 – 100 (2105) 97 15.2 Unit details – No Active Intervention 98 15.3 Unit details – With Present Management 102

16 TOWAN HEAD TO PARK HEAD 107 16.1 Typical coastal evolution 107 16.1.1 Epoch 1, years 0 – 20 (2025) 107 16.1.2 Epoch 2, years 20 – 50 (2055) 107 16.1.3 Epoch 3, years 50 – 100 (2105) 107 16.2 Unit details – No Active Intervention 108 16.3 Unit details – With Present Management 110

17 PARK HEAD TO 114 17.1 Typical coastal evolution 114 17.1.1 Epoch 1, years 0 – 20 (2025) 114 17.1.2 Epoch 2, years 20 – 50 (2055) 114 17.1.3 Epoch 3, years 50 – 100 (2105) 114 17.2 Unit details – No Active Intervention 115 17.3 Unit details – With Present Management 116

18 TREVOSE HEAD TO PENTIRE POINT 119 18.1 Typical coastal evolution 119 18.1.1 Epoch 1, years 0 – 20 (2025) 119 18.1.2 Epoch 2, years 20 – 50 (2055) 119 18.1.3 Epoch 3, years 50 – 100 (2105) 119 18.2 Unit details – No Active Intervention 120 18.3 Unit details – With Present Management 122

19 PENTIRE POINT HARTLAND POINT 125 19.1 Typical coastal evolution 125 19.1.1 Epoch 1, years 0 – 20 (2025) 125 19.1.2 Epoch 2, years 20 – 50 (2055) 125 19.1.3 Epoch 3, years 50 – 100 (2105) 125 19.2 Unit details – No Active Intervention 126 19.3 Unit details – With Present Management 129

20 ISLES OF SCILLY 134 20.1 Typical coastal evolution of the Isles of Scilly 134 20.1.1 Epoch 1, years 0 – 20 (2025) 134

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C - iv - February 2011

20.1.2 Epoch 2, years 20 – 50 (2055) 134 20.1.3 Epoch 3, years 50 – 100 (2105) 134 20.2 St Mary’s unit details – No Active Intervention 135 20.3 St Mary’s unit details – With Present Management 137 20.4 St Agnes and Gough unit details – No Active Intervention 141 20.5 St Agnes and Gough unit details – With Present Management 143 20.6 Tresco and Byher unit details – No Active Intervention 146 20.7 Tresco and Byher unit details – With Present Management 150 20.8 St Martins unit details – No Active Intervention 156 20.9 St Martins unit details – With Present Management 158

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C - v - February 2011

1 WHITSAND BAY

1.1 Typical coastal evolution

1.1.1 Epoch 1, years 0 – 20 (2025)

The coast will continue to erode whilst retaining its current characteristics. Occasional landslides and rockfalls will cause cliff tops to retreat, and will deliver sediment to the foreshores. These processes will be driven by ongoing wave erosion of the cliff base, which will also form new areas of shore platform. The shore platform will be lowered by wave action, where it is not protected by beach material. The beaches will remain relatively stable, and will be fed by the larger sediments released by the ongoing erosion processes. A small acceleration in the rate of relative sea level rise will cause shore platforms to be slightly lower, relative to the mean sea level. The region of beach/ rock platform exposed above low water will become slightly narrower as the sea rise accelerates. This will allow slightly larger waves to arrive at the cliffs, increasing the severity of wave breaking. As a consequence the shore will retreat slightly faster than it has in the past

1.1.2 Epoch 2, years 20 – 50 (2055)

The coast will continue to erode whilst retaining its current characteristics, as in epoch 1. A larger acceleration in rate of relative sea level rise will cause shore platforms to continue to fall, relative to the mean sea level. The region of beach/ rock platform exposed above low water will narrow. High tide will reach the cliff toe more frequently and this will allow larger waves to strike the cliffs, increasing the severity of wave breaking and raising recession rates. As a consequence the proportion of the cliff face comprised of active landslides will tend to increase. This will supply more material to the beach, which will mitigate, although not prevent, the narrowing of the intertidal zone.

1.1.3 Epoch 3, years 50 – 100 (2105)

The coast will continue to erode whilst retaining its current characteristics, as in epochs 1 and 2. Continued acceleration of the rate of relative sea level rise will cause shore platforms to continue to fall, relative to the mean sea level. The region of beach/ rock platform exposed above low water will continue to narrow. High tide will reach the cliff toe more frequently and allow larger waves to strike the cliffs with more energy. The shore will recede at a higher rate than seen in the past. As a consequence the proportion of the cliff face comprised of active landslides will continue to increase. This will supply more material to the beach, which will mitigate, although not prevent, the narrowing of the intertidal zone.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 1 February 2011

1.2 Unit details – No Active Intervention

Location Predicted Change For Years 0 – 20 (2025) Years 20 – 50 (2055) Years 50 – 100 (2105) to No defences No defences No defences The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the will be typical of the will be typical of the region, as described region, as described region, as described above. above. above. Portwrinkle Revetments and walls No defences No defences Coastal evolution will be Coastal evolution will be Coastal evolution will be generally typical of the generally typical of the generally typical of the region, as described region, as described region, as described above. However the above. Failure of the above. Wave action, coastal structures will coastal structures will be increased by relative sea cause the shoreline to be followed by a period of level rise will continue to increasingly seaward of its accelerated recession, as drive coastal retreat at natural position. The lack waves attack over- increasing rates. This will of cliff recession will steepened shore profiles. release sedimentary prevent both the release This will release material that will of some sediment and the sedimentary material that accumulate in formation of new shore will accumulate in neighbouring beaches. platform. Relative lowering neighbouring beaches. of the rock foreshore will The shore retreat will allow larger, more mitigate, although not aggressive waves to prevent, narrowing of the reach the structures. intertidal zone due to sea level rise.

1.3 Unit details – With Present Management

Location Predicted Change For Years 0 – 20 (2025) Years 20 – 50 (2055) Years 50 – 100 (2105) Rame head No defences No defences No defences to Portwrinkle The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Portwrinkle Revetments and walls Revetments and walls Revetments and walls Coastal evolution will be The coastal evolution of the The development of the coast generally typical of the prior epoch will continue. The seen in the first epoch will region, as described above. water line will continue to continue. The frequency with However the coastal translate towards the which the foreshore is structures will cause the structures, increasing the inaccessible at high tide will shoreline to be increasingly number of times that the continue to increase. Greater seaward of its natural foreshore is inaccessible at water depths will allow higher

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 2 February 2011

position. The lack of cliff high tide. waves to reach the structures recession will prevent both causing larger impacts and the release of some sediment greater overtopping. Larger and the formation of new structures will be necessary shore platform. Relative to withstand the growth in lowering of the rock foreshore impact forces. will allow larger, more aggressive waves to reach the structures.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 3 February 2011

2 WHITSAND BAY TO LOOE POINT

2.1 Typical coastal evolution

2.1.1 Epoch 1, years 0 – 20 (2025)

The coast will continue to erode whilst retaining its current characteristics. Occasional landslides and rockfalls will cause cliff tops to retreat, and will deliver sediment to the foreshores. These processes will be driven by ongoing wave erosion of the cliff base, which will also form new areas of shore platform. The shore platform will be lowered by wave action, where it is not protected by beach material. The beaches will remain relatively stable, and will be fed by the larger sediments released by the ongoing erosion processes. A small acceleration in the rate of relative sea level rise will cause shore platforms to be slightly lower, relative to the mean sea level. The region of beach/ rock platform exposed above low water will become slightly narrower as the sea rise accelerates. This will allow slightly larger waves to arrive at the cliffs, increasing the severity of wave breaking. As a consequence the shore will retreat slightly faster than it has in the past. Locations were valleys meet the sea will tend to respond more strongly to sea level rise than rocky areas. The crests of the beaches that form in these valleys will be elevated by the rising sea level, and retreat inland, where there is space to do so.

2.1.2 Epoch 2, years 20 – 50 (2055)

The coast will continue to erode whilst retaining its current characteristics, as in epoch 1. A larger acceleration in rate of relative sea level rise will cause shore platforms to continue to fall, relative to the mean sea level. The region of beach/ rock platform exposed above low water will narrow. High tide will reach the cliff toe more frequently and this will allow larger waves to strike the cliffs, increasing the severity of wave breaking and raising recession rates. As a consequence the proportion of the cliff face comprised of active landslides will tend to increase. This will supply more material to the beach, which will mitigate, although not prevent, the narrowing of the intertidal zone. Beaches not fixed by backing cliffs will be elevated by the rising sea level and ‘roll back’.

2.1.3 Epoch 3, years 50 – 100 (2105)

The coast will continue to erode whilst retaining its current characteristics, as in epochs 1 and 2. Continued acceleration of the rate of relative sea level rise will cause shore platforms to continue to fall, relative to the mean sea level. The region of beach/ rock platform exposed above low water will continue to narrow. High tide will reach the cliff toe more frequently and allow larger waves to strike the cliffs with more energy. The shore will recede at a higher rate than seen in the past. As a consequence the proportion of the cliff face comprised of active landslides will continue to increase. This will supply more material to the beach, which will mitigate, although not prevent, the narrowing of the intertidal zone. Beaches not fixed by backing cliffs will be elevated by the rising sea level and ‘roll back’.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 4 February 2011

2.2 Unit details – No Active Intervention

Location Predicted Change For Years 0 – 20 (2025) Years 20 – 50 (2055) Years 50 – 100 (2105) Portwrinkle No defences No defences No defences to The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Downderry Revetments and walls No defences No defences and coastline to Seaton Coastal evolution will be Coastal evolution will be Coastal evolution will be generally typical of the generally typical of the generally typical of the region, as described above. region, as described above. region, as described above. However the coastal Failure of the coastal Wave action, increased by structures will cause the structures will be followed by relative sea level rise will shoreline to be increasingly a period of accelerated continue to drive coastal seaward of its natural recession, as waves attack retreat. This will release position. The lack of cliff over-steepened shore sedimentary material that will recession will prevent the profiles. This will release accumulate in neighbouring release of some sediment sedimentary material that will beaches. and the formation of new accumulate in neighbouring shore platform. Relative beaches. The shore retreat lowering of the rock foreshore will mitigate, although not will allow larger, more prevent, narrowing of the aggressive waves to reach intertidal zone due to sea the structures. level rise. Seaton Revetments and walls No defences No defence Coastal evolution will be Coastal evolution will be The evolution of this coast generally typical of the generally typical of the will be typical of the region, region, as described above. region, as described above. as described above. The The coastal structures will Failure of the coastal beaches and spit will rise with cause the shoreline to be structures will be followed by the sea level, utilising the increasingly seaward of its a period of accelerated greater availability of natural position. Lack of cliff recession, as waves attack sediments. The intertidal recession will prevent the over-steepened shore zones will become narrower release of some sediment. profiles. This will release due to relative sea level rise. Relative lowering of the rock sedimentary material that will Rising sea levels will tend to foreshore will allow larger, accumulate in local beaches. move Seaton’s spit landward, more aggressive waves to The shore retreat will although this will be reach the structures. Rising mitigate, although not constrained by the slow rate sea levels will tend to move prevent, narrowing of the of hard rock recession on Seaton’s spit slightly intertidal zone due to sea either side of the valley. The landward. level rise. intertidal zones will become generally narrower, due to relative sea level rise. Seaton to No defences No defences No defences Millendreath

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 5 February 2011

The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Millendreath Numerous revetments and No defences except Looe No defences and Looe seawalls breakwater Coastal evolution will be Coastal evolution will be The evolution of this coast generally typical of the generally typical of the will be typical of the region, region, as described above. region, as described above. as described above. Coastal The coastal structures will Failure of the coastal erosion rates will become cause the shoreline to be structures will be followed by relatively stable, although will increasingly seaward of its a period of accelerated be higher than historic natural position. Lack of cliff recession, as waves attack recession. Failure of the Looe recession will prevent the over-steepened shore breakwater will reduce its release of some sediments. profiles. This will release effectiveness as a groyne, Relative lowering of rock sedimentary material that will leading to the loss of some of foreshores will allow larger, accumulate in local beaches. the beach at Looe. The more aggressive waves to The shore retreat will beaches throughout this unit reach the structures. mitigate, although not will rise with the sea level, prevent, narrowing of the utilising the greater intertidal zone due to sea availability of sediments. The level rise. Rising sea levels intertidal zones will become will tend to move the beaches generally narrower, due to landward, particularly at Looe relative sea level rise. and Millendreath; elsewhere they will be partially constrained by cliffs.

2.3 Unit details – With Present Management

Location Predicted Change For Years 0 – 20 (2025) Years 20 – 50 (2055) Years 50 – 100 (2105) Portwrinkle to No defences No defences No defences Downderry The evolution of this coast will The evolution of this coast will The evolution of this coast will be typical of the region, as be typical of the region, as be typical of the region, as described above. described above. described above. Downderry Revetments and walls Revetments and walls Revetments and walls and coastline to Seaton Coastal evolution will be The development of the coast The development of the coast generally typical of the region, seen in the first epoch will seen in the first two epochs as described above. However continue. The water line will will continue. The frequency the coastal structures will continue to translate towards with which the foreshore is cause the shoreline to be the structures, increasing the inaccessible at high tide will increasingly seaward of its number of times that the continue to increase. Greater natural position. The lack of foreshore is inaccessible at water depths will mean that cliff recession will prevent the high tide. higher waves will reach the release of some sediment and structures and will cause

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 6 February 2011

the formation of new shore larger wave impacts and platform. Relative lowering of greater uprush and the rock foreshore will allow overtopping. Larger structures larger, more aggressive will be necessary to withstand waves to reach the structures. the growth in impact forces. Seaton Revetments and walls Revetments and walls Revetments and walls Coastal evolution will be The development of the coast The development of the coast generally typical of the region, seen in the first epoch will seen in the first two epochs as described above. The continue. The water line will will continue. The frequency coastal structures will cause continue to translate towards with which the foreshore is the shoreline to be the structures, increasing the inaccessible at high tide will increasingly seaward of its number of times that the continue to increase. Greater natural position. Lack of cliff foreshore is inaccessible at water depths will mean that recession will prevent the high tide. higher waves will reach the release of some sediments. structures and will cause Relative lowering of the rock larger wave impacts and foreshore will allow larger, greater uprush and more aggressive waves to overtopping. Larger structures reach the structures. Rising will be necessary to withstand sea levels will tend to move the growth in impact forces. Seaton’s spit slightly The presence of the landward. structures reduces beach ‘roll back’. Seaton to No defences No defences No defences Millendreath The evolution of this coast will The evolution of this coast will The evolution of this coast will be typical of the region, as be typical of the region, as be typical of the region, as described above. described above. described above. Millendreath Numerous revetments and Numerous revetments and Numerous revetments and and Looe seawalls, shore attached seawalls, shore attached seawalls, shore attached breakwater at Looe breakwater at Looe breakwater at Looe Coastal evolution will be The development of the coast The development of the coast generally typical of the region, seen in the first epoch will seen in the first two epochs as described above. The continue. The water line will will continue. The frequency coastal structures will cause continue to translate towards with which the foreshore is the shoreline to be the structures, increasing the inaccessible at high tide will increasingly seaward of its number of times that the continue to increase. Greater natural position. Lack of cliff foreshore is inaccessible at water depths will mean that recession will prevent the high tide. higher waves will reach the release of some sediments. structures and will cause Relative lowering of rock larger wave impacts and foreshores will allow larger, greater uprush and more aggressive waves to overtopping. Larger structures reach the structures. will be necessary to withstand the growth in impact forces.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 7 February 2011

3 THE LOOE RIVERS

3.1 Typical evolution

Rising sea level will raise the levels of the tidal sections of the east and west Looe rivers. However these stretches of the rivers are mostly bounded by steeply sloping valleys, and this will constrain the resulting growth in their surface area. Growth in the tidal prism will also be minimised by the steep boundaries, however some increase in tidal flows at the river mouth should be expected. This may allow the estuary to draw in more fine sediments which then allow the mudflats to grow.

3.2 Unit details – No Active Intervention

Location Predicted Change For Years 0 – 20 (2025) Years 20 – 50 (2055) Years 50 – 100 (2105) Looe Pier to Walls No defences No defences Looe train station Water depths will increase Water depths will further Water depths will further slightly but the river margin increase but the river margin increase. Failure of some will remain essentially will remain essentially structures leads to localised unchanged. unchanged. Localised river widening. structure failures may occur. Looe station Railway embankment No defences No defences to Trewith Minor shoreline retreat due to Minor shoreline retreat as Continued sea level rise inundation caused by a small rising seas inundate the causes a slight widening of rise in sea level. steep margin of the river. the river as its steep sides are inundated.

Trewith No defences No defences No defences The riverbank will remain Accelerated sea level risk will Accelerated sea level risk will much as it is today. tend to drive the waterline tend to drive the beach Accelerated sea level risk will back into the valley. further back into the valley. drive some retreat of waterline but this will be difficult to distinguish from natural variability. Trewith to No defences No defences No defences Watergate Minor shoreline retreat due to Minor shoreline retreat as Continued sea level rise inundation caused by a small rising seas inundate the causes a slight widening of rise in sea level. steep margin of the river. the river as its steep sides are inundated.

Watergate to No defences No defences No defences

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 8 February 2011

West Looe car park Minor shoreline retreat due to Minor shoreline retreat as Continued sea level rise inundation caused by a small rising seas inundate the causes a slight widening of rise in sea level. steep margin of the river. the river as its steep sides are inundated.

West Looe Walls No defences No defences car park Water depths will increase Water depths will further Water depths will further slightly but the river margin increase and localised failure increase. More generalised will remain essentially of defences may lead to failure of defences may lead unchanged. recession of the car park to rapid recession of the car area. park area. West Looe Walls No defences No defences car park to The Blind Water depths will increase Water depths will further Water depths will further slightly but the river margin increase but the river margin increase. Failure of some will remain essentially will remain essentially structures leads to localised unchanged. unchanged. Localised river widening. structure failures may occur.

3.3 Unit details – With Present Management

Location Predicted Change For Years 0 – 20 (2025) Years 20 – 50 (2055) Years 50 – 100 (2105) Looe Pier to Walls Walls Walls Looe train station Water depths will increase Water depths will further Water depths will further slightly but the river margin increase but the river with will increase but the river with will will remain essentially be maintained by the be maintained by the unchanged. structures. structures Looe station Railway embankment Railway embankment Railway embankment to Trewith Minor shoreline retreat due to Minor shoreline retreat as Continued sea level rise inundation caused by a small rising seas inundate the causes a slight widening of rise in sea level. steep margin of the river. the river as its steep sides are inundated.

Trewith No defences No defences No defences The riverbank will remain Accelerated sea level risk will Accelerated sea level risk will much as it is today. tend to drive the waterline tend to drive the beach Accelerated sea level risk will back into the valley. further back into the valley. drive some retreat of waterline but this will be difficult to distinguish from

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 9 February 2011

natural variability. Trewith to No defences No defences No defences Watergate Minor shoreline retreat due to Minor shoreline retreat as Continued sea level rise inundation caused by a small rising seas inundate the causes a slight widening of rise in sea level. steep margin of the river. the river as its steep sides are inundated.

Watergate to No defences No defences No defences West Looe car park Minor shoreline retreat due to Minor shoreline retreat as Continued sea level rise inundation caused by a small rising seas inundate the causes a slight widening of rise in sea level. steep margin of the river. the river as its steep sides are inundated.

West Looe Walls Walls Walls car park Water depths will increase Water depths will further Water depths will further slightly but the river margin increase but the river with will increase but the river with will will remain essentially be maintained by the be maintained by the unchanged. structures. structures West Looe Walls Walls Walls car park to The Blind Water depths will increase Water depths will further Water depths will further slightly but the river margin increase but the river with will increase but the river with will will remain essentially be maintained by the be maintained by the unchanged. structures. structures

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 10 February 2011

4 LOOE POINT TO GRIBBIN HEAD

4.1 Typical coastal evolution

4.1.1 Epoch 1, years 0 – 20 (2025)

The coast will continue to erode whilst retaining its current characteristics. Occasional landslides and rockfalls will cause cliff tops to retreat, and will deliver sediment to the foreshores. These processes will be driven by ongoing wave erosion of the cliff base, which will also form new areas of shore platform. The shore platform will be lowered by wave action, where it is not protected by beach material. The beaches will remain relatively stable, and will be fed by the larger sediments released by the ongoing erosion processes. A small acceleration in the rate of relative sea level rise will cause shore platforms to be slightly lower, relative to the mean sea level. The region of beach/ rock platform exposed above low water will become slightly narrower as the sea rise accelerates. This will allow slightly larger waves to arrive at the cliffs, increasing the severity of wave breaking. As a consequence the shore will retreat slightly faster than it has in the past. Locations were valleys meet the sea will tend to respond more strongly to sea level rise than rocky areas. The crests of the beaches that form in these valleys will be elevated by the rising sea level, and retreat inland, where there is space to do so.

4.1.2 Epoch 2, years 20 – 50 (2055)

The coast will continue to erode whilst retaining its current characteristics, as in epoch 1. A larger acceleration in rate of relative sea level rise will cause shore platforms to continue to fall, relative to the mean sea level. The region of beach/ rock platform exposed above low water will narrow. High tide will reach the cliff toe more frequently and this will allow larger waves to strike the cliffs, increasing the severity of wave breaking and raising recession rates. As a consequence the proportion of the cliff face comprised of active landslides will tend to increase. This will supply more material to the beach, which will mitigate, although not prevent, the narrowing of the intertidal zone. Beaches not fixed by backing cliffs will be elevated by the rising sea level and ‘roll back’.

4.1.3 Epoch 3, years 50 – 100 (2105)

The coast will continue to erode whilst retaining its current characteristics, as in epochs 1 and 2. Continued acceleration of the rate of relative sea level rise will cause shore platforms to continue to fall, relative to the mean sea level. The region of beach/ rock platform exposed above low water will continue to narrow. High tide will reach the cliff toe more frequently and allow larger waves to strike the cliffs with more energy. The shore will recede at a higher rate than seen in the past. As a consequence the proportion of the cliff face comprised of active landslides will continue to increase. This will supply more material to the beach, which will mitigate, although not prevent, the narrowing of the intertidal zone. Beaches not fixed by backing cliffs will be elevated by the rising sea level and ‘roll back’.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 11 February 2011

4.2 Unit details – No Active Intervention

Location Predicted Change For Years 0 – 20 (2025) Years 20 – 50 (2055) Years 50 – 100 (2105) Looe Point to Defence at No defences No defences Polperro The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. The as described above. Failure as described above. small scale defences at of the defences at Talland will Talland will continue to fix the result in a short period of rear of the local beach, accelerated recession, preventing roll back and the followed by ongoing roll back release of new sediments. of the beach, in response to Wave loading on the sea level rise. structure will increase. Polperro Harbour structures Harbour structures Deteriorated harbour structures Water depths increase within Water depths increase within Water depths increase within the harbour, with no effect on the harbour, with no effect on the harbour, with no effect on the surrounding coast. the surrounding coast. the surrounding coast. Localised structure failures Failure of some harbour may occur. structures leads to loss of the harbour margin. Polperro to No defences No defences No defences The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Fowey to Minor defence at Polridmouth No defences No defences Gribbin head The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. The as described above. Failure as described above. small scale defences at of the defences at Polridmouth will continue to Polridmouth will result in a fix the rear of the local beach, short period of accelerated preventing roll back and the recession, followed by release of new sediments. ongoing roll back of the Wave loading on the beach, in response to sea structure will increase. level rise.

4.3 Unit details – With Present Management

Location Predicted Change For Years 0 – 20 (2025) Years 20 – 50 (2055) Years 50 – 100 (2105)

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 12 February 2011

Loe Point to Defence at Talland Defence at Talland Defence at Talland Polperro The evolution of this coast will The evolution of this coast will The evolution of this coast will be typical of the region, as be typical of the region, as be typical of the region, as described above. The small described above. Defences at described above. Defences at scale defences at Talland will Talland will prevent the local Talland will prevent the local continue to fix the rear of the beach rolling back, leading to beach rolling back, leading to local beach, preventing roll narrowing of the beach and narrowing of the beach and back and the release of new increase in wave loading and increase in wave loading and sediments. Wave loading on overtopping. overtopping. the structure will increase. Polperro Harbour structures Harbour structures Harbour structures Water depths increase within Water depths increase within Water depths increase within the harbour, with no effect on the harbour, with no effect on the harbour, with no effect on the surrounding coast. the surrounding coast. the surrounding coast. Polperro to No defences No defences No defences Fowey The evolution of this coast will The evolution of this coast will The evolution of this coast will be typical of the region, as be typical of the region, as be typical of the region, as described above. described above. described above. Fowey to Minor defence at Polridmouth Minor defence at Polridmouth Minor defence at Polridmouth Gribbin head The evolution of this coast will The evolution of this coast will The evolution of this coast will be typical of the region, as be typical of the region, as be typical of the region, as described above. The small described above. Defences at described above. Defences at scale defences at Polridmouth Polridmouth will prevent the Polridmouth will prevent the will continue to fix the rear of local beach rolling back, local beach rolling back, the local beach, preventing leading to narrowing of the leading to narrowing of the roll back and the release of beach and increase in wave beach and increase in wave new sediments. Wave loading loading and overtopping. loading and overtopping. on the structure will increase.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 13 February 2011

5 GRIBBIN HEAD TO BLACK HEAD

5.1 Typical coastal evolution

5.1.1 Epoch 1, years 0 – 20 (2025)

The coast will continue to erode whilst retaining its current characteristics. Occasional landslides and rockfalls will cause cliff tops to retreat, and will deliver sediment to the foreshores. These processes will be driven by ongoing wave erosion of the cliff base, which will also form new areas of shore platform. The shore platform will be lowered by wave action, where it is not protected by beach material. The beaches will be fed by the larger sediments released by the ongoing erosion processes. A small acceleration in the rate of relative sea level rise will cause shore platforms to be slightly lower, relative to the mean sea level. The region of beach/ rock platform exposed above low water will become slightly narrower as the sea rise accelerates. This will allow slightly larger waves to arrive at the cliffs, increasing the severity of wave breaking. As a consequence the shore will retreat slightly faster than it has in the past. Locations were valleys meet the sea will tend to respond more strongly to sea level rise than rocky areas. The crests of the beaches that form in these valleys will be elevated by the rising sea level, and retreat inland, where there is space to do so.

5.1.2 Epoch 2, years 20 – 50 (2055)

The coast will continue to erode whilst retaining its current characteristics, as in epoch 1. A larger acceleration in rate of relative sea level rise will cause shore platforms to continue to fall, relative to the mean sea level. The region of beach/ rock platform exposed above low water will narrow. High tide will reach the cliff toe more frequently and this will allow larger waves to strike the cliffs, increasing the severity of wave breaking and raising recession rates. As a consequence the proportion of the cliff face comprised of active landslides will tend to increase. This will supply more material to the beach, which will mitigate, although not prevent, the narrowing of the intertidal zone. Beaches not fixed by backing cliffs or hard structures will be elevated by the rising sea level and ‘roll back’. This will involve some dune erosion.

5.1.3 Epoch 3, years 50 – 100 (2105)

The coast will continue to erode whilst retaining its current characteristics, as in epochs 1 and 2. Continued acceleration of the rate of relative sea level rise will cause shore platforms to continue to fall, relative to the mean sea level. The region of beach/ rock platform exposed above low water will continue to narrow. High tide will reach the cliff toe more frequently and allow larger waves to strike the cliffs with more energy. The shore will recede at a higher rate than seen in the past. As a consequence the proportion of the cliff face comprised of active landslides will continue to increase. This will supply more material to the beach, which will mitigate, although not prevent, the narrowing of the intertidal zone. Beaches not fixed by backing cliffs will be elevated by the rising sea level and ‘roll back’. This will involve some dune erosion.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 14 February 2011

5.2 Unit details – No Active Intervention

Location Predicted Change For Years 0 – 20 (2025) Years 20 – 50 (2055) Years 50 – 100 (2105) Gribbin Head Defences at Polkerris No defences No defences to Polkerris The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Polkerris Seawall No defences No defences The beach will continue to Failure of the coastal Accelerated relative sea level narrow. The coastal defences structures will be followed by rise will continue to cause the will prevent recession and so a transient period of beach to roll back, at cause the shoreline to be accelerated recession, as increasing rates. Continued increasingly seaward of its waves attack over-steepened erosion will release fresh natural position. The shore profiles. This will sediments that will defences will also prevent the release sedimentary material, accumulate and provide formation of new shore some of which will some protection to wave platform and reduce the accumulate in the beach. The attack. release of material for the beach will begin to roll back beach. Relative lowering of and this will mitigate, the rock foreshore and beach although not prevent, will allow larger, more narrowing of the intertidal aggressive waves to reach zone due to sea level rise. the structures. Par No defences No defences No defences The beach and dunes will The form of the beach and Ongoing acceleration in the remain essentially dunes will remain essentially rate of sea level rise will drive unchanged, apart from unchanged. Sea level rise will increasing erosion of the natural short term and drive some erosion of the dune face. However this will seasonal fluctuations in form front of the dune, and this will be accompanied by release sand into the beach. increasing release of sediment into the beach which will allow it to rise with the sea level. As a result the beach will appear relatively unchanged. Very little dune width will be left by the end of the epoch. Par docks Harbour walls Harbour walls Degraded harbour walls Water depths increase within Water depths increase within Water depths increase within the harbour, with no effect on the harbour, with no effect on the harbour, with no effect on the surrounding coast. the surrounding coast. the surrounding coast. Localised structure failures Failure of some harbour may occur. structures leads to loss of the harbour margin. Par to No defences No defences No defences Carlyon

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 15 February 2011

The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Carlyon Bay No defences No defences No defences The beach will remain The form of the beach will Ongoing acceleration in the essentially unchanged, apart remain essentially rate of sea level rise will drive from natural short term and unchanged. Sea level rise will increasing retreat of the seasonal fluctuations in form drive some retreat of the shoreline as more material is shoreline as material is mined from the lower profile mined from the lower profile to form a higher berm. The to form a higher berm. vertical and landward translation will mean that, although narrower, the beach will look similar to its current form. Carlyon to No defences No defences No defences Charlestown The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Charlestown Harbour structures Harbour structures Degraded harbour structures The beach will narrow. The Failure of the coastal Accelerated relative sea level coastal defences will prevent structures will be followed by rise will continue to cause the recession and so cause the a transient period of beach to roll back, at shoreline to be increasingly accelerated recession, as increasing rates. Continued seaward of its natural waves attack over-steepened erosion will release fresh position. The defences will shore profiles. This will sediments that will also prevent the formation of release sedimentary material, accumulate and provide new shore platform and some of which will some protection to wave reduce the release of accumulate in the beach. The attack. Water depths will material for the beach. beach will begin to roll back increase within the harbour, Relative lowering of the rock and this will mitigate, with no effect on the foreshore and beach will although not prevent, surrounding coast. Failure of allow larger, more aggressive narrowing of the intertidal some harbour structures will waves to reach the structures zone due to sea level rise. lead to loss of the harbour Water depths will increase Water depths will increase margin. Cliff instability will within the harbour, with no within the harbour, with no increase as a result of the effect on the surrounding effect on the surrounding increased cliff base coast. coast. Localised structure recession. failures may occur. Duporth No defences No defences No defences The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. Cliff tops as described above. Cliff top as described above. Cliff top will continue to recede recession will begin to recession will continue to naturally. accelerate due to increased accelerate due to increased sea level rise. sea level rise. Porthpean Seawall No defences No defences The beach will continue to Failure of the coastal Accelerated relative sea level

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 16 February 2011

narrow. The coastal defences structures will be followed by rise will continue to cause the will prevent recession and so a transient period of beach to roll back, at cause the shoreline to be accelerated recession, as increasing rates. Continued increasingly seaward of its waves attack over-steepened erosion will release fresh natural position. The shore profiles. This will sediments that will defences will also prevent the release sedimentary material, accumulate and provide formation of new shore some of which will some protection to wave platform and reduce the accumulate in the beach. The attack. release of material for the beach will begin to roll back beach. Relative lowering of and this will mitigate, the rock foreshore and beach although not prevent, will allow larger, more narrowing of the intertidal aggressive waves to reach zone due to sea level rise. the structures. Porthpean to No defences No defences No defences Black head The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above.

5.3 Unit details – With Present Management

Location Predicted Change For Years 0 – 20 (2025) Years 20 – 50 (2055) Years 50 – 100 (2105) Gribbin Head Defences at Polkerris Defences at Polkerris Defences at Polkerris to Polkerris The evolution of this coast will The evolution of this coast will The evolution of this coast will be typical of the region, as be typical of the region, as be typical of the region, as described above. described above. described above. Polkerris Seawall Seawall Seawall The beach will continue to The trend seen in the prior The trend seen in the prior narrow. The coastal defences epoch will continue. epoch will continue. Wave will prevent recession and so impact forces and overtopping cause the shoreline to be will grow at an exponential increasingly seaward of its rate, necessitating larger natural position. The defences structures to maintain current will also prevent the formation levels of defence. Beach of new shore platform and accessibility will reduce as the reduce the release of material sea level rises. for the beach. Relative lowering of the rock foreshore and beach will allow larger, more aggressive waves to reach the structures.

Par No defences No defences No defences The beach and dunes will The form of the beach and Ongoing acceleration in the remain essentially dunes will remain essentially rate of sea level rise will drive

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 17 February 2011

unchanged, apart from natural unchanged. Sea level rise will increasing erosion of the dune short term and seasonal drive some erosion of the face. However this will be fluctuations in form front of the dune, and this will accompanied by increasing release sand into the beach. release of sediment into the beach which will allow it to rise with the sea level. As a result the beach will appear relatively unchanged. Very little dune will be left by the end of the epoch. Par docks Harbour walls Harbour walls Harbour walls Water depths will increase Water depths will increase Water depths will increase within the harbour, with no within the harbour, with no within the harbour, with no effect on the surrounding effect on the surrounding effect on the surrounding coast. coast.. coast. Par to No defences No defences No defences Carlyon The evolution of this coast will The evolution of this coast will The evolution of this coast will be typical of the region, as be typical of the region, as be typical of the region, as described above. described above. described above. Carlyon Bay No defences No defences No defences The beach will remain The form of the beach will Ongoing acceleration in the essentially unchanged, apart remain essentially rate of sea level rise will drive from natural short term and unchanged. Sea level rise will increasing retreat of the seasonal fluctuations in form drive some retreat of the shoreline as more material is shoreline as material is mined mined from the lower profile to from the lower profile to form form a higher berm. The a higher berm. vertical and landward translation will mean that, although narrower, the beach will look similar to its current form. Carlyon to No defences No defences No defences Charlestown The evolution of this coast will The evolution of this coast will The evolution of this coast will be typical of the region, as be typical of the region, as be typical of the region, as described above. described above. described above. Charlestown Harbour structures Harbour structures Harbour structures The evolution of this coast will The evolution of this coast will The evolution of this coast will be typical of the region, as be typical of the region, as be typical of the region, as described above. described above. Increased described above. Cliff recession due to sea level rise instability will worsen as sea will aggravate cliff instability. level rise accelerates coastal recession. Duporth No defences No defences No defences The beach will continue to The trend seen in the prior The trend seen in the prior narrow. The coastal defences epoch will continue. epoch will continue. Wave will prevent recession and so impact forces and overtopping cause the shoreline to be will grow at an exponential

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 18 February 2011

increasingly seaward of its rate, necessitating larger natural position. The defences structures to maintain current will also prevent the formation levels of defence. Beach of new shore platform and accessibility will reduce as the reduce the release of material sea level rises. Water depths for the beach. Relative will increase within the lowering of the rock foreshore harbour, with no effect on the and beach will allow larger, surrounding coast. more aggressive waves to reach the structures. Water depths will increase within the harbour, with no effect on the surrounding coast. Porthpean Seawall Seawall Seawall The beach will continue to The trend seen in the prior The trend seen in the prior narrow. The coastal defences epoch will continue. epoch will continue. Wave will prevent recession and so impact forces and overtopping cause the shoreline to be will grow at an exponential increasingly seaward of its rate, necessitating larger natural position. The defences structures to maintain current will also prevent the formation levels of defence. Beach of new shore platform and accessibility will reduce as the reduce the release of material sea level rises. for the beach. Relative lowering of the rock foreshore and beach will allow larger, more aggressive waves to reach the structures.

Porthpean to No defences No defences No defences Black head The evolution of this coast will The evolution of this coast will The evolution of this coast will be typical of the region, as be typical of the region, as be typical of the region, as described above. described above. described above.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 19 February 2011

6 BLACK HEAD TO DODMAN POINT

6.1 Typical coastal evolution

6.1.1 Epoch 1, years 0 – 20 (2025)

The coast will continue to erode whilst retaining its current characteristics. Occasional landslides and rockfalls will cause cliff tops to retreat, and will deliver sediment to the foreshores. These processes will be driven by ongoing wave erosion of the cliff base, which will also form new areas of shore platform. The shore platform will be lowered by wave action, where it is not protected by beach material. The beaches will be fed by the larger sediments released by the ongoing erosion processes. A small acceleration in the rate of relative sea level rise will cause shore platforms to be slightly lower, relative to the mean sea level. The region of beach/ rock platform exposed above low water will become slightly narrower as the sea rise accelerates. This will allow slightly larger waves to arrive at the cliffs, increasing the severity of wave breaking. As a consequence the shore will retreat slightly faster than it has in the past. Locations were valleys meet the sea will tend to respond more strongly to sea level rise than rocky areas. The crests of the beaches that form in these valleys will be elevated by the rising sea level, and retreat inland, where there is space to do so.

6.1.2 Epoch 2, years 20 – 50 (2055)

The coast will continue to erode whilst retaining its current characteristics, as in epoch 1. A larger acceleration in rate of relative sea level rise will cause shore platforms to continue to fall, relative to the mean sea level. The region of beach/ rock platform exposed above low water will narrow. High tide will reach the cliff toe more frequently and this will allow larger waves to strike the cliffs, increasing the severity of wave breaking and raising recession rates. As a consequence the proportion of the cliff face comprised of active landslides will tend to increase. This will supply more material to the beach, which will mitigate, although not prevent, the narrowing of the intertidal zone. Beaches not fixed by backing cliffs or hard structures will be elevated by the rising sea level and ‘roll back’.

6.1.3 Epoch 3, years 50 – 100 (2105)

The coast will continue to erode whilst retaining its current characteristics, as in epochs 1 and 2. Continued acceleration of the rate of relative sea level rise will cause shore platforms to continue to fall, relative to the mean sea level. The region of beach/ rock platform exposed above low water will continue to narrow. High tide will reach the cliff toe more frequently and allow larger waves to strike the cliffs with more energy. The shore will recede at a higher rate than seen in the past. As a consequence the proportion of the cliff face comprised of active landslides will continue to increase. This will supply more material to the beach, which will mitigate, although not prevent, the narrowing of the intertidal zone. Beaches not fixed by backing cliffs will be elevated by the rising sea level and ‘roll back’.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 20 February 2011

6.2 Unit details – No Active Intervention

Location Predicted Change For Years 0 – 20 (2025) Years 20 – 50 (2055) Years 50 – 100 (2105) Black head No defences No defences No defences to Pentewan The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Pentewan Short length of rock armour, No defences No defences redundant breakwater The beach will continue to Accelerated relative sea level Retreat of the beach and retreat. rise will accelerate beach erosion of the dunes will retreat, and failure of the continue at accelerated rates, defence will allow erosion of due to sea level rise. the dunes. The sediments released will partially mitigate shoreline retreat. Pentewan to No defences No defences No defences Mevagissey The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Mevagissey Breakwater and harbour Breakwater and harbour No defences walls walls Water depths increase within Water depths increase within Water depths increase within the harbour, with no effect on the harbour, with no effect on the harbour, with no effect on the surrounding coast. the surrounding coast. the surrounding coast. Localised structure failures Failure of some harbour may occur. structures leads to loss of the harbour margin. Mevagissey No defences No defences No defences to Portmellon The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Portmellon Seawalls No defences No defences The coastal defences will Failure of the coastal Accelerated relative sea level prevent recession and so structures will be followed by rise will continue to cause the cause the shoreline to be a transient period of beach to roll back, at increasingly seaward of its accelerated recession, as increasing rates. Continued natural position. The waves attack over-steepened erosion will release fresh defences will also prevent the shore profiles. This will sediments that will formation of new shore release sedimentary material, accumulate and provide platform and reduce the some of which will some protection to wave release of material for the accumulate in the beach. The attack. beach. Relative lowering of beach will begin to roll back the rock foreshore and beach and this will mitigate,

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 21 February 2011

will allow larger, more although not prevent, aggressive waves to reach narrowing of the intertidal the structures. zone due to sea level rise. Portmellon to No defences No defences No defences Gorran Haven The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Gorran Seawalls and small pier No defences No defences Haven The beach will continue to Failure of the coastal Accelerated relative sea level retreat. The coastal defences structures will be followed by rise will continue to cause the will prevent recession and so a transient period of beach to roll back, at cause the shoreline to be accelerated recession, as increasing rates. Continued increasingly seaward of its waves attack over-steepened erosion will release fresh natural position. The shore profiles. This will sediments that will defences will also prevent the release sedimentary material, accumulate and provide formation of new shore some of which will some protection to wave platform and reduce the accumulate in the beach. The attack. At Little Perhaver release of material for the beach will begin to roll back ongoing sea level rise will beach. Relative lowering of and this will mitigate, continue to narrow the beach the rock foreshore and beach although not prevent, and increase wave loading will allow larger, more narrowing of the intertidal on the cliff toe. Landslides aggressive waves to reach zone due to sea level rise. At and cliff top retreat will the structures. At Little Little Perhaver ongoing sea increase Perhaver coastal evolution level rise will further narrow will be typical of the region. the beach, increasing the The beach will begin to period that the cliff toe is narrow as the sea level rises. submerged at high tide. Wave loading on the cliff toe will increases. Gorran No defences No defences No defences Haven to Dodman Point The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above.

6.3 Unit details – With Present Management

Location Predicted Change For Years 0 – 20 (2025) Years 20 – 50 (2055) Years 50 – 100 (2105) Black head No defences No defences No defences to Pentewan The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 22 February 2011

Pentewan Short length of rock armour, Short length of rock armour, Short length of rock armour, redundant breakwater redundant breakwater breakwater The beach will continue to Accelerated relative sea level Accelerated relative sea level retreat. The beach level in rise will increase beach and rise will increase beach and front of the defences will fall. dune retreat rates. The dune retreat rates. The structure will tend to be structure will tend to be outflanked as recession of outflanked as recession of the dunes continues on either the dunes continues on either side of it. Larger and longer side of it. Larger and longer structures will be required to structures will be required to maintain the shore position maintain the shore position and manage outflanking. and manage outflanking. Pentewan to No defences No defences No defences Mevagissey The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Mevagissey Breakwater and harbour Breakwater and harbour Breakwater and harbour walls walls walls Water depths will increase Water depths will increase Water depths will increase within the harbour, with no within the harbour, with no within the harbour, with no effect on the surrounding effect on the surrounding effect on the surrounding coast. coast. coast. Mevagissey No defences No defences No defences to Portmellon The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Portmellon Seawalls Seawalls Seawalls The coastal defences will The trend seen in the prior The trend seen in the prior prevent recession and so epoch will continue. epoch will continue. Wave cause the shoreline to be impact forces and increasingly seaward of its overtopping will grow at an natural position. The exponential rate, defences will also prevent the necessitating larger formation of new shore structures to maintain current platform and reduce the levels of defence. Beach release of material for the accessibility will reduce as beach. Relative lowering of the sea level rises. the rock foreshore and beach will allow larger, more aggressive waves to reach the structures. Portmellon to No defences No defences No defences Gorran Haven The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 23 February 2011

Gorran Seawalls and small pier Seawalls and small pier Seawalls and small pier Haven The beach will continue to The trend seen in the prior The trend seen in the prior narrow. The coastal defences epoch will continue. epoch will continue. Wave will prevent recession and so At Little Perhaver ongoing impact forces and cause the shoreline to be sea level rise will further overtopping will grow at an increasingly seaward of its narrow the beach, increasing exponential rate, natural position. The the period that the cliff toe is necessitating larger defences will also prevent the submerged at high tide. structures to maintain current formation of new shore Wave loading on the cliff toe levels of defence. Beach platform and reduce the will increase. accessibility will reduce as release of material for the the sea level rises. At Little beach. Relative lowering of Perhaver ongoing sea level the rock foreshore and beach rise will continue to narrow will allow larger, more the beach and increase wave aggressive waves to reach loading on the cliff toe. the structures. At Little Landslides and cliff top Perhaver coastal evolution retreat will increase. will be typical of the region. The beach will begin to narrow as the sea level rises. Gorran No defences No defences No defences Haven to Dodman Point The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 24 February 2011

7 DODMAN POINT TO LIZARD POINT

7.1 Typical coastal evolution

7.1.1 Epoch 1, years 0 – 20 (2025)

The coast will continue to erode whilst retaining its current characteristics. Occasional landslides and rockfalls will cause cliff tops to retreat, and will deliver sediment to the foreshores. These processes will be driven by ongoing wave erosion of the cliff base, which will also form new areas of shore platform. The shore platform will be lowered by wave action, where it is not protected by beach material. The beaches will be fed by the larger sediments released by the ongoing erosion processes. A small acceleration in the rate of relative sea level rise will cause shore platforms to be slightly lower, relative to the mean sea level. The region of beach/ rock platform exposed above low water will become slightly narrower as the sea rise accelerates. This will allow slightly larger waves to arrive at the cliffs, increasing the severity of wave breaking. As a consequence the shore will retreat slightly faster than it has in the past. Locations were valleys meet the sea will tend to respond more strongly to sea level rise than rocky areas. The crests of the beaches that form in these valleys will be elevated by the rising sea level, and retreat inland, where there is space to do so.

7.1.2 Epoch 2, years 20 – 50 (2055)

The coast will continue to erode whilst retaining its current characteristics, as in epoch 1. A larger acceleration in rate of relative sea level rise will cause shore platforms to continue to fall, relative to the mean sea level. The region of beach/ rock platform exposed above low water will narrow. High tide will reach the cliff toe more frequently and this will allow larger waves to strike the cliffs, increasing the severity of wave breaking and raising recession rates. As a consequence the proportion of the cliff face comprised of active landslides will tend to increase. This will supply more material to the beach, which will mitigate, although not prevent, the narrowing of the intertidal zone. Beaches not fixed by backing cliffs or hard structures will be elevated by the rising sea level and ‘roll back’.

7.1.3 Epoch 3, years 50 – 100 (2105)

The coast will continue to erode whilst retaining its current characteristics, as in epochs 1 and 2. Continued acceleration of the rate of relative sea level rise will cause shore platforms to continue to fall, relative to the mean sea level. The region of beach/ rock platform exposed above low water will continue to narrow. High tide will reach the cliff toe more frequently and allow larger waves to strike the cliffs with more energy. The shore will recede at a higher rate than seen in the past. As a consequence the proportion of the cliff face comprised of active landslides will continue to increase. This will supply more material to the beach, which will mitigate, although not prevent, the narrowing of the intertidal zone. Beaches not fixed by backing cliffs will be elevated by the rising sea level and ‘roll back’.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 25 February 2011

7.2 Unit details – No Active Intervention

Location Predicted Change For Years 0 – 20 (2025) Years 20 – 50 (2055) Years 50 – 100 (2105) Dodman No defences No defences No defences Point to Hemmick The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Hemmick Wall No defences No defences Beach The coastal defences will Failure of the coastal Accelerated relative sea level prevent recession and so structures will be followed by rise will continue to cause the cause the shoreline to be a transient period of beach to roll back, at increasingly seaward of its accelerated recession, as increasing rates. Continued natural position. The waves attack over-steepened erosion will release fresh defences will also prevent the shore profiles. This will sediments that will formation of new shore release sedimentary material, accumulate and provide platform and reduce the some of which will some protection to wave release of material for the accumulate in the beach. The attack. beach. Relative lowering of beach will begin to roll back the beach will allow larger, and this will mitigate, more aggressive waves to although not prevent, reach the structures. narrowing of the intertidal zone due to sea level rise. Hemmick No defences No defences No defences Beach to Porthluney Cove The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Porthluney Wall No defences No defences Cove The coastal defences will Failure of the coastal Accelerated relative sea level prevent recession and so structures will be followed by rise will continue to cause the cause the shoreline to be a transient period of beach to roll back, at increasingly seaward of its accelerated recession, as increasing rates. Continued natural position. The waves attack over-steepened erosion will release fresh defences will also prevent the shore profiles. This will sediments that will formation of new shore release sedimentary material, accumulate and provide platform and reduce the some of which will some protection to wave release of material for the accumulate in the beach. The attack. beach. Relative lowering of beach will begin to roll back the beach will allow larger, and this will mitigate, more aggressive waves to although not prevent, reach the structures. narrowing of the intertidal zone due to sea level rise.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 26 February 2011

Porthluney No defences No defences No defences Cove to Portholland The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Portholland Wall No defences No defences The beach will continue to Failure of the coastal Accelerated relative sea level narrow. The coastal defences structures will be followed by rise will continue to cause the will prevent recession and so a transient period of beach to roll back, at cause the shoreline to be accelerated recession, as increasing rates. Continued increasingly seaward of its waves attack over-steepened erosion will release fresh natural position. The shore profiles. This will sediments that will defences will also prevent the release sedimentary material, accumulate and provide formation of new shore some of which will some protection to wave platform and reduce the accumulate in the beach. The attack. release of material for the beach will begin to roll back beach. Relative lowering of and this will mitigate, the beach will allow larger, although not prevent, more aggressive waves to narrowing of the intertidal reach the structures. zone due to sea level rise. Portholland No defences No defences No defences to Portloe The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Portloe Small breakwater No defences No defences Erosion will be small; The trend seen in the Accelerated relative sea level however increasing sea previous epoch will continue. rise will continue to increase levels will increase the water Wave run-up and overtopping wave activity at the shore. depths, allowing slightly will increase. larger waves to reach the shore. Portloe to No defences No defences No defences Carne The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Carne Beach Wall No defences No defences The coastal defences will Failure of the coastal Accelerated relative sea level prevent recession and so structures will be followed by rise will continue to cause the cause the shoreline to be a transient period of beach to roll back, at increasingly seaward of its accelerated recession, as increasing rates. Continued natural position. The waves attack over-steepened erosion will release fresh defences will also prevent the shore profiles. This will sediments that will formation of new shore release sedimentary material, accumulate and provide platform and reduce the some of which will some protection to wave release of material for the accumulate in the beach. The attack. beach. Relative lowering of beach will begin to roll back

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 27 February 2011

the beach will allow larger, and this will mitigate, more aggressive waves to although not prevent, reach the structures. narrowing of the intertidal zone due to sea level rise. Pendower No defences No defences No defences Beach The beach and dune will Accelerated relative sea level Higher rates of sea level rise remain largely stable rise will cause the beach and will cause the beach and dunes to retreat up the valley dunes to retreat up the valley naturally. naturally. Pendower to No defences No defences No defences Porthcurnick The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Porthcurnick Discontinuous seawall No defences No defences Sea level rise will cause a Failure of the coastal Accelerated relative sea level low recession rate. In front of structures will be followed by rise will continue to cause the the wall beach levels will tend a transient period of beach to roll back, at to drop, elsewhere the beach accelerated recession, as increasing rates. Continued will roll back. Loading on the waves attack over-steepened erosion will release fresh structure will tend to shore profiles. The previously sediments into the beach. increase. protected area will realign to catch up with the remainder of the beach. Portscatho Seawalls No defences No defences The beach will continue to Failure of the coastal Accelerated relative sea level narrow. The coastal defences structures will be followed by rise will continue to cause the will prevent recession and so a transient period of beach to roll back, at cause the shoreline to be accelerated recession, as increasing rates. Continued increasingly seaward of its waves attack over-steepened erosion will release fresh natural position. The shore profiles. This will sediments that will defences will also prevent the release sedimentary material, accumulate and provide formation of new shore some of which will some protection to wave platform and reduce the accumulate in the beach. The attack. release of material for the beach will begin to roll back beach. Relative lowering of and this will mitigate, the rock foreshore and beach although not prevent, will allow larger, more narrowing of the intertidal aggressive waves to reach zone due to sea level rise. the structures. Portscatho to No defences No defences No defences The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Pendennis Gabions No defences No defences Point to

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 28 February 2011

Gyllyngvase The beach and dunes will The form of the beach and Ongoing acceleration in the remain essentially dunes will remain essentially rate of sea level rise will drive unchanged, apart from unchanged. Sea level rise will increasing erosion of the natural short term and drive some erosion of the dune face. However this will seasonal fluctuations in form front of the dune, and this will be accompanied by release sand into the beach. increasing release of sediment into the beach which will allow it to rise with the sea level. As a result the beach will appear relatively unchanged. Gyllyngvase Seawalls No defences No defences The beach will continue to Failure of the coastal Accelerated relative sea level narrow. The coastal defences structures will be followed by rise will continue to cause the will prevent recession and so a transient period of beach to roll back, at cause the shoreline to be accelerated recession, as increasing rates. Continued increasingly seaward of its waves attack over-steepened erosion will release fresh natural position. The shore profiles. This will sediments that will defences will also prevent the release sedimentary material, accumulate and provide formation of new shore some of which will some protection to wave platform and reduce the accumulate in the beach. The attack. release of material for the beach will begin to roll back beach. Relative lowering of and this will mitigate, the rock foreshore and beach although not prevent, will allow larger, more narrowing of the intertidal aggressive waves to reach zone due to sea level rise. the structures. Gyllyngvase No defences No defences No defences to Swanpool The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Swanpool Seawall and revetment No defences No defences The beach will continue to Failure of the coastal Accelerated relative sea level narrow. The coastal defences structures will be followed by rise will continue to cause the will prevent recession and so a transient period of beach to roll back, at cause the shoreline to be accelerated recession, as increasing rates. Continued increasingly seaward of its waves attack over-steepened erosion will release fresh natural position. The shore profiles. This will sediments that will defences will also prevent the release sedimentary material, accumulate and provide formation of new shore some of which will some protection to wave platform and reduce the accumulate in the beach. The attack. release of material for the beach will begin to roll back beach. Relative lowering of and this will mitigate, the rock foreshore and beach although not prevent, will allow larger, more narrowing of the intertidal aggressive waves to reach zone due to sea level rise. the structures.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 29 February 2011

Swanpool to No defences No defences No defences Maenporth The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Maenporth Wall No defences No defences The beach will continue to Failure of the coastal Accelerated relative sea level narrow. The coastal defences structures will be followed by rise will continue to cause the will prevent recession and so a transient period of beach to roll back, at cause the shoreline to be accelerated recession, as increasing rates. Continued increasingly seaward of its waves attack over-steepened erosion will release fresh natural position. The shore profiles. This will sediments that will defences will also prevent the release sedimentary material, accumulate and provide formation of new shore some of which will some protection to wave platform and reduce the accumulate in the beach. The attack. release of material for the beach will begin to roll back beach. Relative lowering of and this will mitigate, the rock foreshore and beach although not prevent, will allow larger, more narrowing of the intertidal aggressive waves to reach zone due to sea level rise. the structures. Maenporth to No defences No defences No defences Toll Point The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Dennis head No defences No defences No defences The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. St Anthony- No defences No defences No defences in-Meneage The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above as described above. as described above.

Gillan creek No defences No defences No defences The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above as described above. as described above.

Flushing Seawall No defences No defences The coastal defences will Failure of the coastal Accelerated relative sea level prevent recession and so structures at Flushing will be rise will continue to cause the cause the shoreline to be followed by a transient period Flushing beach to roll back, increasingly seaward of its of accelerated recession, as at increasing rates. natural position. The waves attack over-steepened Continued erosion will defences will also prevent the shore profiles. This will release fresh sediments that formation of new shore release sedimentary material, will accumulate and provide

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 30 February 2011

platform and reduce the some of which will some protection to wave release of material for the accumulate in the beach. The attack. beach. Relative lowering of beach will begin to roll back the beach will allow larger, and this will mitigate, more aggressive waves to although not prevent, reach the structures. narrowing of the intertidal zone due to sea level rise.

Gillan Seawall No defences No defences The coastal defences will Failure of the coastal Accelerated relative sea level prevent recession and so structures at Flushing will be rise will continue to cause the cause the shoreline to be followed by a transient period Flushing beach to roll back, increasingly seaward of its of accelerated recession, as at increasing rates. natural position. The waves attack over-steepened Continued erosion will defences will also prevent the shore profiles. This will release fresh sediments that formation of new shore release sedimentary material, will accumulate and provide platform and reduce the some of which will some protection to wave release of material for the accumulate in the beach. The attack. beach. Relative lowering of beach will begin to roll back the beach will allow larger, and this will mitigate, more aggressive waves to although not prevent, reach the structures. narrowing of the intertidal zone due to sea level rise.

Gillan Creek No defences No defences No defences to Porthallow The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Porthallow No defences No defences No defences The beach will remain The form of the beach will Ongoing acceleration in the essentially unchanged, apart remain essentially rate of sea level rise will drive from natural short term and unchanged. Sea level rise will increasing retreat of the seasonal fluctuations in form drive some retreat of the shoreline as more material is shoreline as material is mined from the lower profile mined from the lower profile to form a higher berm. The to form a higher berm. vertical and landward translation will mean that, although narrower, the beach will look similar to its current form. Porthallow to No defences No defences No defences Porthoustock The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Porthoustock No defences No defences No defences The beach will remain The form of the beach will Ongoing acceleration in the essentially unchanged, apart remain essentially rate of sea level rise will drive

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 31 February 2011

from natural short term and unchanged. Sea level rise will increasing retreat of the seasonal fluctuations in form drive some retreat of the shoreline as more material is shoreline as material is mined from the lower profile mined from the lower profile to form a higher berm. The to form a higher berm. vertical and landward translation will mean that, although narrower, the beach will look similar to its current form. Porthoustock No defences No defences No defences to The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Coverack Seawall No defences No defences The beach will continue to Failure of the coastal Accelerated relative sea level narrow. The coastal defences structures will be followed by rise will continue to cause the will prevent recession and so a transient period of beach to roll back, at cause the shoreline to be accelerated recession, as increasing rates. Continued increasingly seaward of its waves attack over-steepened erosion will release fresh natural position. The shore profiles. This will sediments that will defences will also prevent the release sedimentary material, accumulate and provide formation of new shore some of which will some protection to wave platform and reduce the accumulate in the beach. The attack. release of material for the beach will begin to roll back beach. Relative lowering of and this will mitigate, the rock foreshore and beach although not prevent, will allow larger, more narrowing of the intertidal aggressive waves to reach zone due to sea level rise. the structures. Coverack to No defences No defences No defences Kennack Towans The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Kennack Discontinuous defences No defences No defences Towans Sea level rise will cause a Failure of the coastal Accelerated relative sea level low recession rate. In front of structures will be followed by rise will continue to cause the the wall beach levels will tend a transient period of beach to roll back, at to drop, elsewhere the beach accelerated recession, as increasing rates. Continued will roll back. Loading on the waves attack over-steepened erosion will release fresh structure will tend to shore profiles. Sediments sediments into the beach. increase. released will tend to raise beach levels. The previously protected area will realign to the remainder of the beach.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 32 February 2011

Kennack No defences No defences No defences Towans to Cadgwith The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Cadgwith Discontinuous revetment No defences No defences Sea level rise will cause a Failure of the coastal Accelerated relative sea level low recession rate. In front of structures will be followed by rise will continue to cause the the wall beach levels will tend a transient period of beach to roll back, at to drop, elsewhere the beach accelerated recession, as increasing rates. Continued will roll back. Loading on the waves attack over-steepened erosion will release fresh structure will tend to shore profiles. Sediments sediments into the beach. increase. released will tend to raise beach levels. The previously protected area will realign to the remainder of the beach. Cadgwith to No defences No defences No defences Lizard Point The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above.

7.3 Unit details – With Present Management

Location Predicted Change For Years 0 – 20 (2025) Years 20 – 50 (2055) Years 50 – 100 (2105) Dodman No defences No defences No defences Point to Hemmick The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Hemmick Wall No defences No defences Beach The coastal defences will The trend seen in the prior The trend seen in the prior prevent recession and so epoch will continue. epoch will continue. Wave cause the shoreline to be impact forces and increasingly seaward of its overtopping will grow at an natural position. The exponential rate, defences will also prevent the necessitating larger formation of new shore structures to maintain current platform and reduce the levels of defence. Beach release of material for the accessibility will reduce as beach. Relative lowering of the sea level rises. the beach will allow larger, more aggressive waves to reach the structures.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 33 February 2011

Hemmick No defences No defences No defences Beach to Porthluney Cove The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Porthluney Wall No defences No defences Cove The coastal defences will The trend seen in the prior The trend seen in the prior prevent recession and so epoch will continue. epoch will continue. Wave cause the shoreline to be impact forces and increasingly seaward of its overtopping will grow at an natural position. The exponential rate, defences will also prevent the necessitating larger formation of new shore structures to maintain current platform and reduce the levels of defence. Beach release of material for the accessibility will reduce as beach. Relative lowering of the sea level rises. the beach will allow larger, more aggressive waves to reach the structures. Porthluney No defences No defences No defences Cove to Portholland The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Portholland Wall No defences No defences The beach will continue to The trend seen in the prior The trend seen in the prior narrow. The coastal defences epoch will continue. epoch will continue. Wave will prevent recession and so impact forces and cause the shoreline to be overtopping will grow at an increasingly seaward of its exponential rate, natural position. The necessitating larger defences will also prevent the structures to maintain current formation of new shore levels of defence. Beach platform and reduce the accessibility will reduce as release of material for the the sea level rises. beach. Relative lowering of the rock foreshore and beach will allow larger, more aggressive waves to reach the structures. Portholland No defences No defences No defences to Portloe The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 34 February 2011

Portloe Small breakwater No defences No defences Erosion will be small, The trend seen in the Accelerated relative sea level however increasing sea previous epoch will continue. rise will continue to increase levels will increase the water Wave run-up and overtopping wave activity at the shore. depths, allowing slightly will increase. larger waves to reach the shore. Portloe to No defences No defences No defences Carne The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Carne Beach Wall No defences No defences The coastal defences will The trend seen in the prior The trend seen in the prior prevent recession and so epoch will continue. epoch will continue. Wave cause the shoreline to be impact forces and increasingly seaward of its overtopping will grow at an natural position. The exponential rate, defences will also prevent the necessitating larger formation of new shore structures to maintain current platform and reduce the levels of defence. Beach release of material for the accessibility will reduce as beach. Relative lowering of the sea level rises. the beach will allow larger, more aggressive waves to reach the structures. Pendower No defences No defences No defences Beach The beach and dune will Accelerated relative sea level Higher rates of sea level rise remain largely stable rise will cause the beach and will cause the beach and dunes to retreat up the valley dunes to retreat up the valley naturally. naturally. Pendower to No defences No defences No defences Porthcurnick The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Porthcurnick Discontinuous seawall No defences No defences Sea level rise will cause a Accelerated sea level rise will Accelerated sea level rise will low recession rate. In front of increase the recession rate of further increase the recession the wall beach levels will tend the areas not fronted by a rate of the areas not fronted to drop, elsewhere the beach structure. This will release by a structure. This will will roll back. Loading on the sediments that will tend to release sediments that will structure will tend to raise the level of the beach. tend to raise the level of the increase. In front of the wall beach beach. The wall will tend to levels will continue to fall and be outflanked by this so wave loading on the recession. In front of the wall structure will continue to beach levels will continue to

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 35 February 2011

increase. fall and so wave loading on the structure will continue to increase. Portscatho Seawalls No defences No defences The beach will continue to The trend seen in the prior The trend seen in the prior narrow. The coastal defences epoch will continue. epoch will continue. Wave will prevent recession and so impact forces and cause the shoreline to be overtopping will grow at an increasingly seaward of its exponential rate, natural position. The necessitating larger defences will also prevent the structures to maintain current formation of new shore levels of defence. Beach platform and reduce the accessibility will reduce as release of material for the the sea level rises. beach. Relative lowering of the rock foreshore and beach will allow larger, more aggressive waves to reach the structures. Portscatho to No defences No defences No defences St Anthony Head The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Pendennis Gabions No defences No defences Point to Gyllyngvase The beach and dunes will The form of the beach and Ongoing acceleration in the remain essentially dunes will remain essentially rate of sea level rise will drive unchanged, apart from unchanged. Sea level rise will increasing erosion of the natural short term and drive some erosion of the dune face. However this will seasonal fluctuations in form front of the dune, and this will be accompanied by release sand into the beach. increasing release of sediment into the beach which will allow it to rise with the sea level. As a result the beach will appear relatively unchanged. Gyllyngvase Seawalls No defences No defences The beach will continue to Failure of the coastal Accelerated relative sea level narrow. The coastal defences structures will be followed by rise will continue to cause the will prevent recession and so a transient period of beach to roll back, at cause the shoreline to be accelerated recession, as increasing rates. Continued increasingly seaward of its waves attack over-steepened erosion will release fresh natural position. The shore profiles. This will sediments that will defences will also prevent the release sedimentary material, accumulate and provide formation of new shore some of which will some protection to wave platform and reduce the accumulate in the beach. The attack.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 36 February 2011

release of material for the beach will begin to roll back beach. Relative lowering of and this will mitigate, the rock foreshore and beach although not prevent, will allow larger, more narrowing of the intertidal aggressive waves to reach zone due to sea level rise. the structures. Gyllyngvase No defences No defences No defences to Swanpool The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Swanpool Seawall and revetment No defences No defences The beach will continue to The trend seen in the prior The trend seen in the prior narrow. The coastal defences epoch will continue. epoch will continue. Wave will prevent recession and so impact forces and cause the shoreline to be overtopping will grow at an increasingly seaward of its exponential rate, natural position. The necessitating larger defences will also prevent the structures to maintain current formation of new shore levels of defence. Beach platform and reduce the accessibility will reduce as release of material for the the sea level rises. beach. Relative lowering of the rock foreshore and beach will allow larger, more aggressive waves to reach the structures. Swanpool to No defences No defences No defences Maenporth The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Maenporth Wall No defences No defences The beach will continue to The trend seen in the prior The trend seen in the prior narrow. The coastal defences epoch will continue. epoch will continue. Wave will prevent recession and so impact forces and cause the shoreline to be overtopping will grow at an increasingly seaward of its exponential rate, natural position. The necessitating larger defences will also prevent the structures to maintain current formation of new shore levels of defence. Beach platform and reduce the accessibility will reduce as release of material for the the sea level rises. beach. Relative lowering of the rock foreshore and beach will allow larger, more aggressive waves to reach the structures. Maenporth to No defences No defences No defences

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 37 February 2011

Toll Point The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Dennis head No defences No defences No defences The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. St Anthony- No defences No defences No defences in-Meneage The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above as described above. as described above. Gillan creek No defences No defences No defences The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above as described above. as described above. Flushing Seawall No defences No defences The coastal defences will The trend seen in the prior The trend seen in the prior prevent recession and so epoch will continue. epoch will continue. Wave cause the shoreline to be impact forces and increasingly seaward of its overtopping will grow at an natural position. The exponential rate, defences will also prevent the necessitating larger formation of new shore structures to maintain current platform and reduce the levels of defence. Beach release of material for the accessibility will reduce as beach. Relative lowering of the sea level rises. the beach will allow larger, more aggressive waves to reach the structures. Gillan Seawall No defences No defences The coastal defences will The trend seen in the prior The trend seen in the prior prevent recession and so epoch will continue. epoch will continue. Wave cause the shoreline to be impact forces and increasingly seaward of its overtopping will grow at an natural position. The exponential rate, defences will also prevent the necessitating larger formation of new shore structures to maintain current platform and reduce the levels of defence. Beach release of material for the accessibility will reduce as beach. Relative lowering of the sea level rises. the beach will allow larger, more aggressive waves to reach the structures.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 38 February 2011

Gillan Creek No defences No defences No defences to Porthallow The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Porthallow No defences No defences No defences The beach will remain The form of the beach will Ongoing acceleration in the essentially unchanged, apart remain essentially rate of sea level rise will drive from natural short term and unchanged. Sea level rise will increasing retreat of the seasonal fluctuations in form drive some retreat of the shoreline as more material is shoreline as material is mined from the lower profile mined from the lower profile to form a higher berm. The to form a higher berm. vertical and landward translation will mean that, although narrower, the beach will look similar to its current form. Porthallow to No defences No defences No defences Porthoustock The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Porthoustock No defences No defences No defences The beach will remain The form of the beach will Ongoing acceleration in the essentially unchanged, apart remain essentially rate of sea level rise will drive from natural short term and unchanged. Sea level rise will increasing retreat of the seasonal fluctuations in form drive some retreat of the shoreline as more material is shoreline as material is mined from the lower profile mined from the lower profile to form a higher berm. The to form a higher berm. vertical and landward translation will mean that, although narrower, the beach will look similar to its current form. Porthoustock No defences No defences No defences to Coverack The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Coverack Seawall No defences No defences The beach will continue to The trend seen in the prior The trend seen in the prior narrow. The coastal defences epoch will continue. epoch will continue. Wave will prevent recession and so impact forces and cause the shoreline to be overtopping will grow at an increasingly seaward of its exponential rate, natural position. The necessitating larger defences will also prevent the structures to maintain current formation of new shore levels of defence. Beach platform and reduce the accessibility will reduce as

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 39 February 2011

release of material for the the sea level rises. beach. Relative lowering of the rock foreshore and beach will allow larger, more aggressive waves to reach the structures. Coverack to No defences No defences No defences Kennack Towans The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Kennack Discontinuous defences No defences No defences Towans Sea level rise will cause a Accelerated sea level rise will Accelerated sea level rise will low recession rate. In front of increase the recession rate of further increase the recession the wall beach levels will tend the areas not fronted by a rate of the areas not fronted to drop, elsewhere the beach structure. This will release by a structure. This will will roll back. Loading on the sediments that will tend to release sediments that will structure will tend to raise the level of the beach. tend to raise the level of the increase. In front of the wall beach beach. The wall will tend to levels will continue to fall and be outflanked by this so wave loading on the recession. In front of the wall structure will continue to beach levels will continue to increase. fall and so wave loading on the structure will continue to increase. Kennack No defences No defences No defences Towans to Cadgwith The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above.

Cadgwith Discontinuous revetment No defences No defences Sea level rise will cause a Accelerated sea level rise will Accelerated sea level rise will low recession rate. In front of increase the recession rate of further increase the recession the wall beach levels will tend the areas not fronted by a rate of the areas not fronted to drop, elsewhere the beach structure. This will release by a structure. This will will roll back. Loading on the sediments that will tend to release sediments that will structure will tend to raise the level of the beach. tend to raise the level of the increase. In front of the wall beach beach. The wall will tend to levels will continue to fall and be outflanked by this so wave loading on the recession. In front of the wall structure will continue to beach levels will continue to increase. fall and so wave loading on the structure will continue to increase.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 40 February 2011

Cadgwith to No defences No defences No defences Lizard Point The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 41 February 2011

8 HELFORD RIVER

8.1 Typical evolution

Over the next century water levels in the Helford River will rise, with global sea levels. The geomorphic effects of this will be smaller than the changes expected along the open coast, because this area is sheltered from wave attack. In addition changes in the tidal volume (due to the deeper waters) are not expected to drive a large increase in sedimentation, because there seem to be insufficient sources of sedimentary material. Consequently the general behaviour of the river over the coming century is likely to be one of inundation of the (often quite steep) shoreline with some deepening of mudflats, where they occur, but large areas where the water depth simply increases.

8.2 Unit details – No Active Intervention

Location Predicted Change For Years 0 – 20 (2025) Years 20 – 50 (2055) Years 50 – 100 (2105) Toll Point to No defence No defence No defence Porth Saxon Minor shoreline retreat due to Minor shoreline retreat as Continued sea level rise inundation caused by a small rising seas inundate the causes a slight widening of rise in sea level. steep margin of the river. the river as its steep sides are inundated. Porth Saxon ‘Defacto’ defence No defence No defence The coastal defences will Failure of the coastal Accelerated relative sea level prevent recession and so structures will be followed by rise will continue to cause the cause the shoreline to be a transient period of beach to roll back, at increasingly seaward of its accelerated recession, as increasing rates. Continued natural position. The over-steepened shore erosion will release fresh defences will also prevent the profiles fail. This will release sediments that will formation of new shore sedimentary material, some accumulate and provide platform and reduce the of which will accumulate in some protection to wave release of material for the the beach. The beach will attack. beach. begin to roll back and this will mitigate, although not prevent, narrowing of the intertidal zone due to sea level rise. Porth Saxon No defence No defence No defence to Durgan Minor shoreline retreat due to Minor shoreline retreat as Continued sea level rise inundation caused by a small rising seas inundate the causes a slight widening of rise in sea level. steep margin of the river. the river as its steep sides are inundated. Durgan Seawalls No defence No defence The coastal defences will Failure of the coastal Accelerated relative sea level prevent recession and so structures will be followed by rise will continue to cause the

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 42 February 2011

cause the shoreline to be a transient period of beach to roll back, at increasingly seaward of its accelerated recession, as increasing rates. Continued natural position. The over-steepened shore erosion will release fresh defences will also prevent the profiles fail. This will release sediments that will formation of new shore sedimentary material, some accumulate and provide platform and reduce the of which will accumulate in some protection to wave release of material for the the beach. The beach will attack. beach. begin to roll back and this will mitigate, although not prevent, narrowing of the intertidal zone due to sea level rise. Durgan to No defence No defence No defence Passage Cove Minor shoreline retreat due to Minor shoreline retreat as Continued sea level rise inundation caused by a small rising seas inundate the causes a slight widening of rise in sea level. steep margin of the river. the river as its steep sides are inundated. Passage Seawalls No defence No defence Cove The coastal defences will Failure of the coastal Accelerated relative sea level prevent recession and so structures will be followed by rise will continue to cause the cause the shoreline to be a transient period of beach to roll back, at increasingly seaward of its accelerated recession, as increasing rates. Continued natural position. The over-steepened shore erosion will release fresh defences will also prevent the profiles fail. This will release sediments that will formation of new shore sedimentary material, some accumulate and provide platform and reduce the of which will accumulate in some protection to wave release of material for the the beach. The beach will attack. beach. begin to roll back and this will mitigate, although not prevent, narrowing of the intertidal zone due to sea level rise. Passage No defence No defence No defence Cove to Porth Navas Minor shoreline retreat due to Minor shoreline retreat as Continued sea level rise inundation caused by a small rising seas inundate the causes a slight widening of rise in sea level. steep margin of the river. the river as its steep sides are inundated. Porth Navas Quayside walls No defence No defence Where defended, the Failure of the structures will Ongoing sea level rise will shoreline will be held. Overall be followed by a period of continue to drive the beach the beach will tend to retreat localised accelerated landward, up the valley. slightly, although this may be recession, as more natural Sediments released by difficult to distinguish from profiles are reformed. Sea recession through the natural variability. level rise will drive further hinterland will mitigate the

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 43 February 2011

retreat and narrowing of the effects of the rising seas to a beach. small degree. Porth Navas No defence No defence No defence to Gweek Minor shoreline retreat due to Minor shoreline retreat as Continued sea level rise inundation caused by a small rising seas inundate the causes a slight widening of rise in sea level. steep margin of the river. the river as its steep sides are inundated. Gweek Quayside walls No defence No defence Where defended, the Failure of the structures will Ongoing sea level rise will shoreline will be held. Overall be followed by a period of continue to drive the beach the beach will tend to retreat localised accelerated landward, up the valley. slightly, although this may be recession, as more natural Sediments released by difficult to distinguish from profiles are reformed. Sea recession through the natural variability. level rise will drive further hinterland will mitigate the retreat and narrowing of the effects of the rising seas to a beach. small degree. Gweek to No defence No defence No defence Helford Point Minor shoreline retreat due to Minor shoreline retreat as Continued sea level rise inundation caused by a small rising seas inundate the causes a slight widening of rise in sea level. steep margin of the river. the river as its steep sides are inundated. Helford Quay walls No defence No defence Where defended, the Failure of the structures will Ongoing sea level rise will shoreline will be held. Overall be followed by a period of continue to drive the beach the beach will tend to retreat localised accelerated landward, up the valley. slightly, although this may be recession, as more natural Sediments released by difficult to distinguish from profiles are reformed. Sea recession through the natural variability. level rise will drive further hinterland will mitigate the retreat and narrowing of the effects of the rising seas to a beach. small degree. Helford to No defence No defence No defence Dennis Head Minor shoreline retreat due to Minor shoreline retreat as Continued sea level rise inundation caused by a small rising seas inundate the causes a slight widening of rise in sea level. steep margin of the river. the river as its steep sides are inundated.

8.3 Unit details – With Present Management

Location Predicted Change For Years 0 – 20 (2025) Years 20 – 50 (2055) Years 50 – 100 (2105) Toll Point to No defence No defence No defence Porth Saxon Minor shoreline retreat due to Minor shoreline retreat as Continued sea level rise inundation caused by a small rising seas inundate the causes a slight widening of rise in sea level. steep margin of the river. the river as its steep sides

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 44 February 2011

are inundated.

Porth Saxon ‘Defacto’ defence ‘Defacto’ defence ‘Defacto’ defence The coastal defences will The trend seen in the prior The trend seen in the prior prevent recession and so epoch will continue. epoch will continue. Wave cause the shoreline to be impact forces and increasingly seaward of its overtopping will grow at an natural position. The exponential rate, defences will also prevent the necessitating larger formation of new shore structures to maintain current platform and reduce the levels of defence. Beach release of material for the accessibility will reduce as beach. the sea level rises.

Porth Saxon No defence No defence No defence to Durgan Minor shoreline retreat due to Minor shoreline retreat as Continued sea level rise inundation caused by a small rising seas inundate the causes a slight widening of rise in sea level. steep margin of the river. the river as its steep sides are inundated.

Durgan Seawalls Seawalls Seawalls The coastal defences will The trend seen in the prior The trend seen in the prior prevent recession and so epoch will continue. epoch will continue. Wave cause the shoreline to be impact forces and increasingly seaward of its overtopping will grow at an natural position. The exponential rate, defences will also prevent the necessitating larger formation of new shore structures to maintain current platform and reduce the levels of defence. Beach release of material for the accessibility will reduce as beach. the sea level rises.

Durgan to No defence No defence No defence Passage Cove Minor shoreline retreat due to Minor shoreline retreat as Continued sea level rise inundation caused by a small rising seas inundate the causes a slight widening of rise in sea level. steep margin of the river. the river as its steep sides are inundated.

Passage Seawalls Seawalls Seawalls Cove The coastal defences will The trend seen in the prior The trend seen in the prior prevent recession and so epoch will continue. epoch will continue. Wave cause the shoreline to be impact forces and increasingly seaward of its overtopping will grow at an natural position. The exponential rate, defences will also prevent the necessitating larger

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 45 February 2011

formation of new shore structures to maintain current platform and reduce the levels of defence. Beach release of material for the accessibility will reduce as beach. the sea level rises.

No defence No defence No defence No defence Minor shoreline retreat due to Minor shoreline retreat as Continued sea level rise inundation caused by a small rising seas inundate the causes a slight widening of rise in sea level. steep margin of the river. the river as its steep sides are inundated.

Porth Navas Quaywalls Quaywalls Quaywalls Where defended, the The trend seen in the prior The trend seen in the prior shoreline will be held. Overall epoch will continue. Sea level epoch will continue. the beach will tend to retreat rise will drive further retreat. Outflanking processes will slightly, although this may be Erosive processes adjacent continue, possibly difficult to distinguish from to the defences will tend to necessitating an increase in natural variability. cause outflanking. structure length. Elsewhere ongoing sea level rise will continue to drive the beach landward, up the valley. Porth Navas No defence No defence No defence to Gweek Minor shoreline retreat due to Minor shoreline retreat as Continued sea level rise inundation caused by a small rising seas inundate the causes a slight widening of rise in sea level. steep margin of the river. the river as its steep sides are inundated.

Gweek Quaywalls Quaywalls Quaywalls Where defended, the The trend seen in the prior The trend seen in the prior shoreline will be held. Overall epoch will continue. Sea level epoch will continue. the beach will tend to retreat rise will drive further retreat. Outflanking processes will slightly, although this may be Erosive processes adjacent continue, possibly difficult to distinguish from to the defences will tend to necessitating an increase in natural variability. cause outflanking. structure length. Elsewhere ongoing sea level rise will continue to drive the beach landward, up the valley. Gweek to No defence No defence No defence Helford Point Minor shoreline retreat due to Minor shoreline retreat as Continued sea level rise inundation caused by a small rising seas inundate the causes a slight widening of rise in sea level. steep margin of the river. the river as its steep sides are inundated.

Helford Quaywalls Quaywalls Quaywalls Where defended, the The trend seen in the prior The trend seen in the prior shoreline will be held. Overall epoch will continue. Sea level epoch will continue. the beach will tend to retreat rise will drive further retreat. Outflanking processes will

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 46 February 2011

slightly, although this may be Erosive processes adjacent continue, possibly difficult to distinguish from to the defences will tend to necessitating an increase in natural variability. cause outflanking. structure length. Elsewhere ongoing sea level rise will continue to drive the beach landward, up the valley. Helford to No defence No defence No defence Dennis Head Minor shoreline retreat due to Minor shoreline retreat as Continued sea level rise inundation caused by a small rising seas inundate the causes a slight widening of rise in sea level. steep margin of the river. the river as its steep sides are inundated.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 47 February 2011

9 LIZARD POINT TO PENLEE POINT

9.1 Typical coastal evolution

9.1.1 Epoch 1, years 0 – 20 (2025)

The coast will continue to erode whilst retaining its current characteristics. Occasional landslides and rockfalls will cause cliff tops to retreat, and will deliver sediment to the foreshores. These processes will be driven by ongoing wave erosion of the cliff base, which will also form new areas of shore platform. The shore platform will be lowered by wave action, where it is not protected by beach material. The beaches will be fed by the larger sediments released by the ongoing erosion processes. A small acceleration in the rate of relative sea level rise will cause shore platforms to be slightly lower, relative to the mean sea level. The region of beach/ rock platform exposed above low water will become slightly narrower as the sea rise accelerates. This will allow slightly larger waves to arrive at the cliffs, increasing the severity of wave breaking. As a consequence the shore will retreat slightly faster than it has in the past. Locations were valleys meet the sea will tend to respond more strongly to sea level rise than rocky areas. The crests of the beaches that form in these valleys will be elevated by the rising sea level, and retreat inland, where there is space to do so.

9.1.2 Epoch 2, years 20 – 50 (2055)

The coast will continue to erode whilst retaining its current characteristics, as in epoch 1. A larger acceleration in rate of relative sea level rise will cause shore platforms to continue to fall, relative to the mean sea level. The region of beach/ rock platform exposed above low water will narrow. High tide will reach the cliff toe more frequently and this will allow larger waves to strike the cliffs, increasing the severity of wave breaking and raising recession rates. As a consequence the proportion of the cliff face comprised of active landslides will tend to increase. This will supply more material to the beach, which will mitigate, although not prevent, the narrowing of the intertidal zone. Beaches not fixed by backing cliffs or hard structures will be elevated by the rising sea level and ‘roll back’. This will involve some dune erosion.

9.1.3 Epoch 3, years 50 – 100 (2105)

The coast will continue to erode whilst retaining its current characteristics, as in epochs 1 and 2. Continued acceleration of the rate of relative sea level rise will cause shore platforms to continue to fall, relative to the mean sea level. The region of beach/ rock platform exposed above low water will continue to narrow. High tide will reach the cliff toe more frequently and allow larger waves to strike the cliffs with more energy. The shore will recede at a higher rate than seen in the past. As a consequence the proportion of the cliff face comprised of active landslides will continue to increase. This will supply more material to the beach, which will mitigate, although not prevent, the narrowing of the intertidal zone. Beaches not fixed by backing cliffs will be elevated by the rising sea level and ‘roll back’. This will involve some dune erosion.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 48 February 2011

9.2 Unit details – No Active Intervention

Location Predicted Change For Years 0 – 20 (2025) Years 20 – 50 (2055) Years 50 – 100 (2105) Lizard Point No defences No defences No defences to Kynance Cove The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Kynance No defences No defences No defences Cove The evolution of this coast Ongoing sea level rise will Ongoing sea level rise will will be typical of the region, further narrow the beach, continue to narrow the beach as described above. The increasing the period that the and increase wave loading beach will begin to narrow as cliff toe is submerged at high on the cliff toe. Landslides the sea level rises. tide. Wave loading on the cliff and cliff top retreat will toe will increase. increase. Kynance No defences No defences No defences Cove to Mullion Cove The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Mullion Cove Breakwater Breakwater Breakwater Historic retreat of the beach The form of the beach and Ongoing acceleration in the will continue. However the dunes will remain essentially rate of sea level rise will drive beach and dunes will retain unchanged. Sea level rise will increasing erosion of the their current characteristics. cause higher beach retreat dune face. However this will Natural short term and rates than occurred in the be accompanied by seasonal fluctuations in form past. Erosion of the front of increasing release of will continue. the dune will release sand sediment into the beach into the beach. which will allow it to rise with the sea level. As a result although the seaward margin of the dunes will be lost, the beach will appear relatively unchanged. Mullion Cove No defences No defences No defences to Polurrian Cove The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Polurrian No defences No defences No defences Cove The beach and dunes will The form of the beach and Ongoing acceleration in the remain essentially dunes will remain essentially rate of sea level rise will drive

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 49 February 2011

unchanged, apart from unchanged. Sea level rise will increasing erosion of the natural short term and drive some erosion of the dune face. However this will seasonal fluctuations in form front of the dune, and this will be accompanied by release sand into the beach. increasing release of sediment into the beach which will allow it to rise with the sea level. As a result the beach will appear relatively unchanged. Polurrian No defences No defences No defences Cove to Cove The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Poldhu Cove No defences No defences No defences Historic retreat of the beach The form of the beach and Ongoing acceleration in the will continue. However the dunes will remain essentially rate of sea level rise will drive beach and dunes will retain unchanged. Sea level rise will increasing erosion of the their current characteristics. cause higher beach retreat dune face. However this will Natural short term and rates than occurred in the be accompanied by seasonal fluctuations in form past. Erosion of the front of increasing release of will continue. the dune will release sand sediment into the beach into the beach. which will allow it to rise with the sea level. As a result although the seaward margin of the dunes will be lost, the beach will appear relatively unchanged. Poldhu Cove No defences No defences No defences to Church Cove The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Church Cove No defences No defences No defences The coast will remain much Accelerated sea level risk will Accelerated sea level risk will as it is today. Accelerated tend to drive the beach up tend to drive the beach sea level risk will drive some and back, eroding the dunes. further up and back leading retreat of shoreline but this Failure of defences will lead to significant dune erosion. will be difficult to distinguish to rapid localised erosion Recession of the shoreline from natural variability. will be mitigated to a degree by the release of sediments from the dunes. Jangye-ryn Wall No defences No defences (Winnianton) Sea level rise will cause a Failure of the coastal Accelerated relative sea level low recession rate. In front of structures will be followed by rise will continue to cause the the wall beach levels will tend a transient period of beach to roll back, at

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 50 February 2011

to drop, elsewhere the beach accelerated recession, as increasing rates. Continued will roll back. Loading on the waves attack over-steepened erosion will release fresh structure will tend to shore profiles. Sediments sediments into the beach. increase. released will tend to raise beach levels. The previously protected area will realign to the remainder of the beach. Jangye-ryn No defences No defences No defences (Winnianton) to Gunwalloe Fishing Cove The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Gunwalloe No defences No defences No defences Fishing Cove Beach The shoreline will continue to Ongoing sea level rise will Ongoing sea level rise will retreat. This will tend to tend to narrow the beach and continue to narrow the beach happen at a higher rate, increase wave loading on the and increase wave loading although this increase should cliffs, increasing recession on the cliff toe. Landslides be difficult to distinguish from rates. and cliff top retreat will natural variability. increase. This will to release additional sediments into the beach, although this will only partly mitigate the overall narrowing of the intertidal zone. Loe Bar No defences No defences No defences The ridge will continue to Sea level rise will tend to Sea level rise will tend to grow as it has in the recent drive the bar landward and drive the bar landward and past. raise the crest. Overall this raise the crest. Overall this may lead to a slight may lead to a steeper narrowing of the crest. landward face and narrowing of the crest. The overall retreat rate is likely to be governed by the recession of the cliffs on either side. Discontinuous seawalls No defences No defences Sands The shoreline will continue to Ongoing sea level rise will Ongoing sea level rise will retreat. This will tend to tend to narrow the beach and continue to narrow the beach happen at a higher rate, increase wave loading on the and increase wave loading although this increase should cliffs, increasing recession on the cliff toe. Landslides be difficult to distinguish from rates. and cliff top retreat will natural variability. increase. This will to release additional sediments into the beach, although this will only partly mitigate the overall

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 51 February 2011

narrowing of the intertidal zone. Porthleven Recurved Wall No defences No defences frontage (Gravesend) The beach will continue to Failure of the coastal Accelerated relative sea level narrow. The coastal defences structures will be followed by rise will continue to cause the will prevent recession and so a transient period of beach to roll back, at cause the shoreline to be accelerated recession, as increasing rates. Continued increasingly seaward of its waves attack over-steepened erosion will release fresh natural position. The shore profiles. This will sediments that will defences will also prevent the release sedimentary material, accumulate and provide formation of new shore some of which will some protection to wave platform and reduce the accumulate in the beach. The attack. release of material for the beach will begin to roll back beach. Relative lowering of and this will mitigate, the rock foreshore and beach although not prevent, will allow larger, more narrowing of the intertidal aggressive waves to reach zone due to sea level rise. the structures. Porthleven Harbour and Quay Walls Harbour and Quay Walls Harbour and Quay Walls harbour Water depths increase within Water depths increase within Water depths increase within the harbour, with no effect on the harbour, with no effect on the harbour, with no effect on the surrounding coast. the surrounding coast. the surrounding coast. Localised structure failures Failure of some harbour may occur. structures leads to loss of the harbour margin. Porthleven Wall No defences No defences (Great Trigg Rocks) Erosion will be small, The trend seen in the Accelerated relative sea level however increasing sea previous epoch will continue. rise will continue to increase levels will increase the water Collapse of defences will lead wave activity at the shore. depths, allowing slightly to localised cliff failures. The shore platform will be larger waves to reach the Wave run-up and impacts on submerged for a greater shore. the cliff face will increase. proportion of the tide, and so access will be reduced. Wave impacts on the cliff face will continue to increase, causing higher shore recession rates. Porthleven No defences No defences No defences (Great Trigg Rocks) to Praa Sands The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 52 February 2011

Praa Sands No defences No defences No defences East The beach will continue to Failure of the coastal Accelerated relative sea level narrow. The coastal defences structures will be followed by rise will continue to cause the will prevent recession and so a transient period of beach to roll back, at cause the shoreline to be accelerated recession, as increasing rates. Continued increasingly seaward of its waves attack over-steepened erosion will release fresh natural position. The shore profiles. This will sediments that will defences will also prevent the release sedimentary material, accumulate and provide formation of new shore some of which will some protection to wave platform and reduce the accumulate in the beach. The attack. release of material for the beach will begin to roll back beach. Relative lowering of and this will mitigate, the rock foreshore and beach although not prevent, will allow larger, more narrowing of the intertidal aggressive waves to reach zone due to sea level rise. the structures. Praa Sands Wall and structure No defences No defences West (Sydney Cove) Sea level rise will cause a Failure of the coastal Accelerated relative sea level low recession rate. In front of structures will be followed by rise will continue to cause the the wall beach levels will tend a transient period of beach to roll back, at to drop, elsewhere the beach accelerated recession, as increasing rates. Continued will roll back. Loading on the waves attack over-steepened erosion will release fresh structure will tend to shore profiles. Sediments sediments into the beach. increase. released will tend to raise beach levels. The previously protected area will realign to the remainder of the beach. Praa Sands No defences No defences No defences to Perran Sands The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Perran Rock revetment No defences No defences Sands The shoreline will continue to Ongoing sea level rise will Ongoing sea level rise will retreat where it is not tend to narrow the beach and continue to narrow the beach defended. This will tend to increase wave loading on the and increase wave loading happen at a higher rate, cliffs, increasing recession on the cliff toe. Landslides although this increase should rates. Failure of the and cliff top retreat will be difficult to distinguish from structures will be followed by increase. This will to release natural variability. In front of a period of accelerated additional sediments into the defended areas the water recession, as more natural beach, although this will only depth will tend to increase, as shore profiles are reformed. partly mitigate the overall foreshores lower and sea narrowing of the intertidal

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 53 February 2011

levels rise. zone. Perran No defences No defences No defences Sands to Trevelyan Cove The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Trevelyan No defences No defences No defences Cove to Venton Cove Erosion will continue and will Erosion will accelerate as Accelerated relative sea level tend to be accelerated by rising seas allow larger rise will continue to increase rising seas, although this waves to attack the cliffs. wave activity at the shore. increase is likely to be difficult Wave run-up and impacts on The shore platform will be to distinguish from natural the cliff face. submerged for a greater variability. proportion of the tide, and so access will be reduced. Wave impacts on the cliff face will continue to increase, causing higher shore recession rates. Walls No defences No defences East (Venton Cove) The shoreline will continue to Ongoing sea level rise will Ongoing sea level rise will retreat where it is not tend to narrow the beach and continue to narrow the beach defended. This will tend to increase wave loading on the and increase wave loading happen at a higher rate, cliffs, increasing recession on the cliff toe. Landslides although this increase should rates. Failure of the and cliff top retreat will be difficult to distinguish from structures will be followed by increase. This will to release natural variability. In front of a period of accelerated additional sediments into the defended areas the water recession, as more natural beach, although this will only depth will tend to increase, as shore profiles are reformed. partly mitigate the overall foreshores lower and sea narrowing of the intertidal levels rise. zone. Marazion Walls No defences No defences town frontage The beach will continue to Failure of the coastal Accelerated relative sea level narrow. The coastal defences structures will be followed by rise will continue to cause the will prevent recession and so a transient period of beach to roll back, at cause the shoreline to be accelerated recession, as increasing rates. Continued increasingly seaward of its waves attack over-steepened erosion will release fresh natural position. The shore profiles. This will sediments that will defences will also prevent the release sedimentary material, accumulate and provide formation of new shore some of which will some protection to wave platform and reduce the accumulate in the beach. The attack. release of material for the beach will begin to roll back beach. Relative lowering of and this will mitigate,

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 54 February 2011

the rock foreshore and beach although not prevent, will allow larger, more narrowing of the intertidal aggressive waves to reach zone due to sea level rise. the structures. St Michael’s Breakwater and quay walls Breakwater and quay walls Breakwater and quay walls Mount harbour Water depths increase within Water depths increase within Water depths increase within the harbour, with no effect on the harbour, with no effect on the harbour, with no effect on the surrounding coast. the surrounding coast. the surrounding coast. Localised structure failures Failure of some harbour may occur. structures leads to loss of the harbour margin. St Michaels No defences No defences No defences Mount Erosion will continue and will Erosion will accelerate as Accelerated relative sea level tend to be accelerated by rising seas allow larger rise will continue to increase rising seas, although this waves to attack the cliffs. wave activity at the shore. increase is likely to be difficult Wave run-up and impacts on The shore platform will be to distinguish from natural the cliff face. submerged for a greater variability. proportion of the tide, and so access will be reduced. Wave impacts on the cliff face will continue to increase, causing higher shore recession rates. Marazion Walls and revetments No defences No defences west Sea level rise will cause a Failure of the coastal Accelerated relative sea level low recession rate. In front of structures will be followed by rise will continue to cause the the wall beach levels will tend a transient period of beach to roll back, at to drop, elsewhere the beach accelerated recession, as increasing rates. Continued will roll back. Loading on the waves attack over-steepened erosion will release fresh structure will tend to shore profiles. Sediments sediments into the beach. increase. released will tend to raise beach levels. The previously protected area will realign to the remainder of the beach. Marazion Walls and revetments No defences No defences Marsh Sea level rise will tend to Structure failure, coupled with Ongoing sea level rise will drive the beach back, and increased sea level will lead allow more extensive erosion increase wave forces on the to quite rapid erosion. Where and flooding. If the system structures. breaching occurs to lower retains sufficient shelter, a land, inundation should be saltmarsh might be expected. expected. The resulting hydrodynamic flows should redistribute sediments, reforming the area.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 55 February 2011

Longrock Walls, revetments and dune No defences No defences The beach will continue to Failure of the coastal Accelerated relative sea level narrow. The coastal defences structures will be followed by rise will continue to cause the will prevent recession and so a transient period of beach to retreat, at cause the shoreline to be accelerated recession, as increasing rates. Continued increasingly seaward of its waves attack over-steepened erosion will release fresh natural position. The shore profiles. This will sediments that will defences will also prevent the release sedimentary material, accumulate and provide formation of new shore some of which will some protection to wave platform and reduce the accumulate in the beach. The attack. release of material for the beach will begin to roll back beach. Relative lowering of and this will mitigate, the rock foreshore and beach although not prevent, will allow larger, more narrowing of the intertidal aggressive waves to reach zone due to sea level rise. the structures. Longrock to Revetment and rock armour No defences No defences Ponsadane Bridge The beach will continue to Failure of the coastal Accelerated relative sea level narrow. The coastal defences structures will be followed by rise will continue to cause the will prevent recession and so a transient period of beach to roll back, at cause the shoreline to be accelerated recession, as increasing rates. Continued increasingly seaward of its waves attack over-steepened erosion will release fresh natural position. The shore profiles. This will sediments that will defences will also prevent the release sedimentary material, accumulate and provide formation of new shore some of which will some protection to wave platform and reduce the accumulate in the beach. The attack. The sea will tend to release of material for the beach will begin to roll back encroach at Ponsandane beach. Relative lowering of and this will mitigate, Brook, but the shoreline here the rock foreshore and beach although not prevent, is likely to be quite dynamic, will allow larger, more narrowing of the intertidal during quieter periods sand aggressive waves to reach zone due to sea level rise. will accrete to form a partial the structures. The sea will tend to encroach barrier at Ponsandane Brook, but the shoreline here is likely to be quite dynamic, during quieter periods sand will accrete to form a partial barrier Ponsandane Walls and gabions No defences No defences Bridge (Chyandour) The coastal defences will Failure of the coastal Accelerated relative sea level prevent recession and so structures will be followed by rise will continue to cause the cause the shoreline to be a transient period of beach to roll back, at increasingly seaward of its accelerated recession, as increasing rates. Continued natural position. The waves attack over-steepened erosion will release fresh defences will also prevent the shore profiles. This will sediments that will

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 56 February 2011

formation of new shore release sedimentary material, accumulate and provide platform and reduce the some of which will some protection to wave release of material for the accumulate in the beach. The attack. beach. Relative lowering of beach will begin to roll back the beach will allow larger, and this will mitigate, more aggressive waves to although not prevent, reach the structures. narrowing of the intertidal zone due to sea level rise. Chyandour Wall No defences No defences Coombe to Harbour The beach will continue to Failure of the coastal Accelerated relative sea level narrow. The coastal defences structures will be followed by rise will continue to cause the will prevent recession and so a transient period of beach to roll back, at cause the shoreline to be accelerated recession, as increasing rates. Continued increasingly seaward of its waves attack over-steepened erosion will release fresh natural position. The shore profiles. This will sediments that will defences will also prevent the release sedimentary material, accumulate and provide formation of new shore some of which will some protection to wave platform and reduce the accumulate in the beach. The attack. release of material for the beach will begin to roll back beach. Relative lowering of and this will mitigate, the rock foreshore and beach although not prevent, will allow larger, more narrowing of the intertidal aggressive waves to reach zone due to sea level rise. the structures. Penzance Breakwater, quay walls and Breakwater, quay walls and Breakwater, quay walls and Harbour and revetments revetments revetments docks Water depths increase within Water depths increase within Water depths increase within the harbour, with no effect on the harbour, with no effect on the harbour, with no effect on the surrounding coast. the surrounding coast. the surrounding coast. Localised structure failures Failure of some harbour may occur. structures leads to loss of the harbour margin. Penzance Walls No defences No defences promenade The beach will continue to Failure of the coastal Accelerated relative sea level narrow. The coastal defences structures will be followed by rise will continue to cause the will prevent recession and so a transient period of beach to roll back, at cause the shoreline to be accelerated recession, as increasing rates. Continued increasingly seaward of its waves attack over-steepened erosion will release fresh natural position. The shore profiles. This will sediments that will defences will also prevent the release sedimentary material, accumulate and provide formation of new shore some of which will some protection to wave platform and reduce the accumulate in the beach. The attack. release of material for the beach will begin to roll back beach. Relative lowering of and this will mitigate,

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 57 February 2011

the rock foreshore and beach although not prevent, will allow larger, more narrowing of the intertidal aggressive waves to reach zone due to sea level rise. the structures. Wherry Town Walls No defences No defences The beach will continue to Failure of the coastal Accelerated relative sea level narrow. The coastal defences structures will be followed by rise will continue to cause the will prevent recession and so a transient period of beach to roll back, at cause the shoreline to be accelerated recession, as increasing rates. Continued increasingly seaward of its waves attack over-steepened erosion will release fresh natural position. The shore profiles. This will sediments that will defences will also prevent the release sedimentary material, accumulate and provide formation of new shore some of which will some protection to wave platform and reduce the accumulate in the beach. The attack. release of material for the beach will begin to roll back beach. Relative lowering of and this will mitigate, the rock foreshore and beach although not prevent, will allow larger, more narrowing of the intertidal aggressive waves to reach zone due to sea level rise. the structures. Breakwater, quay walls and Breakwater, quay walls and Breakwater, quay walls and Harbour revetments, pier revetments, pier revetments, pier Water depths increase within Water depths increase within Water depths increase within the harbour, with no effect on the harbour, with no effect on the harbour, with no effect on the surrounding coast. the surrounding coast. the surrounding coast. Localised structure failures Failure of some harbour may occur. structures leads to loss of the harbour margin. Sandy Cove Walls and revetment No defences No defences to Penlee Point The shoreline will be held by Failure of the structures will Ongoing sea level rise will the defences. The water be followed by a period of continue to submerge the depth over the shore platform accelerated recession, as shore platform. Larger waves will increase slightly. more natural shore profiles will be able to attack the are reformed. Sea level rise cliffs, driving them back. The will further submerge the sediments released by shore platform, allowing recession and the formation larger waves to pass over of new shore platform will them. mitigate the effects of the rising seas to some degree, but overall there will be a narrowing of the intertidal zone.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 58 February 2011

9.3 Unit details – With Present Management

Location Predicted Change For Years 0 – 20 (2025) Years 20 – 50 (2055) Years 50 – 100 (2105) Lizard Point No defences No defences No defences to Kynance Cove The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Kynance No defences No defences No defences Cove Coastal evolution will be Ongoing sea level rise will Ongoing sea level rise will typical of the region as further narrow the beach, continue to narrow the beach described above. The beach increasing the period that the and increase wave loading will begin to narrow as the cliff toe is submerged at high on the cliff toe. Landslides sea level rises. tide. Wave loading on the cliff and cliff top retreat will toe will increase. increase. Kynance No defences No defences No defences Cove to Mullion Cove The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Mullion Cove Breakwater Breakwater Breakwater Historic retreat of the beach The form of the beach and Ongoing acceleration in the will continue. However the dunes will remain essentially rate of sea level rise will drive beach and dunes will retain unchanged. Sea level rise will increasing erosion of the their current characteristics. cause higher beach retreat dune face. However this will Natural short term and rates than occurred in the be accompanied by seasonal fluctuations in form past. Erosion of the front of increasing release of will continue. the dune will release sand sediment into the beach into the beach. which will allow it to rise with the sea level. As a result although the seaward margin of the dunes will be lost, the beach will appear relatively unchanged. Mullion Cove No defences No defences No defences to Polurrian Cove The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Polurrian No defences No defences No defences Cove The beach and dunes will The form of the beach and Ongoing acceleration in the remain essentially dunes will remain essentially rate of sea level rise will drive unchanged, apart from unchanged. Sea level rise will increasing erosion of the

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 59 February 2011

natural short term and drive some erosion of the dune face. However this will seasonal fluctuations in form front of the dune, and this will be accompanied by release sand into the beach. increasing release of sediment into the beach which will allow it to rise with the sea level. As a result the beach will appear relatively unchanged. Polurrian No defences No defences No defences Cove to Poldhu Cove The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Poldhu Cove No defences No defences No defences Historic retreat of the beach The form of the beach and Ongoing acceleration in the will continue. However the dunes will remain essentially rate of sea level rise will drive beach and dunes will retain unchanged. Sea level rise will increasing erosion of the their current characteristics. cause higher beach retreat dune face. However this will Natural short term and rates than occurred in the be accompanied by seasonal fluctuations in form past. Erosion of the front of increasing release of will continue. the dune will release sand sediment into the beach into the beach. which will allow it to rise with the sea level. As a result although the seaward margin of the dunes will be lost, the beach will appear relatively unchanged. Poldhu Cove No defences No defences No defences to Church Cove The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Church Cove Wall Wall Wall The coast will remain much Accelerated sea level risk will Accelerated sea level risk will as it is today. Accelerated tend to drive the beach up tend to drive the beach sea level risk will drive some and back, eroding the dunes. further up and back leading retreat of shoreline but this Wave loading on the to significant dune erosion. will be difficult to distinguish defences will increase as the Recession of the shoreline from natural variability. water depth increases. will be mitigated to a degree by the release of sediments from the dunes. Wave loading on the structures will continue to increase. Jangye-ryn Wall Wall Wall (Winnianton) b Sea level rise will cause a Accelerated sea level rise will Accelerated sea level rise will low recession rate. In front of increase the recession rate of further increase the recession

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 60 February 2011

the wall beach levels will tend the areas not fronted by a rate of the areas not fronted to drop, elsewhere the beach structure. This will release by a structure. This will will roll back. Loading on the sediments that will tend to release sediments that will structure will tend to raise the level of the beach. tend to raise the level of the increase. In front of the wall beach beach. The wall will tend to levels will continue to fall and be outflanked by this so wave loading on the recession. In front of the wall structure will continue to beach levels will continue to increase. fall and so wave loading on the structure will continue to increase. Jangye-ryn No defences No defences No defences (Winnianton) to Gunwalloe Fishing Cove The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Gunwalloe No defences No defences No defences Fishing Cove Beach The shoreline will continue to Ongoing sea level rise will Ongoing sea level rise will retreat. This will tend to tend to narrow the beach and continue to narrow the beach happen at a higher rate, increase wave loading on the and increase wave loading although this increase should cliffs, increasing recession on the cliff toe. Landslides be difficult to distinguish from rates. and cliff top retreat will natural variability. increase. This will to release additional sediments into the beach, although this will only partly mitigate the overall narrowing of the intertidal zone. Loe Bar No defences No defences No defences The ridge will continue to Sea level rise will tend to Sea level rise will tend to grow as it has in the recent drive the bar landward and drive the bar landward and past. raise the crest. Overall this raise the crest. Overall this may lead to a slight may lead to a steeper narrowing of the crest. landward face and narrowing of the crest. The overall retreat rate is likely to be governed by the recession of the cliffs on either side. Porthleven Discontinuous seawalls Discontinuous seawalls Discontinuous seawalls Sands The shoreline will continue to Ongoing sea level rise will Ongoing sea level rise will retreat. This will tend to tend to narrow the beach and continue to narrow the beach happen at a higher rate, increase wave loading on the and increase wave loading although this increase should cliffs, increasing recession on the cliff toe. Landslides be difficult to distinguish from rates. and cliff top retreat will

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 61 February 2011

natural variability. increase. This will to release additional sediments into the beach, although this will only partly mitigate the overall narrowing of the intertidal zone. Porthleven Recurved Wall Recurved Wall Recurved Wall frontage (Gravesend) The beach will continue to The trend seen in the prior The trend seen in the prior narrow. The coastal defences epoch will continue. epoch will continue. Wave will prevent recession and so impact forces and cause the shoreline to be overtopping will grow at an increasingly seaward of its exponential rate, natural position. The necessitating larger defences will also prevent the structures to maintain current formation of new shore levels of defence. Beach platform and reduce the accessibility will reduce as release of material for the the sea level rises. beach. Relative lowering of the rock foreshore and beach will allow larger, more aggressive waves to reach the structures. Porthleven Harbour and Quay Walls Harbour and Quay Walls Harbour and Quay Walls harbour Water depths will increase Water depths will increase Water depths will increase within the harbour, with no within the harbour, with no within the harbour, with no effect on the surrounding effect on the surrounding effect on the surrounding coast. coast.. coast. Porthleven Wall Wall Wall (Great Trigg Rocks) Erosion will be small, The trend seen in the Accelerated relative sea level however increasing sea previous epoch will continue. rise will continue to increase levels will increase the water Wave run-up and impacts on wave activity at the shore. depths, allowing slightly the cliff face and structures The shore platform will be larger waves to reach the will increase. The increased submerged for a greater shore. wave loading will necessitate proportion of the tide, and so the construction of more access will be reduced. Wave substantial defences. impacts on the cliff face and structures will continue to increase, causing higher shore recession rates in the unprotected areas. The increased wave loading will necessitate the construction of more substantial defences.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 62 February 2011

Porthleven No defences No defences No defences (Great Trigg Rocks) to Praa Sands The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Praa Sands Defences No defences No defences East The beach will continue to The trend seen in the prior The trend seen in the prior narrow. The coastal defences epoch will continue. epoch will continue. Wave will prevent recession and so impact forces and cause the shoreline to be overtopping will grow at an increasingly seaward of its exponential rate, natural position. The necessitating larger defences will also prevent the structures to maintain current formation of new shore levels of defence. Beach platform and reduce the accessibility will reduce as release of material for the the sea level rises. beach. Relative lowering of the rock foreshore and beach will allow larger, more aggressive waves to reach the structures. Praa Sands Wall and structure Wall and structure Wall and structure West (Sydney Cove) Sea level rise will cause a Accelerated sea level rise will Accelerated sea level rise will low recession rate. In front of increase the recession rate of further increase the recession the wall beach levels will tend the areas not fronted by a rate of the areas not fronted to drop, elsewhere the beach structure. This will release by a structure. This will will roll back. Loading on the sediments that will tend to release sediments that will structure will tend to raise the level of the beach. tend to raise the level of the increase. In front of the wall beach beach. The wall will tend to levels will continue to fall and be outflanked by this so wave loading on the recession. In front of the wall structure will continue to beach levels will continue to increase. fall and so wave loading on the structure will continue to increase. Praa Sands No defences No defences No defences to Perran Sands The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Perran Rock revetment Rock revetment Rock revetment Sands

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 63 February 2011

The shoreline will continue to Ongoing sea level rise will Ongoing sea level rise will retreat where it is not tend to narrow the beach and continue to narrow the beach defended. This will tend to increase wave loading on the and increase wave loading happen at a higher rate, cliffs, where they are not on the cliff toe. Landslides although this increase should defended, increasing and cliff top retreat will be difficult to distinguish from recession rates. Water increase. This will to release natural variability. In front of depths will continue to additional sediments into the defended areas the water increase, in front of the beach, and new shore depth will tend to increase, as structures, increasing wave platform will be formed, foreshores lower and sea loads on them. although this will only partly levels rise. mitigate overall narrowing of the intertidal zone. In defended areas the intertidal zone will narrow more sharply, decreasing the period during which they can be accessed at low tide. Wave loading on the structures will increase. Perran No defences No defences No defences Sands to Trevelyan Cove The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Trevelyan No defences No defences No defences Cove to Venton Cove Erosion will continue and will Erosion will accelerate as Accelerated relative sea level tend to be accelerated by rising seas allow larger rise will continue to increase rising seas, although this waves to attack the cliffs. wave activity at the shore. increase is likely to be difficult Wave run-up and impacts on The shore platform will be to distinguish from natural the cliff face. submerged for a greater variability. proportion of the tide, and so access will be reduced. Wave impacts on the cliff face will continue to increase, causing higher shore recession rates.

Marazion Walls Walls Walls East (Venton Cove) The shoreline will continue to Ongoing sea level rise will Ongoing sea level rise will retreat where it is not tend to narrow the beach and continue to narrow the beach defended. This will tend to increase wave loading on the and increase wave loading happen at a higher rate, cliffs, where they are not on the cliff toe. Landslides although this increase should defended, increasing and cliff top retreat will be difficult to distinguish from recession rates. Water increase. This will to release

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 64 February 2011

natural variability. In front of depths will continue to additional sediments into the defended areas the water increase, in front of the beach, and new shore depth will tend to increase, as structures, increasing wave platform will be formed, foreshores lower and sea loads on them. although this will only partly levels rise. mitigate overall narrowing of the intertidal zone. In defended areas the intertidal zone will narrow more sharply, decreasing the period during which they can be accessed at low tide. Wave loading on the structures will increase. Marazion Walls Walls Walls town frontage The beach will continue to The trend seen in the prior The trend seen in the prior narrow. The coastal defences epoch will continue. epoch will continue. Wave will prevent recession and so impact forces and cause the shoreline to be overtopping will grow at an increasingly seaward of its exponential rate, natural position. The necessitating larger defences will also prevent the structures to maintain current formation of new shore levels of defence. Beach platform and reduce the accessibility will reduce as release of material for the the sea level rises. beach. Relative lowering of the rock foreshore and beach will allow larger, more aggressive waves to reach the structures. St Michael’s Breakwater and quay walls Breakwater and quay walls Breakwater and quay walls Mount harbour Water depths will increase Water depths will increase Water depths will increase within the harbour, with no within the harbour, with no within the harbour, with no effect on the surrounding effect on the surrounding effect on the surrounding coast. coast.. coast. St Michaels No defences No defences No defences Mount Erosion will continue and will Erosion will accelerate as Accelerated relative sea level tend to be accelerated by rising seas allow larger rise will continue to increase rising seas, although this waves to attack the cliffs. wave activity at the shore. increase is likely to be difficult Wave run-up and impacts on The shore platform will be to distinguish from natural the cliff face. submerged for a greater variability. proportion of the tide, and so access will be reduced. Wave impacts on the cliff face will continue to increase, causing

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 65 February 2011

higher shore recession rates. Marazion Walls and revetments Walls and revetments Walls and revetments west (Chapel Rock to Marazion Bridge) b Sea level rise will cause a Accelerated sea level rise will Accelerated sea level rise will low recession rate. In front of increase the recession rate of further increase the recession the wall beach levels will tend the areas not fronted by a rate of the areas not fronted to drop, elsewhere the beach structure. This will release by a structure. This will will roll back. Loading on the sediments that will tend to release sediments that will structure will tend to raise the level of the beach. tend to raise the level of the increase. In front of the wall beach beach. The wall will tend to levels will continue to fall and be outflanked by this so wave loading on the recession. In front of the wall structure will continue to beach levels will continue to increase. fall and so wave loading on the structure will continue to increase. Marazion Walls and revetments Walls and revetments Walls and revetments Marsh The beach will continue to The trend seen in the prior The trend seen in the prior narrow. The coastal defences epoch will continue. epoch will continue. Wave will prevent recession and so impact forces and cause the shoreline to be overtopping will grow at an increasingly seaward of its exponential rate, natural position. The necessitating larger defences will also prevent the structures to maintain current formation of new shore levels of defence. Beach platform and reduce the accessibility will reduce as release of material for the the sea level rises. beach. Relative lowering of the rock foreshore and beach will allow larger, more aggressive waves to reach the structures. Longrock Walls, revetments and dune No defences No defences The beach will continue to The trend seen in the prior The trend seen in the prior narrow. The coastal defences epoch will continue. epoch will continue. Wave will prevent recession and so impact forces and cause the shoreline to be overtopping will grow at an increasingly seaward of its exponential rate, natural position. The necessitating larger defences will also prevent the structures to maintain current formation of new shore levels of defence. Beach platform and reduce the accessibility will reduce as release of material for the the sea level rises. beach. Relative lowering of the rock foreshore and beach

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 66 February 2011

will allow larger, more aggressive waves to reach the structures. Longrock to Revetment and rock armour Revetment and rock armour Revetment and rock armour Ponsadane Bridge The beach will continue to The trend seen in the prior The trend seen in the prior narrow. The coastal defences epoch will continue. epoch will continue. Wave will prevent recession and so impact forces and cause the shoreline to be overtopping will grow at an increasingly seaward of its exponential rate, natural position. The necessitating larger defences will also prevent the structures to maintain current formation of new shore levels of defence. Beach platform and reduce the accessibility will reduce as release of material for the the sea level rises. beach. Relative lowering of the rock foreshore and beach will allow larger, more aggressive waves to reach the structures. Ponsandane Walls and gabions Walls and gabions Walls and gabions Bridge (Chyandour) The coastal defences will The trend seen in the prior The trend seen in the prior prevent recession and so epoch will continue. epoch will continue. Wave cause the shoreline to be impact forces and increasingly seaward of its overtopping will grow at an natural position. The exponential rate, defences will also prevent the necessitating larger formation of new shore structures to maintain current platform and reduce the levels of defence. Beach release of material for the accessibility will reduce as beach. Relative lowering of the sea level rises. the beach will allow larger, more aggressive waves to reach the structures. Chyandour Wall Wall Wall Coombe to Penzance Harbour The beach will continue to The trend seen in the prior The trend seen in the prior narrow. The coastal defences epoch will continue. epoch will continue. Wave will prevent recession and so impact forces and cause the shoreline to be overtopping will grow at an increasingly seaward of its exponential rate, natural position. The necessitating larger defences will also prevent the structures to maintain current formation of new shore levels of defence. Beach

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 67 February 2011

platform and reduce the accessibility will reduce as release of material for the the sea level rises. beach. Relative lowering of the rock foreshore and beach will allow larger, more aggressive waves to reach the structures. Penzance Breakwater, quay walls and Breakwater, quay walls and Breakwater, quay walls and Harbour and revetments revetments revetments docks Water depths will increase Water depths will increase Water depths will increase within the harbour, with no within the harbour, with no within the harbour, with no effect on the surrounding effect on the surrounding effect on the surrounding coast. coast.. coast. Penzance Walls Wall Wall promenade The beach will continue to The trend seen in the prior The trend seen in the prior narrow. The coastal defences epoch will continue. epoch will continue. Wave will prevent recession and so impact forces and cause the shoreline to be overtopping will grow at an increasingly seaward of its exponential rate, natural position. The necessitating larger defences will also prevent the structures to maintain current formation of new shore levels of defence. Beach platform and reduce the accessibility will reduce as release of material for the the sea level rises. beach. Relative lowering of the rock foreshore and beach will allow larger, more aggressive waves to reach the structures. Wherry Town Walls Wall Wall The beach will continue to The trend seen in the prior The trend seen in the prior narrow. The coastal defences epoch will continue. epoch will continue. Wave will prevent recession and so impact forces and cause the shoreline to be overtopping will grow at an increasingly seaward of its exponential rate, natural position. The necessitating larger defences will also prevent the structures to maintain current formation of new shore levels of defence. Beach platform and reduce the accessibility will reduce as release of material for the the sea level rises. beach. Relative lowering of the rock foreshore and beach will allow larger, more aggressive waves to reach the structures. Newlyn Breakwater, quay walls and Breakwater, quay walls and Breakwater, quay walls and Harbour revetments, pier revetments, pier revetments, pier

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 68 February 2011

Water depths will increase Water depths will increase Water depths will increase within the harbour, with no within the harbour, with no within the harbour, with no effect on the surrounding effect on the surrounding effect on the surrounding coast. coast.. coast. Sandy Cove Walls and revetment Walls and revetment Walls and revetment to Penlee Point The shoreline will be held by The shoreline will be held by The shoreline will be held by the defences. The water the defences. Sea level rise the defences. Sea level rise depth over the shore platform will submerge the shore will submerge the shore will increase slightly. platform allowing larger platform allowing larger waves to attack the waves to attack the structures. Consequently structures. Consequently wave forces and overtopping wave forces and overtopping rates will increase. rates will continue to grow. Access along the shore platform will be noticeably reduced as it is submerged during more of the tide. .

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 69 February 2011

10 PENLEE POINT TO LANDS END

10.1 Typical coastal evolution

10.1.1 Epoch 1, years 0 – 20 (2025)

The coast will continue to erode whilst retaining its current characteristics. Occasional landslides and rockfalls will cause cliff tops to retreat, and will deliver sediment to the foreshores. These processes will be driven by ongoing wave erosion of the cliff base, which will also form new areas of shore platform. The shore platform will be lowered by wave action, where it is not protected by beach material. The beaches will be fed by the larger sediments released by the ongoing erosion processes. A small acceleration in the rate of relative sea level rise will cause shore platforms to be slightly lower, relative to the mean sea level. The region of beach/ rock platform exposed above low water will become slightly narrower as the sea rise accelerates. This will allow slightly larger waves to arrive at the cliffs, increasing the severity of wave breaking. As a consequence the shore will retreat slightly faster than it has in the past. Locations were valleys meet the sea will tend to respond more strongly to sea level rise than rocky areas. The crests of the beaches that form in these valleys will be elevated by the rising sea level, and retreat inland, where there is space to do so.

10.1.2 Epoch 2, years 20 – 50 (2055)

The coast will continue to erode whilst retaining its current characteristics, as in epoch 1. A larger acceleration in rate of relative sea level rise will cause shore platforms to continue to fall, relative to the mean sea level. The region of beach/ rock platform exposed above low water will narrow. High tide will reach the cliff toe more frequently and this will allow larger waves to strike the cliffs, increasing the severity of wave breaking and raising recession rates. As a consequence the proportion of the cliff face comprised of active landslides will tend to increase. This will supply more material to the beach, which will mitigate, although not prevent, the narrowing of the intertidal zone. Beaches not fixed by backing cliffs or hard structures will be elevated by the rising sea level and ‘roll back’. This will involve some dune erosion.

10.1.3 Epoch 3, years 50 – 100 (2105)

The coast will continue to erode whilst retaining its current characteristics, as in epochs 1 and 2. Continued acceleration of the rate of relative sea level rise will cause shore platforms to continue to fall, relative to the mean sea level. The region of beach/ rock platform exposed above low water will continue to narrow. High tide will reach the cliff toe more frequently and allow larger waves to strike the cliffs with more energy. The shore will recede at a higher rate than seen in the past. As a consequence the proportion of the cliff face comprised of active landslides will continue to increase. This will supply more material to the beach, which will mitigate, although not prevent, the narrowing of the intertidal zone. Beaches not fixed by backing cliffs will be elevated by the rising sea level and ‘roll back’. This will involve some dune erosion.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 70 February 2011

10.2 Unit details – No Active Intervention

Location Predicted Change For Years 0 – 20 (2025) Years 20 – 50 (2055) Years 50 – 100 (2105) Penlee Point Walls and revetment No defences No defences to Mousehole harbour The shoreline will be held by Failure of the structures will Ongoing sea level rise will the defences. The water be followed by a period of continue to submerge the depth over the shore platform accelerated recession, as shore platform. Larger waves will increase slightly. more natural shore profiles will be able to attack the are reformed. Sea level rise cliffs, driving them back. The will further submerge the sediments released by shore platform, allowing recession and the formation larger waves to pass over of new shore platform will them. mitigate the effects of the rising seas to some degree, but overall there will be a narrowing of the intertidal zone. Mousehole Breakwater and quay walls Breakwater and quay walls Breakwater and quay walls harbour Water depths increase within Water depths increase within Water depths increase within the harbour, with no effect on the harbour, with no effect on the harbour, with no effect on the surrounding coast. the surrounding coast. the surrounding coast. Localised structure failures Failure of some harbour may occur. structures leads to loss of the harbour margin. Mousehole Wall No defences No defences south The shoreline will be held by Failure of the structures will Ongoing sea level rise will the defences. The water be followed by a period of continue to submerge the depth over the shore platform accelerated recession, as shore platform. Larger waves will increase slightly. more natural shore profiles will be able to attack the are reformed. Sea level rise cliffs, driving them back. The will further submerge the sediments released by shore platform, allowing recession and the formation larger waves to pass over of new shore platform will them. mitigate the effects of the rising seas to some degree, but overall there will be a narrowing of the intertidal zone. Mousehole No defences No defences No defences south to Lamorna Cove The evolution of this coast The evolution of this coast The evolution of this coast

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 71 February 2011

will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Lamorna Quay and wall No defences No defences Cove Sea level rise will cause a Failure of the coastal Accelerated relative sea level low recession rate. In front of structures will be followed by rise will continue to cause the the wall beach levels will tend a transient period of beach to roll back, at to drop, elsewhere the beach accelerated recession, as increasing rates. Continued will roll back. Loading on the waves attack over-steepened erosion will release fresh structure will tend to shore profiles. Sediments sediments into the beach. increase. released will tend to raise beach levels. The previously protected area will realign to the remainder of the beach. Lamorna No defences No defences No defences Cove to Porthcurno The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Porthcurno No defences No defences No defences The coast will remain much Accelerated sea level risk will Accelerated sea level risk will as it is today. Accelerated tend to drive the beach up tend to drive the beach sea level risk will drive some and back into the valley. further up and back into the retreat of shoreline but this valley. will be difficult to distinguish from natural variability. Porthcurno to No defences No defences No defences Lands End The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above.

10.3 Unit details – With Present Management

Location Predicted Change For Years 0 – 20 (2025) Years 20 – 50 (2055) Years 50 – 100 (2105) Penlee Point Walls and revetment Walls and revetment Walls and revetment to Mousehole harbour The shoreline will be held by The shoreline will be held by The shoreline will be held by the defences. The water the defences. Sea level rise the defences. Sea level rise depth over the shore platform will submerge the shore will submerge the shore will increase slightly. platform allowing larger platform allowing larger waves to attack the waves to attack the structures. Consequently structures. Consequently wave forces and overtopping wave forces and overtopping rates will increase. rates will continue to grow. Access along the shore

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 72 February 2011

platform will be noticeably reduced as it is submerged during more of the tide. . Mousehole Breakwater and quay walls Breakwater and quay walls Breakwater and quay walls harbour Water depths will increase Water depths will increase Water depths will increase within the harbour, with no within the harbour, with no within the harbour, with no effect on the surrounding effect on the surrounding effect on the surrounding coast. coast.. coast. Mousehole Wall Wall Wall south The shoreline will be held by The shoreline will be held by The shoreline will be held by the defences. The water the defences. Sea level rise the defences. Sea level rise depth over the shore platform will submerge the shore will submerge the shore will increase slightly. platform allowing larger platform allowing larger waves to attack the waves to attack the structures. Consequently structures. Consequently wave forces and overtopping wave forces and overtopping rates will increase. rates will continue to grow. Access along the shore platform will be noticeably reduced as it is submerged during more of the tide. . Mousehole No defences No defences No defences south to Lamorna Cove The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Lamorna Quay and wall No defences No defences Cove Sea level rise will cause a Accelerated sea level rise will Accelerated sea level rise will low recession rate. In front of increase the recession rate of further increase the recession the wall beach levels will tend the areas not fronted by a rate of the areas not fronted to drop, elsewhere the beach structure. This will release by a structure. This will will roll back. Loading on the sediments that will tend to release sediments that will structure will tend to raise the level of the beach. tend to raise the level of the increase. In front of the wall beach beach. The wall will tend to levels will continue to fall and be outflanked by this so wave loading on the recession. In front of the wall structure will continue to beach levels will continue to increase. fall and so wave loading on the structure will continue to increase. Lamorna No defences No defences No defences Cove to Porthcurno The evolution of this coast The evolution of this coast The evolution of this coast

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 73 February 2011

will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Porthcurno No defences No defences No defences The coast will remain much Accelerated sea level risk will Accelerated sea level risk will as it is today. Accelerated tend to drive the beach up tend to drive the beach sea level risk will drive some and back into the valley. further up and back into the retreat of shoreline but this valley. will be difficult to distinguish from natural variability. Porthcurno to No defences No defences No defences Lands End The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 74 February 2011

11 LANDS END TO ST IVES HEAD

11.1 Typical coastal evolution

11.1.1 Epoch 1, years 0 – 20 (2025)

The coast will continue to erode whilst retaining its current characteristics. Occasional landslides and rockfalls will cause cliff tops to retreat, and will deliver sediment to the foreshores. These processes will be driven by ongoing wave erosion of the cliff base, which will also form new areas of shore platform. The shore platform will be lowered by wave action, where it is not protected by beach material. The beaches will be fed by the larger sediments released by the ongoing erosion processes. A small acceleration in the rate of relative sea level rise will cause shore platforms to be slightly lower, relative to the mean sea level. The region of beach/ rock platform exposed above low water will become slightly narrower as the sea rise accelerates. This will allow slightly larger waves to arrive at the cliffs, increasing the severity of wave breaking. As a consequence the shore will retreat slightly faster than it has in the past. Locations were valleys meet the sea will tend to respond more strongly to sea level rise than rocky areas. The crests of the beaches that form in these valleys will be elevated by the rising sea level, and retreat inland, where there is space to do so.

11.1.2 Epoch 2, years 20 – 50 (2055)

The coast will continue to erode whilst retaining its current characteristics, as in epoch 1. A larger acceleration in rate of relative sea level rise will cause shore platforms to continue to fall, relative to the mean sea level. The region of beach/ rock platform exposed above low water will narrow. High tide will reach the cliff toe more frequently and this will allow larger waves to strike the cliffs, increasing the severity of wave breaking and raising recession rates. As a consequence the proportion of the cliff face comprised of active landslides will tend to increase. This will supply more material to the beach, which will mitigate, although not prevent, the narrowing of the intertidal zone. Beaches not fixed by backing cliffs or hard structures will be elevated by the rising sea level and ‘roll back’. This will involve some dune erosion.

11.1.3 Epoch 3, years 50 – 100 (2105)

The coast will continue to erode whilst retaining its current characteristics, as in epochs 1 and 2. Continued acceleration of the rate of relative sea level rise will cause shore platforms to continue to fall, relative to the mean sea level. The region of beach/ rock platform exposed above low water will continue to narrow. High tide will reach the cliff toe more frequently and allow larger waves to strike the cliffs with more energy. The shore will recede at a higher rate than seen in the past. As a consequence the proportion of the cliff face comprised of active landslides will continue to increase. This will supply more material to the beach, which will mitigate, although not prevent, the narrowing of the intertidal zone. Beaches not fixed by backing cliffs will be elevated by the rising sea level and ‘roll back’. This will involve some dune erosion.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 75 February 2011

11.2 Unit details – No Active Intervention

Location Predicted Change For Years 0 – 20 (2025) Years 20 – 50 (2055) Years 50 – 100 (2105) Sennen Breakwater ? ? Cove harbour Water depths increase within Water depths increase within Water depths increase within the harbour, with no effect on the harbour, with no effect on the harbour, with no effect on the surrounding coast. the surrounding coast. the surrounding coast. Localised structure failures Failure of some harbour may occur. structures leads to loss of the harbour margin. Sennen Walls No defences No defences Cove village The beach will continue to Failure of the coastal Accelerated relative sea level narrow. The coastal defences structures will be followed by rise will continue to cause the will prevent recession and so a transient period of beach to roll back, at cause the shoreline to be accelerated recession, as increasing rates. Continued increasingly seaward of its waves attack over-steepened erosion will release fresh natural position. The shore profiles. This will sediments that will defences will also prevent the release sedimentary material, accumulate and provide formation of new shore some of which will some protection to wave platform and reduce the accumulate in the beach. The attack. release of material for the beach will begin to roll back beach. Relative lowering of and this will mitigate, the rock foreshore and beach although not prevent, will allow larger, more narrowing of the intertidal aggressive waves to reach zone due to sea level rise. the structures. Sennen No defences No defences No defences Cove and Gwynver beach The beach and dune will Accelerated relative sea level Higher rates of sea level rise remain largely stable rise will cause the beach and will cause the beach and dunes to retreat up the valley dunes to retreat up the valley naturally. naturally. Aire Point to No defences No defences No defences Carrick Du The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Porthmeor Walls No defences No defences The shoreline will be held by Failure of the structures will Ongoing sea level rise will the defences and the beach be followed by a period of continue to drive the beach will tend to retreat slightly. accelerated recession, as landward. Sediments more natural profiles are released by recession and reformed. Sea level rise will the formation of new shore

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 76 February 2011

drive further retreat of the platform will mitigate the beach. effects of the rising seas to some degree. St Ives Head No defences No defences No defences The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above.

11.3 Unit details – With Present Management

Location Predicted Change For Years 0 – 20 (2025) Years 20 – 50 (2055) Years 50 – 100 (2105) Sennen Breakwater Breakwater Breakwater Cove harbour Water depths will increase Water depths will increase Water depths will increase within the harbour, with no within the harbour, with no within the harbour, with no effect on the surrounding effect on the surrounding effect on the surrounding coast. coast.. coast. Sennen Walls Walls Walls Cove village The beach will continue to The trend seen in the prior The trend seen in the prior narrow. The coastal defences epoch will continue. epoch will continue. Wave will prevent recession and so impact forces and cause the shoreline to be overtopping will grow at an increasingly seaward of its exponential rate, natural position. The necessitating larger defences will also prevent the structures to maintain current formation of new shore levels of defence. Beach platform and reduce the accessibility will reduce as release of material for the the sea level rises. beach. Relative lowering of the rock foreshore and beach will allow larger, more aggressive waves to reach the structures. Sennen No defences No defences No defences Cove and Gwynver beach The beach and dune will Accelerated relative sea level Higher rates of sea level rise remain largely stable rise will cause the beach and will cause the beach and dunes to retreat up the valley dunes to retreat up the valley naturally. naturally. Aire Point to No defences No defences No defences Carrick Du The evolution of this coast The evolution of this coast The evolution of this coast

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 77 February 2011

will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Porthmeor Walls Walls Walls The beach will tend to narrow The trend seen in the prior The trend seen in the prior slightly. The defences will epoch will continue. epoch will continue. Wave prevent recession and so impact forces and cause the shoreline to be overtopping will grow at an somewhat seaward of its exponential rate, natural position. The necessitating larger defences will also prevent the structures to maintain current formation of new shore levels of defence. Beach platform and reduce the accessibility will reduce as release of material for the the sea level rises. beach. Relative lowering of the rock foreshore and beach will allow larger, more aggressive waves to reach the structures. St Ives Head No defences No defences No defences The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 78 February 2011

12 CARBIS BAY (ST IVES HEAD TO GODREVY POINT)

12.1 General coastal evolution

Most of the shoreline of Carbis Bay is composed of sand; this is only interrupted in a few locations in the west. This sand will enable the coast to adapt to sea level rise, by raising of the beach profiles. This will require sediment, which will be mined from the backshore, where possible. For much of the bay the beach is backed by wide dunes, and so plenty of material will be available for this reshaping. The western pocket beaches are backed by cliffs and here the profiles may struggle to adapt so readily.

12.2 Unit details – No Active Intervention

Location Predicted Change For Years 0 – 20 (2025) Years 20 – 50 (2055) Years 50 – 100 (2105) Porth Walls No defences No defences Gwidden The shoreline will be held by Failure of the structures will Ongoing sea level rise will the defences and the beach be followed by a period of continue to drive the beach will tend to retreat slightly. accelerated recession, as landward. Sediments more natural profiles are released by recession and reformed. Sea level rise will the formation of new shore drive further retreat of the platform will mitigate the beach. effects of the rising seas to some degree. Bamaluz No defences No defences No defences Point Erosion will be small, The trend seen in the Accelerated relative sea level however increasing sea previous epoch will continue. rise will continue to increase levels will increase the water Wave run-up and overtopping wave activity at the shore. depths, allowing slightly will increase. larger waves to reach the shore. Bamaluz Walls No defences No defences Point to the pier The shoreline will be held by Failure of the structures will Ongoing sea level rise will the defences and the beach be followed by a period of continue to drive the beach will tend to retreat slightly. accelerated recession, as landward. Sediments more natural profiles are released by recession and reformed. Sea level rise will the formation of new shore drive further retreat of the platform will mitigate the beach. effects of the rising seas to some degree. St Ives Walls No defences No defences harbour beach Water depths increase within Water depths increase within Water depths increase within the harbour, with no effect on the harbour, with no effect on the harbour, with no effect on

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 79 February 2011

the surrounding coast. the surrounding coast. the surrounding coast. Localised structure failures Failure of some harbour may occur. structures leads to loss of the harbour margin. Men an Mor No defences No defences No defences Erosion will be small, The trend seen in the Accelerated relative sea level however increasing sea previous epoch will continue. rise will continue to increase levels will increase the water Wave run-up and overtopping wave activity at the shore. depths, allowing slightly will increase. larger waves to reach the shore. Porthminster Intermittent defences No defences No defences Beach Where defended, the Failure of the structures will Ongoing sea level rise will shoreline will be held and the be followed by a period of continue to drive the beach beach will tend to retreat accelerated recession, as landward. Sediments slightly. more natural profiles are released by recession and reformed. Sea level rise will the formation of new shore drive further retreat and platform will mitigate the narrowing of the beach. effects of the rising seas to some degree. Porthminster No defences No defences No defences Point to Carbis Bay Erosion will be small, The trend seen in the Accelerated relative sea level however increasing sea previous epoch will continue. rise will continue to increase levels will increase the water Wave run-up and overtopping wave activity at the shore. depths, allowing slightly will increase. larger waves to reach the shore. Carbis Bay Walls No defences No defences Where defended, the Failure of the structures will Ongoing sea level rise will shoreline will be held and the be followed by a period of continue to drive the beach beach will tend to retreat accelerated recession, as landward. Sediments slightly. more natural profiles are released by recession and reformed. Sea level rise will the formation of new shore drive further retreat and platform will mitigate the narrowing of the beach. effects of the rising seas to some degree. Carrack No defences No defences No defences Gladden to Hawks Point The beach will begin to Ongoing sea level rise will Ongoing sea level rise will narrow as the sea level rises. further narrow the beach, continue to narrow the beach increasing the period that the and increase wave loading cliff toe is submerged at high on the cliff toe. Landslides tide. Wave loading on the cliff and cliff top retreat will toe will increase. increase.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 80 February 2011

Porthkidney No defences No defences No defences Sands The beach and dunes will The form of the beach and Ongoing acceleration in the remain essentially dunes will remain essentially rate of sea level rise will drive unchanged, apart from unchanged. Sea level rise will increasing erosion of the natural short term and drive some erosion of the dune face. However this will seasonal fluctuations in form front of the dune, and this will be accompanied by release sand into the beach. increasing release of sediment into the beach which will allow it to rise with the sea level. As a result the beach will appear relatively unchanged. Black Cliff No defences No defences No defences The beach will begin to Ongoing sea level rise will Ongoing sea level rise will narrow as the sea level rises. further narrow the beach, continue to narrow the beach increasing the period that the and increase wave loading cliff toe is submerged at high on the cliff toe. Landslides tide. Wave loading on the cliff and cliff top retreat will toe will increase. increase. Mexico to No defences No defences No defences Gwithian Towans The beach and dunes will The form of the beach and Ongoing acceleration in the remain essentially dunes will remain essentially rate of sea level rise will drive unchanged, apart from unchanged. Sea level rise will increasing erosion of the natural short term and drive some erosion of the dune face. However this will seasonal fluctuations in form front of the dune, and this will be accompanied by release sand into the beach. increasing release of sediment into the beach which will allow it to rise with the sea level. As a result the beach will appear relatively unchanged. Gwithian No defences No defences No defences Towans The beach and dunes will The form of the beach and Ongoing acceleration in the remain essentially dunes will remain essentially rate of sea level rise will drive unchanged, apart from unchanged. Sea level rise will increasing erosion of the natural short term and drive some erosion of the dune face. However this will seasonal fluctuations in form front of the dune, and this will be accompanied by release sand into the beach. increasing release of sediment into the beach which will allow it to rise with the sea level. As a result the beach will appear relatively unchanged. Gwithian No defences No defences No defences Beach

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 81 February 2011

Historic retreat of the beach The form of the beach and Ongoing acceleration in the will continue. However the dunes will remain essentially rate of sea level rise will drive beach and dunes will retain unchanged. Sea level rise will increasing erosion of the their current characteristics. cause higher beach retreat dune face. However this will Natural short term and rates than occurred in the be accompanied by seasonal fluctuations in form past. Erosion of the front of increasing release of will continue. the dune will release sand sediment into the beach into the beach. which will allow it to rise with the sea level. As a result although the seaward margin of the dunes will be lost, the beach will appear relatively unchanged. Magow No defences No defences No defences Rocks to Godrevy Point The shoreline will continue to Ongoing sea level rise will Ongoing sea level rise will retreat. This will tend to tend to narrow the beach and continue to narrow the beach happen at a higher rate, increase wave loading on the and increase wave loading although this increase should cliffs, increasing recession on the cliff toe. Landslides be difficult to distinguish from rates. and cliff top retreat will natural variability. increase. This will to release additional sediments into the beach, although this will only partly mitigate the overall narrowing of the intertidal zone.

12.3 Unit details – With Present Management

Location Predicted Change For Years 0 – 20 (2025) Years 20 – 50 (2055) Years 50 – 100 (2105) St Ives Head No defences No defences No defences Erosion will be small, The trend seen in the Accelerated relative sea level however increasing sea previous epoch will continue. rise will continue to increase levels will increase the water Wave run-up and overtopping wave activity at the shore. depths, allowing slightly will increase. larger waves to reach the shore. Porth Walls Walls Walls Gwidden The beach will tend to narrow The trend seen in the prior The trend seen in the prior slightly. The defences will epoch will continue. epoch will continue. Wave prevent recession and so impact forces and cause the shoreline to be overtopping will grow at an somewhat seaward of its exponential rate,

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 82 February 2011

natural position. The necessitating larger defences will also prevent the structures to maintain current formation of new shore levels of defence. Beach platform and reduce the accessibility will reduce as release of material for the the sea level rises. beach. Relative lowering of the rock foreshore and beach will allow larger, more aggressive waves to reach the structures. Bamaluz No defences No defences No defences Point Erosion will be small, The trend seen in the Accelerated relative sea level however increasing sea previous epoch will continue. rise will continue to increase levels will increase the water Wave run-up and overtopping wave activity at the shore. depths, allowing slightly will increase. larger waves to reach the shore.

Bamaluz Walls Walls Walls Point to the pier The beach will tend to narrow The trend seen in the prior The trend seen in the prior slightly. The defences will epoch will continue. epoch will continue. Wave prevent recession and so impact forces and cause the shoreline to be overtopping will grow at an somewhat seaward of its exponential rate, natural position. The necessitating larger defences will also prevent the structures to maintain current formation of new shore levels of defence. Beach platform and reduce the accessibility will reduce as release of material for the the sea level rises. beach. Relative lowering of the rock foreshore and beach will allow larger, more aggressive waves to reach the structures. St Ives Walls Walls Walls harbour beach Water depths will increase Water depths will increase Water depths will increase within the harbour, with no within the harbour, with no within the harbour, with no effect on the surrounding effect on the surrounding effect on the surrounding coast. coast.. coast. Men an Mor No defences No defences No defences Erosion will be small, The trend seen in the Accelerated relative sea level however increasing sea previous epoch will continue. rise will continue to increase levels will increase the water Wave run-up and overtopping wave activity at the shore. depths, allowing slightly will increase.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 83 February 2011

larger waves to reach the shore.

Porthminster No defences No defences No defences Beach The beach will tend to narrow The trend seen in the prior The trend seen in the prior slightly. The defences will epoch will continue. Erosive epoch will continue. Wave prevent recession and so processes adjacent to the impact forces on the cause the shoreline to be defences will tend to cause structures and overtopping somewhat seaward of its outflanking. rates will grow at an natural position. The exponential rate, defences will also prevent the necessitating larger formation of new shore structures to maintain current platform and reduce the levels of defence. Beach release of material for the accessibility will reduce as beach. Relative lowering of the sea level rises. the rock foreshore and beach Outflanking processes will will allow larger, more continue, possibly aggressive waves to reach necessitating an increase in the structures. structure length. Porthminster No defences No defences No defences Point to Carbis Bay Erosion will be small, The trend seen in the Accelerated relative sea level however increasing sea previous epoch will continue. rise will continue to increase levels will increase the water Wave run-up and overtopping wave activity at the shore. depths, allowing slightly will increase. larger waves to reach the shore. Carbis Bay Walls Walls Walls The beach will tend to narrow The trend seen in the prior The trend seen in the prior slightly. The defences will epoch will continue. Erosive epoch will continue. Wave prevent recession and so processes adjacent to the impact forces on the cause the shoreline to be defences will tend to cause structures and overtopping somewhat seaward of its outflanking. rates will grow at an natural position. The exponential rate, defences will also prevent the necessitating larger formation of new shore structures to maintain current platform and reduce the levels of defence. Beach release of material for the accessibility will reduce as beach. Relative lowering of the sea level rises. the rock foreshore and beach Outflanking processes will will allow larger, more continue, possibly aggressive waves to reach necessitating an increase in the structures. structure length.

Carrack No defences No defences No defences Gladden to Hawks Point

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 84 February 2011

The beach will begin to Ongoing sea level rise will Ongoing sea level rise will narrow as the sea level rises. further narrow the beach, continue to narrow the beach increasing the period that the and increase wave loading cliff toe is submerged at high on the cliff toe. Landslides tide. Wave loading on the cliff and cliff top retreat will toe will increase. increase. Porthkidney No defences No defences No defences Sands The beach and dunes will The form of the beach and Ongoing acceleration in the remain essentially dunes will remain essentially rate of sea level rise will drive unchanged, apart from unchanged. Sea level rise will increasing erosion of the natural short term and drive some erosion of the dune face. However this will seasonal fluctuations in form front of the dune, and this will be accompanied by release sand into the beach. increasing release of sediment into the beach which will allow it to rise with the sea level. As a result the beach will appear relatively unchanged. Black Cliff No defences No defences No defences The beach will begin to Ongoing sea level rise will Ongoing sea level rise will narrow as the sea level rises. further narrow the beach, continue to narrow the beach increasing the period that the and increase wave loading cliff toe is submerged at high on the cliff toe. Landslides tide. Wave loading on the cliff and cliff top retreat will toe will increase. increase. Mexico to No defences No defences No defences Gwithian Towans The beach and dunes will The form of the beach and Ongoing acceleration in the remain essentially dunes will remain essentially rate of sea level rise will drive unchanged, apart from unchanged. Sea level rise will increasing erosion of the natural short term and drive some erosion of the dune face. However this will seasonal fluctuations in form front of the dune, and this will be accompanied by release sand into the beach. increasing release of sediment into the beach which will allow it to rise with the sea level. As a result the beach will appear relatively unchanged. Gwithian No defences No defences No defences Towans The beach and dunes will The form of the beach and Ongoing acceleration in the remain essentially dunes will remain essentially rate of sea level rise will drive unchanged, apart from unchanged. Sea level rise will increasing erosion of the natural short term and drive some erosion of the dune face. However this will seasonal fluctuations in form front of the dune, and this will be accompanied by release sand into the beach. increasing release of sediment into the beach

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 85 February 2011

which will allow it to rise with the sea level. As a result the beach will appear relatively unchanged. Gwithian No defences No defences No defences Beach Historic retreat of the beach The form of the beach and Ongoing acceleration in the will continue. However the dunes will remain essentially rate of sea level rise will drive beach and dunes will retain unchanged. Sea level rise will increasing erosion of the their current characteristics. cause higher beach retreat dune face. However this will Natural short term and rates than occurred in the be accompanied by seasonal fluctuations in form past. Erosion of the front of increasing release of will continue. the dune will release sand sediment into the beach into the beach. which will allow it to rise with the sea level. As a result although the seaward margin of the dunes will be lost, the beach will appear relatively unchanged. Magow No defences No defences No defences Rocks to Godrevy Point The shoreline will continue to Ongoing sea level rise will Ongoing sea level rise will retreat. This will tend to tend to narrow the beach and continue to narrow the beach happen at a higher rate, increase wave loading on the and increase wave loading although this increase should cliffs, increasing recession on the cliff toe. Landslides be difficult to distinguish from rates. and cliff top retreat will natural variability. increase. This will to release additional sediments into the beach, although this will only partly mitigate the overall narrowing of the intertidal zone.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 86 February 2011

13 HAYLE ESTUARY

13.1 General estuarial evolution

The future evolution of the margins of the Hayle estuary is quite uncertain. The estuary has been developed for a long time, which means that its natural behaviours have not been well established. In addition it is rather atypical in its form, which makes it difficult to extrapolate behaviour from other locations.

Clearly the estuary will be subject to accelerated sea level rise, and its margins are in many areas quite flat. This implies inundation of the hinterlands. At the same time the estuary appears to be drawing sediment in from the adjacent coast, as evidenced by the history of sand dredging from the estuary mouth. If the estuary is a strong sink for coastal sediments, and dredging is discontinued, then its future evolution may involve sedimentation; growth of sandy areas at the harbour margins. Consequently the range of possible future extents of the estuary is quite wide, especially for the last epoch

13.2 Unit details – No Active Intervention

Location Predicted Change For Years 0 – 20 (2025) Years 20 – 50 (2055) Years 50 – 100 (2105) Porth Kidney Discontinuous walls No defences No defences to Lelant Towans Where defended, the Failure of the structures will Ongoing sea level rise will shoreline will be held and the be followed by a period of continue to drive the beach beach will tend to retreat localised accelerated landward. Sediments slightly. recession, as more natural released by recession are profiles are reformed. Sea likely to be removed by level rise will drive further increased flows at the retreat and narrowing of the estuary mouth. beach. Lelant Discontinuous walls No defences No defences Towans Where defended, the Failure of the structures will Increased flow rates at the shoreline will be held and the be followed by a period of estuary mouth due to sea beach will tend to retreat accelerated recession, as level rise will continue to slightly. Elsewhere the beach more natural profiles are drive the beach and dunes will tend to retreat more reformed. Increased flows at landward. Sediments noticeably.. the mouth of the estuary may released by this recession tend to strip material from the will tend to be carried Towans, retreating the elsewhere. shoreline further. Lelant Railway embankment and No defences No defences Towans to quaywall The Causeway The shoreline will be held by Degradation of the structures Ongoing degradation of the

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 87 February 2011

the embankment. will be followed by localised embankment will be followed retreat, although this is by more generalised retreat, expected to be quite although this is still expected marginal. Generally the sea to be quite marginal. level rise will tend to raise Generally the sea level rise water levels along the will tend to raise water levels degraded embankment. along the degraded embankment. The Wall No defences No defences Causeway Water levels will increase at Rising water levels may Rising water levels may the wall. Any breaching breach the structures. This breach the structures. This would allow inundation up the would allow inundation up the would allow more extensive River Hale, which may , which may inundation up the River extend to Little Mill. extend to around Battery Mill. Hayle, which may extend to Should the estuary accrete, around Battery Mill. Should sand/ mud flats may develop the estuary accrete, sand/ around along this frontage. mud flats may develop around along this frontage. The Rock Gabions and No defences No defences Causeway to discontinuous walls South Quay Where defended, the Localised failure of the Ongoing sea level rise will shoreline will be held and the structures will allow patches continue to drive the beach will tend to retreat of recession, as the shore shoreline landward. More slightly. margin collapses. Should the generalised structure failure estuary accrete, sand/ mud will allow larger areas of flats may develop along this collapse at the estuary frontage. margin. Should the estuary accrete, sand/ mud flats may develop along this frontage. East Quay Walls Degraded walls Degraded walls Water depths increase within Water depths continue to Water depths increase at the the quay walls, with no effect increase at the quay walls. quay walls. Failure of some on the surrounding shore. Localised structure failures structures leads to loss of the may occur. estuary margin. Copperhouse ‘Defacto’ defences No defences No defences Pool, southeast bank Where defended, the Failure of the structures will Ongoing sea level rise will shoreline will be held and the be followed by a period of continue to drive the shore beach will tend to retreat accelerated recession, as landward. Continued slightly. more natural profiles are degradation of margin will reformed. Sea level rise will allow more generalised drive further retreat and retreat. Should the estuary narrowing of the foreshore. accrete, sand/ mud flats may Should the estuary accrete, develop along this frontage. sand/ mud flats may develop

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 88 February 2011

along this frontage. Copperhouse ‘Defacto’ defences No defences No defences Pool northeast bank The shore will tend to retreat If the estuary des not accrete, If the estuary des not accrete, due to sea level rise. ongoing sea level rise will ongoing sea level rise will tend to narrow the foreshore tend to narrow the foreshore and increase loading on the and increase loading on the embankment. Should the embankment. Should the embankment fail, the embankment fail, the hinterland to Lethlean lane hinterland to Lethlean lane would be flooded. Should the would be flooded. Should the estuary accrete, sand/ mud estuary accrete, sand/ mud flats may develop. flats may develop. Copperhouse Road Margin No defences No defences Pool northwest bank Where defended, the Failure of the structures will Ongoing sea level rise will shoreline will be held and the be followed by a period of continue to drive the shore beach will tend to retreat accelerated recession, as landward. Continued slightly. more natural profiles are degradation of margin will reformed. Sea level rise will allow more generalised drive further retreat and retreat. Should the estuary narrowing of the foreshore. accrete, sand/ mud flats may Should the estuary accrete, develop along this frontage. sand/ mud flats may develop along this frontage. North Quay Wall Degraded walls Degraded walls Water depths increase within Water depths continue to Water depths increase at the the quay walls, with no effect increase at the quay walls. quay walls. Failure of some on the surrounding shore. Localised structure failures structures leads to loss of the may occur. estuary margin. Harvey No defences No defences No defences Towans The beach and dunes will The beach and dunes will The beach and dunes will remain essentially tend to retreat due to tend to retreat due to unchanged, apart from increased flow rates at the increased flow rates at the natural short term and estuary mouth. The sand estuary mouth. The sand seasonal fluctuations in form released will tend to be released will tend to be carried away. carried away.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 89 February 2011

13.3 Unit details – With Present Management

Location Predicted Change For Years 0 – 20 (2025) Years 20 – 50 (2055) Years 50 – 100 (2105) Porth Kidney Discontinuous walls Discontinuous walls Discontinuous walls to Lelant Towans Where defended, the Where defended, the Where defended, the shoreline will be held and the shoreline will be held and the shoreline will be held and the beach will tend to retreat beach will tend to retreat; beach will tend to retreat; slightly. structure foundations may be structure foundations may be undermined. Elsewhere sea undermined. Elsewhere sea level rise will drive retreat level rise will drive retreat and and narrowing of the beach. narrowing of the beach, as flow rates in the estuary mouth increase. Sediments released by recession are likely to be removed the water flow.. Lelant Discontinuous walls Discontinuous walls Discontinuous walls Towans Where defended, the Where defended, the Where defended, the shoreline will be held and the shoreline will be held and the shoreline will be held and the beach will tend to retreat beach will tend to retreat; beach will tend to retreat; slightly. Elsewhere the beach structure foundations may be structure foundations may be will tend to retreat more undermined. Increased flows undermined. Elsewhere sea noticeably.. at the mouth of the estuary level rise will drive the may tend to strip material Towans back narrowing the from , retreating beach, as flow rates in the the shoreline further. estuary mouth increase. Sediments released by recession are likely to be removed the water flow. Lelant Railway embankment and Railway embankment and Railway embankment and Towans to quaywall quaywall quaywall The Causeway The shoreline will be held by The shoreline will be held by The shoreline will be held by the embankment. the embankment. Sea level the embankment. Sea level rise will generally raise water rise will generally raise water levels along it. Should the levels along it. Should the estuary accrete, sand/ mud estuary accrete, sand/ mud flats may develop. flats may develop. The Wall Wall Wall Causeway Water levels will tend to Water levels will tend to Water levels will tend to increase at the wall. increase at the wall. Should increase at the wall. Should the estuary accrete, sand/ the estuary accrete, sand/ mud flats may develop mud flats may develop

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 90 February 2011

around along this frontage. around along this frontage. The Rock Gabions and Rock Gabions and Rock Gabions and Causeway to discontinuous walls discontinuous walls discontinuous walls South Quay Where defended, the Where defended, the Where defended, the shoreline will be held and the shoreline will be held and the shoreline will be held and the shore will tend to retreat shore will tend to retreat. shore will tend to retreat. slightly. Should the estuary accrete, Should the estuary accrete, sand/ mud flats may develop more extensive sand/ mud along this frontage. flats may develop. East Quay Walls Walls Walls Water depths increase at the Water depths increase at the Water depths increase at the quay walls, with no effect on quay walls. quay walls. the surrounding shore. Copperhouse ‘Defacto’ defences ‘Defacto’ defences ‘Defacto’ defences Pool, southeast bank Where defended, the Where defended, the Where defended, the shoreline will be held and the shoreline will be held. shoreline will be held. shore will tend to retreat Generally the shore will tend Generally the shore will tend slightly. to retreat, unless the estuary to retreat, unless the estuary begins to accrete, in which begins to accrete, in which case sand/ mud flats may case sand/ mud flats may grow. grow. Copperhouse ‘Defacto’ defences ‘Defacto’ defences ‘Defacto’ defences Pool northeast bank The shore will tend to retreat If the estuary des not If the estuary des not accrete, due to sea level rise. accrete, ongoing sea level ongoing sea level rise will rise will tend to narrow the tend to narrow the foreshore foreshore and increase and increase loading on the loading on the embankment. embankment. Should the Should the estuary accrete, estuary accrete, sand/ mud sand/ mud flats may develop. flats may develop. Copperhouse Road Margin Road Margin Road Margin Pool northwest bank Where defended, the Where defended, the Where defended, the shoreline will be held and the shoreline will be held. shoreline will be held. shore will tend to retreat Generally the shore will tend Generally the shore will tend slightly. to retreat, unless the estuary to retreat, unless the estuary begins to accrete, in which begins to accrete, in which case sand/ mud flats may case sand/ mud flats may grow. grow. North Quay Wall Wall Wall Water depths increase at the Water depths increase at the Water depths increase at the

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 91 February 2011

quay walls, with no effect on quay walls. quay walls. the surrounding shore. Harvey No defences No defences No defences Towans The beach and dunes will The beach and dunes will The beach and dunes will remain essentially tend to retreat due to tend to retreat due to unchanged, apart from increased flow rates at the increased flow rates at the natural short term and estuary mouth. The sand estuary mouth. The sand seasonal fluctuations in form released will tend to be released will tend to be carried away. carried away.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 92 February 2011

14 GODREVY POINT TO ST AGNES HEAD

14.1 Typical coastal evolution

14.1.1 Epoch 1, years 0 – 20 (2025)

The coast will continue to erode whilst retaining its current characteristics. Occasional landslides and rockfalls will cause cliff tops to retreat, and will deliver sediment to the foreshores. These processes will be driven by ongoing wave erosion of the cliff base, which will also form new areas of shore platform. The shore platform will be lowered by wave action, where it is not protected by beach material. The beaches will be fed by the larger sediments released by the ongoing erosion processes. A small acceleration in the rate of relative sea level rise will cause shore platforms to be slightly lower, relative to the mean sea level. The region of beach/ rock platform exposed above low water will become slightly narrower as the sea rise accelerates. This will allow slightly larger waves to arrive at the cliffs, increasing the severity of wave breaking. As a consequence the shore will retreat slightly faster than it has in the past. Locations were valleys meet the sea will tend to respond more strongly to sea level rise than rocky areas. The crests of the beaches that form in these valleys will be elevated by the rising sea level, and retreat inland, where there is space to do so.

14.1.2 Epoch 2, years 20 – 50 (2055)

The coast will continue to erode whilst retaining its current characteristics, as in epoch 1. A larger acceleration in rate of relative sea level rise will cause shore platforms to continue to fall, relative to the mean sea level. The region of beach/ rock platform exposed above low water will narrow. High tide will reach the cliff toe more frequently and this will allow larger waves to strike the cliffs, increasing the severity of wave breaking and raising recession rates. As a consequence the proportion of the cliff face comprised of active landslides will tend to increase. This will supply more material to the beach, which will mitigate, although not prevent, the narrowing of the intertidal zone. Beaches not fixed by backing cliffs or hard structures will be elevated by the rising sea level and ‘roll back’. This will involve some dune erosion.

14.1.3 Epoch 3, years 50 – 100 (2105)

The coast will continue to erode whilst retaining its current characteristics, as in epochs 1 and 2. Continued acceleration of the rate of relative sea level rise will cause shore platforms to continue to fall, relative to the mean sea level. The region of beach/ rock platform exposed above low water will continue to narrow. High tide will reach the cliff toe more frequently and allow larger waves to strike the cliffs with more energy. The shore will recede at a higher rate than seen in the past. As a consequence the proportion of the cliff face comprised of active landslides will continue to increase. This will supply more material to the beach, which will mitigate, although not prevent, the narrowing of the intertidal zone. Beaches not fixed by backing cliffs will be elevated by the rising sea level and ‘roll back’. This will involve some dune erosion.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 93 February 2011

14.2 Unit details – No Active Intervention

Location Predicted Change For Years 0 – 20 (2025) Years 20 – 50 (2055) Years 50 – 100 (2105) Godrevy No defences No defences No defences Point to Beach The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Portreath Walls No defences No defences Beach Sea level rise will cause a Failure of the coastal Accelerated relative sea level low recession rate. In front of structures will be followed by rise will continue to cause the the wall beach levels will tend a transient period of beach to roll back, at to drop, elsewhere the beach accelerated recession, as increasing rates. Continued will roll back. Loading on the waves attack over-steepened erosion will release fresh structure will tend to shore profiles. Sediments sediments into the beach. increase. released will tend to raise beach levels. The previously protected area will realign to the remainder of the beach. Portreath Breakwater and harbour Harbour Water depths increase within Water depths increase within Water depths increase within the harbour, with no effect on the harbour, with no effect on the harbour, with no effect on the surrounding coast. the surrounding coast. the surrounding coast. Localised structure failures Failure of some harbour may occur. structures leads to loss of the harbour margin. Portreath No defences No defences No defences harbour to Porthtowan The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Porthtowan Gabions No defences No defences Sea level rise will cause a Failure of the coastal Accelerated relative sea level low recession rate. In front of structures will be followed by rise will continue to cause the the structures beach levels a transient period of beach to roll back, at will tend to drop, elsewhere accelerated recession, as increasing rates. Continued the beach will roll back. waves attack over-steepened erosion will release fresh Loading on the structure will shore profiles. Sediments sediments into the beach. tend to increase. released will tend to raise beach levels. The previously protected area will realign to the remainder of the beach.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 94 February 2011

Porthtowan No defences No defences No defences to St Agnes Head The evolution of this coast Ongoing sea level rise will Ongoing sea level rise will will be typical of the region, further narrow the beach, continue to narrow the beach as described above. The increasing the period that the and increase wave loading beach will begin to narrow as cliff toe is submerged at high on the cliff toe. Landslides the sea level rises. tide. Wave loading on the cliff and cliff top retreat will toe will increase. increase.

14.3 Unit details – With Present Management

Location Predicted Change For Years 0 – 20 (2025) Years 20 – 50 (2055) Years 50 – 100 (2105) Godrevy No defences No defences No defences Point to Portreath Beach The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Portreath Walls Walls Walls Beach Sea level rise will cause a Accelerated sea level rise will Accelerated sea level rise will low recession rate. In front of increase the recession rate of further increase the recession the wall beach levels will tend the areas not fronted by a rate of the areas not fronted to drop, elsewhere the beach structure. This will release by a structure. This will will roll back. Loading on the sediments that will tend to release sediments that will structure will tend to raise the level of the beach. tend to raise the level of the increase. In front of the wall beach beach. The wall will tend to levels will continue to fall and be outflanked by this so wave loading on the recession. In front of the wall structure will continue to beach levels will continue to increase. fall and so wave loading on the structure will continue to increase. Portreath Breakwater and harbour Breakwater and harbour Breakwater and harbour Harbour Water depths will increase Water depths will increase Water depths will increase within the harbour, with no within the harbour, with no within the harbour, with no effect on the surrounding effect on the surrounding effect on the surrounding coast. coast.. coast. Portreath No defences No defences No defences harbour to Porthtowan The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 95 February 2011

Porthtowan Gabions Gabions Gabions Sea level rise will cause a Accelerated sea level rise will Accelerated sea level rise will low recession rate. In front of increase the recession rate of further increase the recession the wall beach levels will tend the areas not fronted by a rate of the areas not fronted to drop, elsewhere the beach structure. This will release by a structure. This will will roll back. Loading on the sediments that will tend to release sediments that will structure will tend to raise the level of the beach. tend to raise the level of the increase. In front of the wall beach beach. The wall will tend to levels will continue to fall and be outflanked by this so wave loading on the recession. In front of the wall structure will continue to beach levels will continue to increase. fall and so wave loading on the structure will continue to increase. Porthtowan No defences No defences No defences to St Agnes Head Coastal evolution will be Ongoing sea level rise will Ongoing sea level rise will typical of the region as further narrow the beach, continue to narrow the beach described above. The beach increasing the period that the and increase wave loading will begin to narrow as the cliff toe is submerged at high on the cliff toe. Landslides sea level rises. tide. Wave loading on the cliff and cliff top retreat will toe will increase. increase.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 96 February 2011

15 ST AGNES HEAD TO TOWAN HEAD

15.1 Typical coastal evolution

15.1.1 Epoch 1, years 0 – 20 (2025)

The coast will continue to erode whilst retaining its current characteristics. Occasional landslides and rockfalls will cause cliff tops to retreat, and will deliver sediment to the foreshores. These processes will be driven by ongoing wave erosion of the cliff base, which will also form new areas of shore platform. The shore platform will be lowered by wave action, where it is not protected by beach material. The beaches will be fed by the larger sediments released by the ongoing erosion processes. A small acceleration in the rate of relative sea level rise will cause shore platforms to be slightly lower, relative to the mean sea level. The region of beach/ rock platform exposed above low water will become slightly narrower as the sea rise accelerates. This will allow slightly larger waves to arrive at the cliffs, increasing the severity of wave breaking. As a consequence the shore will retreat slightly faster than it has in the past. Locations were valleys meet the sea will tend to respond more strongly to sea level rise than rocky areas. The crests of the beaches that form in these valleys will be elevated by the rising sea level, and retreat inland, where there is space to do so. The substantial beaches within this region may begin to be driven back by rising seas, although this may be difficult to distinguish from natural variability.

15.1.2 Epoch 2, years 20 – 50 (2055)

The coast will continue to erode whilst retaining its current characteristics, as in epoch 1. A larger acceleration in rate of relative sea level rise will cause shore platforms to continue to fall, relative to the mean sea level. The region of beach/ rock platform exposed above low water will narrow. High tide will reach the cliff toe more frequently and this will allow larger waves to strike the cliffs, increasing the severity of wave breaking and raising recession rates. As a consequence the proportion of the cliff face comprised of active landslides will tend to increase. This will supply more material to the beach, which will mitigate, although not prevent, the narrowing of the intertidal zone. Beaches not fixed by backing cliffs or hard structures will be elevated by the rising sea level and ‘roll back’. This will involve some dune erosion.

15.1.3 Epoch 3, years 50 – 100 (2105)

The coast will continue to erode whilst retaining its current characteristics, as in epochs 1 and 2. Continued acceleration of the rate of relative sea level rise will cause shore platforms to continue to fall, relative to the mean sea level. The region of beach/ rock platform exposed above low water will continue to narrow. High tide will reach the cliff toe more frequently and allow larger waves to strike the cliffs with more energy. The shore will recede at a higher rate than seen in the past. As a consequence the proportion of the cliff face comprised of active landslides will continue to increase. This will supply more material to the beach, which will mitigate, although not prevent, the narrowing of the intertidal zone. Beaches not fixed by backing cliffs will be elevated by the rising sea level and ‘roll back’. This will involve some dune erosion.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 97 February 2011

15.2 Unit details – No Active Intervention

Location Predicted Change For Years 0 – 20 (2025) Years 20 – 50 (2055) Years 50 – 100 (2105) St Agnes No defences No defences No defences Head to Trevaunance Cove The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Trevaunance Wall and splash wall No defences No defences Cove Where defended, the Failure of the structures will Ongoing sea level rise will shoreline will be held and the be followed by a period of continue to drive the beach beach will tend to retreat accelerated recession, as landward. Sediments slightly. more natural profiles are released by recession and reformed. Sea level rise will the formation of new shore drive further retreat and platform will mitigate the narrowing of the beach. effects of the rising seas to some degree. Trevaunance No defences No defences No defences Cove to The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Perranporth Walls No defences No defences The shoreline will be held by Failure of the structures will Ongoing sea level rise will the defences and the beach be followed by a period of continue to drive the beach will tend to retreat slightly. accelerated recession, as landward. Sediments more natural profiles are released by recession and reformed. Sea level rise will the formation of new shore drive further retreat of the platform will mitigate the beach. effects of the rising seas to some degree. Perran No defences No defences No defences Sands The beach and dunes will The form of the beach and Ongoing acceleration in the remain essentially dunes will remain essentially rate of sea level rise will drive unchanged, apart from unchanged. Sea level rise will increasing erosion of the natural short term and drive some erosion of the dune face. However this will seasonal fluctuations in form front of the dune, and this will be accompanied by release sand into the beach. increasing release of sediment into the beach which will allow it to rise with the sea level. As a result the beach will appear relatively unchanged.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 98 February 2011

Cottys Point No defences No defences No defences to Carn Haut The evolution of this coast Ongoing sea level rise will Ongoing sea level rise will will be typical of the region, further narrow the beach, continue to narrow the beach as described above. The increasing the period that the and increase wave loading beach will begin to narrow as cliff toe is submerged at high on the cliff toe. Landslides the sea level rises. tide. Wave loading on the cliff and cliff top retreat will toe will increase. increase. Penhale No defences No defences No defences Sands The beach and dunes will The form of the beach and Ongoing acceleration in the remain essentially dunes will remain essentially rate of sea level rise will drive unchanged, apart from unchanged. Sea level rise will increasing erosion of the natural short term and drive some erosion of the dune face. However this will seasonal fluctuations in form front of the dune, and this will be accompanied by release sand into the beach. increasing release of sediment into the beach which will allow it to rise with the sea level. As a result the beach will appear relatively unchanged. Penhale No defences No defences No defences Sands to Holywell The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Holywell No defences No defences No defences Beach Historic retreat of the beach The form of the beach and Ongoing acceleration in the will continue. However the dunes will remain essentially rate of sea level rise will drive beach and dunes will retain unchanged. Sea level rise will increasing erosion of the their current characteristics. cause higher beach retreat dune face. However this will Natural short term and rates than occurred in the be accompanied by seasonal fluctuations in form past. Erosion of the front of increasing release of will continue. the dune will release sand sediment into the beach into the beach. which will allow it to rise with the sea level. As a result although the seaward margin of the dunes will be lost, the beach will appear relatively unchanged. Holywell No defences No defences No defences Beach to Porth Joke The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 99 February 2011

Porth Joke No defences No defences No defences Beach The beach and dune will Accelerated relative sea level Higher rates of sea level rise remain largely stable. rise will cause the beach and will cause the beach and dunes to retreat up the valley dunes to retreat up the valley naturally. naturally. Porth Joke to No defences No defences No defences Crantock The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Crantock No defences No defences No defences Beach The beach and dunes will The form of the beach and Ongoing acceleration in the remain essentially dunes will remain essentially rate of sea level rise will drive unchanged, apart from unchanged. Sea level rise will increasing erosion of the natural short term and drive some erosion of the dune face. However this will seasonal fluctuations in form front of the dune, and this will be accompanied by release sand into the beach. increasing release of sediment into the beach which will allow it to rise with the sea level. As a result the beach will appear relatively unchanged. The Gannel: No defences No defences No defences south bank The beach will begin to Ongoing sea level rise will Ongoing sea level rise will narrow as the sea level rises. further narrow the beach, continue to narrow the beach. increasing the period that the Localised rockfalls may cliff toe is submerged at high cause some retreat of the tide. This will be mitigated to river margins. This will be some degree by an increased mitigated to some degree by tendency for accretion within an increased tendency for the river. accretion within the river. Trevemper No defences No defences No defences Sea level rise will drive the Sea level rise will drive the Sea level rise will drive the tidal limit further upriver. tidal limit further upriver and tidal limit further upriver and will spread the upper reaches will spread the upper reaches across a broader floodplain. . across a broader floodplain. This will be mitigated to a degree by an increased tendency for accretion within the river, particularly in the upper reaches. The Gannel Intermittent defences No defences No defences north bank Where defended, the Failure of the structures will Ongoing sea level rise will shoreline will be held and the be followed by a period of continue to drive the shore beach will tend to retreat accelerated recession in landward. This will be

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 100 February 2011

slightly. localised areas, as more mitigated to some degree by natural profiles are reformed. an increased tendency for Sea level rise will drive accretion within the river. further retreat and narrowing of the beach. This will be mitigated to some degree by an increased tendency for accretion within the river. Pentire Point No defences No defences No defences East The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. South Fistral Walls and revetments No defences No defences Where defended, the Failure of the structures will Ongoing sea level rise will shoreline will be held and the be followed by a period of continue to drive the beach beach will tend to retreat accelerated recession, as landward. Sediments slightly. more natural profiles are released by recession and reformed. Sea level rise will the formation of new shore drive further retreat and platform will mitigate the narrowing of the beach. effects of the rising seas to some degree. Fistral Dunes No defences No defences No defences The beach and dunes will The form of the beach and Ongoing acceleration in the remain essentially dunes will remain essentially rate of sea level rise will drive unchanged, apart from unchanged. Sea level rise will increasing erosion of the natural short term and drive some erosion of the dune face. However this will seasonal fluctuations in form front of the dune, and this will be accompanied by release sand into the beach. increasing release of sediment into the beach which will allow it to rise with the sea level. As a result the beach will appear relatively unchanged. North Fistral Walls and revetments No defences No defences Where defended, the Failure of the structures will Ongoing sea level rise will shoreline will be held and the be followed by a period of continue to drive the beach beach will tend to retreat accelerated recession, as landward. Sediments slightly. more natural profiles are released by recession and reformed. Sea level rise will the formation of new shore drive further retreat and platform will mitigate the narrowing of the beach. effects of the rising seas to some degree. North Fistral No defences No defences No defences to Towan Head The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 101 February 2011

15.3 Unit details – With Present Management

Location Predicted Change For Years 0 – 20 (2025) Years 20 – 50 (2055) Years 50 – 100 (2105) St Agnes No defences No defences No defences Head to Trevaunance Cove The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Trevaunance Wall and splash wall Wall and splash wall Wall and splash wall Cove The beach will tend to narrow The trend seen in the prior The trend seen in the prior slightly. The defences will epoch will continue. Erosive epoch will continue. Wave prevent recession and so processes adjacent to the impact forces on the cause the shoreline to be defences will tend to cause structures and overtopping somewhat seaward of its outflanking. rates will grow at an natural position. The exponential rate, defences will also prevent the necessitating larger formation of new shore structures to maintain current platform and reduce the levels of defence. Beach release of material for the accessibility will reduce as beach. Relative lowering of the sea level rises. the rock foreshore and beach Outflanking processes will will allow larger, more continue, possibly aggressive waves to reach necessitating an increase in the structures. structure length. Trevaunance No defences No defences No defences Cove to Perranporth The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Perranporth Walls Walls Walls The beach will tend to narrow The trend seen in the prior The trend seen in the prior slightly. The defences will epoch will continue. epoch will continue. Wave prevent recession and so impact forces and cause the shoreline to be overtopping will grow at an somewhat seaward of its exponential rate, natural position. The necessitating larger defences will also prevent the structures to maintain current formation of new shore levels of defence. Beach platform and reduce the accessibility will reduce as release of material for the the sea level rises. beach. Relative lowering of the rock foreshore and beach will allow larger, more

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 102 February 2011

aggressive waves to reach the structures.

Perran No defences No defences No defences Sands The beach and dunes will The form of the beach and Ongoing acceleration in the remain essentially dunes will remain essentially rate of sea level rise will drive unchanged, apart from unchanged. Sea level rise will increasing erosion of the natural short term and drive some erosion of the dune face. However this will seasonal fluctuations in form front of the dune, and this will be accompanied by release sand into the beach. increasing release of sediment into the beach which will allow it to rise with the sea level. As a result the beach will appear relatively unchanged. Cottys Point No defences No defences No defences to Carn Haut Coastal evolution will be Ongoing sea level rise will Ongoing sea level rise will typical of the region as further narrow the beach, continue to narrow the beach described above. The beach increasing the period that the and increase wave loading will begin to narrow as the cliff toe is submerged at high on the cliff toe. Landslides sea level rises. tide. Wave loading on the cliff and cliff top retreat will toe will increase. increase. Penhale No defences No defences No defences Sands The beach and dunes will The form of the beach and Ongoing acceleration in the remain essentially dunes will remain essentially rate of sea level rise will drive unchanged, apart from unchanged. Sea level rise will increasing erosion of the natural short term and drive some erosion of the dune face. However this will seasonal fluctuations in form front of the dune, and this will be accompanied by release sand into the beach. increasing release of sediment into the beach which will allow it to rise with the sea level. As a result the beach will appear relatively unchanged. Penhale No defences No defences No defences Sands to Holywell Typical The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Holywell No defences No defences No defences Beach Historic retreat of the beach The form of the beach and Ongoing acceleration in the will continue. However the dunes will remain essentially rate of sea level rise will drive beach and dunes will retain unchanged. Sea level rise will increasing erosion of the their current characteristics. cause higher beach retreat dune face. However this will

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 103 February 2011

Natural short term and rates than occurred in the be accompanied by seasonal fluctuations in form past. Erosion of the front of increasing release of will continue. the dune will release sand sediment into the beach into the beach. which will allow it to rise with the sea level. As a result although the seaward margin of the dunes will be lost, the beach will appear relatively unchanged. Holywell No defences No defences No defences Beach to Porth Joke The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Porth Joke No defences No defences No defences Beach The beach and dune will Accelerated relative sea level Higher rates of sea level rise remain largely stable rise will cause the beach and will cause the beach and dunes to retreat up the valley dunes to retreat up the valley naturally. naturally. Porth Joke to No defences No defences No defences Crantock The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Crantock No defences No defences No defences Beach The beach and dunes will The form of the beach and Ongoing acceleration in the remain essentially dunes will remain essentially rate of sea level rise will drive unchanged, apart from unchanged. Sea level rise will increasing erosion of the natural short term and drive some erosion of the dune face. However this will seasonal fluctuations in form front of the dune, and this will be accompanied by release sand into the beach. increasing release of sediment into the beach which will allow it to rise with the sea level. As a result the beach will appear relatively unchanged. The Gannel: No defences No defences No defences south bank The beach will begin to Ongoing sea level rise will Ongoing sea level rise will narrow as the sea level rises. further narrow the beach, continue to narrow the beach. increasing the period that the Localised rockfalls may cliff toe is submerged at high cause some retreat of the tide. This will be mitigated to river margins. This will be some degree by an increased mitigated to some degree by tendency for accretion within an increased tendency for the river. accretion within the river.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 104 February 2011

Trevemper No defences No defences No defences Sea level rise will drive the Sea level rise will drive the Sea level rise will drive the tidal limit further upriver. tidal limit further upriver and tidal limit further upriver and will spread the upper reaches will spread the upper reaches across a broader floodplain. . across a broader floodplain. This will be mitigated to a degree by an increased tendency for accretion within the river, particularly in the upper reaches. The Gannel Discontinuous defacto Discontinuous defacto Discontinuous defacto north bank defences defences defences Where defended, the Sea level rise will drive Ongoing sea level rise will shoreline will be held and the further retreat and narrowing continue to drive the shore beach will tend to retreat of the beach. This will be landward. This will be slightly. mitigated to some degree by mitigated to some degree by an increased tendency for an increased tendency for accretion within the river. accretion within the river. Pentire Point No defences No defences No defences East The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. South Fistral Walls and revetments Walls and revetments Walls and revetments The beach will tend to narrow The trend seen in the prior The trend seen in the prior slightly. The defences will epoch will continue. Erosive epoch will continue. Wave prevent recession and so processes adjacent to the impact forces on the cause the shoreline to be defences will tend to cause structures and overtopping somewhat seaward of its outflanking. rates will grow at an natural position. The exponential rate, defences will also prevent the necessitating larger formation of new shore structures to maintain current platform and reduce the levels of defence. Beach release of material for the accessibility will reduce as beach. Relative lowering of the sea level rises. the rock foreshore and beach Outflanking processes will will allow larger, more continue, possibly aggressive waves to reach necessitating an increase in the structures. structure length. Fistral Dunes No defences No defences No defences The beach and dunes will The form of the beach and Ongoing acceleration in the remain essentially dunes will remain essentially rate of sea level rise will drive unchanged, apart from unchanged. Sea level rise will increasing erosion of the natural short term and drive some erosion of the dune face. However this will seasonal fluctuations in form front of the dune, and this will be accompanied by release sand into the beach. increasing release of sediment into the beach which will allow it to rise with the sea level. As a result the

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 105 February 2011

beach will appear relatively unchanged. North Fistral Walls and revetments Walls and revetments Walls and revetments The beach will tend to narrow The trend seen in the prior The trend seen in the prior slightly. The defences will epoch will continue. Erosive epoch will continue. Wave prevent recession and so processes adjacent to the impact forces on the cause the shoreline to be defences will tend to cause structures and overtopping somewhat seaward of its outflanking. rates will grow at an natural position. The exponential rate, defences will also prevent the necessitating larger formation of new shore structures to maintain current platform and reduce the levels of defence. Beach release of material for the accessibility will reduce as beach. Relative lowering of the sea level rises. the rock foreshore and beach Outflanking processes will will allow larger, more continue, possibly aggressive waves to reach necessitating an increase in the structures. structure length. North Fistral No defences No defences No defences to Towan Head The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 106 February 2011

16 TOWAN HEAD TO PARK HEAD

16.1 Typical coastal evolution

16.1.1 Epoch 1, years 0 – 20 (2025)

The coast will continue to erode whilst retaining its current characteristics. Occasional landslides and rockfalls will cause cliff tops to retreat, and will deliver sediment to the foreshores. These processes will be driven by ongoing wave erosion of the cliff base, which will also form new areas of shore platform. The shore platform will be lowered by wave action, where it is not protected by beach material. The beaches will be fed by the larger sediments released by the ongoing erosion processes. A small acceleration in the rate of relative sea level rise will cause shore platforms to be slightly lower, relative to the mean sea level. The region of beach/ rock platform exposed above low water will become slightly narrower as the sea rise accelerates. This will allow slightly larger waves to arrive at the cliffs, increasing the severity of wave breaking. As a consequence the shore will retreat slightly faster than it has in the past. Locations were valleys meet the sea will tend to respond more strongly to sea level rise than rocky areas. The crests of the beaches that form in these valleys will be elevated by the rising sea level, and retreat inland, where there is space to do so. The substantial beaches within this region may begin to be driven back by rising seas, although this may be difficult to distinguish from natural variability.

16.1.2 Epoch 2, years 20 – 50 (2055)

The coast will continue to erode whilst retaining its current characteristics, as in epoch 1. A larger acceleration in rate of relative sea level rise will cause shore platforms to continue to fall, relative to the mean sea level. The region of beach/ rock platform exposed above low water will narrow. High tide will reach the cliff toe more frequently and this will allow larger waves to strike the cliffs, increasing the severity of wave breaking and raising recession rates. As a consequence the proportion of the cliff face comprised of active landslides will tend to increase. This will supply more material to the beach, which will mitigate, although not prevent, the narrowing of the intertidal zone. Beaches not fixed by backing cliffs or hard structures will be elevated by the rising sea level and ‘roll back’.

16.1.3 Epoch 3, years 50 – 100 (2105)

The coast will continue to erode whilst retaining its current characteristics, as in epochs 1 and 2. Continued acceleration of the rate of relative sea level rise will cause shore platforms to continue to fall, relative to the mean sea level. The region of beach/ rock platform exposed above low water will continue to narrow. High tide will reach the cliff toe more frequently and allow larger waves to strike the cliffs with more energy. The shore will recede at a higher rate than seen in the past. As a consequence the proportion of the cliff face comprised of active landslides will continue to increase. This will supply more material to the beach, which will mitigate, although not prevent, the narrowing of the intertidal zone. Beaches not fixed by backing cliffs will be elevated by the rising sea level and ‘roll back’.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 107 February 2011

16.2 Unit details – No Active Intervention

Location Predicted Change For Years 0 – 20 (2025) Years 20 – 50 (2055) Years 50 – 100 (2105) Towan Head No defences No defences No defences to Fly Cove The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Fly Cove Wall No defences No defences Erosion will be small, The trend seen in the Accelerated relative sea level however increasing sea previous epoch will continue. rise will continue to increase levels will increase the water Collapse of defences will lead wave activity at the shore. depths, allowing slightly to localised cliff failures. The shore platform will be larger waves to reach the Wave run-up and impacts on submerged for a greater shore. the cliff face will increase. proportion of the tide, and so access will be reduced. Wave impacts on the cliff face will continue to increase, causing higher shore recession rates. Fly Cove to No defences No defences No defences North Pier The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Breakwater Breakwater Breakwater Harbour Water depths increase within Water depths increase within Water depths increase within the harbour, with no effect on the harbour, with no effect on the harbour, with no effect on the surrounding coast. the surrounding coast. the surrounding coast. Localised structure failures Failure of some harbour may occur. structures leads to loss of the harbour margin. Towan Walls No defences No defences Beach Where defended, the Failure of the structures will Ongoing sea level rise will shoreline will be held and the be followed by a period of continue to drive the beach beach will tend to retreat accelerated recession, as landward. Sediments slightly. more natural profiles are released by recession and reformed. Sea level rise will the formation of new shore drive further retreat and platform will mitigate the narrowing of the beach. effects of the rising seas to some degree. The Island No defences No defences No defences The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 108 February 2011

Great Wall No defences No defences Western Beach to Wine Cove Where defended, the Failure of the structures will Ongoing sea level rise will shoreline will be held and the be followed by a period of continue to drive the beach beach will tend to retreat accelerated recession, as landward. Sediments slightly. more natural profiles are released by recession and reformed. Sea level rise will the formation of new shore drive further retreat and platform will mitigate the narrowing of the beach. effects of the rising seas to some degree. Wine Cove to No defences No defences No defences Porth The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Porth Beach The shoreline will be held by Failure of the structures will Ongoing sea level rise will the defences and the beach be followed by a period of continue to drive the beach will tend to retreat slightly. accelerated recession, as landward. Sediments more natural profiles are released by recession and reformed. Sea level rise will the formation of new shore drive further retreat of the platform will mitigate the beach. effects of the rising seas to some degree. Porth / No defences No defences No defences to Watergate The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Watergate Wall No defences No defences beach Where defended, the Failure of the structures will Ongoing sea level rise will shoreline will be held and the be followed by a period of continue to drive the beach beach will tend to retreat accelerated recession, as landward. Sediments slightly. more natural profiles are released by recession and reformed. Sea level rise will the formation of new shore drive further retreat and platform will mitigate the narrowing of the beach. effects of the rising seas to some degree. Watergate No defences No defences No defences Beach to Mawgan Porth) The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region,

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 109 February 2011

as described above. as described above. as described above. Mawgan Walls and revetments No defences No defences Porth Beach Where defended, the Failure of the structures will Ongoing sea level rise will shoreline will be held and the be followed by a period of continue to drive the beach beach will tend to retreat accelerated recession, as landward. Sediments slightly. Elsewhere the beach more natural profiles are released by recession will tend to retreat slightly, but reformed. Sea level rise will through the dunes will this may be difficult to drive further retreat and mitigate the effects of the distinguish from natural narrowing of the beach into rising seas to some degree. variability. the dunes. Mawgan No defences No defences No defences Porth to Park Head The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above.

16.3 Unit details – With Present Management

Location Predicted Change For Years 0 – 20 (2025) Years 20 – 50 (2055) Years 50 – 100 (2105) Towan Head No defences No defences No defences to Fly Cove The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Fly Cove Wall Wall Wall Erosion will be small, The trend seen in the Accelerated relative sea level however increasing sea previous epoch will continue. rise will continue to increase levels will increase the water Wave run-up and impacts on wave activity at the shore. depths, allowing slightly the cliff face and structures The shore platform will be larger waves to reach the will increase. The increased submerged for a greater shore. wave loading will necessitate proportion of the tide, and so the construction of more access will be reduced. Wave substantial defences. impacts on the cliff face and structures will continue to increase, causing higher shore recession rates in the unprotected areas. The increased wave loading will necessitate the construction of more substantial defences. Fly Cove to No defences No defences No defences North Pier The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 110 February 2011

Newquay Breakwater Breakwater Breakwater Harbour Water depths will increase Water depths will increase Water depths will increase within the harbour, with no within the harbour, with no within the harbour, with no effect on the surrounding effect on the surrounding effect on the surrounding coast. coast.. coast. Towan Walls Walls Walls Beach The beach will tend to narrow The trend seen in the prior The trend seen in the prior slightly. The defences will epoch will continue. Erosive epoch will continue. Wave prevent recession and so processes adjacent to the impact forces on the cause the shoreline to be defences will tend to cause structures and overtopping somewhat seaward of its outflanking. rates will grow at an natural position. The exponential rate, defences will also prevent the necessitating larger formation of new shore structures to maintain current platform and reduce the levels of defence. Beach release of material for the accessibility will reduce as beach. Relative lowering of the sea level rises. the rock foreshore and beach Outflanking processes will will allow larger, more continue, possibly aggressive waves to reach necessitating an increase in the structures. structure length. The Island No defences No defences No defences The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Great Wall Walls Walls Western Beach to Wine Cove The beach will tend to narrow The trend seen in the prior The trend seen in the prior slightly. The defences will epoch will continue. Erosive epoch will continue. Wave prevent recession and so processes adjacent to the impact forces on the cause the shoreline to be defences will tend to cause structures and overtopping somewhat seaward of its outflanking. rates will grow at an natural position. The exponential rate, defences will also prevent the necessitating larger formation of new shore structures to maintain current platform and reduce the levels of defence. Beach release of material for the accessibility will reduce as beach. Relative lowering of the sea level rises. the rock foreshore and beach Outflanking processes will will allow larger, more continue, possibly aggressive waves to reach necessitating an increase in the structures. structure length. Wine Cove to No defences No defences No defences Porth The evolution of this coast The evolution of this coast The evolution of this coast

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 111 February 2011

will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Porth Beach Walls Walls Walls The beach will tend to narrow The trend seen in the prior The trend seen in the prior slightly. The defences will epoch will continue. epoch will continue. Wave prevent recession and so impact forces and cause the shoreline to be overtopping will grow at an somewhat seaward of its exponential rate, natural position. The necessitating larger defences will also prevent the structures to maintain current formation of new shore levels of defence. Beach platform and reduce the accessibility will reduce as release of material for the the sea level rises. beach. Relative lowering of the rock foreshore and beach will allow larger, more aggressive waves to reach the structures. Porth / No defences No defences No defences Trevelgue Head to Watergate The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Watergate Wall Wall Wall beach The beach will tend to narrow The trend seen in the prior The trend seen in the prior slightly. The defences will epoch will continue. Erosive epoch will continue. Wave prevent recession and so processes adjacent to the impact forces on the cause the shoreline to be defences will tend to cause structures and overtopping somewhat seaward of its outflanking. rates will grow at an natural position. The exponential rate, defences will also prevent the necessitating larger formation of new shore structures to maintain current platform and reduce the levels of defence. Beach release of material for the accessibility will reduce as beach. Relative lowering of the sea level rises. the rock foreshore and beach Outflanking processes will will allow larger, more continue, possibly aggressive waves to reach necessitating an increase in the structures. structure length. Watergate No defences No defences No defences beach to Mawgan Porth The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 112 February 2011

Mawgan Walls and revetments Walls and revetments Walls and revetments Porth Beach Where defended, the The trend seen in the prior The trend seen in the prior shoreline will be held. Overall epoch will continue. Sea level epoch will continue. At the the beach will tend to retreat rise will drive further retreat. defences wave impact forces slightly, although this may be Erosive processes adjacent and overtopping rates will difficult to distinguish from to the defences will tend to grow at an exponential rate, natural variability. cause outflanking. necessitating larger structures to maintain current levels of defence. Outflanking processes will continue, possibly necessitating an increase in structure length. Elsewhere ongoing sea level rise will continue to drive the beach landward. Sediments released by recession of the dunes will mitigate the effects of the rising seas to some degree. Mawgan No defences No defences No defences Porth to Park Head The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 113 February 2011

17 PARK HEAD TO TREVOSE HEAD

17.1 Typical coastal evolution

17.1.1 Epoch 1, years 0 – 20 (2025)

The coast will continue to erode whilst retaining its current characteristics. Occasional landslides and rockfalls will cause cliff tops to retreat, and will deliver sediment to the foreshores. These processes will be driven by ongoing wave erosion of the cliff base, which will also form new areas of shore platform. The shore platform will be lowered by wave action, where it is not protected by beach material. The beaches will be fed by the larger sediments released by the ongoing erosion processes. A small acceleration in the rate of relative sea level rise will cause shore platforms to be slightly lower, relative to the mean sea level. The region of beach/ rock platform exposed above low water will become slightly narrower as the sea rise accelerates. This will allow slightly larger waves to arrive at the cliffs, increasing the severity of wave breaking. As a consequence the shore will retreat slightly faster than it has in the past. Locations were valleys meet the sea will tend to respond more strongly to sea level rise than rocky areas. The crests of the beaches that form in these valleys will be elevated by the rising sea level, and retreat inland, where there is space to do so. The substantial beaches within this region may begin to be driven back by rising seas, although this may be difficult to distinguish from natural variability.

17.1.2 Epoch 2, years 20 – 50 (2055)

The coast will continue to erode whilst retaining its current characteristics, as in epoch 1. A larger acceleration in rate of relative sea level rise will cause shore platforms to continue to fall, relative to the mean sea level. The region of beach/ rock platform exposed above low water will narrow. High tide will reach the cliff toe more frequently and this will allow larger waves to strike the cliffs, increasing the severity of wave breaking and raising recession rates. As a consequence the proportion of the cliff face comprised of active landslides will tend to increase. This will supply more material to the beach, which will mitigate, although not prevent, the narrowing of the intertidal zone. Beaches not fixed by backing cliffs or hard structures will be elevated by the rising sea level and ‘roll back’. This will involve some dune erosion.

17.1.3 Epoch 3, years 50 – 100 (2105)

The coast will continue to erode whilst retaining its current characteristics, as in epochs 1 and 2. Continued acceleration of the rate of relative sea level rise will cause shore platforms to continue to fall, relative to the mean sea level. The region of beach/ rock platform exposed above low water will continue to narrow. High tide will reach the cliff toe more frequently and allow larger waves to strike the cliffs with more energy. The shore will recede at a higher rate than seen in the past. As a consequence the proportion of the cliff face comprised of active landslides will continue to increase. This will supply more material to the beach, which will mitigate, although not prevent, the narrowing of the intertidal zone. Beaches not fixed by backing cliffs will be elevated by the rising sea level and ‘roll back’. This will involve some dune erosion.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 114 February 2011

17.2 Unit details – No Active Intervention

Location Predicted Change For Years 0 – 20 (2025) Years 20 – 50 (2055) Years 50 – 100 (2105) Park Head to No defences No defences No defences Porthcothan The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Porthcothan Defacto defence Defacto defence Defacto defence Beach The coastal defences will Failure of the coastal Accelerated relative sea level prevent recession and so structures will be followed by rise will continue to cause the cause the shoreline to be a transient period of beach to roll back, at increasingly seaward of its accelerated recession, as increasing rates. Continued natural position. The waves attack over-steepened erosion will release fresh defences will also prevent the shore profiles. This will sediments that will formation of new shore release sedimentary material, accumulate and provide platform and reduce the some of which will some protection to wave release of material for the accumulate in the beach. The attack. beach. Relative lowering of beach will begin to roll back the beach will allow larger, and this will mitigate, more aggressive waves to although not prevent, reach the structures. narrowing of the intertidal zone due to sea level rise. Porthcothan No defences No defences No defences to Treyarnon The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Treyarnon No defences No defences No defences Beach The beach and dunes will The form of the beach and Ongoing acceleration in the remain essentially dunes will remain essentially rate of sea level rise will drive unchanged, apart from unchanged. Sea level rise will increasing erosion of the natural short term and drive some erosion of the dune face. However this will seasonal fluctuations in form front of the dune, and this will be accompanied by release sand into the beach. increasing release of sediment into the beach which will allow it to rise with the sea level. As a result the beach will appear relatively unchanged. Treyarnon to Walls No defences No defences Constantine Bay Erosion will be small, The trend seen in the Accelerated relative sea level however increasing sea previous epoch will continue. rise will continue to increase levels will increase the water Collapse of defences will lead wave activity at the shore.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 115 February 2011

depths, allowing slightly to localised cliff failures. The shore platform will be larger waves to reach the Wave run-up and impacts on submerged for a greater shore. the cliff face will increase. proportion of the tide, and so access will be reduced. Wave impacts on the cliff face will continue to increase, causing higher shore recession rates. Constantine No defences No defences No defences Bay The beach and dunes will The form of the beach and Ongoing acceleration in the remain essentially dunes will remain essentially rate of sea level rise will drive unchanged, apart from unchanged. Sea level rise will increasing erosion of the natural short term and drive some erosion of the dune face. However this will seasonal fluctuations in form front of the dune, and this will be accompanied by release sand into the beach. increasing release of sediment into the beach which will allow it to rise with the sea level. As a result the beach will appear relatively unchanged. Constantine No defences No defences No defences Island to Trevose Head The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above.

17.3 Unit details – With Present Management

Location Predicted Change For Years 0 – 20 (2025) Years 20 – 50 (2055) Years 50 – 100 (2105) Park Head to No defences No defences No defences Porthcothan The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Porthcothan Defacto defence Defacto defence Defacto defence Beach The coastal defences will The trend seen in the prior The trend seen in the prior prevent recession and so epoch will continue. epoch will continue. Wave cause the shoreline to be impact forces and increasingly seaward of its overtopping will grow at an natural position. The exponential rate, defences will also prevent the necessitating larger formation of new shore structures to maintain current platform and reduce the levels of defence. Beach release of material for the accessibility will reduce as beach. Relative lowering of the sea level rises.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 116 February 2011

the beach will allow larger, more aggressive waves to reach the structures.

Porthcothan No defences No defences No defences to Treyarnon The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Treyarnon No defences No defences No defences Beach The beach and dunes will The form of the beach and Ongoing acceleration in the remain essentially dunes will remain essentially rate of sea level rise will drive unchanged, apart from unchanged. Sea level rise will increasing erosion of the natural short term and drive some erosion of the dune face. However this will seasonal fluctuations in form front of the dune, and this will be accompanied by release sand into the beach. increasing release of sediment into the beach which will allow it to rise with the sea level. As a result the beach will appear relatively unchanged. Treyarnon to Walls Walls Walls Constantine Bay Erosion will be small, The trend seen in the Accelerated relative sea level however increasing sea previous epoch will continue. rise will continue to increase levels will increase the water Wave run-up and impacts on wave activity at the shore. depths, allowing slightly the cliff face and structures The shore platform will be larger waves to reach the will increase. The increased submerged for a greater shore. wave loading will necessitate proportion of the tide, and so the construction of more access will be reduced. Wave substantial defences. impacts on the cliff face and structures will continue to increase, causing higher shore recession rates in the unprotected areas. The increased wave loading will necessitate the construction of more substantial defences. Constantine No defences No defences No defences Bay The beach and dunes will The form of the beach and Ongoing acceleration in the remain essentially dunes will remain essentially rate of sea level rise will drive unchanged, apart from unchanged. Sea level rise will increasing erosion of the natural short term and drive some erosion of the dune face. However this will seasonal fluctuations in form front of the dune, and this will be accompanied by release sand into the beach. increasing release of sediment into the beach

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 117 February 2011

which will allow it to rise with the sea level. As a result the beach will appear relatively unchanged. Constantine No defences No defences No defences Island to Trevose Head The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 118 February 2011

18 TREVOSE HEAD TO PENTIRE POINT

18.1 Typical coastal evolution

18.1.1 Epoch 1, years 0 – 20 (2025)

The coast will continue to erode whilst retaining its current characteristics. Occasional landslides and rockfalls will cause cliff tops to retreat, and will deliver sediment to the foreshores. These processes will be driven by ongoing wave erosion of the cliff base, which will also form new areas of shore platform. The shore platform will be lowered by wave action, where it is not protected by beach material. The beaches will be fed by the larger sediments released by the ongoing erosion processes. A small acceleration in the rate of relative sea level rise will cause shore platforms to be slightly lower, relative to the mean sea level. The region of beach/ rock platform exposed above low water will become slightly narrower as the sea rise accelerates. This will allow slightly larger waves to arrive at the cliffs, increasing the severity of wave breaking. As a consequence the shore will retreat slightly faster than it has in the past. Locations were valleys meet the sea will tend to respond more strongly to sea level rise than rocky areas. The crests of the beaches that form in these valleys will be elevated by the rising sea level, and retreat inland, where there is space to do so. The substantial beaches within this region may begin to be driven back by rising seas, although this may be difficult to distinguish from natural variability.

18.1.2 Epoch 2, years 20 – 50 (2055)

The coast will continue to erode whilst retaining its current characteristics, as in epoch 1. A larger acceleration in rate of relative sea level rise will cause shore platforms to continue to fall, relative to the mean sea level. The region of beach/ rock platform exposed above low water will narrow. High tide will reach the cliff toe more frequently and this will allow larger waves to strike the cliffs, increasing the severity of wave breaking and raising recession rates. As a consequence the proportion of the cliff face comprised of active landslides will tend to increase. This will supply more material to the beach, which will mitigate, although not prevent, the narrowing of the intertidal zone. Beaches not fixed by backing cliffs or hard structures will be elevated by the rising sea level and ‘roll back’. This will involve some dune erosion.

18.1.3 Epoch 3, years 50 – 100 (2105)

The coast will continue to erode whilst retaining its current characteristics, as in epochs 1 and 2. Continued acceleration of the rate of relative sea level rise will cause shore platforms to continue to fall, relative to the mean sea level. The region of beach/ rock platform exposed above low water will continue to narrow. High tide will reach the cliff toe more frequently and allow larger waves to strike the cliffs with more energy. The shore will recede at a higher rate than seen in the past. As a consequence the proportion of the cliff face comprised of active landslides will continue to increase. This will supply more material to the beach, which will mitigate, although not prevent, the narrowing of the intertidal zone. Beaches not fixed by backing cliffs will be elevated by the rising sea level and ‘roll back’. This will involve some dune erosion.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 119 February 2011

18.2 Unit details – No Active Intervention

Location Predicted Change For Years 0 – 20 (2025) Years 20 – 50 (2055) Years 50 – 100 (2105) Trevose No defences No defences No defences Head to Harlyn The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Harlyn Beach No defences No defences No defences The beach and dunes will The form of the beach and Ongoing acceleration in the remain essentially dunes will remain essentially rate of sea level rise will drive unchanged, apart from unchanged. Sea level rise will increasing erosion of the natural short term and drive some erosion of the dune face. However this will seasonal fluctuations in form front of the dune, and this will be accompanied by release sand into the beach. increasing release of sediment into the beach which will allow it to rise with the sea level. As a result the beach will appear relatively unchanged. Harlyn to No defences No defences No defences Cliffs The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Trevone Wall No defences No defences Cliffs Erosion will be small, The trend seen in the Accelerated relative sea level however increasing sea previous epoch will continue. rise will continue to increase levels will increase the water Collapse of defences will lead wave activity at the shore. depths, allowing slightly to localised cliff failures. The shore platform will be larger waves to reach the Wave run-up and impacts on submerged for a greater shore. the cliff face will increase. proportion of the tide, and so access will be reduced. Wave impacts on the cliff face will continue to increase, causing higher shore recession rates. Porthmissen No defences No defences No defences Beach Where defended, the Failure of the structures will Ongoing sea level rise will shoreline will be held and the be followed by a period of continue to drive the beach beach will tend to retreat accelerated recession, as landward. Sediments slightly. Elsewhere the beach more natural profiles are released by recession will tend to retreat slightly, but reformed. Sea level rise will through the dunes will this may be difficult to drive further retreat and mitigate the effects of the distinguish from natural narrowing of the beach into rising seas to some degree.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 120 February 2011

variability. the dunes. Porthmissen No defences No defences No defences Beach to The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Padstow Harbour and Quay walls Harbour and Quay walls Harbour and Quay walls Harbour Water depths increase within Water depths increase within Water depths increase within the harbour, with no effect on the harbour, with no effect on the harbour, with no effect on the surrounding coast. the surrounding coast. the surrounding coast. Localised structure failures Failure of some harbour may occur. structures leads to loss of the harbour margin. Daymer Bay No defences No defences No defences The beach and dunes will The form of the beach and Ongoing acceleration in the remain essentially dunes will remain essentially rate of sea level rise will drive unchanged, apart from unchanged. Sea level rise will increasing erosion of the natural short term and drive some erosion of the dune face. However this will seasonal fluctuations in form front of the dune, and this will be accompanied by release sand into the beach. increasing release of sediment into the beach which will allow it to rise with the sea level. As a result the beach will appear relatively unchanged. Daymer Bay No defences No defences No defences to Polzeath The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Polzeath Intermittent defences No defences No defences

New Polzeath Where defended, the Failure of the structures will Ongoing sea level rise will shoreline will be held and the be followed by a period of continue to drive the beach beach will tend to retreat accelerated recession, as landward. Sediments slightly. more natural profiles are released by recession and reformed. Sea level rise will the formation of new shore drive further retreat and platform will mitigate the narrowing of the beach. effects of the rising seas to some degree. Pentireglaze No defences No defences No defences Haven The coast will remain much Accelerated sea level risk will Accelerated sea level risk will as it is today. Accelerated tend to drive the beach up tend to drive the beach sea level risk will drive some and back into the valley. further up and back into the

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 121 February 2011

retreat of shoreline but this valley. will be difficult to distinguish from natural variability. Pentireglaze No defences No defences No defences Haven to Pentire Point The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above.

18.3 Unit details – With Present Management

Location Predicted Change For Years 0 – 20 (2025) Years 20 – 50 (2055) Years 50 – 100 (2105) Trevose No defences No defences No defences Head to Harlyn The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Harlyn Beach No defences No defences No defences The beach and dunes will The form of the beach and Ongoing acceleration in the remain essentially dunes will remain essentially rate of sea level rise will drive unchanged, apart from unchanged. Sea level rise will increasing erosion of the natural short term and drive some erosion of the dune face. However this will seasonal fluctuations in form front of the dune, and this will be accompanied by release sand into the beach. increasing release of sediment into the beach which will allow it to rise with the sea level. As a result the beach will appear relatively unchanged. Harlyn to No defences No defences No defences Trevone Cliffs The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Trevone Wall No defences No defences Cliffs Erosion will be small, The trend seen in the Accelerated relative sea level however increasing sea previous epoch will continue. rise will continue to increase levels will increase the water Wave run-up and impacts on wave activity at the shore. depths, allowing slightly the cliff face and structures The shore platform will be larger waves to reach the will increase. The increased submerged for a greater shore. wave loading will necessitate proportion of the tide, and so the construction of more access will be reduced. Wave substantial defences. impacts on the cliff face and structures will continue to

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 122 February 2011

increase, causing higher shore recession rates in the unprotected areas. The increased wave loading will necessitate the construction of more substantial defences. Porthmissen No defences No defences No defences Beach Where defended, the The trend seen in the prior The trend seen in the prior shoreline will be held. Overall epoch will continue. Sea level epoch will continue. At the the beach will tend to retreat rise will drive further retreat. defences wave impact forces slightly, although this may be Erosive processes adjacent and overtopping rates will difficult to distinguish from to the defences will tend to grow at an exponential rate, natural variability. cause outflanking. necessitating larger structures to maintain current levels of defence. Outflanking processes will continue, possibly necessitating an increase in structure length. Elsewhere ongoing sea level rise will continue to drive the beach landward. Sediments released by recession of the dunes will mitigate the effects of the rising seas to some degree. Porthmissen No defences No defences No defences Beach to Padstow The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Padstow Harbour and Quay walls Harbour and Quay walls Harbour and Quay walls Harbour Water depths will increase Water depths will increase Water depths will increase within the harbour, with no within the harbour, with no within the harbour, with no effect on the surrounding effect on the surrounding effect on the surrounding coast. coast.. coast. Daymer Bay No defences No defences No defences Dunes The beach and dunes will The form of the beach and Ongoing acceleration in the remain essentially dunes will remain essentially rate of sea level rise will drive unchanged, apart from unchanged. Sea level rise will increasing erosion of the natural short term and drive some erosion of the dune face. However this will seasonal fluctuations in form front of the dune, and this will be accompanied by release sand into the beach. increasing release of sediment into the beach which will allow it to rise with the sea level. As a result the

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 123 February 2011

beach will appear relatively unchanged. Daymer Bay No defences No defences No defences to Polzeath The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Polzeath Intermittent defences Intermittent defences Intermittent defences

New No defences No defences No defences Polzeath The beach will tend to narrow The trend seen in the prior The trend seen in the prior slightly. The defences will epoch will continue. Erosive epoch will continue. Wave prevent recession and so processes adjacent to the impact forces on the cause the shoreline to be defences will tend to cause structures and overtopping somewhat seaward of its outflanking. rates will grow at an natural position. The exponential rate, defences will also prevent the necessitating larger formation of new shore structures to maintain current platform and reduce the levels of defence. Beach release of material for the accessibility will reduce as beach. Relative lowering of the sea level rises. the rock foreshore and beach Outflanking processes will will allow larger, more continue, possibly aggressive waves to reach necessitating an increase in the structures. structure length. Pentireglaze No defences No defences No defences Haven The coast will remain much Accelerated sea level risk will Accelerated sea level risk will as it is today. Accelerated tend to drive the beach up tend to drive the beach sea level risk will drive some and back into the valley. further up and back into the retreat of shoreline but this valley. will be difficult to distinguish from natural variability. Pentireglaze No defences No defences No defences Haven to Pentire Point The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 124 February 2011

19 PENTIRE POINT HARTLAND POINT

19.1 Typical coastal evolution

19.1.1 Epoch 1, years 0 – 20 (2025)

The coast will continue to erode whilst retaining its current characteristics. Occasional landslides and rockfalls will cause cliff tops to retreat, and will deliver sediment to the foreshores. These processes will be driven by ongoing wave erosion of the cliff base, which will also form new areas of shore platform. The shore platform will be lowered by wave action, where it is not protected by beach material. The beaches will be fed by the larger sediments released by the ongoing erosion processes. A small acceleration in the rate of relative sea level rise will cause shore platforms to be slightly lower, relative to the mean sea level. The region of beach/ rock platform exposed above low water will become slightly narrower as the sea rise accelerates. This will allow slightly larger waves to arrive at the cliffs, increasing the severity of wave breaking. As a consequence the shore will retreat slightly faster than it has in the past. Locations were valleys meet the sea will tend to respond more strongly to sea level rise than rocky areas. The crests of the beaches that form in these valleys will be elevated by the rising sea level, and retreat inland, where there is space to do so. The substantial beaches within this region may begin to be driven back by rising seas, although this may be difficult to distinguish from natural variability.

19.1.2 Epoch 2, years 20 – 50 (2055)

The coast will continue to erode whilst retaining its current characteristics, as in epoch 1. A larger acceleration in rate of relative sea level rise will cause shore platforms to continue to fall, relative to the mean sea level. The region of beach/ rock platform exposed above low water will narrow. High tide will reach the cliff toe more frequently and this will allow larger waves to strike the cliffs, increasing the severity of wave breaking and raising recession rates. As a consequence the proportion of the cliff face comprised of active landslides will tend to increase. This will supply more material to the beach, which will mitigate, although not prevent, the narrowing of the intertidal zone. Beaches not fixed by backing cliffs or hard structures will be elevated by the rising sea level and ‘roll back’. This will involve some dune erosion.

19.1.3 Epoch 3, years 50 – 100 (2105)

The coast will continue to erode whilst retaining its current characteristics, as in epochs 1 and 2. Continued acceleration of the rate of relative sea level rise will cause shore platforms to continue to fall, relative to the mean sea level. The region of beach/ rock platform exposed above low water will continue to narrow. High tide will reach the cliff toe more frequently and allow larger waves to strike the cliffs with more energy. The shore will recede at a higher rate than seen in the past. As a consequence the proportion of the cliff face comprised of active landslides will continue to increase. This will supply more material to the beach, which will mitigate, although not prevent, the narrowing of the intertidal zone. Beaches not fixed by backing cliffs will be elevated by the rising sea level and ‘roll back’. This will involve some dune erosion.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 125 February 2011

19.2 Unit details – No Active Intervention

Location Predicted Change For Years 0 – 20 (2025) Years 20 – 50 (2055) Years 50 – 100 (2105) Pentire Point No defences No defences No defences to Port Quinn The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Port Quinn Wall No defences No defences Where defended, the Failure of the structures will Ongoing sea level rise will shoreline will be held. Overall be followed by a period of continue to drive the beach the beach will tend to retreat localised accelerated landward, up the valley. slightly, although this may be recession, as more natural Sediments released by difficult to distinguish from profiles are reformed. Sea recession through the natural variability. level rise will drive further hinterland will mitigate the retreat and narrowing of the effects of the rising seas to a beach. small degree. Port Quinn to No defences No defences No defences Port Isaac The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Port Isaac Breakwater Breakwater Breakwater harbour Where defended, the Failure of the structures will Ongoing sea level rise will shoreline will be held. Overall be followed by a period of continue to drive the beach the beach will tend to retreat localised accelerated landward, up the valley. slightly, although this may be recession, as more natural Sediments released by difficult to distinguish from profiles are reformed. Sea recession through the natural variability. level rise will drive further hinterland will mitigate the retreat and narrowing of the effects of the rising seas to a beach. small degree. Port Isaac to No defences No defences No defences Port Gaverne The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Port Gaverne Walls No defences No defences Where defended, the Failure of the structures will Ongoing sea level rise will shoreline will be held. Overall be followed by a period of continue to drive the beach the beach will tend to retreat localised accelerated landward, up the valley. slightly, although this may be recession, as more natural Sediments released by difficult to distinguish from profiles are reformed. Sea recession through the natural variability. level rise will drive further hinterland will mitigate the retreat and narrowing of the effects of the rising seas to a beach. small degree. Port Gaverne No defences No defences No defences to Boscastle

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 126 February 2011

The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Boscastle Breakwater and walls Breakwater and walls Breakwater and walls harbour Water depths increase within Water depths increase within Water depths increase within the harbour, with no effect on the harbour, with no effect on the harbour, with no effect on the surrounding coast. the surrounding coast. the surrounding coast. Localised structure failures Failure of some harbour may occur. structures leads to loss of the harbour margin. Boscastle to No defences No defences No defences The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Crackington Walls No defences No defences Haven Where defended, the Failure of the structures will Ongoing sea level rise will shoreline will be held. Overall be followed by a period of continue to drive the beach the beach will tend to retreat localised accelerated landward, up the valley. slightly, although this may be recession, as more natural Sediments released by difficult to distinguish from profiles are reformed. Sea recession through the natural variability. level rise will drive further hinterland will mitigate the retreat and narrowing of the effects of the rising seas to a beach. small degree. Crackington No defences No defences No defences Haven to Widemouth Bay The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Widemouth Walls and revetment No defences No defences Sand south The evolution of this coast Ongoing sea level rise will Ongoing sea level rise will will be typical of the region, further narrow the beach, continue to narrow the beach as described above. The increasing the period that the and increase wave loading beach will begin to narrow as cliff toe is submerged at high on the cliff toe. Landslides the sea level rises. tide. Wave loading on the cliff and cliff top retreat will toe will increase. increase. Widemouth Walls and revetment No defences No defences Sand north The shoreline will continue to Ongoing sea level rise will Ongoing sea level rise will retreat where it is not tend to narrow the beach and continue to narrow the beach defended. This will tend to increase wave loading on the and increase wave loading happen at a higher rate, cliffs, increasing recession on the cliff toe. Landslides although this increase should rates. Failure of the and cliff top retreat will

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 127 February 2011

be difficult to distinguish from structures will be followed by increase. This will to release natural variability. In front of a period of accelerated additional sediments into the defended areas the water recession, as more natural beach, although this will only depth will tend to increase, as shore profiles are reformed. partly mitigate the overall foreshores lower and sea narrowing of the intertidal levels rise. zone. Widemouth No defences No defences No defences Sand to Sheephouse Down The shoreline will continue to Ongoing sea level rise will Ongoing sea level rise will retreat. This will tend to tend to narrow the beach and continue to narrow the beach happen at a higher rate, increase wave loading on the and increase wave loading although this increase should cliffs, increasing recession on the cliff toe. Landslides be difficult to distinguish from rates. and cliff top retreat will natural variability. increase. This will to release additional sediments into the beach, although this will only partly mitigate the overall narrowing of the intertidal zone. Sheephouse No defences No defences No defences Down to Summerleaze The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Breakwater, walls, gabion No defences No defences wall, Where defended, the Failure of the structures will Ongoing sea level rise will shoreline will be held and the be followed by a period of continue to drive the beach beach will tend to retreat accelerated recession, as landward. Sediments slightly. Elsewhere the beach more natural profiles are released by recession will tend to retreat slightly, but reformed. Sea level rise will through the dunes will this may be difficult to drive further retreat and mitigate the effects of the distinguish from natural narrowing of the beach into rising seas to some degree. variability. the dunes. Crooklets Seawalls No defences No defences Beach The coastal defences will Failure of the coastal Accelerated relative sea level prevent recession and so structures will be followed by rise will continue to cause the cause the shoreline to be a transient period of beach to roll back, at increasingly seaward of its accelerated recession, as increasing rates. Continued natural position. The waves attack over-steepened erosion will release fresh defences will also prevent the shore profiles. This will sediments that will formation of new shore release sedimentary material, accumulate and provide platform and reduce the some of which will some protection to wave release of material for the accumulate in the beach. The attack. beach. Relative lowering of beach will begin to roll back

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 128 February 2011

the beach will allow larger, and this will mitigate, more aggressive waves to although not prevent, reach the structures. narrowing of the intertidal zone due to sea level rise. Maer Down No defences No defences No defences to Hartland Point The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above.

19.3 Unit details – With Present Management

Location Predicted Change For Years 0 – 20 (2025) Years 20 – 50 (2055) Years 50 – 100 (2105) Pentire Point No defences No defences No defences to Port Quinn The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Port Quinn Wall Wall Wall Where defended, the The trend seen in the prior The trend seen in the prior shoreline will be held. Overall epoch will continue. Sea level epoch will continue. At the the beach will tend to retreat rise will drive further retreat. defences wave impact forces slightly, although this may be Erosive processes adjacent and overtopping rates will difficult to distinguish from to the defences will tend to grow at an exponential rate, natural variability. cause outflanking. necessitating larger structures to maintain current levels of defence. Outflanking processes will continue, possibly necessitating an increase in structure length. Elsewhere ongoing sea level rise will continue to drive the beach landward, up the valley. Port Quinn to No defences No defences No defences Port Isaac The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Port Isaac Breakwater Breakwater Breakwater harbour Where defended, the The trend seen in the prior The trend seen in the prior shoreline will be held. Overall epoch will continue. Sea level epoch will continue. At the the beach will tend to retreat rise will drive further retreat. defences wave impact forces slightly, although this may be Erosive processes adjacent and overtopping rates will difficult to distinguish from to the defences will tend to grow at an exponential rate,

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 129 February 2011

natural variability. cause outflanking. necessitating larger structures to maintain current levels of defence. Outflanking processes will continue, possibly necessitating an increase in structure length. Elsewhere ongoing sea level rise will continue to drive the beach landward, up the valley. Port Isaac to No defences No defences No defences Port Gaverne The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Port Gaverne Walls Walls Walls Where defended, the The trend seen in the prior The trend seen in the prior shoreline will be held. Overall epoch will continue. Sea level epoch will continue. At the the beach will tend to retreat rise will drive further retreat. defences wave impact forces slightly, although this may be Erosive processes adjacent and overtopping rates will difficult to distinguish from to the defences will tend to grow at an exponential rate, natural variability. cause outflanking. necessitating larger structures to maintain current levels of defence. Outflanking processes will continue, possibly necessitating an increase in structure length. Elsewhere ongoing sea level rise will continue to drive the beach landward, up the valley. Port Gaverne No defences No defences No defences to Boscastle The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Boscastle Breakwater and walls Breakwater and walls Breakwater and walls harbour Water depths will increase Water depths will increase Water depths will increase within the harbour, with no within the harbour, with no within the harbour, with no effect on the surrounding effect on the surrounding effect on the surrounding coast. coast.. coast. Boscastle to No defences No defences No defences Crackington Haven The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Crackington Walls Walls Walls

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 130 February 2011

Haven Where defended, the The trend seen in the prior The trend seen in the prior shoreline will be held. Overall epoch will continue. Sea level epoch will continue. At the the beach will tend to retreat rise will drive further retreat. defences wave impact forces slightly, although this may be Erosive processes adjacent and overtopping rates will difficult to distinguish from to the defences will tend to grow at an exponential rate, natural variability. cause outflanking. necessitating larger structures to maintain current levels of defence. Outflanking processes will continue, possibly necessitating an increase in structure length. Elsewhere ongoing sea level rise will continue to drive the beach landward, up the valley. Crackington No defences No defences No defences Haven to Widemouth Bay The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Widemouth Walls and revetment Walls and revetment Walls and revetment Sand south Coastal evolution will be Ongoing sea level rise will Ongoing sea level rise will typical of the region as further narrow the beach, continue to narrow the beach described above. The beach increasing the period that the and increase wave loading will begin to narrow as the cliff toe is submerged at high on the cliff toe. Landslides sea level rises. tide. Wave loading on the cliff and cliff top retreat will toe will increase. increase. Widemouth Walls and revetment Walls and revetment Walls and revetment Sand north The shoreline will continue to Ongoing sea level rise will Ongoing sea level rise will retreat where it is not tend to narrow the beach and continue to narrow the beach defended. This will tend to increase wave loading on the and increase wave loading happen at a higher rate, cliffs, where they are not on the cliff toe. Landslides although this increase should defended, increasing and cliff top retreat will be difficult to distinguish from recession rates. Water increase. This will to release natural variability. In front of depths will continue to additional sediments into the defended areas the water increase, in front of the beach, and new shore depth will tend to increase, as structures, increasing wave platform will be formed, foreshores lower and sea loads on them. although this will only partly levels rise. mitigate overall narrowing of the intertidal zone. In defended areas the intertidal zone will narrow more sharply, decreasing the period during which they can

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 131 February 2011

be accessed at low tide. Wave loading on the structures will increase. Widemouth No defences No defences No defences Sand to Sheephouse Down The shoreline will continue to Ongoing sea level rise will Ongoing sea level rise will retreat. This will tend to tend to narrow the beach and continue to narrow the beach happen at a higher rate, increase wave loading on the and increase wave loading although this increase should cliffs, increasing recession on the cliff toe. Landslides be difficult to distinguish from rates. and cliff top retreat will natural variability. increase. This will to release additional sediments into the beach, although this will only partly mitigate the overall narrowing of the intertidal zone. Sheephouse No defences No defences No defences Down to Summerleaz e The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above. Bude Breakwater, walls, gabion Breakwater, walls, gabion Breakwater, walls, gabion wall, wall, wall, Where defended, the The trend seen in the prior The trend seen in the prior shoreline will be held. Overall epoch will continue. Sea level epoch will continue. At the the beach will tend to retreat rise will drive further retreat. defences wave impact forces slightly, although this may be Erosive processes adjacent and overtopping rates will difficult to distinguish from to the defences will tend to grow at an exponential rate, natural variability. cause outflanking. necessitating larger structures to maintain current levels of defence. Outflanking processes will continue, possibly necessitating an increase in structure length. Elsewhere ongoing sea level rise will continue to drive the beach landward. Sediments released by recession of the dunes will mitigate the effects of the rising seas to some degree. Crooklets Seawalls Seawalls Seawalls Beach The coastal defences will The trend seen in the prior The trend seen in the prior prevent recession and so epoch will continue. epoch will continue. Wave

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 132 February 2011

cause the shoreline to be impact forces and increasingly seaward of its overtopping will grow at an natural position. The exponential rate, defences will also prevent the necessitating larger formation of new shore structures to maintain current platform and reduce the levels of defence. Beach release of material for the accessibility will reduce as beach. Relative lowering of the sea level rises. the beach will allow larger, more aggressive waves to reach the structures. Maer Down No defences No defences No defences to Hartland Point The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the region, will be typical of the region, will be typical of the region, as described above. as described above. as described above.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 133 February 2011

20 ISLES OF SCILLY

20.1 Typical coastal evolution of the Isles of Scilly

20.1.1 Epoch 1, years 0 – 20 (2025)

Although the underlying geology is hard, in many places the foreshores are very gently sloping, and backing cliffs are quite low and composed of relatively soft weathered material. This combination is likely to make some locations in the islands quite sensitive to sea level rise. This is generally an erosional coast and this will continue, allowing the coast to retain its current characteristics. As the shoreline retreats occasional rockfalls will cause the cliff tops to retreat, delivering sediment to the foreshores. These processes will be driven by ongoing wave erosion of the cliff base, which will also form new areas of shore platform. The shore platform will be lowered by wave action, where it is not protected by beach material. The beaches will remain relatively stable, and will be fed by the larger sediments released by the ongoing erosion processes. A small acceleration in the rate of relative sea level rise will cause shore platforms to be slightly lower, relative to the mean sea level. The region of beach/ rock platform exposed above low water will become slightly narrower as the sea rise accelerates. This will allow slightly larger waves to arrive at the cliffs, increasing the severity of wave breaking. As a consequence the shore will retreat slightly faster than it has in the past.

20.1.2 Epoch 2, years 20 – 50 (2055)

The coast will continue to erode whilst retaining its current characteristics, as in epoch 1. A larger acceleration in rate of relative sea level rise will cause shore platforms to continue to fall, relative to the mean sea level. The region of beach/ rock platform exposed above low water will narrow. High tide will reach the low cliffs more frequently and this will allow larger waves to strike them, increasing the severity of wave breaking and raising recession rates. As a consequence the frequency of rock falls will tend to increase. This will supply more material to the beach, which will mitigate, although not prevent, the narrowing of the intertidal zone. Beaches not fixed by backing cliffs will be elevated by the rising sea level and ‘roll back’.

20.1.3 Epoch 3, years 50 – 100 (2105)

The coast will continue to erode whilst generally retaining its current characteristics, as in epochs 1 and 2. Continued acceleration of the rate of relative sea level rise will cause shore platforms to continue to fall, relative to the mean sea level. The region of beach/ rock platform exposed above low water will continue to narrow. High tide will reach the cliff toe more frequently and allow larger waves to strike the cliffs with more energy. The shore will recede at a higher rate than seen in the past. As a consequence the frequency of landsliding will continue to increase. This will supply more material to the beach, which will mitigate narrowing of the intertidal zone. Beaches not fixed by backing cliffs will be elevated by the rising sea level and ‘roll back’. Access along the shore will be reduced in some places at higher stages of the tide, due to the rising seas.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 134 February 2011

20.2 St Mary’s unit details – No Active Intervention

Location Predicted Change For Years 0 – 20 (2025) Years 20 – 50 (2055) Years 50 – 100 (2105) Taylors No defences No defences No defences Island to Point The evolution of this coast will The evolution of this coast The evolution of this coast be typical of the islands, as will be typical of the islands, will be typical of the islands, described above. as described above. as described above. Porth Hellick Embankment Degraded embankment Degraded embankment The shoreline will continue to Ongoing sea level rise will Ongoing sea level rise will retreat. This will tend to tend to narrow the beach and continue to narrow the beach happen at a higher rate, increase wave loading on the and increase wave loading although this increase should embankment, increasing on the embankment and its be difficult to distinguish from recession rates. erosion. This will release natural variability. some additional material into the beach, although this will only partly mitigate the overall narrowing of the intertidal zone. Pig Rock to No defences No defences No defences Tolman Point The evolution of this coast will The evolution of this coast The evolution of this coast be typical of the islands, as will be typical of the islands, will be typical of the islands, described above. as described above. as described above. Porth Minick Revetment No defences No defences The shoreline will continue to Ongoing sea level rise will Ongoing sea level rise will retreat. This will tend to tend to narrow the beach and continue to narrow the beach happen at a higher rate, increase wave loading on the and increase wave loading although this increase should cliffs, increasing recession on the cliff toe. Cliff retreat be difficult to distinguish from rates. will increase, creating new natural variability. shore platform. This will to release additional sediments into the beach, although this will only partly mitigate the overall narrowing of the intertidal zone. Old Town Seawalls No defences No defences Bay The shoreline will continue to Ongoing sea level rise will Ongoing sea level rise will retreat where it is not tend to narrow the beach and continue to narrow the beach defended. This will tend to increase wave loading on the and increase wave loading happen at a higher rate, cliffs, increasing recession on the cliff toe. Cliff retreat although this increase should rates. Failure of the will increase, creating new be difficult to distinguish from structures will be followed by shore platform. This will to natural variability. In front of a period of accelerated release additional sediments

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 135 February 2011

defended areas the water recession, as more natural into the beach, although this depth will tend to increase, as shore profiles are reformed. will only partly mitigate the foreshores lower and sea overall narrowing of the levels rise. intertidal zone. Carn Leh to No defences No defences No defences Nicholl’s Rock The evolution of this coast will The evolution of this coast The evolution of this coast be typical of the islands, as will be typical of the islands, will be typical of the islands, described above. as described above. as described above. Porth Cressa Seawalls No defences No defences The beach will continue to Failure of the coastal Accelerated relative sea level narrow. The coastal defences structures will be followed by rise will continue to cause the will prevent recession and so a transient period of beach to roll back, at cause the shoreline to be accelerated recession, as increasing rates. Continued increasingly seaward of its waves attack over-steepened erosion will release fresh natural position. The shore profiles. This will sediments that will defences will also prevent the release sedimentary material, accumulate and provide formation of new shore some of which will some protection to wave platform and reduce the accumulate in the beach. The attack. release of material for the beach will begin to roll back beach. Relative lowering of and this will mitigate, the rock foreshore and beach although not prevent, will allow larger, more narrowing of the intertidal aggressive waves to reach zone due to sea level rise. the structures. Garrison Breakwater Breakwater Breakwater farm to Rat Island Erosion will continue and will Erosion will accelerate as Accelerated relative sea level tend to be accelerated by rising seas allow larger rise will continue to increase rising seas, although this waves to attack the cliffs. wave activity at the shore. increase is likely to be difficult Wave run-up and impacts on The shore platform will be to distinguish from natural the cliff face. submerged for a greater variability. proportion of the tide, and so access will be reduced. Wave impacts on the cliff face will continue to increase, causing higher shore recession rates. Town Beach Seawalls No defences No defences The shoreline will be held by Failure of the structures will Ongoing sea level rise will the defences and the beach be followed by a period of continue to drive the beach will tend to retreat slightly. accelerated recession, as landward. Sediments more natural profiles are released by recession and reformed. Sea level rise will the formation of new shore drive further retreat of the platform will mitigate the beach. effects of the rising seas to some degree.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 136 February 2011

Porth Mellon Dune embankment No defences No defences Where defended, the Failure of the structures will Ongoing sea level rise will shoreline will be held and the be followed by a period of continue to drive the beach beach will tend to retreat accelerated recession, as landward. Sediments slightly. more natural profiles are released by recession and reformed. Sea level rise will the formation of new shore drive further retreat and platform will mitigate the narrowing of the beach. effects of the rising seas to some degree. Thomas No defences No defences No defences Porth The evolution of this coast will Ongoing sea level rise will Ongoing sea level rise will be typical of the region, as further narrow the beach, continue to narrow the beach described above. The beach increasing the period that the and increase wave loading will begin to narrow as the cliff toe is submerged at high on the cliff toe. Cliff retreat sea level rises. tide. Wave loading on the cliff will increase, creating new toe will increase. shore platform. Porth Loo Rock revetment No defences No defences The beach will continue to Failure of the coastal Accelerated relative sea level narrow. The coastal defences structures will be followed by rise will continue to cause the will prevent recession and so a transient period of beach to roll back, at cause the shoreline to be accelerated recession, as increasing rates. Continued increasingly seaward of its waves attack over-steepened erosion will release fresh natural position. The shore profiles. This will sediments that will defences will also prevent the release sedimentary material, accumulate and provide formation of new shore some of which will some protection to wave platform and reduce the accumulate in the beach. The attack. release of material for the beach will begin to roll back beach. Relative lowering of and this will mitigate, the rock foreshore and beach although not prevent, will allow larger, more narrowing of the intertidal aggressive waves to reach zone due to sea level rise. the structures.

20.3 St Mary’s unit details – With Present Management

Location Predicted Change For Years 0 – 20 (2025) Years 20 – 50 (2055) Years 50 – 100 (2105) Taylors No defences No defences No defences Island to Porth Hellick Point The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the islands, will be typical of the islands, will be typical of the islands, as described above. as described above. as described above. Porth Hellick Embankment Embankment Embankment The shoreline will continue to Ongoing sea level rise will Ongoing sea level rise will retreat. This will tend to tend to narrow the beach and continue to narrow the beach happen at a higher rate, increase wave loading on the and increase wave loading

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 137 February 2011

although this increase should embankment. on the embankment. be difficult to distinguish from Because the embankment natural variability. fixes the shoreline, the intertidal zone will narrow. Pig Rock to No defences No defences No defences Tolman Point The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the islands, will be typical of the islands, will be typical of the islands, as described above. as described above. as described above. Porth Minick Revetment Revetment Revetment The shoreline will continue to Ongoing sea level rise will Ongoing sea level rise will retreat. This will tend to tend to narrow the beach and continue to narrow the beach happen at a higher rate, increase wave loading on the and increase wave loading although this increase should cliffs, increasing recession on the cliff toe. Cliff retreat be difficult to distinguish from rates. will increase, creating new natural variability. shore platform. This will to release additional sediments into the beach, although this will only partly mitigate the overall narrowing of the intertidal zone. Old Town Seawalls Seawalls Seawalls Bay The shoreline will continue to Ongoing sea level rise will Ongoing sea level rise will retreat where it is not tend to narrow the beach and continue to narrow the beach defended. This will tend to increase wave loading on the and increase wave loading happen at a higher rate, cliffs, where they are not on the cliff toe. Cliff retreat although this increase should defended, increasing will increase, creating new be difficult to distinguish from recession rates. Water shore platform. This will to natural variability. In front of depths will continue to release additional sediments defended areas the water increase, in front of the into the beach, and new depth will tend to increase, as structures, increasing wave shore platform will be formed, foreshores lower and sea loads on them. although this will only partly levels rise. mitigate overall narrowing of the intertidal zone. In defended areas the intertidal zone will narrow more sharply, decreasing the period during which they can be accessed at low tide. Wave loading on the structures will increase. Carn Leh to No defences No defences No defences Nicholl’s Rock The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the islands, will be typical of the islands, will be typical of the islands, as described above. as described above. as described above.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 138 February 2011

Porth Cressa Seawalls Seawalls Seawalls The beach will continue to The trend seen in the prior The trend seen in the prior narrow. The coastal defences epoch will continue. epoch will continue. Wave will prevent recession and so impact forces and cause the shoreline to be overtopping will grow at an increasingly seaward of its exponential rate, natural position. The necessitating larger defences will also prevent the structures to maintain current formation of new shore levels of defence. Beach platform and reduce the accessibility will reduce as release of material for the the sea level rises. beach. Relative lowering of the rock foreshore and beach will allow larger, more aggressive waves to reach the structures.

Garrison No defences No defences No defences farm to Rat Island Erosion will continue and will Erosion will accelerate as Accelerated relative sea level tend to be accelerated by rising seas allow larger rise will continue to increase rising seas, although this waves to attack the cliffs. wave activity at the shore. increase is likely to be difficult Wave run-up and impacts on The shore platform will be to distinguish from natural the cliff face. submerged for a greater variability. proportion of the tide, and so access will be reduced. Wave impacts on the cliff face will continue to increase, causing higher shore recession rates. Town Beach Seawalls Seawalls Seawalls The beach will tend to narrow The trend seen in the prior The trend seen in the prior slightly. The defences will epoch will continue. epoch will continue. Wave prevent recession and so impact forces and cause the shoreline to be overtopping will grow at an somewhat seaward of its exponential rate, natural position. The necessitating larger defences will also prevent the structures to maintain current formation of new shore levels of defence. Beach platform and reduce the accessibility will reduce as release of material for the the sea level rises. beach. Relative lowering of the rock foreshore and beach will allow larger, more aggressive waves to reach the structures. Porth Mellon Dune embankment Dune embankment Dune embankment The beach will tend to narrow The trend seen in the prior The trend seen in the prior slightly. The defences will epoch will continue. Erosive epoch will continue. Wave

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 139 February 2011

prevent recession and so processes adjacent to the impact forces on the cause the shoreline to be defences will tend to cause structures and overtopping somewhat seaward of its outflanking. rates will grow at an natural position. The exponential rate, defences will also prevent the necessitating larger formation of new shore structures to maintain current platform and reduce the levels of defence. Beach release of material for the accessibility will reduce as beach. Relative lowering of the sea level rises. the rock foreshore and beach Outflanking processes will will allow larger, more continue, possibly aggressive waves to reach necessitating an increase in the structures. structure length. Thomas No defences No defences No defences Porth Coastal evolution will be Ongoing sea level rise will Ongoing sea level rise will typical of the region as further narrow the beach, continue to narrow the beach described above. The beach increasing the period that the and increase wave loading will begin to narrow as the cliff toe is submerged at high on the cliff toe. Cliff retreat sea level rises. tide. Wave loading on the cliff will increase, creating new toe will increase. shore platform. Porth Loo Rock revetment Rock revetment Rock revetment The beach will continue to The trend seen in the prior The trend seen in the prior narrow. The coastal defences epoch will continue. epoch will continue. Wave will prevent recession and so impact forces and cause the shoreline to be overtopping will grow at an increasingly seaward of its exponential rate, natural position. The necessitating larger defences will also prevent the structures to maintain current formation of new shore levels of defence. Beach platform and reduce the accessibility will reduce as release of material for the the sea level rises. beach. Relative lowering of the rock foreshore and beach will allow larger, more aggressive waves to reach the structures.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 140 February 2011

20.4 St Agnes and Gough unit details – No Active Intervention

Location Predicted Change For Years 0 – 20 (2025) Years 20 – 50 (2055) Years 50 – 100 (2105) Porth Killer Seawall No defences No defences Where defended, the Failure of the structures will Ongoing sea level rise will shoreline will be held and the be followed by a period of continue to drive the beach beach will tend to retreat accelerated recession, as landward. Sediments slightly. more natural profiles are released by recession and reformed. Sea level rise will the formation of new shore drive further retreat and platform will mitigate the narrowing of the beach. effects of the rising seas to some degree. Killimay Point Quay walls Quay walls Quay walls to the Bar The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the islands, will be typical of the islands, will be typical of the islands, as described above. as described above. as described above. The Bar No defences No defences No defences The bar will persist The bar will persist The bar will persist essentially unchanged in essentially unchanged in essentially unchanged in character. character. Sea level rise will character. Sea level rise will causing a raising and reduce the time that it is narrowing of its crest. revealed by the tide.. The Bar to No defences No defences No defences Dropnose Porth The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the islands, will be typical of the islands, will be typical of the islands, as described above. as described above. as described above. Dropnose No defences No defences No defences Porth The evolution of this coast Ongoing sea level rise will Ongoing sea level rise will will be typical of the region, further narrow the beach, continue to narrow the beach as described above. The increasing the period that the and increase wave loading beach will begin to narrow as cliff toe is submerged at high on the cliff toe. Cliff retreat the sea level rises. tide. Wave loading on the cliff will increase, creating new toe will increase. shore platform. Dropnose No defences No defences No defences Point to The Bite The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the islands, will be typical of the islands, will be typical of the islands, as described above. as described above. as described above. The Bite No defences No defences No defences The evolution of this coast Ongoing sea level rise will Ongoing sea level rise will will be typical of the region, further narrow the beach, continue to narrow the beach as described above. The increasing the period that the and increase wave loading beach will begin to narrow as cliff toe is submerged at high on the cliff toe. Cliff retreat

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 141 February 2011

the sea level rises. tide. Wave loading on the cliff will increase, creating new toe will increase. shore platform. The Bar to No defences No defences No defences Cove vean The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the islands, will be typical of the islands, will be typical of the islands, as described above. as described above. as described above. Cove Vean No defences No defences No defences The evolution of this coast Ongoing sea level rise will Ongoing sea level rise will will be typical of the region, further narrow the beach, continue to narrow the beach as described above. The increasing the period that the and increase wave loading beach will begin to narrow as cliff toe is submerged at high on the cliff toe. Cliff retreat the sea level rises. tide. Wave loading on the cliff will increase, creating new toe will increase. shore platform. Cove Vean No defences No defences No defences to Wingletang bay The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the islands, will be typical of the islands, will be typical of the islands, as described above. as described above. as described above. Wingletang No defences No defences No defences Bay The evolution of this coast Ongoing sea level rise will Ongoing sea level rise will will be typical of the region, further narrow the beach, continue to narrow the beach as described above. The increasing the period that the and increase wave loading beach will begin to narrow as cliff toe is submerged at high on the cliff toe. Cliff retreat the sea level rises. tide. Wave loading on the cliff will increase, creating new toe will increase. shore platform. Wingletang No defences No defences No defences Bay to Porth Askin The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the islands, will be typical of the islands, will be typical of the islands, as described above. as described above. as described above. Porth Askin No defences No defences No defences The evolution of this coast Ongoing sea level rise will Ongoing sea level rise will will be typical of the region, further narrow the beach, continue to narrow the beach as described above. The increasing the period that the and increase wave loading beach will begin to narrow as cliff toe is submerged at high on the cliff toe. Cliff retreat the sea level rises. tide. Wave loading on the cliff will increase, creating new toe will increase. shore platform. Porth Askin No defences No defences No defences to Periglis The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the islands, will be typical of the islands, will be typical of the islands, as described above. as described above. as described above.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 142 February 2011

Periglis and No defences No defences No defences Porth Coose The shoreline will continue to Ongoing sea level rise will Ongoing sea level rise will retreat. This will tend to tend to narrow the beach and continue to narrow the beach happen at a higher rate, increase wave loading on the and increase wave loading although this increase should embankment, increasing on the embankment and its be difficult to distinguish from recession rates. erosion. This will release natural variability. some additional material into the beach, although this will only partly mitigate the overall narrowing of the intertidal zone. Porth Coose Flood defence embankment Degraded flood defence Degraded flood defence to Porth Killer embankment embankment The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the islands, will be typical of the islands, will be typical of the islands, as described above. as described above. as described above.

20.5 St Agnes and Gough unit details – With Present Management

Location Predicted Change For Years 0 – 20 (2025) Years 20 – 50 (2055) Years 50 – 100 (2105) Porth Killer Seawall Seawall Seawall The beach will tend to narrow The trend seen in the prior The trend seen in the prior slightly. The defences will epoch will continue. Erosive epoch will continue. Wave prevent recession and so processes adjacent to the impact forces on the cause the shoreline to be defences will tend to cause structures and overtopping somewhat seaward of its outflanking. rates will grow at an natural position. The exponential rate, defences will also prevent the necessitating larger formation of new shore structures to maintain current platform and reduce the levels of defence. Beach release of material for the accessibility will reduce as beach. Relative lowering of the sea level rises. the rock foreshore and beach Outflanking processes will will allow larger, more continue, possibly aggressive waves to reach necessitating an increase in the structures. structure length. Killimay Point Quay walls Quay walls Quay walls to the Bar The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the islands, will be typical of the islands, will be typical of the islands, as described above. as described above. as described above. The Bar No defences No defences No defences The bar will persist The bar will persist The bar will persist essentially unchanged in essentially unchanged in essentially unchanged in character. character. Sea level rise will character. Sea level rise will causing raising and reduce the time that it is narrowing of its crest. revealed by the tide..

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 143 February 2011

The Bar to No defences No defences No defences Dropnose Porth The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the islands, will be typical of the islands, will be typical of the islands, as described above. as described above. as described above. Dropnose No defences No defences No defences Porth Coastal evolution will be Ongoing sea level rise will Ongoing sea level rise will typical of the region as further narrow the beach, continue to narrow the beach described above. The beach increasing the period that the and increase wave loading will begin to narrow as the cliff toe is submerged at high on the cliff toe. Cliff retreat sea level rises. tide. Wave loading on the cliff will increase, creating new toe will increase. shore platform. Dropnose No defences No defences No defences Point to The Bite The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the islands, will be typical of the islands, will be typical of the islands, as described above. as described above. as described above. The Bite No defences No defences No defences Coastal evolution will be Ongoing sea level rise will Ongoing sea level rise will typical of the region as further narrow the beach, continue to narrow the beach described above. The beach increasing the period that the and increase wave loading will begin to narrow as the cliff toe is submerged at high on the cliff toe. Cliff retreat sea level rises. tide. Wave loading on the cliff will increase, creating new toe will increase. shore platform. The Bar to No defences No defences No defences Cove vean The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the islands, will be typical of the islands, will be typical of the islands, as described above. as described above. as described above. Cove Vean No defences No defences No defences Coastal evolution will be Ongoing sea level rise will Ongoing sea level rise will typical of the region as further narrow the beach, continue to narrow the beach described above. The beach increasing the period that the and increase wave loading will begin to narrow as the cliff toe is submerged at high on the cliff toe. Cliff retreat sea level rises. tide. Wave loading on the cliff will increase, creating new toe will increase. shore platform. Cove Vean No defences No defences No defences to Wingletang bay The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the islands, will be typical of the islands, will be typical of the islands, as described above. as described above. as described above. Wingletang No defences No defences No defences Bay Coastal evolution will be Ongoing sea level rise will Ongoing sea level rise will

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 144 February 2011

typical of the region as further narrow the beach, continue to narrow the beach described above. The beach increasing the period that the and increase wave loading will begin to narrow as the cliff toe is submerged at high on the cliff toe. Cliff retreat sea level rises. tide. Wave loading on the cliff will increase, creating new toe will increase. shore platform. Wingletang No defences No defences No defences Bay to Porth Askin The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the islands, will be typical of the islands, will be typical of the islands, as described above. as described above. as described above. Porth Askin No defences No defences No defences Coastal evolution will be Ongoing sea level rise will Ongoing sea level rise will typical of the region as further narrow the beach, continue to narrow the beach described above. The beach increasing the period that the and increase wave loading will begin to narrow as the cliff toe is submerged at high on the cliff toe. Cliff retreat sea level rises. tide. Wave loading on the cliff will increase, creating new toe will increase. shore platform. Porth Askin No defences No defences No defences to Periglis The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the islands, will be typical of the islands, will be typical of the islands, as described above. as described above. as described above. Periglis and No defences No defences No defences Porth Coose The shoreline will continue to Ongoing sea level rise will Ongoing sea level rise will retreat. This will tend to tend to narrow the beach and continue to narrow the beach happen at a higher rate, increase wave loading on the and increase wave loading although this increase should embankment. on the embankment. be difficult to distinguish from Because the embankment natural variability. fixes the shoreline, the intertidal zone will narrow. Porth Coose Flood defence embankment Flood defence embankment Flood defence embankment to Porth Killer The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the islands, will be typical of the islands, will be typical of the islands, as described above. as described above. as described above.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 145 February 2011

20.6 Tresco and Byher unit details – No Active Intervention

Location Predicted Change For Years 0 – 20 (2025) Years 20 – 50 (2055) Years 50 – 100 (2105) Square Rock No defences No defences No defences to Kitchen Porth The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the islands, will be typical of the islands, will be typical of the islands, as described above. as described above. as described above. Kitchen Porth No defences No defences No defences The evolution of this coast Ongoing sea level rise will Ongoing sea level rise will will be typical of the region, further narrow the beach, continue to narrow the beach as described above. The increasing the period that the and increase wave loading beach will begin to narrow as cliff toe is submerged at high on the cliff toe. Cliff retreat the sea level rises. tide. Wave loading on the cliff will increase, creating new toe will increase. shore platform. Tresco Flats Ferry Quay Ferry Quay Ferry Quay The evolution of this coast Ongoing sea level rise will Ongoing sea level rise will will be typical of the region, further narrow the beach, continue to narrow the beach as described above. The increasing the period that the and increase wave loading beach will begin to narrow as cliff toe is submerged at high on the cliff toe. Cliff retreat the sea level rises. tide. Wave loading on the cliff will increase, creating new toe will increase. shore platform. Green Bay No defences No defences No defences The shoreline will continue to Ongoing sea level rise will Ongoing sea level rise will retreat. This will tend to tend to narrow the beach and continue to narrow the beach happen at a higher rate, increase wave loading on the and increase wave loading although this increase should cliffs, increasing recession on the cliff toe. Cliff retreat be difficult to distinguish from rates. will increase, creating new natural variability. shore platform. This will to release additional sediments into the beach, although this will only partly mitigate the overall narrowing of the intertidal zone. Green bay to No defences No defences No defences Rushy Bay The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the islands, will be typical of the islands, will be typical of the islands, as described above. as described above. as described above. Rushy bay No defences No defences No defences and Stony Porth The shoreline will continue to Ongoing sea level rise will Ongoing sea level rise will retreat. This will tend to tend to narrow the beach and continue to narrow the beach happen at a higher rate, increase wave loading on the and increase wave loading although this increase should cliffs, increasing recession on the cliff toe. Cliff retreat be difficult to distinguish from rates. will increase, creating new

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 146 February 2011

natural variability. shore platform. This will to release additional sediments into the beach, although this will only partly mitigate the overall narrowing of the intertidal zone. Stony Porth No defences No defences No defences to Great Porth The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the islands, will be typical of the islands, will be typical of the islands, as described above. as described above. as described above. Great Porth No defences No defences No defences south The evolution of this coast Ongoing sea level rise will Ongoing sea level rise will will be typical of the region, further narrow the beach, continue to narrow the beach as described above. The increasing the period that the and increase wave loading beach will begin to narrow as cliff toe is submerged at high on the cliff toe. Cliff retreat the sea level rises. tide. Wave loading on the cliff will increase, creating new toe will increase. shore platform. Great Porth Rock defences No defences No defences north The shoreline will continue to Ongoing sea level rise will Ongoing sea level rise will retreat where it is not tend to narrow the beach and continue to narrow the beach defended. This will tend to increase wave loading on the and increase wave loading happen at a higher rate, cliffs, increasing recession on the cliff toe. Cliff retreat although this increase should rates. Failure of the will increase, creating new be difficult to distinguish from structures will be followed by shore platform. This will to natural variability. In front of a period of accelerated release additional sediments defended areas the water recession, as more natural into the beach, although this depth will tend to increase, as shore profiles are reformed. will only partly mitigate the foreshores lower and sea overall narrowing of the levels rise. intertidal zone. Stinking No defences No defences No defences Porth The evolution of this coast Ongoing sea level rise will Ongoing sea level rise will will be typical of the region, further narrow the beach, continue to narrow the beach as described above. The increasing the period that the and increase wave loading beach will begin to narrow as cliff toe is submerged at high on the cliff toe. Cliff retreat the sea level rises. tide. Wave loading on the cliff will increase, creating new toe will increase. shore platform. Stinking No defences No defences No defences Porth to Great Popplestone s The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the islands, will be typical of the islands, will be typical of the islands, as described above. as described above. as described above.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 147 February 2011

Great Rock defences No defences No defences Popplestone s Where defended, the Failure of the structures will Ongoing sea level rise will shoreline will be held and the be followed by a period of continue to drive the beach beach will tend to retreat accelerated recession, as landward. Sediments slightly. more natural profiles are released by recession and reformed. Sea level rise will the formation of new shore drive further retreat and platform will mitigate the narrowing of the beach. effects of the rising seas to some degree. New Grimsby No defences No defences No defences to Merchant’s Rock The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the islands, will be typical of the islands, will be typical of the islands, as described above. as described above. as described above. Raven’s Quay No defences No defences Porth The shoreline will continue to Ongoing sea level rise will Ongoing sea level rise will retreat where it is not tend to narrow the beach and continue to narrow the beach defended. This will tend to increase wave loading on the and increase wave loading happen at a higher rate, cliffs, increasing recession on the cliff toe. Cliff retreat although this increase should rates. Failure of the will increase, creating new be difficult to distinguish from structures will be followed by shore platform. This will to natural variability. In front of a period of accelerated release additional sediments defended areas the water recession, as more natural into the beach, although this depth will tend to increase, as shore profiles are reformed. will only partly mitigate the foreshores lower and sea overall narrowing of the levels rise. intertidal zone. Green Porth No defences No defences No defences The evolution of this coast Ongoing sea level rise will Ongoing sea level rise will will be typical of the region, further narrow the beach, continue to narrow the beach as described above. The increasing the period that the and increase wave loading beach will begin to narrow as cliff toe is submerged at high on the cliff toe. Cliff retreat the sea level rises. tide. Wave loading on the cliff will increase, creating new toe will increase. shore platform. Borough No defences No defences No defences Beach The shoreline will continue to Ongoing sea level rise will Ongoing sea level rise will retreat. This will tend to tend to narrow the beach and continue to narrow the beach happen at a higher rate, increase wave loading on the and increase wave loading although this increase should cliffs, increasing recession on the cliff toe. Cliff retreat be difficult to distinguish from rates. will increase, creating new natural variability. shore platform. This will to release additional sediments into the beach, although this will only partly mitigate the overall narrowing of the

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 148 February 2011

intertidal zone. Rushy Point No defences No defences No defences to Skirt Island The shoreline will continue to Ongoing sea level rise will Ongoing sea level rise will retreat. This will tend to tend to narrow the beach and continue to narrow the beach happen at a higher rate, increase wave loading on the and increase wave loading although this increase should cliffs, increasing recession on the cliff toe. Cliff retreat be difficult to distinguish from rates. will increase, creating new natural variability. shore platform. This will to release additional sediments into the beach, although this will only partly mitigate the overall narrowing of the intertidal zone. Skirt Island No defences No defences No defences to Crow Point The evolution of this coast Ongoing sea level rise will Ongoing sea level rise will will be typical of the region, further narrow the beach, continue to narrow the beach as described above. The increasing the period that the and increase wave loading beach will begin to narrow as cliff toe is submerged at high on the cliff toe. Cliff retreat the sea level rises. tide. Wave loading on the cliff will increase, creating new toe will increase. shore platform. Appletree No defences No defences No defences Bay The shoreline will continue to Ongoing sea level rise will Ongoing sea level rise will retreat. This will tend to tend to narrow the beach and continue to narrow the beach happen at a higher rate, increase wave loading on the and increase wave loading although this increase should cliffs, increasing recession on the cliff toe. Cliff retreat be difficult to distinguish from rates. will increase, creating new natural variability. shore platform. This will to release additional sediments into the beach, although this will only partly mitigate the overall narrowing of the intertidal zone. Appletree No defences No defences No defences Carn to Plumb Hill Erosion will continue and will Erosion will accelerate as Accelerated relative sea level tend to be accelerated by rising seas allow larger rise will continue to increase rising seas, although this waves to attack the cliffs. wave activity at the shore. increase is likely to be difficult Wave run-up and impacts on The shore platform will be to distinguish from natural the cliff face. submerged for a greater variability. proportion of the tide, and so access will be reduced. Wave impacts on the cliff face will continue to increase, causing higher shore recession rates.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 149 February 2011

New Grimsby Quay wall and seawall Quay wall Quay wall The shoreline will continue to Ongoing sea level rise will Ongoing sea level rise will retreat where it is not tend to narrow the beach and continue to narrow the beach defended. This will tend to increase wave loading on the and increase wave loading happen at a higher rate, cliffs, increasing recession on the cliff toe. Cliff retreat although this increase should rates. Failure of the will increase, creating new be difficult to distinguish from structures will be followed by shore platform. This will to natural variability. In front of a period of accelerated release additional sediments defended areas the water recession, as more natural into the beach, although this depth will tend to increase, as shore profiles are reformed. will only partly mitigate the foreshores lower and sea overall narrowing of the levels rise. intertidal zone.

20.7 Tresco and Byher unit details – With Present Management

Location Predicted Change For Years 0 – 20 (2025) Years 20 – 50 (2055) Years 50 – 100 (2105) Square Rock No defences No defences No defences to Kitchen Porth The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the islands, will be typical of the islands, will be typical of the islands, as described above. as described above. as described above. Kitchen Porth No defences No defences No defences Coastal evolution will be Ongoing sea level rise will Ongoing sea level rise will typical of the region as further narrow the beach, continue to narrow the beach described above. The beach increasing the period that the and increase wave loading will begin to narrow as the cliff toe is submerged at high on the cliff toe. Cliff retreat sea level rises. tide. Wave loading on the cliff will increase, creating new toe will increase. shore platform. Tresco Flats Ferry Quay Ferry Quay Ferry Quay Coastal evolution will be Ongoing sea level rise will Ongoing sea level rise will typical of the region as further narrow the beach, continue to narrow the beach described above. The beach increasing the period that the and increase wave loading will begin to narrow as the cliff toe is submerged at high on the cliff toe. Cliff retreat sea level rises. tide. Wave loading on the cliff will increase, creating new toe will increase. shore platform. Green Bay No defences No defences No defences The shoreline will continue to Ongoing sea level rise will Ongoing sea level rise will retreat. This will tend to tend to narrow the beach and continue to narrow the beach happen at a higher rate, increase wave loading on the and increase wave loading although this increase should cliffs, increasing recession on the cliff toe. Cliff retreat be difficult to distinguish from rates. will increase, creating new natural variability. shore platform. This will to release additional sediments into the beach, although this

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 150 February 2011

will only partly mitigate the overall narrowing of the intertidal zone. Green bay to No defences No defences No defences Rushy Bay The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the islands, will be typical of the islands, will be typical of the islands, as described above. as described above. as described above. Rushy bay No defences No defences No defences and Stony Porth The shoreline will continue to Ongoing sea level rise will Ongoing sea level rise will retreat. This will tend to tend to narrow the beach and continue to narrow the beach happen at a higher rate, increase wave loading on the and increase wave loading although this increase should cliffs, increasing recession on the cliff toe. Cliff retreat be difficult to distinguish from rates. will increase, creating new natural variability. shore platform. This will to release additional sediments into the beach, although this will only partly mitigate the overall narrowing of the intertidal zone. Stony Porth No defences No defences No defences to Great Porth The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the islands, will be typical of the islands, will be typical of the islands, as described above. as described above. as described above. Great Porth No defences No defences No defences south Coastal evolution will be Ongoing sea level rise will Ongoing sea level rise will typical of the region as further narrow the beach, continue to narrow the beach described above. The beach increasing the period that the and increase wave loading will begin to narrow as the cliff toe is submerged at high on the cliff toe. Cliff retreat sea level rises. tide. Wave loading on the cliff will increase, creating new toe will increase. shore platform. Great Porth Rock defences Rock defences Rock defences north The shoreline will continue to Ongoing sea level rise will Ongoing sea level rise will retreat where it is not tend to narrow the beach and continue to narrow the beach defended. This will tend to increase wave loading on the and increase wave loading happen at a higher rate, cliffs, where they are not on the cliff toe. Cliff retreat although this increase should defended, increasing will increase, creating new be difficult to distinguish from recession rates. Water shore platform. This will to natural variability. In front of depths will continue to release additional sediments defended areas the water increase, in front of the into the beach, and new depth will tend to increase, as structures, increasing wave shore platform will be formed, foreshores lower and sea loads on them. although this will only partly levels rise. mitigate overall narrowing of

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 151 February 2011

the intertidal zone. In defended areas the intertidal zone will narrow more sharply, decreasing the period during which they can be accessed at low tide. Wave loading on the structures will increase. Stinking No defences No defences No defences Porth Coastal evolution will be Ongoing sea level rise will Ongoing sea level rise will typical of the region as further narrow the beach, continue to narrow the beach described above. The beach increasing the period that the and increase wave loading will begin to narrow as the cliff toe is submerged at high on the cliff toe. Cliff retreat sea level rises. tide. Wave loading on the cliff will increase, creating new toe will increase. shore platform. Stinking No defences No defences No defences Porth to Great Popplestone s The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the islands, will be typical of the islands, will be typical of the islands, as described above. as described above. as described above. Great Rock defences Rock defences Rock defences Popplestone s The beach will tend to narrow The trend seen in the prior The trend seen in the prior slightly. The defences will epoch will continue. Erosive epoch will continue. Wave prevent recession and so processes adjacent to the impact forces on the cause the shoreline to be defences will tend to cause structures and overtopping somewhat seaward of its outflanking. rates will grow at an natural position. The exponential rate, defences will also prevent the necessitating larger formation of new shore structures to maintain current platform and reduce the levels of defence. Beach release of material for the accessibility will reduce as beach. Relative lowering of the sea level rises. the rock foreshore and beach Outflanking processes will will allow larger, more continue, possibly aggressive waves to reach necessitating an increase in the structures. structure length. New Grimsby No defences No defences No defences to Merchant’s Rock The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the islands, will be typical of the islands, will be typical of the islands, as described above. as described above. as described above.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 152 February 2011

Raven’s Quay Quay Quay Porth The shoreline will continue to Ongoing sea level rise will Ongoing sea level rise will retreat where it is not tend to narrow the beach and continue to narrow the beach defended. This will tend to increase wave loading on the and increase wave loading happen at a higher rate, cliffs, where they are not on the cliff toe. Cliff retreat although this increase should defended, increasing will increase, creating new be difficult to distinguish from recession rates. Water shore platform. This will to natural variability. In front of depths will continue to release additional sediments defended areas the water increase, in front of the into the beach, and new depth will tend to increase, as structures, increasing wave shore platform will be formed, foreshores lower and sea loads on them. although this will only partly levels rise. mitigate overall narrowing of the intertidal zone. In defended areas the intertidal zone will narrow more sharply, decreasing the period during which they can be accessed at low tide. Wave loading on the structures will increase. Green Porth No defences No defences No defences Coastal evolution will be Ongoing sea level rise will Ongoing sea level rise will typical of the region as further narrow the beach, continue to narrow the beach described above. The beach increasing the period that the and increase wave loading will begin to narrow as the cliff toe is submerged at high on the cliff toe. Cliff retreat sea level rises. tide. Wave loading on the cliff will increase, creating new toe will increase. shore platform. Borough No defences No defences No defences Beach The shoreline will continue to Ongoing sea level rise will Ongoing sea level rise will retreat. This will tend to tend to narrow the beach and continue to narrow the beach happen at a higher rate, increase wave loading on the and increase wave loading although this increase should cliffs, increasing recession on the cliff toe. Cliff retreat be difficult to distinguish from rates. will increase, creating new natural variability. shore platform. This will to release additional sediments into the beach, although this will only partly mitigate the overall narrowing of the intertidal zone. Rushy Point No defences No defences No defences to Skirt Island The shoreline will continue to Ongoing sea level rise will Ongoing sea level rise will retreat. This will tend to tend to narrow the beach and continue to narrow the beach happen at a higher rate, increase wave loading on the and increase wave loading although this increase should cliffs, increasing recession on the cliff toe. Cliff retreat be difficult to distinguish from rates. will increase, creating new

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 153 February 2011

natural variability. shore platform. This will to release additional sediments into the beach, although this will only partly mitigate the overall narrowing of the intertidal zone. Skirt Island No defences No defences No defences to Crow Point Coastal evolution will be Ongoing sea level rise will Ongoing sea level rise will typical of the region as further narrow the beach, continue to narrow the beach described above. The beach increasing the period that the and increase wave loading will begin to narrow as the cliff toe is submerged at high on the cliff toe. Cliff retreat sea level rises. tide. Wave loading on the cliff will increase, creating new toe will increase. shore platform. Appletree No defences No defences No defences Bay The shoreline will continue to Ongoing sea level rise will Ongoing sea level rise will retreat. This will tend to tend to narrow the beach and continue to narrow the beach happen at a higher rate, increase wave loading on the and increase wave loading although this increase should cliffs, increasing recession on the cliff toe. Cliff retreat be difficult to distinguish from rates. will increase, creating new natural variability. shore platform. This will to release additional sediments into the beach, although this will only partly mitigate the overall narrowing of the intertidal zone. Appletree No defences No defences No defences Carn to Plumb Hill Erosion will continue and will Erosion will accelerate as Accelerated relative sea level tend to be accelerated by rising seas allow larger rise will continue to increase rising seas, although this waves to attack the cliffs. wave activity at the shore. increase is likely to be difficult Wave run-up and impacts on The shore platform will be to distinguish from natural the cliff face. submerged for a greater variability. proportion of the tide, and so access will be reduced. Wave impacts on the cliff face will continue to increase, causing higher shore recession rates. New Grimsby Quay wall and seawall Quay wall and seawall Quay wall and seawall The shoreline will continue to Ongoing sea level rise will Ongoing sea level rise will retreat where it is not tend to narrow the beach and continue to narrow the beach defended. This will tend to increase wave loading on the and increase wave loading happen at a higher rate, cliffs, where they are not on the cliff toe. Cliff retreat although this increase should defended, increasing will increase, creating new be difficult to distinguish from recession rates. Water shore platform. This will to natural variability. In front of depths will continue to release additional sediments defended areas the water increase, in front of the into the beach, and new

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 154 February 2011

depth will tend to increase, as structures, increasing wave shore platform will be formed, foreshores lower and sea loads on them. although this will only partly levels rise. mitigate overall narrowing of the intertidal zone. In defended areas the intertidal zone will narrow more sharply, decreasing the period during which they can be accessed at low tide. Wave loading on the structures will increase.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 155 February 2011

20.8 St Martins unit details – No Active Intervention

Location Predicted Change For Years 0 – 20 (2025) Years 20 – 50 (2055) Years 50 – 100 (2105) Goats Point No defences No defences No defences to Scilly Point The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the islands, will be typical of the islands, will be typical of the islands, as described above. as described above. as described above. St Martin’s No defences No defences No defences Bay The evolution of this coast Ongoing sea level rise will Ongoing sea level rise will will be typical of the region, further narrow the beach, continue to narrow the beach as described above. The increasing the period that the and increase wave loading beach will begin to narrow as cliff toe is submerged at high on the cliff toe. Cliff retreat the sea level rises. tide. Wave loading on the cliff will increase, creating new toe will increase. shore platform. Turfy Hill to No defences No defences No defences Brandy Point Carn The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the islands, will be typical of the islands, will be typical of the islands, as described above. as described above. as described above. Perpitch No defences No defences No defences The shoreline will continue to Ongoing sea level rise will Ongoing sea level rise will retreat. This will tend to tend to narrow the beach and continue to narrow the beach happen at a higher rate, increase wave loading on the and increase wave loading although this increase should cliffs, increasing recession on the cliff toe. Cliff retreat be difficult to distinguish from rates. will increase, creating new natural variability. shore platform. This will to release additional sediments into the beach, although this will only partly mitigate the overall narrowing of the intertidal zone. Higher Town No defences No defences No defences Bay The shoreline will continue to Ongoing sea level rise will Ongoing sea level rise will retreat. This will tend to tend to narrow the beach and continue to narrow the beach happen at a higher rate, increase wave loading on the and increase wave loading although this increase should cliffs, increasing recession on the cliff toe. Cliff retreat be difficult to distinguish from rates. will increase, creating new natural variability. shore platform. This will to release additional sediments into the beach, although this will only partly mitigate the overall narrowing of the intertidal zone. Cruther’s No defences No defences No defences

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 156 February 2011

Point The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the islands, will be typical of the islands, will be typical of the islands, as described above. as described above. as described above. Lawrence’s No defences No defences No defences Bay The shoreline will continue to Ongoing sea level rise will Ongoing sea level rise will retreat. This will tend to tend to narrow the beach and continue to narrow the beach happen at a higher rate, increase wave loading on the and increase wave loading although this increase should cliffs, increasing recession on the cliff toe. Cliff retreat be difficult to distinguish from rates. will increase, creating new natural variability. shore platform. This will to release additional sediments into the beach, although this will only partly mitigate the overall narrowing of the intertidal zone. Yellow Rock No defences No defences No defences Erosion will continue and will Erosion will accelerate as Accelerated relative sea level tend to be accelerated by rising seas allow larger rise will continue to increase rising seas, although this waves to attack the cliffs. wave activity at the shore. increase is likely to be difficult Wave run-up and impacts on The shore platform will be to distinguish from natural the cliff face. submerged for a greater variability. proportion of the tide, and so access will be reduced. Wave impacts on the cliff face will continue to increase, causing higher shore recession rates. Lower Town No defences No defences No defences beach The shoreline will continue to Ongoing sea level rise will Ongoing sea level rise will retreat. This will tend to tend to narrow the beach and continue to narrow the beach happen at a higher rate, increase wave loading on the and increase wave loading although this increase should cliffs, increasing recession on the cliff toe. Cliff retreat be difficult to distinguish from rates. will increase, creating new natural variability. shore platform. This will to release additional sediments into the beach, although this will only partly mitigate the overall narrowing of the intertidal zone.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 157 February 2011

20.9 St Martins unit details – With Present Management

Location Predicted Change For Years 0 – 20 (2025) Years 20 – 50 (2055) Years 50 – 100 (2105) Goats Point No defences No defences No defences to Scilly Point The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the islands, will be typical of the islands, will be typical of the islands, as described above. as described above. as described above. St Martin’s No defences No defences No defences Bay Coastal evolution will be Ongoing sea level rise will Ongoing sea level rise will typical of the region as further narrow the beach, continue to narrow the beach described above. The beach increasing the period that the and increase wave loading will begin to narrow as the cliff toe is submerged at high on the cliff toe . Cliff retreat sea level rises. tide. Wave loading on the cliff will increase, creating new toe will increase. shore platform. Turfy Hill to No defences No defences No defences Brandy Point Carn The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the islands, will be typical of the islands, will be typical of the islands, as described above. as described above. as described above. Perpitch No defences No defences No defences The shoreline will continue to Ongoing sea level rise will Ongoing sea level rise will retreat. This will tend to tend to narrow the beach and continue to narrow the beach happen at a higher rate, increase wave loading on the and increase wave loading although this increase should cliffs, increasing recession on the cliff toe. Cliff retreat be difficult to distinguish from rates. will increase, creating new natural variability. shore platform. This will to release additional sediments into the beach, although this will only partly mitigate the overall narrowing of the intertidal zone. Higher Town No defences No defences No defences Bay The shoreline will continue to Ongoing sea level rise will Ongoing sea level rise will retreat. This will tend to tend to narrow the beach and continue to narrow the beach happen at a higher rate, increase wave loading on the and increase wave loading although this increase should cliffs, increasing recession on the cliff toe. Cliff retreat be difficult to distinguish from rates. will increase, creating new natural variability. shore platform. This will to release additional sediments into the beach, although this will only partly mitigate the overall narrowing of the intertidal zone. Cruther’s No defences No defences No defences

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 158 February 2011

Point The evolution of this coast The evolution of this coast The evolution of this coast will be typical of the islands, will be typical of the islands, will be typical of the islands, as described above. as described above. as described above. Lawrence’s No defences No defences No defences Bay The shoreline will continue to Ongoing sea level rise will Ongoing sea level rise will retreat. This will tend to tend to narrow the beach and continue to narrow the beach happen at a higher rate, increase wave loading on the and increase wave loading although this increase should cliffs, increasing recession on the cliff toe. Cliff retreat be difficult to distinguish from rates. will increase, creating new natural variability. shore platform. This will to release additional sediments into the beach, although this will only partly mitigate the overall narrowing of the intertidal zone. Yellow Rock No defences No defences No defences Erosion will continue and will Erosion will accelerate as Accelerated relative sea level tend to be accelerated by rising seas allow larger rise will continue to increase rising seas, although this waves to attack the cliffs. wave activity at the shore. increase is likely to be difficult Wave run-up and impacts on The shore platform will be to distinguish from natural the cliff face. submerged for a greater variability. proportion of the tide, and so access will be reduced. Wave impacts on the cliff face will continue to increase, causing higher shore recession rates.

Lower Town No defences No defences No defences beach The shoreline will continue to Ongoing sea level rise will Ongoing sea level rise will retreat. This will tend to tend to narrow the beach and continue to narrow the beach happen at a higher rate, increase wave loading on the and increase wave loading although this increase should cliffs, increasing recession on the cliff toe. Cliff retreat be difficult to distinguish from rates. will increase, creating new natural variability. shore platform. This will to release additional sediments into the beach, although this will only partly mitigate the overall narrowing of the intertidal zone.

Cornwall and Isles of Scilly SMP2 NAI & WPM assessment Final Report Appendix C 159 February 2011