Coastal Storms: Detailed Analysis of Observed Sea Level and Wave Events in the SCOPAC Region (Southern England)

SCOPAC RESEARCH PROJECT Coastal storms: detailed analysis of observed sea level and wave events in the SCOPAC region (southern England)

Debris at Milford-on-Sea after the “Valentines Storm” February 2014. Copyright New Forest District Council.

Date: December 2020

Version: 1.1

BCP - SCOPAC 2020 Rev 1.1 Document history

SCOPAC Storm Analysis Study: Coastal storms: detailed analysis of observed sea level and wave events in the SCOPAC region (southern England) Project partners:

• Bournemouth Christchurch Poole (BCP) Council / Dorset Coastal Engineering Partnership • Ocean & Earth Science, University of Southampton (UoS) • Coastal Partners (formerly Eastern Solent Coastal Partnership (ESCP))

Project Manager: Matthew Wadey (BCP Council) Funded: Standing Conference on Problems Associated with the Coastline (SCOPAC) Data analysis: Addina Inayatillah (UoS), Matthew Wadey (BCP/DCEP), Ivan Haigh (UoS), Emily Last (Coastal Partners)

This document has been issued and amended as follows:

Version Date Description Created by Verified by Approved by

1.0 16.11.20 SCOPAC Storm MW, AI, IH, SC Analysis Study EL

1.1 30.12.20 SCOPAC Storm MW, AI, IH, SC SCOPAC Analysis Study EL RSG

BCP - SCOPAC 2020 Rev 1.1 SCOPAC Storm Analysis Study

PROLOGUE

Dear SCOPAC members,

Our coastline is exposed to storm surges and swell waves from the Atlantic that as we know can result in flooding and erosion. Changing extreme sea levels and waves over time need to be assessed so risks can be understood; as both one-off events and as a consequence of successive events (“storm clustering”). The notable winter of 2013/14 saw repeated medium to high magnitude events prevailing over a relatively short time period. Many beaches were stripped of material, resulting in extreme overtopping and undermining of sea defences. In response to the storms regarded as unprecedented, the Environment Agency released £270 million funds for emergency works. The impacts of the 2013/14 winter were severe, with £130 million in damages to residential properties and £170 million in damages to businesses situated on the coast (Environment Agency, 2016). The consequences would have been much worse however, if flood forecasting and warning systems and coastal management practices were not in place.

Since the winter of 2013/14, it has been noted that the SCOPAC region has continued to experience draw down of beaches and localised sea defence failures. We know that sea levels are rising, as updated recent information from the UKCP18 projections is an integral part of our FCERM planning. However, the unknown question is whether storm magnitude and frequency are also increasing, signifying a climate change influence? As part of the National Network of Regional Monitoring Programmes, nearshore wave buoys have been deployed since 2003, providing a valuable dataset for analysis to help answer this question.

At a SCOPAC meeting on the 27th January 2017, the officers and councillors were interested in this subject following another challenging winter in 2015/16 and Storm Angus causing damage to assets at the start of the 2016/17 storm season. Subsequently, SCOPAC commissioned this research project to put the recent winter storm seasons into context with longer datasets. Dr Ivan Haigh and Dr Matthew Wadey, experts in the analysis of sea level, storm surge and wave data sets, led on the investigation. It was decided that this research would form a first phase, focusing on the hydrodynamic forcing factors, with a potential second phase focusing on the impacts of storms on SCOPAC’s beaches and sea defences.

This technical report summarises the work undertaken by the project team, for which there is a supporting info-graphic for SCOPAC members and the public, highlighting the key findings.

We hope you find this research as interesting as we do,

Dr Samantha Cope

SCOPAC Research Chair

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EXECUTIVE SUMMARY

Prompted by concerns over climate change and recent stormy winters, in particular that of 2013/14 (W2013/14), this study assesses sea level and wave data along the south coast of the UK to determine context and extremity of events and winters within the spans of these data sets. These data are available as 15-30 minutely spaced time series since the early 20th century for sea level and since 2003 for waves. In terms of the conceptual flood system known as the “source-pathway- receptor-consequence” model, this study focuses upon coastal flood “sources”. “Consequences” are briefly reviewed to extend the context but future focus on the other components is recommended.

This formulation of regional and local scale results within the SCOPAC region is quite unique amongst other studies and gives up to date guidance on possible indicators of climate change and winter extremities for a range of audiences (coastal practitioners, academics, politicians).

In terms of TRENDS AND PATTERNS, 9 sea level (tide gauge) sites were assessed across the English Channel. At all sites, mean sea level is rising and the rate of rise has accelerated in recent years - this is the most certain finding to take from this analysis. The most reliable long- term rate relevant to the English Channel (and the SCOPAC region) at Newlyn indicates a rise in mean sea level of 1.86 mm/yr. between 1915 and 2019, increasing to 3.8 mm/yr. between 1990 and 2019. The analysis suggests changes to tidal characteristics such as mean high water and tidal range, although as yet with no consistent spatial trend evident across the region. Statistically significant increases in storm surges are not found, consistent with findings from other parts of the world.

All the 9 wave buoy sites (except the furthest east, Folkestone) have an increasing trend in wave height. There is a signal that wave period has increased at most sites but with trends that are not statistically significant due to the short data span (2003 onwards) – hence the exceedance analysis in the next section is pertinent to understand this. Combining wave height and period into a wave power (indicative of the energy dispensed onto the shoreline) and run up (indicative of overtopping or flood potential), there is an upward trend with time (the report explains how the statistical significance varies). The W2013/14 had notably higher wave power across all sites. Combining waves and sea level into time series of total water level suggests a statistically significant annual increase for the Solent and eastern SCOPAC region across the entirety of the datasets, with the W2013/14 an outlier for clustering and extremes.

Events (peaks in the respective data) were assessed against known limits (e.g. return periods) to count THRESHOLD EXCEEDANCES from 2003-2019 at four “site pairings” (sea level and wave recording sites), as follows: (1) Weymouth-Chesil; (2) Poole Bay, (3) The Solent and (4) Newhaven-Rustington. A consistent statistical trend cannot be found, mostly likely because of the relatively short data lengths. However, comparing winters since 2003 highlights how recent years have seen growing “clusters” of extreme events: in the western-central SCOPAC area, W2013/14 definitively produced the highest count of extreme sea level and wave height events; in the east SCOPAC region W2013/14 and W2015/16 were comparably extreme.

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In terms of STORM EVENTS AND EXTREMES from the four site pairings, in the west of the region W2013/14 recorded the highest surge, wave height, wave run-up, and most powerful waves (all on the 14th February 2014 “Valentines Storm”) since 2003. In the west and central SCOPAC area, the highest water level was on 10th March 2008 although with missing sea level data at Bournemouth considered, the 2014 Valentines Storm is probably the most extreme event in terms of physical loading upon coastal defences and flood potential. The 6th January 2014 is also noteworthy for the prolonged, region-wide, high wave run up and power. In the Solent: W2013/14 had the highest sea level event since 1961 (on the 5th-6th December 2013 when a North Sea surge propagated from the east during calm wave conditions in the Channel). Meanwhile the 5th February 2014 and 14th February 2014 produced the most powerful waves and highest run up since the records began in 2003. The highest waves on record in the eastern part of the region were on the 24th December 2013. The highest total water levels were more recently during Storm Eleanor in January 2018. Again, this is indicative of the past recent decade containing more extreme events than other comparable intervals of time during the past half century.

The next area of investigation was into BIMODAL WAVES AND SWELL. Such conditions are generally considered as unusual and energetic wave conditions that can cause more damage at the coast. For each winter season, this part of the analysis highlighted that the W2013/14 and W2015/16 stand out as the most bimodal since data sets began in 2003; with Jan-Feb 2014 and Dec-2015 being the most extreme months. It seems given events that overlap with these months, that persistent bimodal wave activity could be, as previous studies have alluded to, directly linked to beach drawdown and structural failures. A linear trend through the data suggests the possibility of increasingly bimodal seas over time – further work is needed to assess the cause and nature of this at a regional and local scale, since these findings are consistent with broader scale global studies that suggest a climate change link.

A brief look at CONSEQUENCES was the final step to provide a broader historical perspective including examining events before good quality sea level and wave data sets are available. This is using a longer systematically assessed ‘qualitative’ data set. We found evidence of 187 distinct coastal flood events within the SCOPAC region in a 318-year period from 1703 to present. This again highlights that W2013/14 has seen the most events of any season in this data set (although availability recently of data may bias this). However, it also highlights the role of modern risk management because W2013/14 does not even rank in the top 10 winters for the most severe flooding (even though it is possible that it was the most extreme winter from a waves and sea level perspective). The most severe coastal flood events occurred on 15th January 1918, 13th December 1989, 26th November 1954, 26th December 1912 and 1st January 1877. It is possible that an event in November 1824 was the most severe in every regard (sources to consequences) but a lack of information means this cannot be verified. Further studies should continue to monitor events and winters in context with the ongoing data sets, and take the opportunity to extend the wave data analysis back further in time from numerical model hindcasts.

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TABLE OF CONTENTS

PROLOGUE ...... 3 EXECUTIVE SUMMARY ...... 4 TABLE OF CONTENTS ...... 6 LIST OF FIGURES ...... 8 LIST OF TABLES ...... 14 LIST OF ABBREVIATIONS ...... 16 1 INTRODUCTION ...... 18 1.1 Background ...... 18 1.2 Aim and objectives...... 20 1.3 Report structure ...... 21 2 BACKGROUND, DATA & METHODS ...... 23 2.1 Coastal flood and erosion ‘sources’ ...... 23 2.2 Data ...... 24 2.3 Methods ...... 30 2.3.1 Stage 1: Long term trends...... 30 2.3.2 Stage 2: Threshold exceedance analysis ...... 32 2.3.3 Stage 3: Event analysis ...... 33 2.3.4 Stage 4: Bimodal wave and swell review ...... 34 2.3.5 Stage 5: Coastal flood catalogue ...... 35 3 STAGE 1: TRENDS AND PATTERNS ...... 40 3.1 Trends in still sea level and its component parts ...... 40 3.2 Trends in wave components ...... 46 4 STAGE 2: THRESHOLD EXCEEDANCE EVENTS ...... 58 4.1 Sea level and storm surge ...... 58 4.2 Wave height and wave period ...... 63 4.3 Total water level and run-up level ...... 68 5 STAGE 3: STORM EVENTS AND EXTREMES ...... 77 6 STAGE 4: BIMODAL WAVES AND SWELL ...... 82 7 STAGE 5: OVERVIEW OF CONSEQUENCES – THE SEVEREST INDIVIDUAL EVENTS AND WINTERS ...... 86 7.1 Coastal events catalogue ...... 86

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7.2 Overview of 2013/14 ...... 90 7.3 Aftermath ...... 96 7.4 Observations since W2013/14 ...... 98 8. DISCUSSION, CONCLUSION AND RECOMMENDATIONS ...... 99 APPENDIX A – WEYMOUTH-CHESIL PAIRING: HIGHEST SEA LEVEL AND WAVE EVENTS ..... 107 APPENDIX B – POOLE BAY: HIGHEST SEA LEVEL AND WAVE EVENTS ...... 115 APPENDIX C – SOLENT: HIGHEST SEA LEVEL AND WAVE EVENTS ...... 123 APPENDIX D – EAST SCOPAC: HIGHEST SEA LEVEL AND WAVE EVENTS ...... 132 APPENDIX E – WAVE TIME SERIES PLOTS ...... 140 APPENDIX F – COASTAL FLOOD EVENT TABLES ...... 147 APPENDIX G – MILFORD-ON-SEA WAVE DATA ...... 165

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LIST OF FIGURES

Figure 1.1: Map showing the location of the SCOPAC region and the coastal local authorities. .. 19 Figure 1.2: The Source-Pathway-Receptor-Consequence “conceptual model” for coastal flooding. This study focuses primarily on sources data to determine if recent winters have been more extreme than ever before...... 20 Figure 1.3: Map showing the location of the SCOPAC region wave and tide recorders...... 21 Figure 2.1: Coastal sea level effects caused by tides, storm surge, and wave processes...... 24 Figure 2.2: Location of the tide gauge sites and years from which monthly MSL datasets were available...... 25 Figure 2.3: The location of the tide gauge sites and years for which high-frequency sea level records available from BODC, along the south coast of the UK...... 26 Figure 2.4: Location of the wave buoy sites and years for which high-frequency wave records at sites along the UK south coast...... 27 Figure 2.5: Location of the tide gauges and wave buoys along with available years for high- frequency sea level and wave records at sites along the UK south coast...... 28 Figure 2.6: An example of wave frequency vs. energy that can be used to assess the percentage of bimodal seas (Channel Coastal Observatory, 2020)...... 35 Figure 2.7: An example of commentary of the flood event using SPRC Conceptual Model (Boza, 2018)...... 38 Figure 3.1: Time series of annual relative MSL for sites along the UK south coast (St. Mary’s, Newlyn, Devonport, Weymouth, Bournemouth, Southampton, Portsmouth, Newhaven, and Dover)...... 41 Figure 3.2: Time-series of annual: (a, b, c, d, e, f, g, h, i) MHW and (j, k, l, m, n, o, p, q, r) MLW for Dover, Newhaven, Portsmouth, Southampton, Bournemouth, Weymouth, Devonport, Newlyn and St. Mary’s overlaid with linear trends...... 42 Figure 3.3: Time-series of annual MTR: (a, b, c, d, e, f, g, h, i) before and (j, k, l, m, n, o, p q, r) after removing the 18.6 nodal cycle for Dover, Newhaven, Portsmouth, Southampton, Bournemouth, Weymouth, Devonport, Newlyn and St. Mary’s overlaid with linear trends...... 43

Figure 3.4: Time-series of annual: (a, b, c, d, e, f, g, h, i) 90th and (j, k, l, m, n, o, p, q, r) 99th skew surge percentiles for Dover, Newhaven, Portsmouth, Southampton, Bournemouth, Weymouth, Devonport, Newlyn and St. Mary’s overlaid with linear trends...... 44 Figure 3.5: Time-series of annual 90th extreme sea level percentiles (a, b, c, d, e, f, g, h, i) before and (j, k, l, m, n, o, p q, r) after subtracting the 50th percentile for Dover, Newhaven, Portsmouth, Southampton, Bournemouth, Weymouth, Devonport, Newlyn and St. Mary’s overlaid with linear trends...... 45

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Figure 3.6: Time-series of annual: (a, b, c, d, e, f, g, h, i) 90th and (j, k, l, m, n, o, p, q, r) 99th wave height percentiles for Folkestone, Rustington, Hayling Island, Sandown Bay, Milford, Boscombe, Chesil, Start Bay, and Penzance overlaid with linear trends...... 47 Figure 3.7: Time-series of annual: (a, b, c, d, e, f, g, h, i) 90th and (j, k, l, m, n, o, p, q, r) 99th wave period percentiles for Folkestone, Rustington, Hayling Island, Sandown Bay, Milford, Boscombe, Chesil, Start Bay, and Penzance overlaid with linear trends...... 48

Figure 3.8: Time-series of annual: (a, b, c, d, e, f, g, h, i) 90th and (j, k, l, m, n, o, p, q, r) 99th wave period percentiles when wave heights are above 1 metre for Folkestone, Rustington, Hayling Island, Sandown Bay, Milford, Boscombe, Chesil, Start Bay, and Penzance overlaid with linear trends...... 49 Figure 3.9: Wave roses at each site (a, b, c, d, e, f, g, h, i) for Folkestone, Rustington, Hayling Island, Sandown Bay, Milford, Boscombe, Chesil, Start Bay, and Penzance...... 50

Figure 3.10: Time-series of annual mean wave power: (a, b, c, d, e, f, g, h, i) calculated using Hs and

(j, k, l, m, n, o, p, q, r) calculated using Hmax at Folkestone, Rustington, Hayling Island, Sandown Bay, Milford, Boscombe, Chesil, Start Bay, and Penzance overlaid with linear trends...... 51

Figure 3.11: Time series of average wave power using Hs per season at Folkestone, Rustington, Hayling Island, Sandown Bay, Milford, Boscombe, Chesil, Start Bay, and Penzance...... 52

Figure 3.12: Time-series of average wave power using Hmax per season at Folkestone, Rustington, Hayling Island, Sandown Bay, Milford, Boscombe, Chesil, Start Bay, and Penzance ...... 53

Figure 3.13: Time-series of maximum wave power using Hs per season at Folkestone, Rustington, Hayling Island, Sandown Bay, Milford, Boscombe, Chesil, Start Bay, and Penzance...... 53

Figure 3.14: Time-series of maximum wave power using Hmax per season at Folkestone, Rustington, Hayling Island, Sandown Bay, Milford, Boscombe, Chesil, Start Bay, and Penzance 54

Figure 3.15: Time-series of annual: (a, b, c, d, e, f, g, h, i) 90th and (j, k, l, m, n, o, p, q, r) 99th wave run-up percentiles for 훽 = 0.01 at Folkestone, Rustington, Hayling Island, Sandown Bay, Milford, Boscombe, Chesil, Start Bay, and Penzance overlaid with linear trends...... 55

Figure 3.16: Time-series of annual: (a, b, c, d, e, f, g, h, i) 90th and (j, k, l, m, n, o, p, q, r) 99th wave run-up percentiles for 훽 = 0.03 at Folkestone, Rustington, Hayling Island, Sandown Bay, Milford, Boscombe, Chesil, Start Bay, and Penzance overlaid with linear trends...... 55 Figure 3.17: Time-series of annual: (a, b, c, d) 90th and (e, f, g, h) 99th total water level percentiles for 훽 = 0.01 at Newhaven–Rustington, Portsmouth–Hayling Island, Bournemouth-Boscombe, and Weymouth-Chesil overlaid with linear trends...... 57

Figure 3.18: Time-series of annual: (a, b, c, d) 90th and (e, f, g, h) 99th total water level percentiles for 훽 = 0.03 at Newhaven–Rustington, Portsmouth–Hayling Island, Bournemouth-Boscombe, and Weymouth-Chesil overlaid with linear trends...... 57 Figure 4.1: Time series of (a) observed water level and (c) storm surge in relation to three different return period value with the number of events exceeded each threshold per season for (b) water level and (d) storm surge at Weymouth...... 59 Figure 4.2: Time series of (a) observed water level and (c) storm surge in relation to three different return period value with the number of events exceeded each threshold per season for (b) water level and (d) storm surge at Bournemouth...... 60

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Figure 4.3: Time series of (a) observed water level and (c) storm surge in relation to three different return period value with the number of events exceeded each threshold per season for (b) water level and (d) storm surge at Portsmouth...... 61 Figure 4.4: Time series of (a) observed water level and (c) storm surge in relation to three different return period value with the number of events exceeded each threshold per season for (b) water level and (d) storm surge at Newhaven...... 62 Figure 4.5: Time series of (a) wave height and (c) wave period in relation to three different return period value with the number of events exceeded each threshold per season for (b) wave height and (d) wave period at Chesil...... 64 Figure 4.6: Time series of (a) wave height and (c) wave period in relation to three different return period value with the number of events exceeded each threshold per season for (b) wave height and (d) wave period at Boscombe...... 65 Figure 4.7: Time series of (a) wave height and (c) wave period in relation to three different return period value with the number of events exceeded each threshold per season for (b) wave height and (d) wave period at Hayling Island...... 66 Figure 4.8: Time series of (a) wave height and (c) wave period in relation to three different return period value with the number of events exceeded each threshold per season for (b) wave height and (d) wave period at Rustington...... 67 Time series of total water level and run-up level available for Weymouth-Chesil, Bournemouth- Boscombe, Portsmouth-Hayling Island, and Newhaven-Rustington are plotted in Figure 4.9, Figure 4.11, Figure 4.13, and Figure 4.15 for =0.01 and Figure 4.10, Figure 4.12, Figure 4.14, and Figure 4.16 for =0.03. The events exceeding the thresholds are marked as follows: black dots represent a 1 in 1-year event, blue dots represent a 1 in 5-year event and red dots represent a 1 in 10-year event...... 68 Figure 4.9: Time series of (a) total water level and (c) run-up level (훽=0.01) in relation to three different threshold value with the number of events exceeded each threshold per season for (b) total water level and (d) run-up level at Weymouth-Chesil...... 69 Figure 4.10: Time series of (a) total water level and (c) run-up level (훽=0.03) in relation to three different threshold value with the number of events exceeded each threshold per season for (b) total water level and (d) run-up level at Weymouth-Chesil...... 70 Figure 4.11: Time series of (a) total water level and (c) run-up level (훽=0.01) in relation to three different threshold value with the number of events exceeded each threshold per season for (b) total water level and (d) run-up level at Bournemouth-Boscombe...... 71 Figure 4.12: Time series of (a) total water level and (c) run-up level (훽=0.03) in relation to three different threshold value with the number of events exceeded each threshold per season for (b) total water level and (d) run-up level at Bournemouth-Boscombe...... 72 Figure 4.13: Time series of (a) total water level and (c) run-up level (훽=0.01) in relation to three different threshold value with the number of events exceeded each threshold per season for (b) total water level and (d) run-up level at Portsmouth-Hayling Island...... 73 Figure 4.14: Time series of (a) total water level and (c) run-up level (훽=0.03) in relation to three different threshold value represented with the number of events exceeded each threshold per season for (b) total water level and (d) run-up level at Portsmouth-Hayling Island...... 74

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Figure 4.15: Time series of (a) total water level and (c) run-up level (훽=0.01) in relation to three different threshold value with the number of events exceeded each threshold per season for (b) total water level and (d) run-up level at Newhaven-Rustington...... 75 Figure 4.16: Time series of (a) total water level and (c) run-up level (훽=0.03) in relation to three different threshold value with the number of events exceeded each threshold per season for (b) total water level and (d) run-up level at Newhaven and Rustington...... 76 Figure 6.1: For the 8 wave sites, the sum, average, and maxima of bimodal values is plotted. ... 83 Figure 6.2: Monthly bimodal values plotted for 3 sites...... 84 Figure 6.3: Hours of swell at Boscombe for winter seasons...... 85 Figure 7.1: Number of flood events (a) monthly, (b) seasonally, and (c) in a decade throughout 313-year period...... 87 Figure 7.2: Number of flood events (a) monthly, (b) seasonally, and (c) in a decade throughout 313-year period each showing the severity per flood event ...... 89 Figure 7.3: Property flooding during December 2013 to February 2014 (source: Environment Agency)...... 91 Figure 7.4: Damage to coastal assets in the SCOPAC region during 2013/14...... 94 Figure 7.5: Pom Rock near Portland before and after its collapse, said – a natural stack weighing hundreds of tonnes, was demolished and broken up by the storm (source: Stuart Morris)...... 97

Figure 0.1: (a) Sea wall collapse at Southsea 25th-26th December 2015 (BBC, 2015a); and (b) sea wall failure at Dover on 24 December 2015 (BBC, 2015b)...... 102 Figure A.1: Scatter plots of twice daily high water values against coinciding (a) wave height and (b) wave period, (c) 16-h wave height peaks, and (d) wave rose of 100 highest water level events at Weymouth...... 108 Figure A.2: Scatter plots of twice daily high water values against coinciding (a) wave height and (b) wave period, (c) 16-h wave height peaks, and (d) wave rose of 100 highest skew surge events at Weymouth...... 109 Figure A.3: Scatter plots of twice daily high water values against coinciding (a) wave height and (b) wave period, (c) 16-h wave height peaks, and (d) wave rose of 100 highest wave height event at Chesil...... 111 Figure A.4: Scatter plots of twice daily high water values against coinciding (a) wave height and (b) wave period, (c) 16-h wave height peaks, and (d) wave rose of 100 highest wave period event at Chesil...... 112 Figure B.1: Scatter plots of twice daily high water values against coinciding (a) wave height and (b) wave period, (c) 16-h wave height peaks, and (d) wave rose of 100 highest water level event at Bournemouth...... 116 Figure B.2: Scatter plots of twice daily high water values against coinciding (a) wave height and (b) wave period, (c) 16-h wave height peaks, and (d) wave rose of 100 highest skew surge event at Bournemouth...... 117

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Figure B.3: Scatter plots of twice daily high water values against coinciding (a) wave height and (b) wave period, (c) 16-h wave height peaks, and (d) wave rose of 100 highest wave height event at Boscombe...... 118 Figure B.4: Scatter plots of twice daily high water values against coinciding (a) wave height and (b) wave period, (c) 16-h wave height peaks, and (d) wave rose of 100 highest wave period event at Boscombe...... 120 Figure C.1: Scatter plots of twice daily high water values against coinciding (a) wave height and (b) wave period, (c) 16-h wave height peaks, and (d) wave rose of 100 highest water level event at Portsmouth...... 124 Figure C.2: Scatter plots of twice daily high water values against coinciding (a) wave height and (b) wave period, (c) 16-h wave height peaks, and (d) wave rose of 100 highest skew surge event at Portsmouth...... 125 Figure C.3: Scatter plots of twice daily high water values against coinciding (a) wave height and (b) wave period, (c) 16-h wave height peaks, and (d) wave rose of 100 highest wave height events at Hayling Island...... 127 Figure C.4: Scatter plots of twice daily high water values against coinciding (a) wave height and (b) wave period, (c) 16-h wave height peaks, and (d) wave rose of 100 highest wave period events at Hayling Island...... 128 Figure D.1: Scatter plots of twice daily high water values against coinciding (a) wave height and (b) wave period, (c) 16-h wave height peaks, and (d) wave rose of 100 highest water level event at Newhaven...... 133 Figure D.2: Scatter plots of twice daily high water values against coinciding (a) wave height and (b) wave period, (c) 16-h wave height peaks, and (d) wave rose of 100 highest skew surge event at Newhaven...... 134 Figure D.3: Scatter plots of twice daily high water values against coinciding (a) wave height and (b) wave period, (c) 16-h wave height peaks, and (d) wave rose of 100 highest wave height event at Rustington...... 135 Figure D.4: Scatter plots of twice daily high water values against coinciding (a) wave height and (b) wave period, (c) 16-h wave height peaks, and (d) wave rose of 100 highest wave period at Rustington...... 137

Figure E.1: Time series of (a) Hs and Hmax, (b) Tp and Tz, and (c) Wave power (Po) at Folkestone...... 140

Figure E.2: Time series of (a) Hs and Hmax, (b) Tp and Tz, and (c) Wave power (Po) at Rustington...... 141

Figure E.3: Time series of (a) Hs and Hmax, (b) Tp and Tz, and (c) Wave power (Po) at Hayling Island...... 142

Figure E.4: Time series of (a) Hs and Hmax, (b) Tp and Tz, and (c) Wave power (Po) at Sandown Bay...... 142

Figure E.5: Time series of (a) Hs and Hmax, (b) Tp and Tz, and (c) Wave power (Po) at Milford. . 143

Figure E.6: Time series of (a) Hs and Hmax, (b) Tp and Tz, and (c) Wave power (Po) at Boscombe...... 144

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Figure E.7: Time series of (a) Hs and Hmax, (b) Tp and Tz, and (c) Wave power (Po) at Chesil. ... 144

Figure E.8: Time series of (a) Hs and Hmax, (b) Tp and Tz, and (c) Wave power (Po) at Start Bay...... 145

Figure E.9: Time series of (a) Hs and Hmax, (b) Tp and Tz, and (c) Wave power (Po) at Penzance...... 146 Figure G.1: Green dot shows the Milford buoy location owned by the Channel Coastal Observatory...... 165 Figure G.2: Monthly wave heights and linear trend at Milford (plotted from CCO data) ...... 166

Figure G.3: Monthly wave period (TZ) and linear trend at Milford (plotted from CCO data) .... 166 Figure G.4: Monthly wave direction and linear trend at Milford (plotted from CCO data) ...... 167 Figure G.5: Storm season counts of wave events above thresholds at Milford...... 167

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LIST OF TABLES

Table 2.1: Extreme sea levels for Weymouth, Bournemouth, Portsmouth, and Newhaven (these are in mODN) ...... 29 Table 2.2: Extreme wave height levels for Chesil, Boscombe, Hayling Island, and Rustington. This is using significant wave height (Hs, sometimes referred to as H1/3)...... 29 Table 2.3: Seven theses by University of Southampton’s students with the year, title, tide gauge they analysed, newspapers they used, the date coverage, and the study area...... 36 Table 2.4: Severity chart from 1 (nuisance) to 6 (disastrous) used to rank each of flood event identified (Boza, 2018) ...... 39 Table 3.1: Linear trends in MSL for different time periods ...... 41 Table 3.2: Linear trends in MHW, MLW and MTR ...... 43 Table 3.3: Linear trends in skew surge percentiles ...... 44 Table 3.4: Linear trends in extreme sea level percentiles ...... 46 Table 3.5: Linear trends in wave height percentiles ...... 47 Table 3.6: Linear trends in wave period percentiles ...... 49 Table 3.7: Linear trends in annual mean wave power ...... 52 Table 3.8: Linear trends in run up level percentiles ...... 56 Table 3.9: Linear trends in total water level percentiles ...... 57 Table 5.1: Highest water level event at each site...... 77 Table 5.2: Highest skew surge event at each site...... 77 Table 5.3: Highest significant wave height event at each site...... 78 Table 5.4: Longest wave period at each site...... 78

Table 5.5: Highest wave power (using Hs) events at each site...... 79

Table 5.6: Highest wave power (using Hmax) events at each site...... 79 Table 5.7: Highest run up level (β =0.01) at each site...... 80 Table 5.8: Highest total water level (β =0.01) at each site...... 80 Table 5.9: Highest run up level (β =0.03) at each site...... 81 Table 5.10: Highest total water level (β =0.03) at each site...... 81 Table 6.1: Average bimodality for CCO wave buoys per winter season...... 83 Table 6.2: Maximum bimodality of any given month for CCO wave buoys per winter season. ... 84 Table 6.3: The most bimodal months...... 85 Table A.1: 10 highest water level event at Weymouth...... 107 Table A.2: 10 highest skew surge events at Weymouth...... 108 14 SCOPAC Storm Analysis Study

Table A.3: 10 highest significant wave height (Hs) events at Chesil...... 109

Table A.4: 10 highest wave period (Tp) events at Chesil...... 111 Table A.5: 10 highest run up level (β =0.01) events at Chesil...... 112 Table A.6: 10 highest total water level (β =0.01) events at Weymouth-Chesil ...... 113 Table A.7: 10 highest run up level (β =0.03) events at Chesil ...... 114 Table A.8: 10 highest total water level (β =0.03) events at Weymouth-Chesil ...... 114 Table B.1: 10 highest water level event at Bournemouth ...... 115 Table B.2: 10 highest skew surge events at Bournemouth ...... 116

Table B.3: 10 highest significant wave height (Hs) events at Boscombe ...... 117

Table B.4: 10 highest wave period (Tp) events at Boscombe ...... 119 Table B.5: 10 highest run up level (β =0.01) events at Boscombe ...... 120 Table B.6: 10 highest total water level (β =0.01) events at Bournemouth-Boscombe ...... 121 Table B.7: 10 highest run up level (β =0.03) events at Boscombe ...... 121 Table B.8: 10 highest total water level (β =0.03) events at Bournemouth-Boscombe ...... 122 Table C.1: 10 highest water level event at Portsmouth ...... 123 Table C.2: 10 highest skew surge events at Portsmouth ...... 124

Table C.3: 10 highest significant wave height (Hs) events at Hayling Island ...... 125

Table C.4: 10 highest wave period (Tp) events at Hayling Island ...... 127 Table C.5: 10 highest run up level (β =0.01) events at Hayling Island ...... 128 Table C.6: 10 highest total water level (β =0.01) events at Portsmouth-Hayling Island ...... 129 Table C.7: 10 highest run up level (β =0.03) events at Hayling Island ...... 130 Table C.8: 10 highest total water level (β =0.03) events at Portsmouth-Hayling Island ...... 130 Table D.1: 10 highest water level event at Newhaven ...... 132 Table D.2: 10 highest skew surge events at Newhaven ...... 133

Table D.3: 10 highest significant wave height (Hs) events at Rustington ...... 134

Table D.4: 10 highest wave period (Tp) events at Rustington ...... 136 Table D.5: 10 highest run up level (β =0.01) events at Rustington ...... 137 Table D.6: 10 highest total water level (β =0.01) events at Rustington-Newhaven ...... 138 Table D.7: 10 highest run up level (β =0.03) events at Rustington ...... 138 Table D.8: 10 highest total water level (β =0.03) events at Rustington-Newhaven ...... 139 Table F.1: Coastal flood events recorded from within the SCOPAC region...... 147

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LIST OF ABBREVIATIONS

ABP Associated British Ports

BODC British Oceanographic Data Centre

CCO Channel Coastal Observatory

EA Environment Agency

ESCP Eastern Solent Coastal Partnership

LA Local Authority mCD metres Chart Datum mODN metres Ordnance Newlyn Datum

MHW mean high water

MLW mean low water

MSL mean sea level

MTR mean tidal range

PSMSL Permanent Service for Mean Sea Level

SCOPAC Standing Conference on Problems Association with the Coastline

SE Standard Error

UK United Kingdom

16 SCOPAC Storm Analysis Study

ACKNOWLEDGEMENTS

We thank SCOPAC (the Standing Conference on Problems associated with the Coastline) for funding this work. We would also like to thank the Coastal Channel Observatory (CCO)

and British Oceanographic Data Centre (BODC) for the sea level and wave data.

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1 INTRODUCTION

1.1 Background

Sea-level rise acceleration and climate change are resulting in more damaging storms, flooding and coastal erosion. This is a major global problem with profound social-political, economic and environmental consequences. The UK has a long history of severe coastal flooding (Haigh et al., 2015; 2017; 2020b) and erosion with a long and complex coastline. At present 2.5 million properties and £150 billion of assets are potentially exposed to coastal flooding – whilst the number at risk of erosion is much less, the consequences more permanent. Annual average economic damages from coastal flooding in the UK are estimated to be in the order of around £540 million (Sayers et al., 2015). Flood and erosion risks are also increasing due to rapid population growth, urbanisation and development in low-lying coastal regions (Stevens et al., 2016).

This report presents research that was commissioned in response to recent extreme events and stormy winters (e.g. 2013/14 and 2015/16), across the network of Operating Authorities and other organisations that share an interest in the management of the shoreline of central southern England (“Standing Conference on Problems Association with the Coastline” – SCOPAC, Figure 1.1). It is of interest to place these recent events into context with longer data sets to provide easily accessible and understandable scientific information that can be used to infer causes of coastal flooding and/or erosion.

Data on storm events and their link to flood defence investment and expectations (public and political) is currently quite vague and an area of work that is under development and rapidly changing, with the real and perceived impacts of climate change. Extreme erosion, floods, and failure of defences has occurred over the 20th and early 21st century (Haigh et al., 2020a); notably the 1953 flood which killed approximately 300 people in England and 2,000 in Europe (mostly in the Netherlands) and was an important trigger to investment in the Thames Barrier and improved forecasting and defences on the UK east coast and Europe. There have been severe storms since in the UK – for example the Fleetwood (Lancashire) floods in November 1977 and Towyn (Wales) in February 1990 – both associated with 1,000’s of people being displaced and possibly premature deaths. However, a repeat of 1953 with widespread drowning and destruction of homes has been avoided. For example, despite the 5th – 6th December 2013 event producing higher sea levels along much of the UK east coast (than in 1953) damages were less, due to improvements in flood defences and flood forecasting and warnings that prevented loss of life (Spencer et al., 2015; Wadey et al., 2015).

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Figure 1.1: Map showing the location of the SCOPAC region and the coastal local authorities.

The winter of 2013/14 was exceptionally wet and stormy in northwest Europe with severe coastal and flood related impacts to the British Isles. The storms generated extreme waves and along with high tides, extreme sea levels which were clustered closely together in time and caused extensive erosion and flooding on almost all the UK coast (e.g. Wadey et al, 2015). The events generated extensive press coverage and concern across coastal communities, businesses, and those with responsibility for flood and coastal management (e.g. local authorities and Environment Agency). In this context, the outputs of this project are intended to be useful to the Environment Agency and coastal protection teams within SCOPAC’s local authorities who have responsibilities relating to the Coastal Protection Act and Flood Water Management Act. This can include providing information for all coastal stakeholders, such as flood mapping for emergency response planning, public information, as well as applying for and allocating maintenance and capital expenditure.

With mean sea level (MSL) rise accelerating, and possible changes in storminess, high sea levels will occur more frequently in the future (Palmer et al., 2018; Horsburgh et al., 2020; Haigh et al., 2020b). Therefore, close analysis of the sea level and wave data is required; with extreme events and winters requiring systematic comparison, and also quantification of underlying trends that may be linked to short to long term changes. Over the longer term this enables better public engagement and education, particularly with the pressures of climate change. This project primarily utilises and summarises results obtained from high quality observed tide gauge data that has existed over the past century and wave recorder data that has been available largely since the start of the Regional Monitoring and Wavenet programmes (2002 -2003).

This work is intended to serve as a practical information source for engineers and a broad range of stakeholders across this stretch of coastline. In relation to this research, SCOPAC have also

19 SCOPAC Storm Analysis Study

made minor financial contributions to digitising the Poole Harbour tide gauge (potentially the longest sea level record in the SCOPAC region), and the SurgeWatch website (www.surgewatch.org), which documents historic coastal flood events around the UK.

1.2 Aim and objectives

The aim of this report is to place the ‘record breaking’ storms of 2013/14 into context with longer datasets to analyse the significance of the winter and to understand whether the SCOPAC region is experiencing a stormier climate in terms of frequency and magnitude of events, as well as sea level rise.

A depiction of the Source-Pathway-Receptor-Consequence (SPRC) model is shown in Figure 1.2. The winter of 2013/14 (W2013-14) was known for its prolonged storminess including the sustained large waves, high tides and impacts on the UK coast. The storms also brought heavy rainfall and wind. However as outlined in Figure 1.2, it is the sea level and wave aspects of flooding that are investigated in this study. Analysis of flood ‘sources’ from observed data sets, with a brief overview of events (flood and erosion) and their consequences will also support analysis, conclusions, and directions for future research and educating SCOPAC members and officers.

Figure 1.2: The Source-Pathway-Receptor-Consequence “conceptual model” for coastal flooding. This study focuses primarily on sources data to determine if recent winters have been more extreme than ever before.

The study is based upon analysis of the SCOPAC region’s tide gauges and wave buoy data (Figure 1.3). For tide gauges the data length is longer and these are used as standalone data across the English Channel; and also for shorter analysis these data are applied in conjunction with the wave data (approx. overlap 2003-19) to assess storminess in different sectors of the region, i.e.: (1) West Dorset [Weymouth-Chesil]; (2) Poole Bay [Bournemouth-Boscombe], (3) The Solent [Portsmouth-Hayling] and (4) East SCOPAC [Newhaven-Rustington].

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There are five specific objectives broken down into 5 stages as follows:

Stage 1: To calculate longer-term trends in waves and still sea level and its components (e.g., MSL, astronomical tides and storm surges); Stage 2: To analyse water level, storm surge, wave height, and wave period events exceedance counts per season, above specific thresholds, as well as total water level and run-up events to highlight the most severe events; Stage 3: To examine the characteristics of individual extreme sea levels; Stage 4: To assess unusual bimodal wave and swell events; Stage 5: To produce a catalogue of flood events in the region by synthesizing information from literature and the SurgeWatch database (Haigh et al., 2015; 2017), including details of erosion and asset performance from a former SCOPAC review, and a review of journal and similar literature sources relating to 2013/14.

Outputs will be uploaded onto the coastal group website and will include an infographic, dissemination of findings via presentations, this report, and a spreadsheet ranking storm events with attributes (surge, wave height, etc) up until and including winter 2019/20.

Figure 1.3: Map showing the location of the SCOPAC region wave and tide recorders.

1.3 Report structure

This report is structured as follows:

• Chapter 2 outlines the data types and data sets available to analysis these events and the analysis approaches applied later in the report; • Chapter 3 presents underlying observed trends and patterns: still sea level and its components, and waves (Stage 1);

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• Chapter 4 assesses underlying water level, storm surge, wave height, and wave period events in terms of threshold exceedance counting per season as well as total water level and run-up events (Stage 2); • Chapter 5 analyses extreme events – i.e. largest sea levels, skew surge, waves (and sea level and waves combined) (Stage 3); • Chapter 6 analyses extremes unusual bimodal wave and swell events (Stage 4); • Chapter 7 presents a coastal flood catalogue for SCOPAC region which is a desktop review of coastal flood and erosion in the region – a general synopsis and focus on 2013/14 and events since (Stage 5); • Chapter 8 discusses the temporal and spatial significance of the along with the conclusions and recommendations.

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2 BACKGROUND, DATA & METHODS

2.1 Coastal flood and erosion ‘sources’

The sources we assess in this project are:

Sea level which is equal to MSL + astronomical tide + residual (mainly “surge”) (refer to Pugh (1987) for more detail). Except for bores and currents, sea level refers to what appears at the coast as a slowly fluctuating “still” water level. Tides are predictable and surges are less predictable. The “mean” component is more subject to underlying periodic (e.g. seasonal) mass movements of water, temperature and global ocean volume (including that affected by climate change). Tides are generated by gravitational forces (primarily the differential pull of the moon and sun) acting over the water column in the deep ocean and the rotation of the earth, moon and sun; whereas (meteorological) surges are a response to wind stress and the horizontal atmospheric pressure gradient at the sea surface. Surges rarely exceed 1 m in the SCOPAC region. Most coastal floods (especially on the English south coast) occur when storm surges coincide with the higher “spring” part of the 2-weekly astronomical tidal cycle (Haigh et al., 2015).

Waves here refer to higher frequency sea level oscillations in the form of wind-sea or swell and whose primary restoring force is gravity. They are the dominant source of energy in the nearshore zone (an area captured by the Channel Coastal Observatory (CCO)’s regional monitoring wave buoys). Wave magnitude is dependent upon wind strength, fetch length, and the track of the storm. Upon generation, they propagate in a spread of directions with wavelengths small or comparable to offshore water depth. Locally generated waves from strong winds can cause damage and overtopping, although there is concern over energetic swell waves (transfer of energy from higher to lower frequencies) and bimodal seas (a simultaneous mixture of local wind waves and swell waves) (Lewis, 1979; Mason et al., 2009). These events can cause greater run up (which is collectively the vertical displacement of water at the shoreline) and erosion. For the open coast areas of the SCOPAC region, swell generated in the Arctic and western or tropical Atlantic is an important consideration for coastal flood events and beach erosion (e.g. notably Chesil Beach and Hayling Island).

The effect caused by tides, storm surges and wave processes to coastal sea level is illustrated in Figure 2.1. The relative timing of a surge peak, tidal high water and other wave components is critical to coastal flooding and is influenced by MSL. As explained in Chapter 3, pairs of wave and sea level data time series can be extracted to view how high water and large waves may combine, including as wave run up. To approximate how often an extreme sea level or wave conditions may be expected to occur, ‘return periods’ are often estimated using probabilistic calculations applied

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to observations or model simulations. For example, an extreme event (e.g. the peak elevation of a still water level) defined as having a 1 in 200-year return period may be considered as having a 0.05% chance of occurring in any given year. This study does not focus much on return periods, although in some instances they are utilised in the analysis (because of the shortness of datasets). An important point within this study of how extreme events can occur closely together in time.

Figure 2.1: Coastal sea level effects caused by tides, storm surge, and wave processes.

The next part of this chapter describes the data and methodology used to attain the five objectives of this study. This study utilised data from six main sources as explained in Section 2.2. The five main stages of analysis of this study, each addressing a specific objective, are then described in Section 2.3.

2.2 Data

Six main sources of data were used in this analysis, namely:

(1) Monthly MSL values from the Permanent Service for Mean Sea Level (PSMSL);

(2) High-frequency sea level from the A-Class UK National Tide Gauge Network, downloaded from the British Oceanographic Data Centre (BODC);

(3) Digital records of sea level Southampton and Portsmouth captured previously from historic tidal charts;

(4) High-frequency wave parameters, from the CCO;

(5) Extreme sea levels return period estimates from Environment Agency (EA); and

(6) Extreme wave return level estimates from the CCO.

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The first dataset utilised was monthly MSL values at St. Mary’s, Newlyn, Devonport, Weymouth, Bournemouth, Portsmouth, Newhaven, and Dover, which we use to assess long-term changes in average sea levels. The location of the tide gauges and years for which the monthly MSL values are available at each site are shown in Figure 2.2. These datasets were downloaded from the PSMSL website (http://www.psmsl.org). We used data in the Revised Local Reference (RLR) subset, as this contains the sites that have a full benchmark history, and hence can be used to reliably assess trends in MSL.

Figure 2.2: Location of the tide gauge sites and years from which monthly MSL datasets were available.

The second dataset, high-frequency sea level time-series, was accessed from the UK National Tide Gauge Network. This network is owned and operated by the EA and consists of 43 operational tide gauges. The network was established as a result of the 1953 severe flooding (UK Tide Gauge Network, 2020). The BODC are responsible for the remote monitoring, retrieval, quality-control and archiving of the data. The datasets are freely available to download from the BODC website (https://www.bodc.ac.uk). Some archived data points contain errors due to mechanical or software problems. We excluded all values which the BODC had flagged (as suspected of having errors) and undertook our own extensive checks. The frequency of the records changed from hourly to 15-minutes interval after 1993. Here we used the data from the following tide gauge sites: St. Mary’s, Newlyn, Devonport, Weymouth, Bournemouth, Portsmouth, Newhaven, and Dover. The location of the tide gauge sites and years for which high-frequency sea level records

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are available at each site are shown in Figure 2.3 in black dots and the red dots illustrate years when there was more than 60% of data are available. We only used years that have more than 60% of data available to do trends analysis to avoid any biases due to lack of data. At the time of analysis, quality-controlled records were available until the end of 2019. The high frequency sea level data are obtained in .txt format containing date and time of the measurement, observed sea level, and non-tidal residual.

Figure 2.3: The location of the tide gauge sites and years for which high-frequency sea level records available from BODC, along the south coast of the UK.

The third dataset we used is the (now digitized) records of sea level at Southampton (1935-1990) and Portsmouth (1961-1990) captured from historical sources by Haigh et al. (2009). For Southampton, the digital sea level data for the years 1991 to 2019 were obtained directly from Associated British Ports (ABP). These data are in .txt format containing date and time of the measurement, observed sea level, predicted tide, and the non-tidal residual in 1-minute intervals. For this study we extracted the date and time of the measurement and the observed sea level in 15 minutes intervals. Combining these recent data with the historic data, we have 84 years (missing the year 2012) continuous records of sea level data. For Portsmouth, combining the historical data (1961-1990) with BODC data (1991-2019), we have a 58-year record of sea level.

The fourth dataset we analysed was wave conditions acquired from the CCO website (https://www.channelcoast.org). For this study, data was obtained from wave buoys located at Penzance, Start Bay, Chesil, Boscombe, Milford, Sandown Bay, Hayling Island, Rustington, and 26 SCOPAC Storm Analysis Study

Folkestone. The locations of the wave buoys along with the years for which data is available at each site are shown in Figure 2.4. All years are shown in grey dots. Blue dots show when more than 60% of wave height data are available and red dots indicate when both wave height and wave period have more than 60% available data. We only used years that have more than 60% of data available to do the trends analysis. Wave parameters are recorded using a Datawell Directional WaveRider MkIII buoy at 30-minutes frequency (Channel Coastal Observatory, 2020). The wave data are obtained in .txt format containing date and time of the measurement, latitude, longitude, (data quality) flag, significant wave height (Hs), maximum observed wave height (Hmax), peak wave period (Tp), spectrally-derived zero-crossing wave period (Tz), wave direction (Dir), directional spread (Spd) and sea surface temperature (SST). Each data point has been flagged 0- 9 by the CCO depending on its quality; 0 indicates that all data pass the quality control while 9 means missing data. We have removed all data that were flagged 1 (either Hs or Tz failed, so all data failed) and 7 (when buoy drifted). We have also removed Tp and Tz data when it is flagged 2

(Tp and derivatives failed), as well as direction data when it is flagged 3 (direction failed). Note that we do not remove wave data that was flagged 5 as this indicates wave period only failed the jump test.

Figure 2.4: Location of the wave buoy sites and years for which high-frequency wave records at sites along the UK south coast.

All of the sea level and wave datasets that have been used in this study are shown in Figure 2.5 (combining from multiple sources). Red dots show tide gauge locations and all years for which

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sea level records are available for each site. Blue diamond shows wave buoy locations and all years for which wave records are available for each site. The green line highlights the SCOPAC region which is the focus area of interest in this study.

Figure 2.5: Location of the tide gauges and wave buoys along with available years for high- frequency sea level and wave records at sites along the UK south coast.

The fifth dataset we used is the extreme sea level return estimates obtained from the EA (Environment Agency, 2018). These return levels were used to define threshold for selecting high waters at each site that were likely to have resulted in coastal flooding. We extracted the return levels for 16 return periods from (1 in 1 to 1 in 10,000-years), for each of 4 sites listed in Table 4.2 of the Environment Agency (2018) report. The values we extracted are in metres Ordnance Datum Newlyn (mODN) and listed in Table 2.1. The conversions from mODN to metre chart datum (mCD) are 0.93, 1.40, 2.73, and 3.52 m for Weymouth, Bournemouth, Portsmouth, and Newhaven, respectively. We then interpolated these 16 return period values, at each site to estimate the return period of each extracted high water.

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Table 2.1: Extreme sea levels for Weymouth, Bournemouth, Portsmouth, and Newhaven (these are in mODN) Return Period Weymouth Bournemouth Portsmouth Newhaven (years) 1 1.82 1.40 2.55 3.87 2 1.89 1.47 2.63 3.94 5 1.99 1.56 2.73 4.04 10 2.05 1.63 2.80 4.12 20 2.12 1.69 2.87 4.20 25 2.15 1.71 2.89 4.22 50 2.22 1.78 2.96 4.30 75 2.26 1.81 3.00 4.35 100 2.28 1.84 3.03 4.38 150 2.32 1.88 3.07 4.43 200 2.35 1.90 3.10 4.46 250 2.37 1.93 3.12 4.49 300 2.39 1.94 3.14 4.51 500 2.44 1.99 3.19 4.57 1000 2.51 2.06 3.25 4.66 10000 2.76 2.28 3.49 4.96

The sixth dataset we used is extreme wave height return period estimates obtained from the CCO website. We used the data at four sites (Chesil, Boscombe, Hayling Island, and Rustington) and the values are listed in Table 2.2. The extreme analysis method used to estimate these return level values is described in Dhoop and Thompson (2018).

Table 2.2: Extreme wave height levels for Chesil, Boscombe, Hayling Island, and Rustington. This

is using significant wave height (Hs, sometimes referred to as H1/3). Return Period Chesil Boscombe Hayling Island Rustington (years) 0.25 4.18 2.74 2.72 3.34 1 5.28 3.42 3.31 4.07 2 5.91 3.68 3.57 4.41 5 6.81 3.96 3.87 4.82 10 7.56 4.14 4.07 5.12 20 8.37 4.29 4.25 5.40 50 9.54 4.45 4.46 5.75

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2.3 Methods

The analysis was undertaken in five main stages, each addressing one of the five objectives listed in Section 1.2. The first stage is to analyse the long-term trends of still sea levels and waves. First, we look at sites along the whole of the south coast, then focus on the sites on the SCOPAC region. The second stage is to undertake a threshold exceedance analysis at the four pairs of sites in the SCOPAC region. The third stage is to extract the largest storm events and extremes. The fourth stage is to assess the bimodal waves and swell. The fifth stage is to compile a catalogue of coastal flooding events within the SCOPAC region. These stages are described in detail in the sections below.

2.3.1 Stage 1: Long term trends

Stage one involved an analysis of long-term trends in: (1) still sea level and its component parts (e.g. MSL, tides, skew surge) and (2) waves. Whilst sea level comprises components which are principally waves, when we refer to “waves” in part (2) we are referring to waves commonly seen at the coast as “wind waves” or “swell”.

Still sea level: The first step was to assess trends and uncertainties in MSL. We assessed trends in annual MSL at 9 sites in English Chanel (St. Mary’s, Newlyn, Devonport, Weymouth, Bournemouth, Southampton, Portsmouth, Newhaven, and Dover). We estimated rates of change in MSL by fitting trends to time series of annual MSL using linear regression, with the uncertainty defined as one standard error (SE) (i.e. 68% confidence level). In calculating uncertainties, we assumed that the annual MSL values are not serially correlated. We fitted trends for the available data lengths at each site, and then for the intervals 1970 to 2019, 1990 to 2019, and 2000 to 2019.

For astronomical tidal levels, we estimated trends in mean high water (MHW), mean low water (MLW), and mean tidal range (MTR) at nine sites in English Chanel (St. Mary’s, Newlyn, Devonport, Weymouth, Bournemouth, Southampton, Portsmouth, Newhaven, and Dover). We used a turning point algorithm to automatically extract all twice-daily measured high and low water levels at each site from the high-frequency sea level data and calculated MTR from these. Trends were then fitted using linear regression. A strong 18.6-year nodal cycle can be observed in the time series of MTR (Haigh et al., 2011a) and we removed this by fitting a sine curve with a period of 18.6 years.

For skew surges, we estimated trends in different percentiles for these same 9 sites. We separated the measured sea level at each of the nine sites into tidal and non-tidal components. The tidal component was predicted using the T-Tide harmonic analysis software in MATLAB (Pawlowicz,

30 SCOPAC Storm Analysis Study

et al, 2002). A separate tidal analysis was undertaken for each calendar year using the standard 67 tidal constituents in the software. For years with less than six months of data coverage, the tidal component was predicted using harmonic constituents estimated for the nearest year which had enough data. We then extracted the twice-daily predicted high water levels using a turning point algorithm. The twice-daily values of skew surge were calculated from the difference of twice-daily measured and predicted high water levels at each site. A complete time series of non- leap year contains 8,760 hourly measurements. These can be ordered in terms of height and then used to compute percentile levels (Woodworth and Blackman, 2002). Percentile values for time- series of skew surges at each site have been calculated at five levels (80th, 90th, 95th, 99th, and 99.9th), following the approach of Woodworth and Blackman (2002). Trends were fitted to the different percentile time-series using linear regression.

We then estimated trends in different percentiles of extreme sea levels at the same 9 sites. For the observed sea level at each site, percentile values have been calculated at six levels (50th, 80th, 90th, 95th, 99th, and 99.9th). The 50th percentile corresponds well to MSL and has been subtracted from each individual percentile for each year to obtain a measure of the distribution of hourly sea levels relative to MSL for that year. By removing the 50th percentile, residual trends that are driven by changes in tides or skew surges (rather than MSL) can be assessed. Trends were then again fitted to the different percentile time-series using linear regression, before and after removing MSL.

Waves: The second step was to estimate trends in different percentiles of wave height and wave period at the following nine sites: Penzance, Start Bay, Chesil, Boscombe, Milford, Sandown Bay, Hayling Island, Rustington, and Folkestone. Percentile values for the recorded wave height and wave period at each site were calculated at five levels (80th, 90th, 95th, 99th and 99.9th). Trends were fitted to the different percentile time-series using linear regression. We also fitted trends to wave period for the times when the wave height was above 1 m. We also plotted wave roses for all available years at each site.

In addition, we calculated time-series of wave power (P) using the following Equation 2.1 (e.g. concept and formulae as referred to in Sang et al, 2018 and a similar method used in Wadey et al., 2017):

휌푔2 휌푔2 2.1 푃 = (퐻2푇 ) 표푟 P = (퐻2 푇 ) 64휋 푠 푝 64휋 푚푎푥 푝 where Hs is significant wave height, Tp is peak wave period, and Hmax is maximum observed wave height. Units are in kW/m. We used the g (acceleration due to gravity) value of 9.81 m/s2 and the  (the density of sea water) value of 1025 kg/m3. Wave power was estimated here because it provides a time series parameter that combines simultaneous wave height and wave period

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which have their own respective and combined different influences on coastal (flood and erosion) events (Wadey et al., 2017). We estimated trends in annual mean wave power at the nine wave buoy locations and fitted the trends with linear regression, with the uncertainty defined as one standard error (SE). We also calculated mean wave power per season and extracted maximum wave power value for each site.

Time-series of theoretical wave run-up level was calculated using the following Equation 2.2 (Holman, 1986):

1 2.2 푅2% = 0.75훽(퐻푠퐿표)2 + 0.22퐻푠 where R2% is the two-percent exceedance elevation of wave run-up maxima and Lo is the deep-

푔푇 2 water wave length given by linear wave theory ( 푝 ). We used 0.01 and 0.03 for 훽 (beach slope) 2휋 values to capture a range of possibilities. We then estimated trends in different percentiles of run up levels and fitted the trends with linear regression at these nine sites.

The run up was then added on the observed water level to produce time series of total water level, following the approach of Ruggiero et al. (1998). Time-series of run-up level is at 30-minutes frequency (wave data were available at 30-minutes frequency), so we interpolated these into 15- minutes interval using simple averaging, in order to match with the observed sea level data. We calculated total water level time-series at 4 pairs of sites: (1) Weymouth-Chesil, (2) Bournemouth-Boscombe, (3) Portsmouth-Hayling Island, and (4) Newhaven-Rustington. These four pairs of sites were chosen as they are within the SCOPAC region and are relatively close to each other. For Newhaven-Rustington; Rustington is part of SCOPAC region, yet Newhaven is further to the east. However, this pair is also included in this study. Note that CCO also have a wave buoy at Weymouth deployed since 2006, however, we chose the wave buoy at Chesil to pair with Weymouth tide gauge as the 2013/14 storms were notably impactful at Chesil, while Weymouth wave buoy is in a more sheltered location. Lastly, we also estimated trends in total water levels and fitted the trends with linear regression at these 4 pairs of sites.

2.3.2 Stage 2: Threshold exceedance analysis

In stage two, we undertook a threshold exceedance analysis at the 4 pairs of sites mentioned above. For each pair of sites, events were identified when water level, storm surge, wave height, and wave period exceeded certain thresholds. These thresholds were used to define events that were likely to have resulted in flooding. For water level, the threshold used is the extreme sea level return estimates from Environment Agency (2018) (Table 2.1). We chose 1 in 1-year, 1 in 5- year, and 1 in 10-year return level values as the water level thresholds. For the storm surge

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threshold, we used 1 in 1-year, 1 in 5-year, and 1 in 10-year return levels that we calculated by fitting annual maximum values to a generalized extreme value (GEV) distribution. For the wave height threshold, we used wave height return levels for 1 in 0.25-year, 1 in 1-year, and 1 in-10 year estimated by the CCO (Table 2.2). For wave period, we chose three arbitrary numbers (18 s, 21 s, and 24 s) as thresholds.

The number of events exceeded the thresholds were calculated and compared each season to assess the temporal distributions. For continuity of the typical storm surge season, the events were grouped based on season rather than by calendar year (Wadey et al., 2014). We defined a season as starting on the 1st of July and ending on the 30th June the following year.

For each site, events when total water level and run up level exceeded threshold were also identified. For total water level, the same threshold as for water level were used, so we could directly compare the total water level with water level. For the run up level threshold, the same threshold for storm surge was used to allow for easy comparison. The number of events that exceeded the threshold were then calculated and compared each season to assess the temporal distributions.

2.3.3 Stage 3: Event analysis

In stage three, we analysed specific extreme storm events at the same 4 pairs of sites discussed above. First, we identified the 100 highest water level events at each site using the twice-daily measured high water time-series extracted in the first stage. For each high water level event, we estimated the return period by linearly interpolating the EA return periods (Table 2.1). We then extracted the highest significant wave height (Hs) associated with each high water level event in a 16 hour storm window (Dhoop and Thompson, 2018). The wave period (Tp) and wave direction corresponding with the significant wave height were also extracted. For this analysis, we kept the wave data at 30 minutes interval so that the extracted values could exactly be traced back and verified to the original records. For each of high water level events, we recorded: (1) date-time of the measured high water; (2) high-water return period; (3) high-water level; (4) predicted high- water level; (5) skew surge; (6) significant wave height (Hs); (7) wave period (Tp); and (8) wave direction.

Second, using the skew surge time-series calculated in stage one, we extracted the 100 highest skew surge levels at each site. We estimated the return period based on the values we calculated in stage two. Wave data associated with each highest skew surge event were extracted as explained above. For each high skew surge event, we recorded: (1) date-time of the skew surge;

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(2) skew surge return period; (3) skew surge level; (4) high-water level; (5) predicted high-water;

(6) wave height (Hs); (7) wave period (Tp); and (8) wave direction.

Third, we extracted the 100 highest significant wave height (Hs) events within a 16-hour storm window separation. For each significant wave height event, we estimated the return period by linearly interpolating the CCO return periods (Table 2.2). For each significant wave height event, the nearest (in time) high water levels were extracted along with the associated predicted tidal and skew surge levels. For each high significant wave height event, we recorded: (1) date-time of the significant wave height; (2) significant wave height return period; (3) significant wave height level (Hs); (4) wave period (Tp); (5) wave direction; (6) high-water level; (7) predicted high-water level; and (8) skew surge level.

Fourth, we extracted the 100 longest wave period (Tp) events in a 16-hour storm window. Note, we excluded wave period when significant wave height is below 1 m, as the long wave period event would be more likely to cause flooding when coinciding with significant wave height above 1 m. For each event, high water levels were extracted along with the predicted tidal and skew surge levels. For each event, we recorded: (1) date-time of the wave period; (2) wave period (Tp);

(3) significant wave height (Hs); (4) wave direction; (5) high water level; (6) predicted high water level; and (7) skew surge level.

Additionally, we also extracted the 10 highest run-up and 10 highest total water levels for each site and for each of the 훽 values (0.01 and 0.03) that we had calculated in stage one. For each of these events, we also recorded: (1) date-time of the event; (2) run-up level; (3) significant wave height (Hs); (4) wave period (Tp); (5) wave direction; (6) water level; (7) predicted water level; (8) skew surge level; and (9) total water level. We also identified the 10 most powerful wave events for each site using Hs and Hmax, and recorded: (1) date-time of the event; (2) wave power;

(3) significant wave height (Hs); (4) wave period (Tp); (5) wave direction; (6) water level; (7) predicted water level; and (8) skew surge level.

2.3.4 Stage 4: Bimodal wave and swell review

Given the emerging importance of understanding ‘bimodal’ wave conditions, we assessed this in stage four. As illustrated in Figure 2.6, a bimodal sea state, consisting of a combination of wind- sea and swell, is characterised by two peak frequencies. Storm waves can also include a significant proportion of swell energy within the spectrum.

The CCO provide monthly wave buoy data that has undergone spectral analysis to indicate the percentage (that month) of bimodal waves, available and updated annually at https://www.channelcoast.org/ccoresources/bimodalseas/. This dataset gives the opportunity

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to assess the extent of swell both spatially and temporally, therefore as the first step, we simply extracted and rearranged the CCO data provided in the spreadsheet to indicate which winter seasons were the most bimodal.

Figure 2.6: An example of wave frequency vs. energy that can be used to assess the percentage of bimodal seas (Channel Coastal Observatory, 2020).

2.3.5 Stage 5: Coastal flood catalogue

Stage five involved compiling a catalogue of coastal flooding events within the SCOPAC region. Using a similar approach to Haigh et al. (2015; 2017), a detailed examination of past studies and data sources of reported flood events was done. We looked at seven main sources: (1) Met Office Monthly Weather Reports and UK Climate Summaries; (2) Lamb (1991); (3) Eden (2008); (4) Zong and Tooley (2003); (5) Hickey (1997) Vol. 1; (6) Davison et al. (1993); and (7) research projects undertaken by past students at the University of Southampton.

The Monthly Weather Report was a monthly meteorological publication containing a general summary of the main features of the weather in the UK published by Met Office for each month for a period of January 1884-December 1993 (available from: https://www.metoffice.gov.uk/research/library-and-archive/archive-hidden- treasures/monthly-weather-reports). UK Climate summaries are web-pages updated each month since 2001 to summarise the latest month’s weather across the UK (available from: https://www.metoffice.gov.uk/research/climate/maps-and-data/summaries/index). These reports maintain consistent style of reporting through time, though flood events tend to be mentioned briefly and not always attributed to a specific source. Lamb (1991) recorded historical

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great North Sea storms along with varying details of meteorological conditions and other available information for each storm covering 1509-1990. Eden (2008) documented severe weather events (including snow/wind/hail storms, tornados, flash floods, etc.) of British Isles covering the period of 1901-2008. Zong and Tooley (2003) published a journal paper consisted of historical coastal floods record in Britain compiled by reviewing primarily microfilms of The Times newspaper and other archive sources such as published and manuscript diaries, school logbooks, family and estate letters and papers, and parish registers, covering 1785 to 1994. The text source is the first volume of the unpublished thesis by Hickey (1997), available from Institutional Repository for Coventry University. This thesis provides a record of coastal floods in Northwest Europe (11 countries) excluding Scotland covering the period of 800-1990. ‘The Hampshire and Isle of Wight Weather Book’ by Davison et al. (1993) presented a unique pictorial record of ‘dramatic weather events’ in Hampshire and the Isle of Wight since 1600 to 1993. The last source we examined is the unpublished (with the exception of Ruocco et al., 2011) theses by students at the University of Southampton containing records of coastal flood events in southern regions of England. The events were compiled in each case by analysing tide gauge data for the chosen area then researching in local newspaper to identify coastal floods. Details of the individual projects can be seen in Table 2.3.

Table 2.3: Seven theses by University of Southampton’s students with the year, title, tide gauge they analysed, newspapers they used, the date coverage, and the study area. Date Student No. Year Title Tide Gauges Newspapers Cover Study Area Name age Reconstructing Coastal Flood Occurrence in the • Southern Daily Echo (The Southampton and Amy • Southampton 1935- 1 2009 Solent since 1935 Echo) Portsmouth Ruocco • Portsmouth 2009 using Historical • The News (Solent) Database

• Southern Daily Echo Megan J K Coastal Flooding in 2 2011 • Southampton • Southampton City Council 1950- Southampton Smith Southampton records 2010 Coastal Flooding in The Solent the Solent, an • Isle of Wight County Press (Lymington, Isle Karen • Southampton 3 2011 Analysis using Sea • Chichester Observer 1924- of Wight, Akehurst • Portsmouth Levels and Media • New Milton Advertiser 2008 Chichester) Records • Southern Daily Echo Coastal Floods of the • Isle of Wight County Press Oliver • Portsmouth • Portsmouth News 4 2015 2013/2014 Season 2013- The Solent Bragg in the Solent. • Southampton • Lymington Times 2014 • Belsize Flood Resilience Project

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Date Student No. Year Title Tide Gauges Newspapers Cover Study Area Name age • On the Wight Analysis of Historical Coastal Floods in • Bournemouth Sam • The Bournemouth Echo 1935- 5 2017 Dorset from 1935 - • Southampton Dorset Burrows • The Dorset Echo 2014 2014 • Weymouth

A Historical Analysis of Coastal Flooding • Dover • Chichester Express Angus 1924- South-East 6 2017 in South-East • Newhaven • The Argus Lawrence 2016 England England 1924-2016 • Portsmouth • Dover Express

• Hampshire and Southampton County Newspaper • Hampshire Chronicle • Hampshire Telegraph The Reconstruction • Hampshire Advertiser and Analysis of • Southern Daily Echo Ximena Historical Coastal (Southern Evening Echo) 7 2018 1804- The Solent Boza Flood Events from • Southampton Times 2016 1800s in the Solent, • Portsmouth Daily Times UK • The Isle of Wight Times • Isle of Wight Observer • Isle of Wight County Press • Lymington Times • The Evening News (London)

For each coastal flooding event identified from these sources, the date (year, month, day), the locations affected, and the sources listing the event were recorded. Next, for each flood event, as much information as possible was extracted. The amount of information available for each event varies significantly but at least a date and the locations affected were identified. This information was then used to compile a systematic commentary for each flood event using a similar approach to Haigh et al. (2015; 2017), which is structured around the SPRC conceptual model. Using the template from Boza (2018) shown in Figure 2.7, the event date, a quote from either a newspaper or previous studies, the locations, and a color-coded graphic indicating the severity ranking of the events are collected. This is followed by bullet points of the Sources (the meteorological conditions that caused the flood event, such as storm surge, wind, tide, waves), the Pathways (how the sea progressed into mainland for instance erosion, breaching, overtopping, overflowing), and the Receptors and Consequences (the people, property, infrastructure, and agricultural land that were affected by the flood and the impacts that the flood had on each event). Finally, a list of the references is provided.

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Figure 2.7: An example of commentary of the flood event using SPRC Conceptual Model (Boza, 2018).

We gave each event a severity ranking, based on reported impact, following that of Boza (2018). Using the information from the receptors and consequences component above, each flood event was classified based on the severity of their consequences using the severity chart presented in Table 2.4. All flood events were classified as either: (1) Low-Low, (2) Low-High, (3) Medium-Low, (4) Medium-High, (5) High-Low, or (6) High-High.

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Table 2.4: Severity chart from 1 (nuisance) to 6 (disastrous) used to rank each of flood event identified (Boza, 2018)

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3 STAGE 1: TRENDS AND PATTERNS

This chapter describes the results of the first stage of the analysis. The objective addressed here is to calculate longer-term trends in still sea level and its components (e.g., MSL, astronomical tides and storm surges), and waves. A total of 9 tide gauge sites and 9 wave buoys were assessed across the English Channel to provide a perspective for the SCOPAC Region – this is especially beneficial for sea level analysis because it allows longer data records to be analysed whilst the results are relevant across a broad area.

3.1 Trends in still sea level and its component parts

In the first step, we assess trends in relative MSL. The time series of annual relative MSL for the 9 sites (St. Mary’s, Newlyn, Devonport, Weymouth, Bournemouth, Southampton, Portsmouth, Newhaven, and Dover) are shown in Figure 3.1. The magnitude of the linear trends for the total data length available at each site are shown in Table 3.1. The linear trends vary between 1.69 mm/yr and 3.05 mm/yr, for the sites with statistically significant trends (average of 2.12 mm/yr).

The trends are statistically significant (95% confidence level) at 6 sites. At St. Marys, Weymouth and Bournemouth, the trends are not statistically significant, probably because of the shorter data length available at these sites. MSL is consistently rising along the south coast of the English Channel. Note at Weymouth, the trends are lower (0.29 mm/yr), but this site has shorter record and periods of missing data which biases the trends. The longest most continuous record is at Newlyn. At this site, MSL have risen at 1.86 mm/yr.

The linear trends for the period 1970 to 2019, 1990 to 2019, and 2000 to 2019 are also listed in Table 3.1. The average rates across all sites that are statistically significant for the period of 1970 to 2019, 1990 to 2019, and 2000 to 2019, respectively are 2.66 mm/yr, 2.78 mm/yr, and 3.18 mm/yr, indicating a gradual increase (e.g., acceleration) in the rate of rise of the MSL in recent years.

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Figure 3.1: Time series of annual relative MSL for sites along the UK south coast (St. Mary’s, Newlyn, Devonport, Weymouth, Bournemouth, Southampton, Portsmouth, Newhaven, and Dover).

Table 3.1: Linear trends in MSL for different time periods Linear trend ± one standard error (mm/yr) Site Whole Period 1970 - 2019 1990 - 2019 2000 - 2019 Dover 2.29 ± 0.20 2.55 ± 0.27 2.96 ± 0.53 2.77 ± 0.56 Newhaven 3.05 ± 0.47 3.05 ± 0.47 3.05 ± 0.47 3.32 ± 0.79 Portsmouth 1.77 ± 0.27 1.15 ± 0.31 3.19 ± 0.70 1.84 ± 1.31 Southampton 1.69 ± 0.10 3.71 ± 0.30 2.73 ± 0.70 4.16 ± 1.00 Bournemouth 1.45 ± 0.76 - 1.45 ± 0.76 0.51 ± 1.07 Weymouth 0.29 ± 1.11 - 0.29 ± 1.11 -4.20 ± 2.52 Devonport 2.22 ± 0.45 2.79 ± 0.54 1.06 ± 0.46 2.93 ± 1.06 Newlyn 1.86 ± 0.09 2.70 ± 0.25 3.79 ± 0.60 2.73 ± 1.22 St. Mary’s 1.93 ± 1.02 - 1.93 ± 1.02 -1.30 ± 1.40 Note: Red indicates the trends are statistically significant at 95% confidence.

Next, we assess trends in astronomical tidal levels. Time-series of annual MHW, MLW, and MTR are shown in Figure 3.2 for St. Mary’s, Newlyn, Devonport, Weymouth, Bournemouth, Southampton, Portsmouth, Newhaven, and Dover. Note that high-frequency sea level data for Dover is also available (more than 60% completeness) for 1924, 1926, 1934, 1935, 1938, 1958- 1964, however these data showed datum issues hence we excluded these data for the trend analysis. The magnitude of the linear trends for the data length available at each site are listed in Table 3.2. For MHW, Newlyn, Devonport, Southampton, Portsmouth, Newhaven, and Dover show

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statistically significant positive linear trends. Weymouth and Bournemouth also show positive linear trends but not statistically significant, while St Mary’s show negative linear trends but not statistically significant. Note that these 3 sites have shorter records and periods of missing data which could bias the trends. For MLW, St. Mary’s, Newlyn, Bournemouth, Southampton, Portsmouth, and Dover show statistically significant positive linear trends. Devonport and Newhaven show positive linear trends, but which are not statistically significant, while Weymouth shows negative linear trends but that are not statistically significant. Trends in MLW are higher than those in MHW at St. Marys, Weymouth, Bournemouth, and Southampton and the opposite at the remaining five sites.

Figure 3.2: Time-series of annual: (a, b, c, d, e, f, g, h, i) MHW and (j, k, l, m, n, o, p, q, r) MLW for Dover, Newhaven, Portsmouth, Southampton, Bournemouth, Weymouth, Devonport, Newlyn and St. Mary’s overlaid with linear trends.

Time-series of annual MTR are shown in Figure 3.3 for the 9 sites. It is evident that the time-series follow the 18.6-year nodal with an amplitude of approximately 10 cm. After removing the nodal cycle, a statistically significant increase of MTR is observed at Newlyn, Portsmouth, and Dover while a statistically significant decrease of MTR is spotted at Southampton. An increase of MTR is also observed at Weymouth and Newhaven; however, the trends are not statistically significant at these two sites. At Devonport and Bournemouth, a decrease in MTR is observed but this is also not statistically significant.

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Figure 3.3: Time-series of annual MTR: (a, b, c, d, e, f, g, h, i) before and (j, k, l, m, n, o, p q, r) after removing the 18.6 nodal cycle for Dover, Newhaven, Portsmouth, Southampton, Bournemouth, Weymouth, Devonport, Newlyn and St. Mary’s overlaid with linear trends.

Table 3.2: Linear trends in MHW, MLW and MTR Linear trend ± one standard error (mm/yr) Site MHW MLW MTR Dover 2.97 ± 0.49 1.49 ± 0.38 0.57 ± 0.20 Newhaven 2.73 ± 1.06 0.15 ± 0.95 0.65 ± 0.52 Portsmouth 2.69 ± 0.37 0.92 ± 0.36 1.28 ± 0.19 Southampton 1.33 ± 0.26 2.07 ± 0.28 -0.72 ± 0.26 Bournemouth 0.79 ± 0.82 2.75 ± 1.36 -0.41 ± 0.35 Weymouth 0.04 ± 1.00 -0.14 ± 0.95 0.21 ± 0.41 Devonport 2.41 ± 1.19 1.97 ± 1.02 -0.28 ± 0.34 Newlyn 2.59 ± 0.17 1.08 ± 0.19 1.41 ± 0.20 St. Mary’s -4.52 ± 1.30 7.27 ± 2.16 -2.00 ± 1.35 Note: Red indicates the trends are statistically significant at 95% confidence.

Next, we assess trends in the storm surge component of sea level, considering the skew surge parameter. Time-series of annual 90th and 99th skew surge percentiles are shown in Figure 3.4 for the nine sites. The magnitude of the linear trends, for the data length available at each site, are listed in Table 3.3 for the five percentile levels considered (i.e., 80th, 90th, 95th, 99th, and 99.9th). Most of the trends in these 5 percentile levels are not statistically significant, suggesting that skew surge values have not changed significantly over the data period. The trends that are statistically

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significant (Table 3.3) show a slight decrease in skew surge levels. Portsmouth is the only site that shows an increase in skew surge for all percentile levels considered but these changes are not statistically significant.

Table 3.3: Linear trends in skew surge percentiles Linear trend ± one standard error (mm/yr) Site 80th 90th 95th 99th 99.9th Dover -0.12 ± 0.12 -0.23 ± 0.20 -0.38 ± 0.32 -1.11 ± 0.70 -0.96 ± 1.65 Newhaven -0.49 ± 0.10 -0.51 ± 0.16 -0.64 ± 0.23 -1.32 ± 0.70 -0.72 ± 1.90 Portsmouth 0.04 ± 0.08 0.06 ± 0.12 0.18 ± 0.17 0.62 ± 0.31 0.55 ± 0.67 Southampton -0.02 ± 0.08 -0.13 ± 0.10 -0.12 ± 0.13 -0.35 ± 0.24 -0.23 ± 0.57 Bournemouth -0.62 ± 0.29 -0.69 ± 0.69 -1.65 ± 0.97 -3.42 ± 2.10 -4.08 ± 4.09 Weymouth -0.30 ± 0.23 -0.43 ± 0.31 -0.53 ± 0.41 -0.55 ± 0.81 2.24 ± 2.45 Devonport -0.13 ± 0.20 -0.25 ± 0.27 -0.66 ± 0.49 -0.35 ± 0.82 1.97 ± 2.26 Newlyn 0.02 ± 0.03 0.04 ± 0.05 0.05 ± 0.07 -0.05 ± 0.15 0.33 ± 0.35 St. Mary’s -0.56 ± 0.31 -0.87 ± 0.47 -1.48 ± 0.78 -2.52 ± 1.58 -8.16 ± 3.77 Note: Red indicates the trends are statistically significant at 95% confidence

Next, we consider trends and uncertainties in extreme sea levels, which incorporate changes in MSL, tides, and skew surges. Time-series of annual 90th extreme sea level percentiles before and after subtracting the 50th percentile are shown in Figure 3.5 for the 9 sites: St. Mary’s, Newlyn,

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Devonport, Weymouth, Bournemouth, Southampton, Portsmouth, Newhaven, and Dover. The magnitudes of the linear trends for the data length available at each site are listed in Table 3.4 for the 5 percentile levels considered (i.e., 80th, 90th, 95th, 99th, and 99.9th) before and after removing the 50th percentile. Newlyn and Portsmouth show a statistically significant increase in extreme sea levels in all the 5 percentile levels considered before removing the 50th percentile. After removing the 50th percentile, the trend remains statistically significant at Newlyn while no longer statistically significant in 99th and 99.9th percentile at Portsmouth, indicating that changes in tides are also driving increases in extreme sea levels at Newlyn, but not at Portsmouth. Before removing the 50th percentile, Southampton and Dover show a statistically significant increase in extreme sea levels in four percentiles considered (80th, 90th, 95th, and 99th) while Dover remains statistically significant after removing the 50th percentile. The trend is no longer significant except in the 99th percentile for Southampton showing a decrease in extreme sea levels. Newhaven also shows a statistically significant increase in extreme sea levels before removing the 50th percentile in some percentiles, but none of the trends remain significant after removing the 50th percentile.

Figure 3.5: Time-series of annual 90th extreme sea level percentiles (a, b, c, d, e, f, g, h, i) before and (j, k, l, m, n, o, p q, r) after subtracting the 50th percentile for Dover, Newhaven, Portsmouth, Southampton, Bournemouth, Weymouth, Devonport, Newlyn and St. Mary’s overlaid with linear trends.

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Table 3.4: Linear trends in extreme sea level percentiles Linear trend ± one standard error (mm/yr) Site Before removing 50th percentile (i.e. MSL) 80th 90th 95th 99th 99.9th Dover 2.42 ± 0.46 2.29 ± 0.44 2.28 ± 0.44 2.19 ± 0.52 1.46 ± 0.83 Newhaven 2.41 ± 1.00 2.68 ± 0.92 2.46 ± 0.92 1.83 ± 1.03 1.58 ± 1.34 Portsmouth 2.41 ± 0.32 2.28 ± 0.32 2.32 ± 0.34 2.25 ± 0.42 1.73 ± 0.62 Southampton 1.37 ± 0.22 1.28 ± 0.23 1.17 ± 0.25 0.91 ± 0.29 0.74 ± 0.41 Bournemouth 0.81 ± 0.82 0.30 ± 0.94 0.46 ± 1.10 -0.21 ± 1.58 -2.45 ± 2.51 Weymouth -0.02 ± 0.91 -0.24 ± 1.01 -0.15 ± 1.00 -0.28 ± 1.16 -0.92 ± 1.87 Devonport 3.67 ± 1.28 3.26 ± 1.25 3.21 ± 1.26 2.71 ± 1.42 1.88 ± 1.81 Newlyn 2.18 ± 0.14 2.37 ± 0.16 2.43 ± 0.16 2.44 ± 0.19 2.25 ± 0.25 St. Mary’s -2.51 ± 1.23 -2.91 ± 1.10 -3.61 ± 1.13 -3.50 ± 1.98 -2.87 ± 3.90 After removing 50th percentile (i.e. MSL) Dover 1.86 ± 0.59 1.49 ± 0.60 1.41 ± 0.62 1.66 ± 0.64 1.30 ± 1.36 Newhaven 0.97 ± 0.68 1.13 ± 0.69 0.99 ± 0.68 0.33 ± 0.80 0.27 ± 1.15 Portsmouth 0.66 ± 0.20 0.55 ± 0.19 0.59 ± 0.22 0.58 ± 0.33 0.36 ± 0.56 Southampton -0.13 ± 0.16 -0.24 ± 0.17 -0.33 ± 0.18 -0.62 ± 0.24 -0.71 ± 0.39 Bournemouth -0.31 ± 0.43 -0.67 ± 0.64 -0.72 ± 0.75 -1.30 ± 1.26 -3.79 ± 2.24 Weymouth 0.59 ± 0.66 0.57 ± 0.77 -0.74 ± 0.67 -3.11 ± 1.55 -5.76 ± 2.60 Devonport 0.38 ± 0.71 -0.08 ± 0.74 -0.21 ± 0.80 -0.56 ± 1.01 -1.45 ± 1.37 Newlyn 0.41 ± 0.12 0.63 ± 0.14 0.67 ± 0.15 0.69 ± 0.19 0.55 ± 0.25 St. Mary’s -1.47 ± 1.16 -3.56 ± 1.25 -5.07 ± 1.27 -3.61 ± 1.66 -3.45 ± 2.76 Note: Red indicates the trends are statistically significant at 95% confidence

3.2 Trends in wave components

First, we assess trends in significant wave height. Time-series of annual 90th and 99th significant wave height percentiles are shown in Figure 3.6 for Penzance, Start Bay, Chesil, Boscombe, Milford, Sandown Bay, Hayling Island, Rustington, and Folkestone. The magnitude of the linear trends, for the data length available at each site, are listed in Table 3.5 for the 5 percentile levels considered (i.e., 80th, 90th, 95th, 99th, and 99.9th). All of the sites (except Folkestone) show an increase in wave height over time, however none of the trends in any of the percentile levels are statistically significant due to the short period of data available.

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Table 3.5: Linear trends in wave height percentiles Linear trend ± one standard error (mm/yr) Site 80th 90th 95th 99th 99.9th Folkestone 0.02 ± 3.40 -0.03 ± 4.93 0.17 ± 5.87 -0.87 ± 7.56 -7.65 ± 11.90 Rustington 6.56 ± 5.56 6.74 ± 7.50 5.66 ± 8.37 5.16 ± 10.56 7.93 ± 17.75 Hayling Island 5.84 ± 4.56 5.90 ± 6.41 3.49 ± 6.78 5.58 ± 9.37 0.69 ± 13.69 Sandown Bay 3.66 ± 3.07 6.94 ± 4.25 6.20 ± 5.51 9.01 ± 9.38 0.91 ± 18.38 Milford 3.19 ± 4.08 3.10 ± 4.78 2.00 ± 5.49 0.01 ± 7.33 0.16 ± 10.72 Boscombe 3.68 ± 3.38 3.72 ± 5.14 5.36 ± 6.96 9.47 ± 10.07 8.54 ± 18.22 Chesil 10.38 ± 10.53 13.46 ± 14.03 7.42 ± 16.70 9.80 ± 22.75 11.61 ± 37.22 Start Bay 8.90 ± 8.06 11.47± 10.40 21.27 ± 12.82 33.74 ± 19.54 37.41 ± 40.52 Penzance 12.36 ± 6.36 13.35 ± 8.42 18.52 ± 10.05 36.57 ± 16.86 56.46 ± 37.78 Note: Red indicates the trends are statistically significant at 95% confidence

Next, we assess trends in wave period. Time-series of annual 90th and 99th wave period percentiles are shown in Figure 3.7 for the 9 sites. We also considered only wave period that correspond with higher wave height (above 1 m). Time-series of annual 90th and 99th wave period percentiles when wave height is above 1 m are shown in Figure 3.8. The magnitude of the linear trends, for the data length available at each site, are listed in

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Table 3.6 for the 5 percentile levels considered (i.e., 80th, 90th, 95th, 99th, and 99.9th) for all wave period and wave period when wave height above 1 m. Most of the trends in the 5 percentile levels are not statistically significant, suggesting that wave period values have not changed significantly over the data period.

Table 3.6) show an increase in wave period values.

Figure 3.7: Time-series of annual: (a, b, c, d, e, f, g, h, i) 90th and (j, k, l, m, n, o, p, q, r) 99th wave period percentiles for Folkestone, Rustington, Hayling Island, Sandown Bay, Milford, Boscombe, Chesil, Start Bay, and Penzance overlaid with linear trends.

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Table 3.6: Linear trends in wave period percentiles Linear trend ± one standard error (s/yr) Site All wave period data 80th 90th 95th 99th 99.9th Folkestone 0.00 ± 0.01 0.09 ± 0.03 0.21 ± 0.04 0.19 ± 0.04 0.30 ± 0.10 Rustington 0.09 ± 0.02 0.05 ± 0.02 0.07 ± 0.03 0.02 ± 0.03 0.05 ± 0.06 Hayling Island 0.04 ± 0.02 0.04 ± 0.02 0.03 ± 0.03 0.12 ± 0.03 0.13 ± 0.05 Sandown Bay 0.04 ± 0.01 0.22 ± 0.04 0.12 ± 0.05 0.11 ± 0.04 0.05 ± 0.05 Milford 0.11 ± 0.04 0.07 ± 0.03 0.02 ± 0.04 0.04 ± 0.03 0.26 ± 0.05 Boscombe 0.16 ± 0.04 0.11 ± 0.03 0.08 ± 0.02 0.09 ± 0.04 0.16 ± 0.05 Chesil 0.03 ± 0.05 0.04 ± 0.06 -0.02 ± 0.05 0.01 ± 0.06 0.05 ± 0.14 Start Bay 0.07 ± 0.03 0.10 ± 0.03 0.08 ± 0.04 0.07 ± 0.18 0.15 ± 0.18 Penzance 0.00 ± 0.04 -0.04 ± 0.04 0.00 ± 0.03 0.04 ± 0.06 -0.02 ± 0.06 Only wave period when significant wave height above 1 m Folkestone 0.05 ± 0.01 0.05 ± 0.02 0.13 ± 0.04 0.10 ± 0.03 0.35 ± 0.19 Rustington 0.06 ± 0.02 0.07 ± 0.04 0.07 ± 0.05 0.13 ± 0.08 0.00 ± 0.09 Hayling Island 0.08 ± 0.05 0.09 ± 0.04 0.08 ± 0.05 0.04 ± 0.07 0.13 ± 0.08 Sandown Bay -0.00 ± 0.01 0.03 ± 0.02 0.08 ± 0.05 0.30 ± 0.24 0.52 ± 0.22 Milford 0.19 ± 0.11 0.18 ± 0.11 0.12 ± 0.08 0.01 ± 0.08 0.21 ± 0.09 Boscombe 0.09 ± 0.14 0.05 ± 0.22 0.21 ± 0.15 0.15 ± 0.06 0.21 ± 0.07 Chesil 0.03 ± 0.06 0.07 ± 0.08 0.09 ± 0.15 0.06 ± 0.16 0.14 ± 0.16 Start Bay 0.08 ± 0.04 0.10 ± 0.03 0.08 ± 0.05 0.06 ± 0.11 -0.00 ± 0.17 Penzance 0.04 ± 0.04 0.05 ± 0.05 0.05 ± 0.10 -0.07 ± 0.14 0.05 ± 0.13 Note: Red indicates the trends are statistically significant at 95% confidence

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Next, we consider wave direction parameter. The wave roses for each site displaying the wave heights and the direction the waves coming from are shown in Figure 3.9. Chesil has noticeable higher wave height coming from south-westerly. Milford and Rustington also recorded that most waves are coming from southwest. Most large incoming waves at Penzance, Boscombe, Sandown Bay, and Hayling Island are from the south. For Start Bay and Folkestone, most waves are coming from the south, though some easterly wave are also frequent from these records.

Figure 3.9: Wave roses at each site (a, b, c, d, e, f, g, h, i) for Folkestone, Rustington, Hayling Island, Sandown Bay, Milford, Boscombe, Chesil, Start Bay, and Penzance.

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We then calculated wave power (Po) time-series using Hs and Hmax. We also estimated trends in annual mean wave power at the 9 wave buoy locations and fitted the trends with linear regression. Time series of annual mean wave power at each nine wave buoy sites are shown in Figure 3.10. The magnitude of annual mean wave power trends for the data length available at each site are listed in Table 3.7 for both types of wave power that were calculated. All of the sites

(except Folkestone) show an increase in wave power (both using Hs and Hmax) over time, however this was only statistically significant at 4 sites (Rustington, Hayling Island, Sandown Bay and

Milford) for wave power using Hs and 3 sites (Rustington, Hayling Island, and Milford) for wave power using Hmax. The average rate across the sites that are statistically significant are 0.0625 kW/yr (for wave power with Hs) and 0.0967 kW/yr (for wave power with Hmax).

Figure 3.10: Time-series of annual mean wave power: (a, b, c, d, e, f, g, h, i) calculated using Hs and (j, k, l, m, n, o, p, q, r) calculated using Hmax at Folkestone, Rustington, Hayling Island, Sandown Bay, Milford, Boscombe, Chesil, Start Bay, and Penzance overlaid with linear trends.

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Table 3.7: Linear trends in annual mean wave power Linear trend ± one standard Site error (kW/yr)

with Hs with Hmax Folkestone 0.05 ± 0.06 0.09 ± 0.16 Rustington 0.53 ± 0.27 1.22 ± 0.63 Hayling Island 0.71 ± 0.35 1.46 ± 0.76 Sandown Bay 0.16 ± 0.09 0.36 ± 0.21 Milford 0.94 ± 0.44 1.66 ± 0.89 Boscombe 0.31 ± 0.23 0.68 ± 0.51 Chesil 0.97 ± 0.98 2.50 ± 2.23 Start Bay 0.86 ± 0.44 2.02 ± 1.06 Penzance 0.74 ± 0.45 1.71 ± 1.03 Note: Red indicates the trends are statistically significant at 95% confidence

Time-series of mean wave power per season are displayed in Figure 3.11 (using Hs) and Figure

3.12 (using Hmax). Wave power values calculated using Hmax are higher than calculated using Hs as would be expected – although followed the same pattern. In both figures, Chesil has the most powerful waves, while Sandown Bay and Folkestone have the least powerful waves. On average, seasons 2013/14 and 2014/15 were prominent in exhibiting higher wave power than the other seasons. Time-series of maximum wave power per season are displayed in Figure 3.13 and Figure 3.14. Here we observe that wave power is notably higher in season 2013/14.

Figure 3.11: Time series of average wave power using Hs per season at Folkestone, Rustington, Hayling Island, Sandown Bay, Milford, Boscombe, Chesil, Start Bay, and Penzance.

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Figure 3.12: Time-series of average wave power using Hmax per season at Folkestone, Rustington, Hayling Island, Sandown Bay, Milford, Boscombe, Chesil, Start Bay, and Penzance

Figure 3.13: Time-series of maximum wave power using Hs per season at Folkestone, Rustington, Hayling Island, Sandown Bay, Milford, Boscombe, Chesil, Start Bay, and Penzance.

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Figure 3.14: Time-series of maximum wave power using Hmax per season at Folkestone, Rustington, Hayling Island, Sandown Bay, Milford, Boscombe, Chesil, Start Bay, and Penzance

Next, we calculated two run up time series with two different beach slope coefficients, 0.01 and 0.03 and consider the resultant trends. Time-series of annual 90th and 99th wave run-up percentiles at Folkestone, Rustington, Hayling Island, Sandown Bay, Milford, Boscombe, Chesil, Start Bay, and Penzance are shown in Figure 3.15 (for 훽 = 0.01) and Figure 3.16 (for 훽 = 0.03). The magnitude of the run-up (linear) trends for the data length available at each site, are listed in Table 3.8 for the 5 percentile levels considered (i.e. 80th, 90th, 95th, 99th, and 99.9th) for both beach slope run up levels. The majority of the trends in all of the percentile levels for both run up levels are not statistically significant.

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Table 3.8: Linear trends in run up level percentiles Linear trend ± one standard error (mm/yr) Site Run up level for 휷 = ퟎ. ퟎퟏ 80th 90th 95th 99th 99.9th Folkestone 0.07 ± 0.94 0.34 ± 1.36 0.46 ± 1.63 -0.08 ± 2.08 -0.53 ± 3.75 Rustington 2.05 ± 1.43 2.01 ± 1.91 1.46 ± 2.21 1.27 ± 2.78 1.23 ± 4.60 Hayling Island 2.55 ± 1.25 2.42 ± 1.72 1.65 ± 1.93 1.78 ± 2.52 4.38 ± 4.30 Sandown Bay 1.16 ± 0.84 1.69 ± 1.15 1.33 ± 1.52 1.84 ± 2.42 0.25 ± 4.68 Milford 3.14 ± 1.67 3.53 ± 2.36 4.02 ± 2.71 5.51 ± 4.41 10.53 ± 6.15 Boscombe 1.40 ± 0.96 1.61 ± 1.45 1.16 ± 1.97 2.65 ± 2.95 3.33 ± 4.71 Chesil 3.24 ± 2.98 3.77 ± 4.34 2.74 ± 4.99 4.01 ± 7.03 3.16 ± 12.70 Start Bay 2.96 ± 2.16 3.45 ± 2.59 5.19 ± 3.29 8.76 ± 4.98 10.67 ± 10.33 Penzance 3.47 ± 1.75 3.31 ± 2.47 4.69 ± 2.92 9.84 ± 4.54 15.61 ± 10.00 Run up level for 휷 = ퟎ. ퟎퟑ Folkestone 0.39 ± 1.12 1.08 ± 1.66 1.55 ± 2.02 0.48 ± 2.42 1.01 ± 4.66 Rustington 3.78 ± 1.81 3.33 ± 2.47 3.21 ± 2.89 2.73 ± 3.75 1.97 ± 5.60 Hayling Island 4.67 ± 1.83 4.65 ± 2.54 3.86 ± 3.00 4.28 ± 4.10 14.80 ± 7.26 Sandown Bay 2.23 ± 1.10 3.03 ± 1.51 2.55 ± 2.03 2.98 ± 3.01 2.29 ± 6.15 Milford 5.68 ± 2.22 7.08 ± 3.34 7.04 ± 4.01 9.51 ± 6.91 20.40 ± 9.65 Boscombe 2.91 ± 1.30 3.01 ± 2.08 3.26 ± 3.02 2.98 ± 5.12 10.85 ± 6.53 Chesil 4.57 ± 3.45 4.51 ± 5.33 4.17 ± 6.31 7.09 ± 9.25 9.03 ± 19.81 Start Bay 5.41 ± 2.92 6.68 ± 3.48 6.80 ± 4.37 11.39 ± 6.26 15.38 ± 13.68 Penzance 4.86 ± 2.54 5.65 ± 3.67 6.40 ± 4.46 12.06 ± 6.51 21.05 ± 13.65 Note: Red indicates the trends are statistically significant at 95% confidence

Then we calculated total water levels by combining run-up levels with observed water levels at four pairs of sites: (1) Weymouth-Chesil; (2) Bournemouth-Boscombe; (3) Portsmouth-Hayling Island; and (4) Newhaven-Rustington. Time-series of annual 90th and 99th total water level percentiles at these four pairs of sites are shown in Figure 3.17 (for 훽 = 0.01) and Figure 3.17Error! Reference source not found. (for 훽 = 0.03). The magnitudes of the total water level linear trends at each pair of sites are listed in Table 3.9 for the 5 percentile levels considered (i.e., 80th, 90th, 95th, 99th, and 99.9th) for both total water level. The trends at Newhaven-Rustington and Portsmouth-Hayling Island show a statistically significant increase of total water level over the period of available data. At Bournemouth-Boscombe and Weymouth-Chesil, the trends are not statistically significant due to short period of data.

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Figure 3.17: Time-series of annual: (a, b, c, d) 90th and (e, f, g, h) 99th total water level percentiles for 훽 = 0.01 at Newhaven–Rustington, Portsmouth–Hayling Island, Bournemouth-Boscombe, and Weymouth-Chesil overlaid with linear trends.

Table 3.9: Linear trends in total water level percentiles Linear trend ± one standard error (mm/year) Site Total water level with run-up level for 휷 = ퟎ. ퟎퟏ 80th 90th 95th 99th 99.9th Newhaven- 14.22 ± 2.05 15.10 ± 1.85 14.36 ± 1.94 14.99 ± 3.64 21.30 ± 5.81 Rustington Portsmouth- 12.86 ± 1.92 12.35 ± 1.80 12.07 ± 2.06 13.84 ± 3.99 15.31 ± 6.64 Hayling Island Bournemouth- 4.83 ± 3.20 4.89 ± 4.35 3.88 ± 5.56 -0.91 ± 6.96 -11.31 ± 12.63 Boscombe Weymouth- 7.90 ± 4.39 7.21 ± 5.17 7.33 ± 6.72 10.64 ± 13.62 7.61 ± 19.76 Chesil Total water level with run-up level for 휷 = ퟎ. ퟎퟑ Newhaven- 15.34 ± 2.36 16.40 ± 2.08 15.66 ± 2.29 16.99 ± 4.19 22.28 ± 6.75 Rustington Portsmouth- 14.11 ± 2.08 14.68 ± 2.26 14.16 ± 2.89 16.52 ± 5.57 20.88 ± 7.92 Hayling Island Bournemouth- 5.30 ± 3.60 5.02 ± 5.24 3.35 ± 6.81 2.10 ± 8.63 -6.51 ± 12.81 Boscombe Weymouth- 7.54 ± 5.33 6.31 ± 6.07 7.09 ± 8.80 13.64 ± 17.38 8.17 ± 26.74 Chesil Note: Red indicates the trends are statistically significant at 95% confidence

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4 STAGE 2: THRESHOLD EXCEEDANCE EVENTS

This chapter presents the results from the second stage of analysis, the threshold exceedance approach. Results are presented for the four pairs of sites: (1) Weymouth-Chesil; (2) Bournemouth-Boscombe; (3) Portsmouth-Hayling Island; and (4) Newhaven-Rustington. The threshold exceedance approach was implemented for: (1) sea level and storm surge; (2) wave height and wave period; and (3) total water level and run-up. We also calculated and analysed wave power.

4.1 Sea level and storm surge

Time series of observed sea level and surge for Weymouth, Bournemouth, Portsmouth, and Newhaven are plotted in Figure 4.1, Figure 4.2, Figure 4.3, and Figure 4.4. The events exceeding the thresholds are marked as follows: black dots represent a 1 in 1-year event, blue dots represent a 1 in 5-year event and red dots represent a 1 in 10-year event. Looking at water level events at these 4 sites, the season 2013/14 stands out in term of the number of high-water levels at Weymouth and Portsmouth, with 8 and 14 events exceeding 1 in 1-year threshold, respectively.

Note, for Bournemouth, we are missing sea level data from November 2013 onwards, since the tide gauge was damaged during this period. Since then, the sea level data has been reported as having reliability issues by the BODC, hence we excluded these values from the analysis. We also excluded a large chunk of sea level data from Weymouth over the winter 2015/16 for the same reason. For Newhaven, the 2013/14 season saw 3 events exceed the threshold as well as the 1982/83 season. In term of storm surge events, the 2013/14 season was also prominent at Weymouth (7 events) and Portsmouth (10 events). At Newhaven, the 2013/14 season had the second highest number of exceedances (4 events) after 1992/93 (5 events).

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Figure 4.1: Time series of (a) observed water level and (c) storm surge in relation to three different return period value with the number of events exceeded each threshold per season for (b) water level and (d) storm surge at Weymouth.

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Figure 4.2: Time series of (a) observed water level and (c) storm surge in relation to three different return period value with the number of events exceeded each threshold per season for (b) water level and (d) storm surge at Bournemouth.

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Figure 4.4: Time series of (a) observed water level and (c) storm surge in relation to three different return period value with the number of events exceeded each threshold per season for (b) water level and (d) storm surge at Newhaven.

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4.2 Wave height and wave period

Time series of significant wave height (Hs) and wave period (Tp) for Chesil, Boscombe, Hayling

Island, and Rustington are plotted in Figure 4.5, Figure 4.6, Figure 4.7, and Figure 4.8. For Hs, the events exceeding the thresholds are marked as follows: Hs, black dots represent a 1 in 0.25-year event, blue dots represent a 1 in 1-year event and red dots represent a 1 in 10-year event. For Tp, black dots represent event when wave period reach over 18 s but below 21 s, blue dots represent event when wave period reach over 21 s but below 24 s and red dots represent event when wave period reach above 24 s. Note that we excluded wave period when significant wave height is below 1 m, as the long wave period event would be more likely to cause flooding when coincided with significant wave height above 1 m. Season 2013/14 is prominent at all 4 sites (Chesil, Boscombe, Hayling Island, and Rustington) in term of number of events exceeding threshold for both significant wave height and wave period.

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Figure 4.5: Time series of (a) wave height and (c) wave period in relation to three different return period value with the number of events exceeded each threshold per season for (b) wave height and (d) wave period at Chesil.

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Figure 4.6: Time series of (a) wave height and (c) wave period in relation to three different return period value with the number of events exceeded each threshold per season for (b) wave height and (d) wave period at Boscombe.

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Figure 4.7: Time series of (a) wave height and (c) wave period in relation to three different return period value with the number of events exceeded each threshold per season for (b) wave height and (d) wave period at Hayling Island.

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Figure 4.8: Time series of (a) wave height and (c) wave period in relation to three different return period value with the number of events exceeded each threshold per season for (b) wave height and (d) wave period at Rustington.

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4.3 Total water level and run-up level

Time series of total water level and run-up level available for Weymouth-Chesil, Bournemouth- Boscombe, Portsmouth-Hayling Island, and Newhaven-Rustington are plotted in Figure 4.9, Figure 4.12, Figure 4.14, and Figure 4.16 for =0.01 and Figure 4.11, Figure 4.13, Figure 4.15, and Figure 4.17 for =0.03. The events exceeding the thresholds are marked as follows: black dots represent a 1 in 1-year event, blue dots represent a 1 in 5-year event and red dots represent a 1 in 10-year event.

At Weymouth-Chesil, 2015/16 had the most run-up level exceedances for both coefficients. However, as we are missing large periods of sea level data from Weymouth during this time, season 2013/14 has the most total water level events for both coefficients. At Bournemouth- Boscombe, 2013/14 also stood out in term of run-up events, but we are missing sea level data from November 2013 onwards, so this does not show in total water level records. For Portsmouth-Hayling Island, 2015/16 stood out more than 2013/14, especially when using run- up level (훽 =0.03). At Newhaven-Rustington, 2013/14 had the most events in both run-up and total water level using (훽=0.01). However, when using (훽=0.03), 2015/16 had more extreme events counted by the total water level, though the most events for extreme run-up level remains as season 2013/14.

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Figure 4.10: Time series of (a) total water level and (c) run-up level (훽=0.01) in relation to three different threshold value with the number of events exceeded each threshold per season for (b) total water level and (d) run-up level at Weymouth-Chesil.

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Figure 4.11: Time series of (a) total water level and (c) run-up level (훽=0.03) in relation to three different threshold value with the number of events exceeded each threshold per season for (b) total water level and (d) run-up level at Weymouth-Chesil.

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Figure 4.12: Time series of (a) total water level and (c) run-up level (훽=0.01) in relation to three different threshold value with the number of events exceeded each threshold per season for (b) total water level and (d) run-up level at Bournemouth-Boscombe.

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Figure 4.13: Time series of (a) total water level and (c) run-up level (훽=0.03) in relation to three different threshold value with the number of events exceeded each threshold per season for (b) total water level and (d) run-up level at Bournemouth-Boscombe.

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Figure 4.14: Time series of (a) total water level and (c) run-up level (훽=0.01) in relation to three different threshold value with the number of events exceeded each threshold per season for (b) total water level and (d) run-up level at Portsmouth-Hayling Island.

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Figure 4.15: Time series of (a) total water level and (c) run-up level (훽=0.03) in relation to three different threshold value represented with the number of events exceeded each threshold per season for (b) total water level and (d) run-up level at Portsmouth-Hayling Island.

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Figure 4.16: Time series of (a) total water level and (c) run-up level (훽=0.01) in relation to three different threshold value with the number of events exceeded each threshold per season for (b) total water level and (d) run-up level at Newhaven-Rustington.

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Figure 4.17: Time series of (a) total water level and (c) run-up level (훽=0.03) in relation to three different threshold value with the number of events exceeded each threshold per season for (b) total water level and (d) run-up level at Newhaven and Rustington.

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5 STAGE 3: STORM EVENTS AND EXTREMES

This chapter presents the results from the third stage of analysis where the objective is to examine the characteristics of individual extreme sea levels. Again, as with the previous chapter, results are presented for the 4 pairs of sites: (1) Weymouth-Chesil; (2) Bournemouth-Boscombe; (3) Portsmouth-Hayling Island; and (4) Newhaven-Rustington.

The highest water level events at each site is shown in Table 5.1. At Weymouth and Chesil, the highest water level recorded was on the 10th March 2008 where water level had return periods of 19 years and 21 years, respectively. During that event, flooding was reported in several areas across the Solent – see Chapter 8. At Portsmouth and Newhaven, the highest water level recorded was on the 6th December 2013 (as a result of a North Sea surge), which corresponds to a return period of 15 years and 41 years, respectively.

Table 5.1: Highest water level event at each site. Water Predicted Skew Wave Date and RP Site level tide surge Hs (m) Tp (s) direction time (years) (mCD) (mCD) (m) (degree) Weymouth- 10/03/2008 19 3.04 2.51 0.54 3.86 9.1 219 Chesil 09:00 Bournemouth 10/03/2008 21 3.09 2.43 0.66 1.94 8.3 172 -Boscombe 10:30 Portsmouth- 06/12/2013 Hayling 15 5.56 4.88 0.68 0.86 8.3 211 01:00 Island Newhaven- 06/12/2013 41 7.79 7.06 0.73 1.4 7.7 219 Rustington 01:15

The highest skew surge levels at each site are listed in Table 5.2. At Weymouth, the highest skew surge recorded was on the 14th February 2014 at 18:45. Around 4 hours later that night, Chesil recorded the highest significant wave height level on the same day (Table 5.3). Portsmouth saw the highest skew surge on the 14th October 1976 while at Newhaven was on the 16th October 1987. Coastal flooding was reported on these two days. At Bournemouth the highest skew surge occurred on the 2nd January 2001. However, these was on relatively low tide on that date and therefore there was no flooding during this event.

Table 5.2: Highest skew surge event at each site. Skew Water Predicted Wave Date and RP Site Surge level tide Hs (m) Tp (s) direction time (years) (m) (mCD) (mCD) (degree) Weymouth- 14/02/2014 80 0.86 2.93 2.07 4.59 8.3 215 Chesil 18:45

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Skew Water Predicted Wave Date and RP Site Surge level tide Hs (m) Tp (s) direction time (years) (m) (mCD) (mCD) (degree) Bournemouth 02/01/2001 53 0.76 2.74 1.97 - - - -Boscombe 05:15 Portsmouth- 14/10/1976 Hayling 95 0.91 5.04 4.13 - - - 15:00 Island Newhaven- 16/10/1987 194 1.14 5.77 4.63 - - - Rustington 06:00

The highest significant wave height event at each site is listed in Table 5.3. Boscombe and Hayling Island recorded the highest significant wave height events on the same day, only 30 minutes apart, on the 28th March 2016 during “Storm Katie”. Rustington saw the highest significant wave height on the 24th December 2013.

Table 5.3: Highest significant wave height event at each site. Wave Water Predicted Skew Date and RP Site Hs (m) Tp (s) direction level tide surge time (years) (degree) (mCD) (mCD) (m) Weymouth- 14/02/2014 12 7.70 18.2 220 2.93 2.07 0.86 Chesil 23:30 Bournemout 28/03/2016 50 4.53 9.1 172 - - - h-Boscombe 03:30 Portsmouth- 28/03/2016 Hayling 41 4.40 9.1 169 5.24 4.55 0.69 03:00 Island Newhaven- 24/12/2013 25 5.46 10 203 6.03 5.97 0.06 Rustington 02:30 For wave period, we excluded all the wave period records when wave height was below 1 m. The longest wave period event at each site is shown in Table 5.4. At Chesil, the longest wave period recorded was on the 3rd January 2008 and at Boscombe, the longest wave period was on the 6th January 2014. At Hayling Island and Rustington, the longest wave period recorded was on the 15th February 2011.

Table 5.4: Longest wave period at each site. Wave Water Skew Date and Tp Hs Predicted Site direction level surge time (s) (s) tide (mCD) (degree) (mCD) (m) 03/01/2008 Weymouth-Chesil 25 1.04 208 - - - 22:00 Bournemouth- 06/01/2014 25 1.88 163 - - - Boscombe 13:30 Portsmouth- 15/02/2011 25 1.95 186 4.50 4.08 0.42 Hayling Island 23:00 Newhaven- 15/02/2011 25 1.76 208 5.99 5.60 0.39 Rustington 23:00

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However more insightful to damage at the coast is the wave power events. This highlights for example just how much loading there was on the open coast of the Solent with the Hayling buoy showing the sustained intensity of the 5th February 2014 (the most powerful event considering significant wave height) and the 8th February 2014 (the most powerful event considering maximum wave height). The highest wave power (using Hs) events at each site is listed in Table 5.5. Across the 4 sites, the most powerful waves occurred during the winter of 2013/14. Boscombe and Rustington reported the highest wave power at the same day on the 6th January 2014. The most powerful waves occurred on the 5th February 2014 and the 14th February at Hayling Island and Chesil, respectively.

Table 5.5: Highest wave power (using Hs) events at each site. Wave Wave Water Skew Date and Hs Tp Predicted Site Power direction level surge time (m) (s) tide (mCD) (kW/m) (degree) (mCD) (m) Weymouth- 14/02/2014 9,635,101 7.70 18.2 220 2.93 2.07 0.86 Chesil 23:30 Bournemouth- 06/01/2014 1,766,178 2.40 25.00 190 - - - Boscombe 17:30 Portsmouth- 05/02/2014 3,092,951 3.97 20.00 187 4.90 4.57 0.33 Hayling Island 15:00 Newhaven- 06/01/2014 2,137,076 2.64 25.00 212 6.63 6.66 -0.03 Rustington 15:00

The highest wave power (using Hmax) events at each site is shown in Table 5.6. The most powerful wave event occurred on 8th February 2014 and 6th January 2014 at Hayling Island and Chesil, respectively. Boscombe and Rustington saw the most powerful wave events (using Hmax) during the same event as the most powerful wave event using Hs.

Table 5.6: Highest wave power (using Hmax) events at each site. Wave Wave Water Predicted Skew Date and Hs Hmax Tp Site Power direction level tide surge time (m) (m) (s) (kW/m) (degree) (mCD) (mCD) (m) Weymouth- 06/01/2014 13,478,424 4.12 6.63 25.00 219 2.55 2.37 0.18 Chesil 15:00 Bournemouth- 06/01/2014 5,408,921 2.30 4.20 25.00 188 - - - Boscombe 16:00 Portsmouth- 08/02/2014 7,155,431 3.46 5.44 22.20 186 4.17 3.94 0.23 Hayling Island 18:30 Newhaven- 07/01/2014 5,318,433 2.93 4.69 22.20 208 6.72 6.58 0.14 Rustington 03:00

The highest run-up level (β =0.01) events at each site is listed in Table 5.7. At Chesil, Hayling Island and Rustington the highest run up occurred during 2013/14 on the 14th February 2014, 5th

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February 2014 and 24th December 2013, respectively. At Boscombe the run-up level was highest on the 28th March 2016. The highest total water level (β =0.01) events at each site is listed in Table 5.8. The 14th February 2014 storm produced the highest total water level at Weymouth-Chesil and Newhaven-Rustington, while the highest total water level at Bournemouth-Boscombe and Newhaven-Rustington is on 3rd December 2006 and 4th January 2018, respectively.

Table 5.7: Highest run up level (β =0.01) at each site. Total Run up Wave Water Predicte Skew Date and Water Site Level Hs (m) Tp (s) direction level d tide surge time Level (m) (degree) (mCD) (mCD) (m) (mCD) Weymouth- 14/02/201 2.09 7.69 15.40 224 2.57 1.62 0.95 4.67 Chesil 4 21:00 Bournemouth- 28/03/201 1.18 4.53 9.10 172 - - - - Boscombe 6 03:30:00 Portsmouth- 05/02/201 1.25 3.97 20.00 187 4.84 4.53 0.30 6.08 Hayling Island 4 15:00:00 Newhaven- 24/12/201 1.42 5.46 10.00 203 5.96 5.94 0.02 7.38 Rustington 3 02:30:00

Table 5.8: Highest total water level (β =0.01) at each site. Total Wave Water Predicte Skew Run up Date and Water Site Hs (m) Ts (s) direction level d tide surge Level time Level (degree) (mCD) (mCD) (m) (m) (mCD) Weymouth- 14/02/201 4.67 7.69 15.40 224.0 2.57 1.62 0.95 2.09 Chesil 4 21:00 Bournemouth- 03/12/200 3.72 3.04 7.40 185.0 2.93 2.23 0.70 0.79 Boscombe 6 06:15:00 Portsmouth- 14/02/201 6.63 3.98 11.80 200.5 5.53 4.67 0.86 1.10 Hayling Island 4 23:15:00 Newhaven- 04/01/201 8.27 3.16 10.10 217.5 7.40 7.09 0.31 0.86 Rustington 8 12:45:00

The highest run-up level (β =0.03) events at each site is listed in Table 5.9. At all sites, the highest run-up level occurred during the 2013/14 season. The highest total water level (β =0.03) events at each site is listed in Table 5.10. Here, the 14th February 2014 storm also produced the highest total water level at Weymouth-Chesil and Newhaven-Rustington, while the highest total water level at Bournemouth-Boscombe and Newhaven-Rustington is on 3rd December 2006 and 4th January 2018, respectively (the same as when calculated with run-up level using a value of β =0.01).

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Table 5.9: Highest run up level (β =0.03) at each site. Total Run up Wave Water Predicte Skew Date and Water Site Level Hs (m) Tp (s) direction level d tide surge time Level (m) (degree) (mCD) (mCD) (m) (mCD) Weymouth- 14/02/201 2.89 7.69 15.40 224 2.57 1.62 0.95 5.47 Chesil 4 21:00 Bournemouth- 06/01/201 1.62 2.40 25.00 190 - - - - Boscombe 4 17:30 Portsmouth- 05/02/201 1.99 3.97 20.00 187 4.84 4.53 0.30 6.83 Hayling Island 4 15:00 Newhaven- 24/12/201 1.86 5.46 10.00 213 5.96 5.94 0.02 7.82 Rustington 3 02:30

Table 5.10: Highest total water level (β =0.03) at each site. Total Wave Water Predicte Skew Run up Date and Water Site Hs (m) Tp (s) direction level d tide surge Level time Level (degree) (mCD) (mCD) (m) (m) (mCD) Weymouth- 14/02/201 5.47 7.69 15.40 224.0 2.57 1.62 0.95 2.89 Chesil 4 21:00 Bournemouth- 03/12/200 3.96 3.04 7.40 185.0 2.93 2.23 0.70 1.03 Boscombe 6 06:15 Portsmouth- 14/02/201 7.08 4.05 12.50 198.0 5.48 4.68 0.80 1.60 Hayling Island 4 23:30 Newhaven- 04/01/201 8.62 3.21 11.10 217.0 7.35 7.03 0.33 1.27 Rustington 8 13:00

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6 STAGE 4: BIMODAL WAVES AND SWELL

In this chapter we assess the monthly CCO bimodal wave data to compare year on year storm seasons by extracting this data for each winter season. We assess the CCO data across the south coast of England, which is provided as monthly percentages of swell. The 8 sites assessed were: Rustington; Hayling Island; Sandown Bay; Milford; Boscombe; Chesil; Start Bay; and Penzance. The first 6 of these 8 are within the SCOPAC region.

The data is provided as a monthly value of bimodal sea percentage. The analysis included:

1. Averaging these monthly values for each site for each ‘storm season’ (Table 6.1); 2. Finding the maximum monthly values for each site for each ‘storm season’; 3. Summing the monthly values for each site for each ‘storm season’; 4. Amalgamating the ‘storm season’ bimodal-ness across the 8 sites (Figure 6.1); and 5. Determining the most bimodal months and winters.

Averages for the months across each season are presented in Table 6.1 for each site, and all the sites combined are shown in Figure 6.1. The results show that 2013/14 and 2015/16 are the most bimodal winters in terms of wave activity across these sites when averaging the winter averages for each site (Figure 6.1). In the east SCOPAC region W2015/16 stands out as by far the most bimodal winter, whereas there is less difference between W2013/14 and W2015/16 further west. Chesil is the most consistently bimodal site all year round, however, in the SCOPAC region, Hayling Island, Sandown and Boscombe are subject to a more distinct shift to bimodality in certain months. There is an upward trend in annual winter bimodality across the amalgamated data for the 8 sites that were assessed.

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Figure 6.1: For the 8 wave sites, the sum, average, and maxima of bimodal values is plotted.

Table 6.1: Average bimodality for CCO wave buoys per winter season. SCOPAC West Christchurch Devon Cornwall East Solent Poole Bay Dorset SEASON Sussex Bay AVERAGE Hayling Sandown Start Rustington Milford Boscombe Chesil Penzance Island Bay Bay 2004-5 3% 2% 0% 1% 1% 2005-6 3% 4% 0% 2% 1% 2% 2006-7 6% 7% 1% 6% 3% 6% 2% 1% 4% 2007-8 4% 6% 0% 5% 1% 4% 3% 3% 3% 2008-9 3% 4% 0% 2% 1% 4% 2% 1% 2% 2009-10 4% 5% 0% 4% 2% 6% 5% 3% 3% 2010-11 3% 4% 0% 3% 2% 5% 3% 3% 3% 2011-12 2% 3% 0% 3% 2% 6% 3% 2% 2% 2012-13 4% 5% 0% 3% 2% 5% 4% 3% 3% 2013-14 6% 5% 2% 7% 5% 9% 6% 5% 5% 2014-15 4% 5% 0% 4% 2% 6% 3% 1% 3% 2015-16 8% 9% 1% 8% 3% 9% 6% 3% 5% 2016-17 4% 3% 0% 3% 1% 6% 2% 2% 2% 2017-18 4% 4% 1% 3% 1% 6% 3% 2% 3% 2018-19 6% 7% 1% 6% 2% 7% 4% 3% 4% 2019-20 2% 3% 0% 3% 1% 2% 1% 1% 2% Average 4% 5% 0% 4% 2% 6% 3% 2% Note: Red highlights the highest values within each column.

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Table 6.2: Maximum bimodality of any given month for CCO wave buoys per winter season. SCOPAC West Christchurch Devon Cornwall East Solent Poole Bay Dorset SEASON Sussex Bay AVERAGE Hayling Sandown Start Rustington Milford Boscombe Chesil Penzance Island Bay Bay 2004-5 0% 11% 14% 1% 0% 5% 0% 0% 0% 2005-6 0% 9% 11% 2% 9% 2% 0% 0% 0% 2006-7 1% 22% 25% 5% 22% 8% 10% 2% 1% 2007-8 1% 17% 24% 2% 18% 7% 18% 11% 11% 2008-9 0% 16% 16% 2% 14% 10% 21% 14% 10% 2009-10 0% 15% 23% 0% 17% 9% 14% 15% 11% 2010-11 2% 18% 15% 2% 16% 12% 28% 19% 24% 2011-12 1% 6% 13% 0% 9% 7% 15% 17% 8% 2012-13 0% 13% 15% 1% 15% 8% 15% 8% 7% 2013-14 2% 26% 24% 8% 32% 17% 34% 19% 20% 2014-15 1% 13% 19% 1% 13% 8% 14% 9% 5% 2015-16 2% 32% 38% 4% 34% 14% 26% 24% 11% 2016-17 1% 12% 12% 2% 11% 5% 14% 9% 9% 2017-18 1% 17% 16% 4% 14% 5% 19% 12% 10% 2018-19 2% 21% 23% 3% 23% 12% 27% 14% 10% 2019-20 0% 4% 6% 0% 6% 2% 4% 2% 2% Average 1% 16% 18% 2% 16% 8% 16% 11% 9% Note: Red highlights the highest values within each column.

Next, 3 sites (Chesil, Boscombe and Hayling) are shown in Figure 6.2 for which monthly bimodality values are assessed. At the two westernmost sites (Chesil and Boscombe) February 2014 was the most bimodal month in the data set. At Hayling, December 2015 was the most bimodal month.

Figure 6.2: Monthly bimodal values plotted for 3 sites.

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Table 6.3: The most bimodal months HAYLING SANDOWN START DATE FOLKESTONE RUSTINGTON MILFORD BOSCOMBE CHESIL PENZANCE ISLAND BAY BAY JAN-14 0% 21% - 5% - 17% 25% 13% 15% FEB-14 2% 26% 24% 8% 32% 16% 34% 19% 20% DEC-15 0% 32% 38% 4% 34% 14% 26% 24% - AVERAGE 0% 5% 5% 0% 4% 2% 6% 4% 2%

In a separate analysis, swell was counted using the half hourly time series data, and by setting thresholds (based on “expert judgement”) using the half hourly data at Boscombe – a 1.25m Hs and 14s Tp. This highlights a different perspective than can be viewed via the bimodal data set and the results for the wave period trends and threshold exceedances. It illustrates how W2013/14 stands out with over 220 hours of swell waves above this threshold (from July 2013 to July 2014), more than double the second highest season in 2006/07.

Figure 6.3: Hours of swell at Boscombe for winter seasons.

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7 STAGE 5: OVERVIEW OF CONSEQUENCES – THE SEVEREST INDIVIDUAL EVENTS AND WINTERS

The first part of this chapter (Section 7.1) presents the compilation of coastal flood events within the SCOPAC region using data extracted from the sources described in Section 2.3.5. The second part of this chapter (Section 7.2) discusses in greater detail the winter with the most extreme events (2013/14) and the third part (Section 7.3) describes the aftermath of that winter. The fourth part of this chapter (Section 7.4) briefly describes other severe winters.

7.1 Coastal events catalogue

Having examined all the sources mentioned in Chapter 2, we found evidence of coastal flooding within the SCOPAC region during 187 distinct events from 1703 to present (318-year period). This catalogue is included in Appendix F. The earliest record we found of reported coastal flooding in SCOPAC region was in Lymington on the 26th-27th November 1703 (Davison et al., 1993). Following that we did not find any coastal flood reported up until 1804. This is not to say coastal flooding did not occur during that time, it was just not reported in the sources we assessed.

The temporal distribution of the coastal floods identified is shown in Figure 7.1. Most of the flood events were recorded during winter months (October – March), with few exceptions (1 event in April, 1 event in June, 3 events in August and 7 events in September). There were no flood events recorded in May and July. Most events were recorded in December (43 events), followed by January (41 events). October and November had the same number of events (31 events), while February and March had 22 and 7 events, respectively. The monthly events were divided into 4 periods of century (1701-1800, 1801-1900, 1901-2000, 2001-2016). The monthly occurrence was relatively well distributed in these four periods with most events reported during 1901- 2000.

In Figure 7.1b we plotted every season when coastal flood events were reported. The winter of 2013/14 saw the most flood reported events (10) followed by 1954/55 (8). On average, two coastal flood events were reported in every season. The number of flood events occurred in each decade is shown in Figure 7.1c. The number of flood events reported increased from the 1900’s to the 1960’s and declined slightly after that. The 1960’s decade saw the most coastal floods reported in SCOPAC region.

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Figure 7.1: Number of flood events (a) monthly, (b) seasonally, and (c) in a decade throughout 313-year period.

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The severity of each flood event is plotted through time in Figure 7.2. The number of flood events decreases as the severity increases: 105 events were ranked category 1, 34 events were ranked category 2, 22 events were ranked category 3, 15 events were ranked category 4, 10 events were ranked category 5, and 1 event were ranked category 6. There was only one category 6 event in 1918 which recorded one fatality. Category 5 and 6 events have not occurred after 1989.

In summary, the 10 most severe coastal flood events occurred on:

- 15th January 1918; - 13th December 1989; - 26th November 1954; - 26th December 1912; - 1st January 1877; - 8th October 1960; - 23rd November 1824; - 5th November 1916; - 4th March 1818; and - 19th January 1804;

However, the top 5 seasons with most events reported are:

- 2013/14 (10 events); - 1954/55 (8 events); - 1961/62 (6 events); - 1977/78 (5 events); and - 1994/1995 (5 events);

That 2013/14 season saw many incidents of flooding yet did not cause major consequences (e.g. fatalities). This possibly highlights the role of modern defences and forecasting, although may simply show recent flood event clustering (refer to next section).

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Figure 7.2: Number of flood events (a) monthly, (b) seasonally, and (c) in a decade throughout 313-year period each showing the severity per flood event

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7.2 Overview of 2013/14

The winter of 2013/14 was characterized by a striking pattern of temporal and spatial extreme storm wave “clustering” (a term more widely coined following that winter season) in Western Europe. The unusual number of high intensity storms and their impacts were the impetus for this study. W2013/14 was extreme for coastal impacts and flooding – with an extraordinary number of newsworthy events, notably the North Sea surge of the 5th and 6th December 2013 known as the “Xaver” storm, which triggered mass evacuations, closure of the Thames barrier and an emergency cabinet meeting. Clifftop homes were lost in northeast England and around 3,000 homes were flooded overnight, with the northwest and English Channel coasts also affected (Wadey et al., 2015).

However, the “season” extended for around 18 weeks, from when it began with the ‘St Jude’ Storm in late October with rare neap tide flooding of the quayside at Yarmouth (Isle of Wight) during 99 mph winds, whilst swells and high tides were still causing overtopping in March 2014. There were around a dozen events from a coastal news perspective listed below, including minor events during November, and a rapid sequence of storms from late-January to mid-February including that which destroyed the Dawlish railway line. As indicated in Figure 7.3, many of the coastal flood events on the south coast occurred in January and February 2014.

The impact of the storms extended across the entire European Atlantic seaboard and included erosion at many locations; stripping beaches of all sand and exposing their rocky shore platform. Barrier overwash was felt at many sites, with maximum wave runup levels of more than 15 m above MSL. Some coastal cliffs experienced retreat rates two orders of magnitude greater than the long-term average, and dunes faced erosion of more than 10 m in places.

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Figure 7.3: Property flooding during December 2013 to February 2014 (source: Environment Agency).

The following is a list of known events – the classification of major, moderate or minor relates only to the consequences – the analysis in this study will highlight if any of the flood sources were particularly extreme. Some of the storms in the list below were given names by the UK Met Office and other sources.

1. 28th October 2013 (minor event): St Jude Storm with high winds and floods at Yarmouth on Isle of Wight notable for large waves and surge on a neap tide, and unusual high frequency oscillation of water levels in the English Channel (‘seiching’) attributed to surge (Ozsoy et al., 2016). 2. 4th November 2013 (minor event): storms impacted areas of England and Wales with notable overtopping at Mumbles Head near Swansea and large waves breaking onto the seafront, 89 mph winds, surge, high tide, and waves. 3. 5th – 6th Dec 2013 (major national event): “Xaver” storm which started with flooding in Wales and Liverpool Bay, then advanced to be a North Sea surge. This led to the flooding of up to 3,000 properties. The surge propagated past Dover causing flooding around Shoreham

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and some of the highest sea levels seen in the SCOPAC region but avoiding major impacts because fortunately, there were no big waves on the south coast. Minor flooding was reported in the Solent’s harbours. Several decades of erosion occurred overnight, with new sea level records in the northeast and Lincolnshire. The government called an emergency COBR meeting due to fears dating to 1953, with 800,000 properties at risk. The waves and sea level generated were the largest on record at Liverpool Bay and Lowestoft exceeding the 50-year return period – although in the southern North Sea was not as extreme an event as 1953. 4. 18th - 19th December 2013 (minor coastal event): “Storm Emily” or “Bernd” caused some flood warnings in Scotland and southwest England with flooding in Wales and Ireland due to rain and high tides – and the rain continued to have an impact for 4 or 5 days. 5. 1st – 3rd January 2014 (moderate event): south coast and Wales impacted by swell waves across multiple high tides rolling in from the Atlantic, that eroded beaches and damaged defences. 6. 6th January 2014 (moderate event): similar to the event of 3 days previous, “Storm “Hercules” generated large long period swell waves with probability of 1 in 5 to 1 in10-year wave event in places (UoP, n.d). 7. 4th - 5th February 2014 (moderate-major event): waves destroyed 80 m section of the Dawlish railway line and coastal path as “Storm Petra” impacted mid-Wales, Devon, and Cornwall. This resulted in the loss of direct trains into and out of Cornwall for over 8 weeks. It was the most damaging storm in terms of physical and socio-economic coastal impact on the south coast of Devon and Cornwall for the last 50 years (Scott et al., 2016). 8. 8th - 9th February 2014 (minor coastal event): Storm “Ruth” caused large waves to spectacularly overtop the high walls of the lido in Plymouth and Portcawl in Wales. As shown in Table 5.6 this was an exceptionally powerful wave event at Hayling Island when considering maximum wave recordings. 9. 12th February 2014 (minor coastal event): although not severe at the coast, known as “Cyclone Tini” and “Storm Darwin”. This was considered the strongest Atlantic storm in February. Kendon and McCarthy (2015) note it as “unusually severe”. 10. 14th - 15th February 2014 (moderate-major event): The “Valentine’s Day” Storm caused severe flood warnings, and resulted in flooding across most of the region and especially in Southwest England, with a café evacuated at Milford-on-Sea, damage to Hurst, beach huts destroyed in Bournemouth and Christchurch, severe overtopping and damage to most defences across SCOPAC region. 11. 2nd-3rd March 2014 (moderate coastal event) – high tides and swell waves flooded the Channel Islands, with roads flooded near St Helier in Jersey, and shops flooded in Guernsey;

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with reports also of a tornado and that it was the wettest winter in 101 years in Guernsey (BBC, 2014).

Mapped locations where coastal asset damages in the SCOPAC region were recorded are shown in Figure 7.4.

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Figure 7.4: Damage to coastal assets in the SCOPAC region during 2013/14.

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There were other storms in areas around the British Isles related largely to non-coastal impacts with an ongoing occurrence and overlap of coastal surges, high tides, waves, river, surface and groundwater events. For example, not listed above is the 23rd December 2013 surface run-off flooding in mid Cornwall, whilst amongst the most reported and memorable aspects were the floods in the Somerset Levels from late January to late February 2014, mostly due to heavy persistent rainfall.

Much of the emphasis on the south coast was that it was the “season” rather than individual events that were particularly extreme, which is significant to the damage to beaches and limiting their recovery. However, there were also several record-breaking sea level and wave extremes, some of which are covered by the analysis in this report.

Other studies have noted the following:

• Waves: a wave model hindcast suggested that for most of the Atlantic coast of Europe, W2013/14 winter was the most energetic since 1948 with a storm sequence considered somewhere between a 1 in 50-year and 1 in 250-year event; with 18 individual storms between December 2013 to February 2014, and 4 occurring during March 2014 (Scott et al., 2016; Masselink et al, 2016). There was also an unusually high percentage of swell waves including bimodal sea conditions, linked to the extensive flooding and damage (Reeve et al., 2019). The count of storms varies by method, region and time span – Bradbury and Mason (2014) using the CCO wave buoy network assessed events exceeding the 1 in 1-year return period as being 16 storms (28th October to 10th February); whilst Dhoop and Mason (2018) noted 11 storms. • Sea level: set into context against the then almost 100-year record at Newlyn, Cornwall, Wadey et al. (2014) found that W2013/14 produced the largest recorded water level event (3 February 2014) and five other high-water events above a 1 in 1-year return period, suggesting as a "season" it could be considered the most extreme on record. • Cyclone frequency and intensity: the UK and Ireland experienced the most severe storminess for at least 143 years (Matthew’s et al., 2014) when reviewing multi-decadal variations within large-scale cyclone characteristics. • Causes: a powerful jet stream was attributed to triggering a succession of deep Atlantic low- pressure systems, which were unusually deep and maintained an unusually low latitudinal track (Sibley et al, 2015). These weather systems generated the wettest winter in the UK’s observational records (Kendon and McCarthy, 2015).

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7.3 Aftermath

From a rainfall and overall storm perspective, W2013/14 is regarded nationally as one of the most severe winters on record (e.g. Kendon and McCarthy, 2015).

• Economic damages attributed to flooding in England and Wales between December 2013 and March 2014 were approximately £1.3 billion (mid estimate; source: Environment Agency, 2016) although these may be much higher given that the North Sea event alone may have generated £1.2 billion damages (Wadey et al, 2015). • Across W2013/14 around 55% of the £1.2 billion damages (Environment Agency, 2016) is attributed to coastal events; with the greatest proportion of damages was to residential property, with £320 million worth of damage incurred by up to 10,465 households – of which around 40% was coastal. Insurers funded temporary alternative accommodation for over 2,100 households and loss adjusters made over 6,500 visits to flooded properties to assess the damage, organise emergency payments and drying out repairs (Environment Agency, 2016). • Flood defence damage: cost of repair (including fluvial defences) was estimated to be approximately £147 million (Environment Agency, 2016). • The Thames Barrier was closed 50 times (the maximum recommended number), but the majority of these were due to high river flow. • The government made available a total funding package of £270 million to repair or maintain flood defences, including £10 million for Somerset. This also prompted further defence improvements and major new schemes, for example the Boston and Ipswich Barriers.

The coastal impact may be more than just the damage witnessed to property, business and flood defences at the time. At beaches throughout the UK and France:

• Most were left in their most eroded state since morphological records began (at the time up to around a decade of data: Poate et al., 2014; Castelle et al., 2015; Masselink et al., 2016). • The westerly Atlantic storm approaching waves meant that on west facing coastlines the prevailing storm response was offshore sediment transport and widespread beach/dune erosion, with considerable spatial variability in the geomorphic storm response due to coastal orientation and embayment’s. • On south-facing and east-facing beaches the oblique wave approach resulted in strong littoral drift and beach rotation. The type of storm response is expected to have a significant impact on the rate of post-storm recovery.

In the south-west of England, well-known natural landmarks were lost to the waves. For example, on the Isle of Portland the 10 m high “Pom” rock stack (Figure 7.5) was completely destroyed. At

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Porthcothan Bay in Cornwall, “The Anchor” stone arch that had stood for centuries was also destroyed. Other indicators of how extreme this winter is evident for example by the Environment Agency's flood-sirens being deployed at the Isle of Portland for the first time in approximately 30 years. The Royal National Lifeboat Institution (RNLI) experienced substantial loss of coastal assets whilst many lifeguard teams faced new challenges the following summer because beach profiles had changed dramatically. Sand was washed away or piled up into cliffs, leaving rocks exposed and new or stronger rip currents around them.

Figure 7.5: Pom Rock near Portland before and after its collapse, said – a natural stack weighing hundreds of tonnes, was demolished and broken up by the storm (source: Stuart Morris).

As has happened with unusual weather events since the 1970’s and 1980’s, there has been a tendency to look for links to climate change. As a general scientific rule for parameters such as sea level and wave height, long data sets are required to truly assess where attribution lies (e.g. whether an unusual winter such as W2013/14 is a result of pure randomness or part of a changing pattern). For example, with sea level, broad scale variability occurs due to mass of water movement due to changing temperature and currents in the global oceans, whilst there are multiple interannual astronomical tidal cycles (e.g. the quite well-known 18.6-year lunar nodal cycle). Hence short records will be biased. However, there have been several notable observations since W2013/14 in terms of coastal flood and erosion events.

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7.4 Observations since W2013/14

The weather in 2014 remained unusual, with the month of September 2014 being the driest September on record for the UK (in a series of records from 1910) and also registered as the equal fifth driest in the England & Wales Precipitation series from 1766 (CEH, 2014).

W2013/14 instigated ‘storm naming’ to give a sole, authoritative naming system to avoid confusion with the public and media. This is via collaboration between the Met Office (UK), Met Éireann (Ireland) and since 2019 the Royal Netherlands Meteorological Institute. The first windstorm to be named was “Abigail” (10th November 2015). Another motivation for this study, is that the winters since W2013/14 have been associated with continued coastal damages that, as of yet anecdotally (and without context in observed records) are considered a worsening of loss.

Winters 2015/16, 2016/17 and 2017/18 all produced noteworthy storms and damages with new records for wave heights at Hayling Island and Bournemouth (Storm Katie, 28th March 2016), flooding in Swanage and Southsea (Storm Angus, 20th November 2016) preceded less than a year earlier by sea wall collapse at Southsea in Portsmouth (late December 2015). On the 21st October 2017, Storm Brian led to cancellation of the Great South Run for fears of flooding and spectacularly washed away 20,000 tonnes of newly replenished shingle on Hayling Island. In early January 2018, Storm Eleanor and high tides caused further erosion and flooding problems on the south coast. Southsea’s promenade again underwent major emergency repairs after collapsing as recently as December 2019.

There is again general concern over the gaps in the understanding of swell and bimodal wave conditions, and MSL rise in the SCOPAC region. For example, “how extreme was W2013/14?” in terms of being an outlier in the wave and sea level data sets, and “is the period we are now going through different or more extreme?”. These questions have implications to changes to geomorphic systems (e.g. “did W2013/14 irrevocably trigger losses of sediment sources?”) and the nature of future storms. Not all links and questions can be answered in this work, but the next section describes the methods that will be used to systematically understand trends and events in the SCOPAC wave and sea level data sets.

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8. DISCUSSION, CONCLUSION AND RECOMMENDATIONS

The overall aim of this report is to provide context to “record breaking” storms since late 2013 with a scope to analyse flood ‘sources’ from observed data sets – with a brief overview of events (flood, erosion) and their consequences to support analysis, conclusions, and directions for future research. This report has put into context the extreme and stormy events of winter 2013/14 and provided easily accessible scientific information that can help understand the causes of coastal flooding and/or erosion. To achieve the aim, this report has addressed five key objectives based upon analysis of tide gauge and wave buoy data as well as compiling flood events throughout time in the SCOPAC region. As outlined in Chapter 1, the winter of 2013/14 was extreme in terms of the number of events that were recorded in the media and by the apparent response and aftermath. This requires analysis of the observed coastal flood sources by the methods described in Chapter 2. As a foreword to the conclusions; all of the analyses indicate with varying levels of certainty (i.e. as noted in trends by statistical significance values ascribed to different levels of extremity in sea level and wave parameters) upward trends.

Trends in sea level: Chapter 3 focused on the first objective and assessed trends in sea level and wave data over time and illustrates how, as with the global situation, sea level is changing in the SCOPAC region. The trend analysis showed that MSL along the UK south coast have risen at around 1.84 mm/yr from 1915 to 2019 (average across the 9 sites), increasing to 2.27 mm/yr between 1990 and 2019. As a comparison, global MSL rise rates estimated in the recent Intergovernmental Panel on Climate Change (IPCC) Special Report on the Ocean and Cryosphere in a Changing Climate (SPROCC) were 1.4 mm/yr over the period 1901 to 1990 and 3.2 mm/yr over the period 1993-2015 (Oppenheimer et al., 2019). Over these different periods, the rates of rise along the UK south coast are broadly consistent with global rates, although as expected, the rates along the UK south coast are higher, mainly due to the added influence of land subsidence associated with glacial isostatic adjustment (Palmer et al., 2018). We find that extreme sea levels have increased by 1.18 mm/yr (although with more variation between sites than for MSL). Whilst the fundamental cause of MSLR is understood to be broader scale increases in water temperature and mass due to climate change, there is some indication of changes to tides and skew surges. MTR has increased at 5 out of 9 sites and decreased at the other 4 sites. The reasons for this are not clear, but could be linked to MSL or local changes, as explored in detail in Haigh et al. (2020b). There are no statistically significant increases in skew surges. This result is consistent with several other recent regional and global tide gauge studies (e.g. Marcos et al., 2015; Mawdsley and Haigh, 2015), who also found no statistically significant changes in storm surges, globally.

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Trends in waves: Wave parameters were also assessed, and at most sites there was evidence of an increase in wave height over time although the short data sets limit confidence in this. There is also an indication that wave period has increased but mostly through trends that are not statistically significant. This, however, partially links with the bimodal wave findings summarised below, indicative in those data are a changing swell component. An interesting case is Sandown

Bay where for waves above 1m HS and at the same time in the “extreme” classification for peak wave period (i.e. the 99th percentile values) wave period, have increased by a trend of 0.52 s (± 0.22 s) during 2004-2019. Whilst the caveat should be that this trend seems slight and that these are relatively short data sets, it is interesting because it is noted (albeit with limited statistical significance) amongst a spread of locations.

Also, it is interesting because swell is damaging and potentially responsible for many of the issues that instigated this research; it is therefore an area of results that warrants future work in terms of more advanced statistical analysis and continued inspection of time series data as the years advance. Combining these parameters into a “wave power” time series parameter indicates similar trends but what is striking is the notably higher power across 2013/14. As a trend this was slight and statistically significant for only 4 sites (Rustington, Hayling Island, Sandown Bay and Milford-on-Sea) – although we acknowledge little is known of how sensitively beaches and other morphological systems respond to these subtle changes. An interesting link here can be noted between our regional analysis (of which we do not know of many similar examples), to global observations of an increase in wave power linked to oceanic warming (Reguero et al, 2019) and with profound consequences upon coastal erosion (Leonardi et al, 2016).

Combining the wave parameters with sea level time series to generate “total water level” (TWL) time series (based on the concept of wave run up), the trends in the Solent and eastward show a statistically significant increase in TWL over the period of available data: the TWL (experienced at coastal defences and beaches) may be increasing at about 15 mm/yr in the eastern half of the region, and by about a third of this to the west – although this is impacted by a wide margin of uncertainty at Chesil where wave heights and period are high relative to other areas so the results are more volatile. This run up analysis across the time series is rarely done elsewhere and casts a perspective not often assessed – and in this case study indicates that the observed increases in a coastal storm water level (when sea level and waves are considered jointly) are nonlinear in comparison to assessing sea level and wave changes over time independently. This may be significant to beach response and crest height design and warrants further research.

Number of extreme events each winter: Chapter 4 focused on the second objective and upon threshold exceedances – i.e. counts of extreme events per winter - in terms of sea level (including surges) and waves (including wave height, wave period and run up) and TWL. This is where it

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seems that 2013/14 stands out more than is apparent in the other chapters. Waves seem to be more prominent in season 2013/14, as follows.

• In the west SCOPAC region (the Chesil wave buoy and Weymouth tide gauge pairing), 2013/14 produced the most (8) sea level events that exceeded the annual probability threshold since 1991, also with the largest recorded number of extreme surge events (7 events) in any season contributing to this. Unfortunately, the Poole Bay sea level data is incomplete. • In the Solent region the Portsmouth tide gauge (dating back to 1961) again show 2013/14 to have produced the highest count sea level (14) events, also with the largest recorded number of extreme surge events (10 events) contributing to this. At Portsmouth there is a large drop to second place for extreme sea level event counts (4 events in 1967/68, 1992/93, 1994/95). • In the East, W2013/14 have the same number of high sea level with 1982/83 (3 events). Newhaven tide gauge shows that the highest count of extreme surge was on W1992/93 (5 events), followed by 2013/14 (4 events). • Across all four wave buoy sites assessed in this way, 2013/14 was again the most extreme with 21 notable wave height events at Chesil and 15 events at Boscombe, 16 events at Hayling Island and 24 at Rustington– in all cases these counts being more than double the second placed seasons which were 2015/16 for Chesil, Boscombe, and Rustington and 2006/07 for Hayling Island. • At all sites 2013/14 was the most extreme for long wave period and wave run up events.

The biggest events: Chapter 5 focused on the third objective in which the most extreme events were assessed (sources: wave and sea level). The key messages are as follows:

• The highest sea level on record at the western side of the SCOPAC region (Weymouth and Bournemouth) was the notable 10th March 2008 event (see Haigh et al., 2011b and Wadey et al., 2013 for further details). However, the Bournemouth tide gauge was not operational, and it is considered likely by the authors that the Valentines Storm of 14th February 2014 was a similar sea level to the 10th March 2008 peak in Poole Bay given the impacts and overtopping observed. • The highest sea level recorded in the Solent (1961 to present) and at the East SCOPAC region stands as the 5th-6th December 2013 North Sea storm surge (Spencer et al., 2015; Wadey et al., 2015). Fortunately, this was a calm night on the south coast and only caused minor flooding. However only a few cm behind this event at Portsmouth are the 27th February 1990, 14th February 2014 and 10th March 2008 – the latter two linked with south-westerly waves

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which caused a range of flooding and erosion impacts (especially on south and west facing beaches), although the sea level by itself was not especially extreme (1 in 20-year maximum). • In terms of the most powerful waves, it was the Valentines Storm 2014 that ranks highest at Chesil (when an already battered beach was damaged further), and the 6th January 2014 at Boscombe and Rustington. In the Solent, the 5th February 2014 was the most powerful and despite not being a big tide, still caused flooding at Southsea Common and Hayling Island due to the violence of the waves (the same event which destroyed the Dawlish Railway line 180

km to the west of Hayling). When considering HMAX the 6th January stands out further whilst the 8th February 2014 is also a significant event. • The 14th February 2014 event is associated with the highest wave run up from across the majority of the West and Central SCOPAC region is likely to have generated the most run up and highest total water level; although to the east in Sussex the highest total water level was probably during Storm Eleanor on 4th January 2018 – this event notable for washing away beach hits on Hayling Island and causing heavy overtopping at various locations in the Solent.

Bimodal waves: Chapter 6 utilised the CCO’s higher frequency spectral analysis of monthly bimodal sea percentage at each wave buoy. Whilst separate from sea level and not ‘event’ orientated, this delves into a different wave data set and wave properties that are considered by engineers to be damaging to the coast (but not yet well understood). In late December 2015, which this study highlights as the most “bimodal” month on record for many sites in the English Channel (e.g. 38% of the time the sea was bimodal at Hayling buoy compared to a December average of 11%), there were major structural failures at Southsea (Portsmouth) and on the Kent coast which shut a major coastal route (Figure 0.1). No other wave or sea level events stand out that month. W2013/14 may have weakened various areas but the link between the events of W2015/16 and the winter of two years earlier should be investigated further.

a) b)

Figure 0.1: (a) Sea wall collapse at Southsea 25th-26th December 2015 (BBC, 2015a); and (b) sea wall failure at Dover on 24 December 2015 (BBC, 2015b). Consequences: flood events catalogue and asset damages: Chapter 7 focused on the fifth and final objective and produced a catalogue of events for which coastal flooding has been reported in the Solent. From a number of different sources, 187 distinct events were recorded within the SCOPAC

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region in the 318-year period from 1703 to present, when coastal flooding as occurred. The majority of the flood events were recorded during winter months (October – March), with few exceptions. Most events were reported 1900 onwards. W2013-2014 saw the most flood reported (10 events). The number of flood events reported increased from 1900s to 1960s and declined slightly. The decade 1960’s saw the most coastal flood reported in SCOPAC region. There was only one category 6 event in 1918 which recorded one fatality. W2013/14 obviously stands out in the flood catalogue (Section 7.1) and is explained in more detail in Section 7.2 where a review of additional information highlights how exceptional that winter was for storms and extreme waves and sea levels. Further work should consider the role this season may have played in impacts (sediment budgets etc) since then and the changes (and implications of) underlying mechanisms (e.g. swell) that are rarely assessed in other literature ad FCERM guidance – for example UKCP18.

In summary, coastal flooding and erosion remains one of the most significant risks that the UK and SCOPAC region faces and these risks are growing with climate change and other changes (e.g. population growth). There is high confidence that the dominant cause of global MSL rise since 1970 is anthropogenic forcing (Oppenheimer et al., 2019). There is high certainty that relative MSL will continue to rise, and likely accelerate and as a result, high sea levels will be exceeded more frequently in the future with climate change, increasing the likelihood of coastal flooding and erosion. Without appropriate ongoing adaptation measures, such as defence upgrades and managed retreat, this will have significant impacts on the UK’s and SCOPACs coastal population, economy and infrastructure. Furthermore, it is important to consider our long-term commitment to MSL rise (Nicholls et al., 2018). Reducing human emissions of greenhouse gases will stabilise temperature in about a century, but MSL rise will continue for many centuries even if temperature is stabilised. This is because it takes many hundreds of years for the cryosphere and the deepest parts of the ocean to adjust to increased air temperatures (Haigh et al., 2020b). The UK and SCOPAC coast will be subject to at least 1 m of mean sea-level rise, it is just a matter of when (Committee on Climate Change, 2018).

Moving forward there are three main recommendations as follows:

(1) This study has mainly focused upon the coastal flood “sources” element of the “source- pathway-receptor-consequence” model, with only a brief review of “consequences. We would recommend a detailed follow on study be undertaken to assess changes in the “pathway-receptor-consequence” components. (2) We would recommend that the analysis undertaken here, much of which could be automated, be routinely updated at the end of each winter season, to provide ongoing information to coastal engineers and practitioners. This information could be included for example, on the CCO web-site in a series of interactive tables and figures.

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(3) This study could be extended to cover the whole of the UK coast. 9 REFERENCES

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APPENDIX A – WEYMOUTH-CHESIL PAIRING: HIGHEST SEA LEVEL AND WAVE EVENTS

Table A.1: 10 highest water level event at Weymouth. Water Skew Wave RP Predicted Rank Date and time level surge Hs (m) Tp (s) direction (years) tide (mCD) (mCD) (m) (degree) 10/03/2008 1 19 3.04 2.51 0.54 3.86 9.1 219 09:00 27/10/2004 2 8 2.95 2.35 0.60 - - - 18:00 03/01/2014 3 7 2.95 2.67 0.27 2.67 8.3 225 08:00 14/02/2014 4 6 2.93 2.07 0.86 - - - 19:45 23/12/1995 5 6 2.93 2.69 0.24 - - - 07:30 03/12/2006 6 5 2.90 2.23 0.67 - - - 05:45 12/12/2000 7 4 2.88 2.49 0.39 - - - 19:15 10/03/2001 8 4 2.87 2.65 0.23 - - - 07:15 10/01/1993 9 4 2.87 2.49 0.38 - - - 08:00 14/12/2012 10 3 2.87 2.52 0.34 1.68 6.3 193 07:45 Note: Red indicates the 2013-2014 events

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Figure A.1: Scatter plots of twice daily high water values against coinciding (a) wave height and (b) wave period, (c) 16-h wave height peaks, and (d) wave rose of 100 highest water level events at Weymouth.

Table A.2: 10 highest skew surge events at Weymouth. Skew Water Wave RP Predicted Rank Date and time surge level Hs (m) Tp (s) direction (years) tide (mCD) (m) (mCD) (degree) 14/02/2014 1 80 0.86 2.93 2.07 4.59 8.3 215 18:45 14/11/2002 2 10 0.68 2.18 1.50 - - - 02:00 05/02/2014 3 10 0.68 2.84 2.16 - - - 10:30 03/12/2006 4 9 0.67 2.90 2.23 - - - 04:45 23/12/2013 5 9 0.67 2.37 1.70 4.3 10.5 221 22:00

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Skew Water Wave RP Predicted Rank Date and time surge level Hs (m) Tp (s) direction (years) tide (mCD) (m) (mCD) (degree) 31/01/2004 6 9 0.67 1.99 1.32 - - - 13:00 15/10/2002 7 5 0.63 2.19 1.57 - - - 13:30 01/01/2001 8 5 0.62 2.20 1.58 - - - 22:45 28/10/2013 9 4 0.61 2.02 1.41 3.19 8.3 226 00:15 27/10/2004 10 4 0.60 2.95 2.35 - - - 18:15 Note: Red indicates the 2013-2014 events

Figure A.2: Scatter plots of twice daily high water values against coinciding (a) wave height and (b) wave period, (c) 16-h wave height peaks, and (d) wave rose of 100 highest skew surge events at Weymouth.

Table A.3: 10 highest significant wave height (Hs) events at Chesil. 109 SCOPAC Storm Analysis Study

Wave Water Predicted Skew RP Rank Date and time Hs (m) Tp (s) direction level tide surge (years) (degree) (mCD) (mCD) (m) 14/02/2014 1 12 7.70 18.2 220 2.93 2.07 0.86 23:30 05/02/2014 2 6 6.99 14.3 222 2.84 2.16 0.68 12:00 14/11/2009 3 4 6.50 13.3 226 - - - 14:30 03/02/2017 4 4 6.41 18.2 218 - - - 00:00 15/01/2015 5 3 6.15 10 217 2.09 1.54 0.55 02:30 24/12/2013 6 2 6.00 12.5 217 2.37 1.70 0.67 02:30 03/01/2012 7 2 5.87 11.1 226 1.58 1.35 0.22 12:00 08/02/2014 8 2 5.68 10 222 1.99 1.54 0.46 14:30 12/12/2011 9 1 5.53 10 222 2.40 1.98 0.42 23:30 28/10/2013 10 1 5.52 10.5 219 2.02 1.41 0.61 03:30 Note: Red indicates the 2013-2014 events

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Figure A.3: Scatter plots of twice daily high water values against coinciding (a) wave height and (b) wave period, (c) 16-h wave height peaks, and (d) wave rose of 100 highest wave height event at Chesil.

Table A.4: 10 highest wave period (Tp) events at Chesil. Wave Water Predicted Skew Rank Date and time Tp (s) Hs (m) direction level tide surge (degree) (mCD) (mCD) (m) 03/01/2008 1 25 1.04 208 - - - 22:00 08/03/2012 2 25 1.03 162 2.19 2.15 0.05 11:00 06/01/2014 3 25 4.29 219 2.55 2.37 0.18 15:00 03/03/2014 4 25 2.59 219 2.79 2.67 0.12 13:00 17/11/2018 5 25 1.13 165 - - - 17:30 15/12/2018 6 25 1.55 246 - - - 06:30 11/03/2008 7 22.2 3.41 205 2.53 2.30 0.22 01:00

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09/12/2009 8 22.2 1.19 211 1.78 1.89 -0.11 08:30 09/11/2010 9 22.2 1.42 198 2.35 2.23 0.11 02:00 15/02/2011 10 22.2 1.83 210 1.84 1.47 0.36 15:30 Note: Red indicates the 2013-2014 events

Figure A.4: Scatter plots of twice daily high water values against coinciding (a) wave height and (b) wave period, (c) 16-h wave height peaks, and (d) wave rose of 100 highest wave period event at Chesil.

Table A.5: 10 highest run up level (β =0.01) events at Chesil. Total Run up Wave Water Predict Skew Ra Water Date and time Level Hs (m) Tp (s) direction level ed tide surge nk Level (m) (degree) (mCD) (mCD) (m) (mCD) 14/02/2014 1 2.09 7.69 15.40 224.0 2.57 1.62 0.95 4.67 21:00:00

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05/02/2014 2 1.89 6.99 14.30 222.0 2.39 1.91 0.48 4.28 12:00:00 03/02/2017 3 1.84 6.41 18.20 218.0 - - - - 00:00:00 14/11/2009 4 1.75 6.50 13.30 226.0 - - - - 14:30:00 15/01/2015 5 1.59 6.15 10.00 217.0 2.00 1.43 0.57 3.58 02:30:00 03/01/2012 6 1.54 5.87 11.10 226.0 1.51 1.31 0.20 3.06 12:00:00 06/01/2014 7 1.52 5.02 20.00 218.0 2.18 1.99 0.19 3.70 23:30:00 08/02/2014 8 1.52 5.66 12.50 218.0 1.78 1.47 0.31 3.31 13:30:00 23/12/2013 9 1.51 5.79 10.50 221.0 2.30 1.69 0.62 3.81 22:30:00 02/01/2016 10 1.49 5.25 15.40 210.0 - - - - 13:30:00 Note: Red indicates the 2013-2014 events

Table A.6: 10 highest total water level (β =0.01) events at Weymouth-Chesil Total Wave Water Predict Skew Run up Ra Water Date and time Hs (m) Tp (s) direction level ed tide surge Level nk Level (degree) (mCD) (mCD) (m) (m) (mCD) 14/02/2014 1 4.67 7.69 15.40 224.0 2.57 1.62 0.95 2.09 21:00:00 05/02/2014 2 4.48 6.37 16.70 220.0 2.69 2.08 0.61 1.80 09:45:00 10/03/2008 3 4.06 3.86 9.10 219.0 3.04 2.48 0.56 1.02 09:00:00 07/06/2012 4 3.98 4.89 11.10 224.0 2.67 2.37 0.30 1.31 21:30:00 03/01/2014 5 3.96 5.08 16.70 222.0 2.49 2.43 0.06 1.47 21:00:00 06/01/2014 6 3.83 4.99 20.00 214.0 2.31 2.06 0.26 1.52 22:30:00 23/12/2013 7 3.82 5.58 11.80 221.0 2.33 1.64 0.70 1.49 23:00:00 09/10/2014 8 3.68 3.64 8.30 225.0 2.73 2.56 0.17 0.95 07:00:00 03/01/2018 9 3.68 3.62 9.55 228.0 2.71 2.53 0.19 0.97 07:45:00 21/10/2017 10 3.67 3.99 8.30 225.0 2.64 2.32 0.32 1.03 08:00:00 Note: Red indicates the 2013-2014 events

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Table A.7: 10 highest run up level (β =0.03) events at Chesil Total Run up Wave Water Skew Date and Hs Tp Predicted Water Rank Level direction level surge time (m) (s) tide (mCD) Level (m) (degree) (mCD) (m) (mCD) 14/02/2014 1 2.89 7.69 15.40 224.0 2.57 1.62 0.95 5.47 21:00:00 03/02/2017 2 2.71 6.41 18.20 218.0 - - - - 00:00:00 05/02/2014 3 2.60 6.99 14.30 222.0 2.39 1.91 0.48 4.99 12:00:00 06/01/2014 4 2.40 4.29 25.00 219.0 0.73 0.65 0.08 3.13 15:00:00 14/11/2009 5 2.38 6.50 13.30 226.0 - - - - 14:30:00 03/01/2014 6 2.18 5.08 16.70 222.0 2.49 2.43 0.06 4.66 21:00:00 10/03/2008 7 2.17 4.77 18.20 218.0 2.37 2.22 0.16 4.54 20:00:00 02/01/2016 8 2.15 5.25 15.40 210.0 - - - - 13:30:00 08/02/2014 9 2.08 5.66 12.50 218.0 1.78 1.47 0.31 3.87 13:30:00 15/01/2015 10 2.05 6.15 10.00 217.0 2.00 1.43 0.57 4.05 02:30:00 Note: Red indicates the 2013-2014 events

Table A.8: 10 highest total water level (β =0.03) events at Weymouth-Chesil Total Wave Water Predict Skew Run up Ra Water Date and time Hs (m) Tp (s) direction level ed tide surge Level nk Level (degree) (mCD) (mCD) (m) (m) (mCD) 14/02/2014 1 5.47 7.69 15.40 224.0 2.57 1.62 0.95 2.89 21:00:00 05/02/2014 2 5.27 6.37 16.70 220.0 2.69 2.08 0.61 2.59 09:45:00 06/01/2014 3 4.67 4.99 20.00 214.0 2.31 2.06 0.26 2.35 22:30:00 03/01/2014 4 4.66 5.08 16.70 222.0 2.49 2.43 0.06 2.18 21:00:00 10/03/2008 5 4.54 4.77 18.20 218.0 2.37 2.22 0.16 2.17 20:00:00 07/06/2012 6 4.44 4.89 11.10 224.0 2.67 2.37 0.30 1.77 21:30:00 23/12/2013 7 4.35 5.58 11.80 221.0 2.33 1.64 0.70 2.01 23:00:00 25/04/2012 8 4.12 4.25 13.30 218.0 2.41 1.90 0.51 1.71 21:00:00 15/01/2015 9 4.05 6.15 10.00 217.0 2.00 1.43 0.57 2.05 02:30:00

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Total Wave Water Predict Skew Run up Ra Water Date and time Hs (m) Tp (s) direction level ed tide surge Level nk Level (degree) (mCD) (mCD) (m) (m) (mCD) 03/01/2018 10 4.02 3.62 9.55 228.0 2.71 2.54 0.18 1.31 07:45:00 Note: Red indicates the 2013-2014 events

APPENDIX B – POOLE BAY: HIGHEST SEA LEVEL AND WAVE EVENTS

Table B.1: 10 highest water level event at Bournemouth Water Skew Wave RP Predicted Rank Date and time level surge Hs (m) Tp (s) direction (years) tide (m) (mCD) (mCD) (degree) 10/03/2008 1 21 3.09 2.43 0.66 1.94 8.3 172 10:30 03/12/2006 2 4 2.93 2.28 0.65 3.00 7.1 184 06:15 17/10/2012 3 4 2.92 2.59 0.33 1.48 6.7 180 09:30 14/12/2012 4 4 2.92 2.57 0.35 2.23 6.3 155 09:00 27/10/2004 5 2 2.85 2.25 0.60 2.61 8.3 143 20:15 20/01/2003 6 2 2.84 2.30 0.53 - - - 09:45 12/12/2000 7 1 2.81 2.38 0.43 - - - 22:00 10/02/1997 8 1 2.81 2.43 0.38 - - - 10:30 24/12/1999 9 <1 2.79 2.32 0.48 - - - 22:30 02/01/2003 10 <1 2.79 2.23 0.56 - - - 08:15 Note: Red indicates the 2013-2014 events

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Figure B.1: Scatter plots of twice daily high water values against coinciding (a) wave height and (b) wave period, (c) 16-h wave height peaks, and (d) wave rose of 100 highest water level event at Bournemouth.

Table B.2: 10 highest skew surge events at Bournemouth Skew Water Wave RP Predicted Rank Date and time surge level Hs (m) Tp (s) direction (years) tide (mCD) (m) (mCD) (degree) 02/01/2001 1 53 0.76 2.74 1.97 - - - 05:15 19/11/1996 2 11 0.70 2.79 2.09 - - - 06:45 19/01/2009 3 6 0.67 2.69 2.02 1.90 20 194 06:00 10/03/2008 4 6 0.66 3.09 2.43 1.94 8.3 172 10:15 03/12/2006 5 4 0.65 2.93 2.28 2.56 7.7 184 07:00 14/11/2002 6 4 0.64 2.75 2.11 - - - 08:30 04/01/1998 7 2 0.61 2.75 2.14 - - - 12:30

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27/10/2004 8 2 0.60 2.85 2.25 2.61 8.3 143 20:15 08/01/2004 9 2 0.60 2.67 2.07 3.39 7.7 - 09:15 30/01/2000 10 2 0.60 2.41 1.81 - - - 06:45 Note: Red indicates the 2013-2014 events

Figure B.2: Scatter plots of twice daily high water values against coinciding (a) wave height and (b) wave period, (c) 16-h wave height peaks, and (d) wave rose of 100 highest skew surge event at Bournemouth.

Table B.3: 10 highest significant wave height (Hs) events at Boscombe Wave Water Predicted Skew RP Rank Date and time Hs (m) Tp (s) direction level tide surge (years) (degree) (mCD) (mCD) (m) 28/03/2016 1 50 4.53 9.1 172 - - - 03:30 20/11/2016 2 13 4.18 9.1 166 - - - 04:00

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05/02/2014 3 5 3.95 9.1 170 - - - 01:00 10/03/2008 4 4 3.84 8.3 180 3.09 2.43 2.85 07:00 01/01/2014 5 3 3.81 8.3 177 - - - 16:30 08/01/2004 6 2 3.62 8.3 - 2.67 2.07 0.60 09:30 13/12/2008 7 2 3.55 8.3 177 2.46 2.31 0.15 04:00 14/02/2014 8 1 3.48 11.1 197 - - - 23:30 12/02/2014 9 1 3.47 8.3 184 - - - 14:30 13/02/2018 10 1 3.46 8.3 159 - - - 11:30 Note: Red indicates the 2013-2014 events

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Table B.4: 10 highest wave period (Tp) events at Boscombe Wave Water Predicted Skew Rank Date and time Tp (s) Hs (m) direction level tide surge (degree) (mCD) (mCD) (m) 06/01/2014 1 25 1.88 163 - - - 13:30 02/02/2014 2 25 1.47 188 - - - 02:00 03/03/2014 3 25 1.55 187 - - - 13:30 11/03/2008 4 22.2 1.60 190 2.33 2.21 0.12 02:00 15/02/2011 5 22.2 1.42 187 2.09 1.80 0.29 19:30 30/10/2011 6 22.2 1.18 197 2.40 2.32 0.08 02:30 12/12/2011 7 22.2 1.19 191 2.27 2.17 0.10 12:30 16/12/2012 8 22.2 1.10 197 2.46 2.35 0.11 03:30 27/10/2013 9 22.2 1.67 187 1.96 1.88 0.09 14:30 22/12/2013 10 22.2 1.49 172 - - - 01:00 Note: Red indicates the 2013-2014 events

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Figure B.4: Scatter plots of twice daily high water values against coinciding (a) wave height and (b) wave period, (c) 16-h wave height peaks, and (d) wave rose of 100 highest wave period event at Boscombe.

Table B.5: 10 highest run up level (β =0.01) events at Boscombe Total Run up Wave Water Predict Skew Ra Water Date and time Level Hs (m) Tp (s) direction level ed tide surge nk Level (m) (degree) (mCD) (mCD) (m) (mCD) 28/03/2016 1 1.18 4.53 9.10 172.0 - - - - 03:30:00 20/11/2016 2 1.09 4.18 9.10 166.0 - - - - 04:00:00 05/02/2014 3 1.04 3.95 9.10 170.0 - - - - 01:00:00 10/03/2008 4 1.00 3.84 8.30 180.0 2.18 1.55 0.63 3.18 07:00:00 01/01/2014 5 0.99 3.81 8.30 177.0 - - - - 16:30:00 15/02/2014 6 0.99 3.43 13.30 193.0 - - - - 00:30:00

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28/10/2013 7 0.96 3.01 18.20 190.0 - - - - 05:30:00 08/01/2004 8 0.94 3.62 8.30 - 2.54 2.06 0.47 3.48 09:30:00 13/12/2008 9 0.93 3.55 8.30 177.0 1.19 0.76 0.43 2.12 04:00:00 13/02/2018 10 0.91 3.46 8.30 159.0 - - - - 11:30:00 Note: Red indicates the 2013-2014 events

Table B.6: 10 highest total water level (β =0.01) events at Bournemouth-Boscombe Total Wave Water Predict Skew Run up Ra Water Date and time Hs (m) Tp (s) direction level ed tide surge Level nk Level (degree) (mCD) (mCD) (m) (m) (m) 03/12/2006 1 3.72 3.04 7.40 185.0 2.93 2.23 0.70 0.79 06:15:00 10/03/2008 2 3.63 1.94 8.30 172.0 3.09 2.43 0.67 0.54 10:30:00 08/01/2004 3 3.58 3.55 7.70 - 2.67 2.05 0.62 0.92 08:30:00 27/10/2004 4 3.57 2.74 8.30 143.0 2.84 2.23 0.61 0.73 20:30:00 14/12/2012 5 3.49 2.23 6.30 155.0 2.92 2.57 0.35 0.58 09:00:00 08/11/2010 6 3.39 3.21 8.30 176.0 2.55 2.36 0.18 0.85 08:30:00 13/12/2008 7 3.36 3.43 8.30 171.0 2.46 2.23 0.23 0.90 07:30:00 17/10/2012 8 3.32 1.48 6.70 180.0 2.92 2.59 0.33 0.40 09:30:00 12/12/2011 9 3.32 2.73 8.30 191.0 2.59 2.07 0.51 0.73 22:00:00 19/01/2009 10 3.31 1.86 20.00 195.0 2.65 2.02 0.63 0.66 05:45:00 Note: Red indicates the 2013-2014 events

Table B.7: 10 highest run up level (β =0.03) events at Boscombe Total Run up Wave Water Predict Skew Ra Water Date and time Level Hs (m) Tp (s) direction level ed tide surge nk Level (m) (degree) (mCD) (mCD) (m) (mCD) 06/01/2014 1 1.62 2.40 25.00 190.0 - - - - 17:30:00 28/10/2013 2 1.55 3.01 18.20 190.0 - - - - 05:30:00 28/03/2016 3 1.54 4.53 9.10 172.0 - - - - 03:30:00

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05/02/2014 4 1.47 2.80 18.20 187.0 - - - - 15:30:00 15/02/2014 5 1.45 3.43 13.30 193.0 - - - - 00:30:00 20/11/2016 6 1.44 4.18 9.10 166.0 - - - - 04:00:00 08/02/2014 7 1.44 2.50 20.00 186.0 - - - - 17:30:00 03/01/2014 8 1.44 2.50 20.00 196.0 - - - - 14:30:00 21/10/2017 9 1.38 2.36 20.00 190.0 - - - - 12:30:00 10/03/2008 10 1.30 3.84 8.30 180.0 2.18 1.55 0.63 3.49 07:00:00 Note: Red indicates the 2013-2014 events

Table B.8: 10 highest total water level (β =0.03) events at Bournemouth-Boscombe Total Wave Water Predict Skew Run up Ra Water Date and time Hs (m) Tp (s) direction level ed tide surge Level nk Level (degree) (mCD) (mCD) (m) (m) (mCD) 03/12/2006 1 3.96 3.04 7.40 185.0 2.93 2.23 0.70 1.03 06:15:00 08/01/2004 2 3.85 3.55 7.70 - 2.67 2.05 0.62 1.19 08:30:00 10/03/2008 3 3.84 1.94 8.30 172.0 3.09 2.43 0.67 0.75 10:30:00 27/10/2004 4 3.83 2.74 8.30 143.0 2.84 2.23 0.61 0.99 20:30:00 19/01/2009 5 3.83 1.90 20.00 194.0 2.64 2.02 0.62 1.19 06:00:00 08/11/2010 6 3.67 3.21 8.30 176.0 2.55 2.36 0.18 1.12 08:30:00 14/12/2012 7 3.67 2.23 6.30 155.0 2.92 2.57 0.35 0.76 09:00:00 13/12/2008 8 3.64 3.43 8.30 171.0 2.46 2.23 0.23 1.19 07:30:00 06/03/2007 9 3.58 2.87 8.85 188.0 2.53 1.91 0.62 1.05 02:15:00 12/12/2011 10 3.57 2.73 8.30 191.0 2.59 2.07 0.51 0.99 22:00:00 Note: Red indicates the 2013-2014 events

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APPENDIX C – SOLENT: HIGHEST SEA LEVEL AND WAVE EVENTS

Table C.1: 10 highest water level event at Portsmouth Water Skew Wave RP Predicted Rank Date and time level surge Hs (m) Tp (s) direction (years) tide (mCD) (mCD) (m) (degree) 06/12/2013 1 15 5.56 4.88 0.68 0.86 8.3 211 01:00 14/02/2014 2 11 5.54 4.68 0.86 3.91 11.1 203 23:00 23/12/1995 3 8 5.51 5.08 0.42 - - - 11:45 10/03/2008 4 8 5.50 4.92 0.58 3.12 8.3 181 13:00 03/01/2014 5 7 5.49 5.10 0.40 - - - 12:30 07/12/1994 6 7 5.48 4.80 0.68 - - - 02:00 11/01/1993 7 6 5.48 4.82 0.66 - - - 13:15 10/01/1993 8 6 5.48 4.82 0.66 - - - 12:30 04/01/2018 9 5 5.46 5.01 0.46 2.28 11.8 188 12:45 03/01/2014 10 5 5.46 5.03 0.42 - - - 00:15 Note: Red indicates the 2013-2014 events

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Figure C.1: Scatter plots of twice daily high water values against coinciding (a) wave height and (b) wave period, (c) 16-h wave height peaks, and (d) wave rose of 100 highest water level event at Portsmouth.

Table C.2: 10 highest skew surge events at Portsmouth Skew Water Wave RP Predicted Rank Date and time surge level Hs (m) Tp (s) direction (years) tide (mCD) (m) (mCD) (degree) 14/10/1976 1 95 0.91 5.04 4.13 - - - 15:00 14/02/2014 2 47 0.86 5.54 4.68 4.05 12.5 198 23:30 23/12/2013 3 19 0.80 4.88 4.08 - - - 14:30 21/02/1993 4 15 0.78 5.15 4.37 - - - 11:15 28/10/2013 5 13 0.77 4.70 3.93 3.73 10 190 06:00 16/01/1962 6 10 0.75 4.70 3.94 - - - 21:00 31/12/2013 7 10 0.75 5.33 4.58 - - - 10:00

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Skew Water Wave RP Predicted Rank Date and time surge level Hs (m) Tp (s) direction (years) tide (mCD) (m) (mCD) (degree) 22/09/1999 8 10 0.75 4.62 3.87 - - - 21:30 28/03/1980 9 8 0.73 4.95 4.22 - - - 22:00 02/01/2001 10 7 0.73 4.88 4.16 - - - 04:00 Note: Red indicates the 2013-2014 events

Figure C.2: Scatter plots of twice daily high water values against coinciding (a) wave height and (b) wave period, (c) 16-h wave height peaks, and (d) wave rose of 100 highest skew surge event at Portsmouth.

Table C.3: 10 highest significant wave height (Hs) events at Hayling Island Wave Water Predicted Skew RP Rank Date and time Hs (m) Tp (s) direction level tide surge (years) (degree) (mCD) (mCD) (m) 28/03/2016 1 41 4.40 9.1 169 5.24 4.55 0.69 03:00

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Wave Water Predicted Skew RP Rank Date and time Hs (m) Tp (s) direction level tide surge (years) (degree) (mCD) (mCD) (m) 05/02/2014 2 13 4.13 11.8 194 4.90 4.57 0.33 14:30 15/02/2014 3 10 4.07 11.8 197 5.54 4.68 0.86 00:00 10/03/2008 4 4 3.79 8.3 183 5.50 4.92 0.58 08:00 13/12/2011 5 4 3.77 9.1 187 5.04 4.58 0.46 01:00 28/10/2013 6 4 3.73 10 190 4.70 3.93 0.77 06:00 20/11/2016 7 4 3.73 9.1 165 5.24 4.61 0.63 05:00 02/11/2019 8 3 3.67 14.3 183 4.99 4.47 0.52 14:30 08/01/2004 9 3 3.64 8.3 - 4.57 4.45 0.12 10:30 13/12/2008 10 3 3.64 7.7 169 4.55 4.77 -0.22 10:00 Note: Red indicates the 2013-2014 events

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Figure C.3: Scatter plots of twice daily high water values against coinciding (a) wave height and (b) wave period, (c) 16-h wave height peaks, and (d) wave rose of 100 highest wave height events at Hayling Island.

Table C.4: 10 highest wave period (Tp) events at Hayling Island Wave Water Predicted Skew Rank Date and time Tp (s) Hs (m) direction level tide surge (degree) (mCD) (mCD) (m) 15/02/2011 1 25 1.95 186 4.50 4.08 0.42 23:00 30/10/2011 2 25 1.26 194 4.91 4.79 0.11 04:00 12/12/2011 3 25 1.02 187 4.67 4.54 0.13 02:30 02/02/2014 4 25 1.89 196 5.04 5.08 -0.04 02:30 03/03/2014 5 25 1.78 194 5.23 5.04 0.19 13:00 09/02/2016 6 25 2.13 190 4.90 4.83 0.07 01:00 17/11/2018 7 25 1.27 191 3.63 3.72 -0.09 19:30

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Wave Water Predicted Skew

Rank Date and time Tp (s) Hs (m) direction level tide surge (degree) (mCD) (mCD) (m) 04/01/2008 8 25 1.01 191 3.99 3.94 0.05 02:00 03/11/2011 9 22.2 1.23 190 4.36 4.25 0.12 09:00 24/02/2012 10 22.2 1.09 194 4.60 4.48 0.12 13:30 Note: Red indicates the 2013-2014 events

Figure C.4: Scatter plots of twice daily high water values against coinciding (a) wave height and (b) wave period, (c) 16-h wave height peaks, and (d) wave rose of 100 highest wave period events at Hayling Island.

Table C.5: 10 highest run up level (β =0.01) events at Hayling Island

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Total Run up Wave Water Predict Skew Ra Water Date and time Level Hs (m) Tp (s) direction level ed tide surge nk Level (m) (degree) (mCD) (mCD) (m) (mCD) 05/02/2014 1 1.25 3.97 20.00 187.0 4.84 4.53 0.30 6.08 15:00:00 08/02/2014 2 1.15 3.46 22.20 186.0 4.14 3.94 0.20 5.29 18:30:00 28/03/2016 3 1.15 4.40 9.10 169.0 4.80 4.33 0.47 5.95 03:00:00 14/02/2014 4 1.13 4.05 12.50 198.0 5.48 4.68 0.80 6.60 23:30:00 21/10/2017 5 1.07 3.32 20.00 188.0 4.65 4.58 0.07 5.72 13:30:00 03/11/2005 6 1.04 3.33 18.20 200.0 4.77 4.61 0.16 5.82 13:00:00 02/11/2019 7 1.03 3.60 13.40 185.0 4.98 4.40 0.58 6.01 14:15:00 08/02/2016 8 1.01 3.37 15.40 184.0 4.94 4.76 0.18 5.95 11:30:00 28/10/2013 9 1.00 3.73 10.00 190.0 4.63 3.93 0.70 5.63 06:00:00 13/12/2011 10 0.99 3.77 9.10 187.0 4.86 4.56 0.30 5.85 01:00:00 Note: Red indicates the 2013-2014 events

Table C.6: 10 highest total water level (β =0.01) events at Portsmouth-Hayling Island Total Wave Water Predict Skew Run up Ra Water Date and time Hs (m) Tp (s) direction level ed tide surge Level nk Level (degree) (mCD) (mCD) (m) (m) (mCD) 14/02/2014 1 6.63 3.98 11.80 200.5 5.53 4.67 0.86 1.10 23:15:00 10/03/2008 2 6.32 3.12 8.30 181.0 5.50 4.91 0.58 0.82 13:00:00 28/03/2016 3 6.24 3.91 7.70 167.0 5.24 4.54 0.70 1.00 01:30:00 05/02/2014 4 6.22 3.53 8.30 160.0 5.30 4.74 0.55 0.92 03:00:00 20/11/2016 5 6.22 3.71 9.10 165.5 5.24 4.45 0.79 0.98 04:45:00 04/01/2018 6 6.12 2.29 10.90 190.5 5.46 5.01 0.46 0.66 12:45:00 07/11/2018 7 6.02 2.48 7.70 159.0 5.36 4.92 0.44 0.66 11:00:00 02/11/2019 8 6.01 3.60 13.40 185.0 4.98 4.40 0.58 1.03 14:15:00 03/11/2013 9 6.00 2.32 5.90 188.0 5.41 4.74 0.66 0.59 22:30:00

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21/10/2017 10 5.99 2.96 18.20 184.0 5.05 4.74 0.31 0.94 12:00:00 Note: Red indicates the 2013-2014 events

Table C.7: 10 highest run up level (β =0.03) events at Hayling Island Total Run up Wave Water Predict Skew Ra Water Date and time Level Hs (m) Tp (s) direction level ed tide surge nk Level (m) (degree) (mCD) (mCD) (m) (mCD) 05/02/2014 1 1.99 3.97 20.00 187.0 4.84 4.53 0.30 6.83 15:00:00 08/02/2014 2 1.92 3.46 22.20 186.0 4.14 3.94 0.20 6.06 18:30:00 21/10/2017 3 1.75 3.32 20.00 188.0 4.65 4.58 0.07 6.40 13:30:00 03/11/2005 4 1.67 3.33 18.20 200.0 4.77 4.61 0.16 6.44 13:00:00 28/10/2013 5 1.60 3.16 18.20 173.0 3.52 3.27 0.24 5.12 03:00:00 14/02/2014 6 1.60 4.05 12.50 198.0 5.48 4.68 0.80 7.08 23:30:00 08/02/2016 7 1.59 2.88 20.00 190.0 4.57 4.52 0.05 6.16 22:30:00 15/12/2018 8 1.58 2.87 20.00 169.0 3.00 2.91 0.09 4.58 13:30:00 03/02/2017 9 1.58 2.85 20.00 207.0 4.70 4.38 0.32 6.27 15:30:00 02/11/2019 10 1.58 3.29 16.70 181.0 4.56 4.43 0.13 6.14 15:30:00 Note: Red indicates the 2013-2014 events

Table C.8: 10 highest total water level (β =0.03) events at Portsmouth-Hayling Island Total Wave Water Predict Skew Run up Ra Water Date and time Hs (m) Tp (s) direction level ed tide surge Level nk Level (degree) (mCD) (mCD) (m) (m) (mCD) 14/02/2014 1 7.08 4.05 12.50 198.0 5.48 4.68 0.80 1.60 23:30:00 05/02/2014 2 6.83 3.97 20.00 187.0 4.84 4.53 0.30 1.99 15:00:00 10/03/2008 3 6.60 3.12 8.30 181.0 5.50 4.91 0.58 1.10 13:00:00 21/10/2017 4 6.59 2.99 19.10 183.5 5.00 4.73 0.28 1.58 12:15:00 03/11/2005 5 6.59 3.22 18.20 198.0 4.96 4.75 0.21 1.63 12:30:00 20/11/2016 6 6.55 3.71 9.10 165.5 5.24 4.45 0.79 1.31 04:45:00

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Total Wave Water Predict Skew Run up Ra Water Date and time Hs (m) Tp (s) direction level ed tide surge Level nk Level (degree) (mCD) (mCD) (m) (m) (mCD) 28/03/2016 7 6.53 3.91 7.70 167.0 5.24 4.54 0.70 1.29 01:30:00 03/03/2014 8 6.50 1.78 25.00 194.0 5.17 5.01 0.16 1.33 13:00:00 02/11/2019 9 6.49 3.60 13.40 185.0 4.98 4.40 0.58 1.51 14:15:00 08/02/2016 10 6.48 3.37 15.40 184.0 4.94 4.76 0.18 1.54 11:30:00 Note: Red indicates the 2013-2014 events

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APPENDIX D – EAST SCOPAC: HIGHEST SEA LEVEL AND WAVE EVENTS

Table D.1: 10 highest water level event at Newhaven Water Skew Wave RP Predicted Rank Date and time level surge Hs (m) Tp (s) direction (years) tide (mCD) (mCD) (m) (degree) 06/12/2013 1 41 7.79 7.06 0.73 1.40 7.7 219 01:15 02/02/1983 2 17 7.69 6.93 0.76 - - - 02:00 08/04/1985 3 8 7.61 7.23 0.38 - - - 01:00 31/01/1983 4 4 7.52 7.09 0.43 - - - 13:00 23/12/1995 5 4 7.52 7.22 0.30 - - - 11:45 30/09/2019 6 2 7.47 7.48 -0.01 1.40 10.5 222 12:00 14/01/2017 7 2 7.47 6.96 0.51 1.43 7.1 212 00:15 01/01/1995 8 2 7.46 6.98 0.48 - - - 23:15 01/10/2019 9 2 7.45 7.39 0.07 1.72 6.7 217 12:45 03/11/2013 10 2 7.45 6.92 0.52 - - - 22:45 Note: Red indicates the 2013-2014 events

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Figure D.1: Scatter plots of twice daily high water values against coinciding (a) wave height and (b) wave period, (c) 16-h wave height peaks, and (d) wave rose of 100 highest water level event at Newhaven.

Table D.2: 10 highest skew surge events at Newhaven Skew Water Wave RP Predicted Rank Date and time surge level Hs (m) Tp (s) direction (years) tide (mCD) (m) (mCD) (degree) 16/10/1987 1 194 1.14 5.77 4.63 - - - 06:00 21/02/1993 2 32 0.94 7.31 6.36 - - - 11:15 14/11/2002 3 9 0.80 6.23 5.43 - - - 07:00 02/02/1983 4 6 0.76 7.69 6.93 - - - 02:00 17/12/2004 5 6 0.75 6.89 6.14 2.24 9.1 214 15:00 14/01/1984 6 5 0.74 6.16 5.41 - - - 07:00 06/12/2013 7 5 0.73 7.79 7.06 1.56 7.7 221 01:00

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23/01/2009 8 4 0.70 6.23 5.53 1.86 8.3 221 09:15 01/03/2008 9 4 0.70 5.43 4.73 1.38 8.3 225 17:15 05/01/2012 10 3 0.67 5.95 5.28 1.73 10 224 20:45 Note: Red indicates the 2013-2014 events

Figure D.2: Scatter plots of twice daily high water values against coinciding (a) wave height and (b) wave period, (c) 16-h wave height peaks, and (d) wave rose of 100 highest skew surge event at Newhaven.

Table D.3: 10 highest significant wave height (Hs) events at Rustington Wave Water Predicted Skew RP Rank Date and time Hs (m) Tp (s) direction level tide surge (years) (degree) (mCD) (mCD) (m) 24/12/2013 1 25 5.46 10 203 6.03 5.97 0.06 02:30 13/12/2011 2 8 5.02 - 58 6.78 6.47 0.31 00:00

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15/02/2014 3 7 4.97 11.1 215 7.12 6.56 0.55 00:30 28/03/2016 4 6 4.91 9.1 191 6.74 6.45 0.29 02:30 28/10/2013 5 5 4.82 9.1 201 5.63 5.09 0.54 06:00 03/12/2006 6 5 4.81 9.1 200 6.73 6.65 0.08 08:00 05/02/2014 7 4 4.72 8.3 194 6.50 6.40 0.10 14:30 02/11/2019 8 4 4.69 11.1 211 6.63 6.22 0.40 12:30 20/11/2016 9 4 4.65 9.1 174 6.70 6.34 0.37 05:30 22/11/2016 10 2 4.35 8.3 208 5.85 5.75 0.10 04:00 Note: Red indicates the 2013-2014 events

Figure D.3: Scatter plots of twice daily high water values against coinciding (a) wave height and (b) wave period, (c) 16-h wave height peaks, and (d) wave rose of 100 highest wave height event at Rustington.

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Table D.4: 10 highest wave period (Tp) events at Rustington Wave Water Predicted Skew Rank Date and time Tp (s) Hs (m) direction level tide surge (degree) (mCD) (mCD) (m) 15/02/2011 1 25 1.76 208 5.99 5.60 0.39 23:00 06/01/2014 2 25 2.64 212 6.63 6.66 -0.03 15:00 12/03/2004 3 22.2 1.41 206 6.30 6.38 -0.07 15:00 04/01/2008 4 22.2 1.10 212 5.26 5.26 0.00 09:00 30/10/2011 5 22.2 1.54 215 6.88 6.93 -0.06 02:30 04/03/2014 6 22.2 1.53 208 7.06 7.26 -0.21 02:00 03/02/2017 7 22.2 1.65 200 6.49 6.43 -0.06 06:00 18/04/2018 8 22.2 1.30 219 6.73 7.03 -0.30 02:00 18/11/2018 9 22.2 1.32 212 5.18 5.32 -0.14 09:30 11/09/2003 10 20 1.00 259 6.64 6.66 -0.02 00:00 Note: Red indicates the 2013-2014 events

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Figure D.4: Scatter plots of twice daily high water values against coinciding (a) wave height and (b) wave period, (c) 16-h wave height peaks, and (d) wave rose of 100 highest wave period at Rustington.

Table D.5: 10 highest run up level (β =0.01) events at Rustington Total Run up Wave Water Predict Skew Ra Water Date and time Level Hs (m) Tp (s) direction level ed tide surge nk Level (m) (degree) (mCD) (mCD) (m) (mCD) 24/12/2013 1 1.42 5.46 10.00 203.0 5.96 5.94 0.02 7.38 02:30:00 15/02/2014 2 1.34 4.95 11.80 215.0 6.16 5.61 0.55 7.50 01:00:00 28/03/2016 3 1.27 4.91 9.10 191.0 6.48 6.04 0.44 7.75 02:30:00 02/11/2019 4 1.26 4.69 11.10 211.0 5.82 5.07 0.75 7.08 12:30:00 28/10/2013 5 1.25 4.82 9.10 201.0 5.60 5.01 0.59 6.85 06:00:00 03/12/2006 6 1.25 4.81 9.10 200.0 6.50 5.96 0.54 7.75 08:00:00

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05/02/2014 7 1.21 4.72 8.30 194.0 6.45 6.33 0.12 7.65 14:30:00 20/11/2016 8 1.21 4.65 9.10 174.0 5.45 4.57 0.88 6.66 05:30:00 13/12/2011 9 1.17 4.55 8.30 200.0 6.76 6.46 0.30 7.92 00:30:00 18/01/2007 10 1.15 4.32 10.00 217.0 6.65 6.13 0.52 7.79 10:00:00 Note: Red indicates the 2013-2014 events

Table D.6: 10 highest total water level (β =0.01) events at Rustington-Newhaven Total Wave Water Predict Skew Run up Ra Water Date and time Hs (m) Tp (s) direction level ed tide surge Level nk Level (degree) (mCD) (mCD) (m) (m) (mCD) 04/01/2018 1 8.27 3.16 10.10 217.5 7.40 7.09 0.31 0.86 12:45:00 15/02/2014 2 8.22 4.78 9.10 208.0 6.99 6.40 0.58 1.24 00:00:00 06/12/2013 3 8.22 1.56 7.70 221.0 7.79 7.06 0.73 0.43 01:00:00 05/02/2014 4 8.21 4.41 8.30 170.0 7.08 6.72 0.36 1.13 02:30:00 09/10/2014 5 8.18 3.00 9.10 215.0 7.37 7.34 0.03 0.81 11:30:00 30/03/2010 6 8.12 2.97 8.30 218.0 7.33 7.30 0.03 0.79 23:30:00 03/01/2018 7 8.11 3.10 10.50 219.0 7.26 7.14 0.12 0.86 12:00:00 29/09/2019 8 8.09 2.67 8.30 218.0 7.38 7.39 -0.01 0.71 11:30:00 03/01/2014 9 8.09 2.85 8.00 214.5 7.34 7.25 0.10 0.75 12:15:00 04/01/2014 10 8.06 3.29 7.70 197.0 7.21 7.15 0.05 0.85 13:15:00 Note: Red indicates the 2013-2014 events

Table D.7: 10 highest run up level (β =0.03) events at Rustington Total Run up Wave Water Predict Skew Ra Water Date and time Level Hs (m) Tp (s) direction level ed tide surge nk Level (m) (degree) (mCD) (mCD) (m) (mCD) 24/12/2013 1 1.86 5.46 10.00 203.0 5.96 5.94 0.02 7.82 02:30:00 15/02/2014 2 1.83 4.95 11.80 215.0 6.16 5.61 0.55 7.99 01:00:00 02/11/2019 3 1.81 4.41 14.30 218.0 6.53 6.21 0.32 8.35 14:30:00 06/01/2014 4 1.72 2.64 25.00 212.0 6.62 6.60 0.01 8.34 15:00:00

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28/03/2016 5 1.65 4.91 9.10 191.0 6.48 6.04 0.44 8.13 02:30:00 20/11/2016 6 1.62 4.40 11.10 204.0 3.21 2.43 0.78 4.83 07:30:00 28/10/2013 7 1.62 4.82 9.10 201.0 5.60 5.01 0.59 7.22 06:00:00 03/12/2006 8 1.62 4.81 9.10 200.0 6.50 5.96 0.54 8.12 08:00:00 04/01/2014 9 1.60 2.92 20.00 218.0 5.62 5.97 -0.35 7.23 02:30:00 08/02/2016 10 1.57 3.83 13.30 215.0 6.11 5.82 0.29 7.69 12:30:00 Note: Red indicates the 2013-2014 events

Table D.8: 10 highest total water level (β =0.03) events at Rustington-Newhaven Total Wave Water Predict Skew Run up Ra Water Date and time Hs (m) Tp (s) direction level ed tide surge Level nk Level (degree) (mCD) (mCD) (m) (m) (mCD) 04/01/2018 1 8.62 3.21 11.10 217.0 7.35 7.03 0.33 1.27 13:00:00 15/02/2014 2 8.60 4.78 9.10 208.0 6.99 6.40 0.58 1.61 00:00:00 05/02/2014 3 8.54 4.41 8.30 170.0 7.08 6.72 0.36 1.46 02:30:00 09/10/2014 4 8.47 3.00 9.10 215.0 7.37 7.34 0.03 1.10 11:30:00 03/01/2018 5 8.46 3.18 10.80 219.0 7.22 7.16 0.06 1.24 11:45:00 07/01/2014 6 8.43 2.93 22.20 208.0 6.72 6.59 0.13 1.71 03:00:00 02/11/2019 7 8.40 4.48 13.30 217.0 6.62 6.19 0.44 1.78 14:00:00 06/12/2013 8 8.40 1.56 7.70 221.0 7.79 7.06 0.73 0.61 01:00:00 30/03/2010 9 8.39 2.97 8.30 218.0 7.33 7.30 0.03 1.06 23:30:00 08/02/2016 10 8.38 3.95 10.25 218.0 6.94 6.70 0.24 1.44 11:15:00 Note: Red indicates the 2013-2014 events

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APPENDIX E – WAVE TIME SERIES PLOTS

Figure E.1: Time series of (a) Hs and Hmax, (b) Tp and Tz, and (c) Wave power (Po) at Folkestone.

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Figure E.2: Time series of (a) Hs and Hmax, (b) Tp and Tz, and (c) Wave power (Po) at Rustington.

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Figure E.3: Time series of (a) Hs and Hmax, (b) Tp and Tz, and (c) Wave power (Po) at Hayling Island.

Figure E.4: Time series of (a) Hs and Hmax, (b) Tp and Tz, and (c) Wave power (Po) at Sandown Bay.

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Figure E.5: Time series of (a) Hs and Hmax, (b) Tp and Tz, and (c) Wave power (Po) at Milford.

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Figure E.6: Time series of (a) Hs and Hmax, (b) Tp and Tz, and (c) Wave power (Po) at Boscombe.

Figure E.7: Time series of (a) Hs and Hmax, (b) Tp and Tz, and (c) Wave power (Po) at Chesil.

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Figure E.8: Time series of (a) Hs and Hmax, (b) Tp and Tz, and (c) Wave power (Po) at Start Bay.

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Figure E.9: Time series of (a) Hs and Hmax, (b) Tp and Tz, and (c) Wave power (Po) at Penzance.

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APPENDIX F – COASTAL FLOOD EVENT TABLES

Table F.1: Coastal flood events recorded from within the SCOPAC region.

City, Town, Village Outside SCOPAC Area Road names

Day

Year

Month

Severity Event No. Event Avon, Bristol, Severn 1 1703 11 26 3 Lymington Estuaries Gosport, Portsmouth, 2 1804 1 19 5 Cowes (Isle of Wight), Selsey Bill Portsmouth, Cowes, Isle of 3 1804 1 28 4 Wight 4 1808 11 12 1 Portsmouth 5 1808 11 18 3 Portsmouth, Isle of Wight Folkstone, Leith Portsmouth, Portsea Island, Gosport, Southsea, 6 1818 3 4 5 Ryde, Cowes (Isle of Wight), Hayling Island, Southampton Cowes, Bembridge (Isle of Wight), Spithead, Southsea, Portsmouth, Gosport, 7 1824 11 23 5 Hythe, Eling, Southampton, Chidham, Lymington, Stokes Bay, Chichester Redbridge, Southampton, Southsea, Keyhaven, 8 1840 11 13 4 Lymington, Spithead, Portsmouth 9 1857 10 7 1 Ryde (Isle of Wight) Eastbourne Lymington, Ryde (Isle of 10 1860 12 26 1 Wight) 11 1867 1 5 1 Weymouth, Isle of Portland Penzance, Land's End 12 1872 1 1 1 Northam, Southampton Berwick-upon-Tweed, Weymouth, Worthing, Whitby, Hastings, 13 1875 11 11 1 Portsmouth, Southsea, Eastbourne, Brighton, Southsea Castle Southampton Bude, Helston, Douglas, Thames Estuary 14 1876 12 5 1 Portsmouth, Southampton 15 1876 12 31 1 Portsmouth Maldon, Berwick-upon- Woodmill Lane, Tweed, South Shields, Southampton, Weymouth, Scarborough, Dover, Hayling Island, 16 1877 1 1 5 Douglas, Thames Portobello, Joppa Portsmouth, Northam, Estuary, Edinburgh, Lymington, Cowes, Ryde, Fens, Folkstone, Yarmouth, Newport (Isle of Hastings

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City, Town, Village Outside SCOPAC Area Road names

Day

Year

Month

Severity Event No. Event Wight), Portsea Island, Bevois Valley, Totton, Eling

17 1883 9 17 1 Worthing Brighton, Hove 18 1902 2 28 1 Southampton Portsmouth, Weymouth, 19 1904 2 3 1 London, Bude, Penzance Isle of Portland 20 1907 10 6 1 Portsmouth Ryde, Cowes, Newport, 21 1909 10 27 3 Yarmouth (Isle of Wight), Spithead, Lymington, Eling Worthing, Southsea, Dover, Ilfracombe, Portsmouth, Selsey, 22 1910 12 16 3 Avonmouth, Exmouth, Pagham Harbour, Chesil Neath Beach Old Portsmouth, Cosham, Southsea, Hilsea, Portsmouth, Gosport, Cowes, Ryde, Yarmouth, 23 1912 12 26 5 Newport, Bembridge, Sandown Parade Sandown (Isle of Wight), Lymington, Fareham, Northam, St Denys, Southampton Yarmouth, Cowes (Isle of 24 1913 12 26 2 Wight) Southsea, Portsmouth, Cowes, Ryde (Isle of Wight), Northam, 25 1916 11 5 5 Pennington, Bournemouth, Southampton, Walhampton, Keyhaven, Lymington Shoreham-by-Sea, 26 1918 1 15 6 Littlehampton, Northam, Woolston (Southampton) Hull, Scarborough, Severn Beach, Hastings, 27 1923 10 10 2 Portsmouth Folkestone, Hythe, Sandgate, Dover

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City, Town, Village Outside SCOPAC Area Road names

Day

Year

Month

Severity Event No. Event St. Denys, Totton District, Woolston, Northam, Millbrook, Southampton, Cowes, Yarmouth, 28 1924 11 27 4 Newport, Bembridge, Seaview, (Isle of Wight), Southsea, Portsea, Hayling Island, Emsworth, Farlington, Langstone 29 1924 11 29 1 Cowes Beacon House, West Street, Chichester Selsey, Bosham, Chichester, Harbour, Anchor Inn, 30 1924 12 3 4 Portsmouth, Lymington Portsmouth Road, Cutt Mill, Bath Road, Town Quay Folkstone, Sandgate, Southsea (Portsmouth), Deal, Blackpool, Yarmouth (Isle of Wight), 31 1924 12 26 2 Fleetwood, Sandylands Totten, Eling, Woolston, Promenade, Gretna, Redbridge (Southampton) Dundee, Lytham, Dover Lowestoft, Dover, Deal, Chesil Beach (Isle of 32 1927 12 21 1 England Thames Portland) Estuary, Herne Bay 33 1928 2 16 1 Alum Bay (Isle of Wight) Chesil Beach (Isle of 34 1930 2 1 1 Portland) Cowes, Newport, Ryde, Bembridge, Yarmouth, Seaview, Freshwater Bay (Isle of Wight), Eastney, Southsea, Hilsea, Cosham, Old Portsmouth, 35 1931 11 9 4 Portsmouth, Portchester, Winchelsea, Rye Emsworth, Hayling Island, Chichester harbour, Langstone, Northam, Southampton, Hamble-le- Rice, Littlehampton, Shoreham-by-Sea Southend-on-Sea, 36 1935 2 6 1 Cowes Benfleet Southampton, Milford-on- Sea, Netley, Keyhaven, 37 1935 9 17 2 Cowes, Bournemouth, Woolston, Lymington

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City, Town, Village Outside SCOPAC Area Road names

Day

Year

Month

Severity Event No. Event Lymington, Milford, 38 1935 9 21 2 Sturt Pond Keyhaven Cowes, Bembridge, Colwell Princess Parade, 39 1935 9 25 2 Bay, Freshwater Bay Gurnard Marsh 40 1936 6 18 1 Southsea (Portsmouth) Chesil Beach (Isle of 41 1936 11 12 1 Castletown (Isle of Man) Portland) 42 1938 1 22 1 Isle of Wight Chesil Beach (Isle of 43 1939 1 20 1 Portland) 44 1939 1 23 1 Lymington 45 1942 2 13 1 Isle of Portland Chesil Beach (Isle of Aberystwyth, Solway 46 1942 12 13 4 Portland) Firth Chesil Beach (Isle of 47 1942 12 23 1 Portland) Chesil Beach (Isle of Portland), Southampton, Poole Quay, Sandbanks Poole, Sandbanks, Hayling Road, Stanley Road, 48 1945 12 19 3 Island, Havant, Eastoke, Seaford Culver Road, Duver Bridlington, Sandown, Road, Cowes High Shanklin, Ryde (Isle of Street Wight) 49 1947 12 13 1 Isle of Portland 50 1947 12 27 1 Emsworth Sandgate, Hastings Berwick-upon-Tweed, Eyemouth, Hastings, 51 1948 8 8 1 Felpham, Bridport Folkestone, Sandgate, Jaywick, London 52 1948 8 14 1 Sandown, Ryde, Lymington Ventnor Beach Southampton Hythe, 53 1949 10 23 3 Hastings, Folkestone, Terminus Terrace Sandgate, Cowes 54 1949 10 29 2 Lymington, Keyhaven Lymington, Keyhaven, Milford-on-Sea, Warsash, 55 1950 2 3 1 Southampton, Bournemouth 56 1950 2 6 1 Southampton, Fawley Weymouth Harbour 57 1951 2 5 1 Milford-on-Sea, Totton Southampton, Beaulieu, Hythe, Southsea Weymouth Quay, Rock 58 1951 12 28 2 (Portsmouth), Shanklin, Severn Valley Gardens Sandown (Isle of Wight), Woolston, Woodmill Lane 59 1953 10 31 1 Southampton

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City, Town, Village Outside SCOPAC Area Road names

Day

Year

Month

Severity Event No. Event Terminus Drive, Davis 60 1954 11 11 1 St Denys (Southampton) Strood, Southend, Hull Hotel Titchfield, Eling, A27 (Worthing to Redbridge, Southampton, Lancing); Kingsway, Milford-on-Sea, Keyhaven, Teignmouth, Newhaven, A259, Marine Parade Lymington, Ryde, Newport, Seaford, Southampton, (Newhaven to Bembridge (Isle of Wight), 61 1954 11 26 5 Lostwithie, Gunnislake, Seaford),Undercliff Totton, Worthing, Lancing, Truro, Mevagissey, Drive, Bridge Street, Chesil Beach (Isle of Perranporth Green Road, Poole Portland), Bournemouth, Quay, Eling Harbour, Christchurch, Poole, Bath Road (Lymington) Woolston Christchurch, Lymington, 62 1954 11 30 5 Southampton, Milford-on- Bittern Road Sea, Keyhaven 63 1954 12 1 1 Isle of Portland Duver Road, Bath Road, Seaview, Lymington, Waterloo Road, Kinfs 64 1954 12 4 2 Christchurch, Keyhaven, St Helens Saltern Road, Wick Milford-on-Sea Holiday Park, Red Lion Hotel Ryde, Lymington, Bridge Road, Poole Southampton, Quay, Green Road, Christchurch, Poole, Undercliff Drive, New- 65 1954 12 8 2 Bournemouth, Hamworthy, Quay Road, Woodmill, Keyhaven, Milford-on-Sea, Bitterne, Weston Shire, Hythe, Fareham, Totton Terminus Terrace High Street, Bridge 66 1954 12 11 1 Cowes Road Poole Quay, Shore Southampton, Road, New-Quay Road, Christchurch, Poole, 67 1955 3 24 1 Bridge Street, Stony Sandbanks, Hamworthy, Lane, Woodmill Road, Redbridge Royal Pier Rec. Ground Bournemouth- Lymington, Milford-on-Sea, 68 1956 1 7 3 Lymington road, Manor Sway Road Starcross, Saltash, Weymouth to 69 1957 12 10 1 Weymouth, Bournemouth Topsham Bournemouth Road High Street, Bridge 70 1958 12 20 2 Cowes Road, Medina Road, Brunswick Road Southampton, Yarmouth, 71 1959 10 17 1 Gurnard, Newport, Lymington, Keyhaven

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City, Town, Village Outside SCOPAC Area Road names

Day

Year

Month

Severity Event No. Event Cornwall Street, Vectis boating and fishing 72 1959 10 24 1 Ryde, Ventnor club, Ryde rowing club, Keyhaven Yacht Club, Lymington Quay Cowes, Hythe, Marchwood, 73 1959 12 3 1 Southampton Fairlee Road, High 74 1960 1 2 1 Ventnor, Freshwater Street, Junction of East Street Hythe, Millbrook, Portswood, Shirley, Mansbridge, Woodmill Lane (Southampton), Exmouth, Torquay, 75 1960 10 8 5 Lymington, Keyhaven, Brendon Langstone, Hayling Island, Cowes, Yarmouth, Ryde, Newport, Seaview (Isle of Wight) Eastney, Old Portsmouth, Drayton, Portsmouth, Emsworth, Fareham, Langstone, Northney Broad Street, Belgrave 76 1961 10 24 4 (Hayling Island), Cowes, Road Newport, Ryde (Isle of Wight), Totton, Southampton 77 1961 10 27 1 Selsey, Medmerry Mill Pagham Harbour Southampton, Hythe, Bournemouth, Ryde, Undercliff, Drive, Chesil 78 1962 1 10 4 Weymouth, Portland, Beach Bridport Southampton, Portsmouth, 79 1962 1 12 2 Eastoke (Hayling Island), Lymington, Milford-on-Sea Cowes, Lymington, Milford, Town Quay Lower 80 1962 1 13 1 Keyhaven, Christchurch Quay Street 81 1962 1 18 2 Bracklesham Bracklesham Lane Havant, Northney (Hayling Island), Emsworth, Langstone, Fareham, Undercliff Drive, Warsash, Woodmill Lane, 82 1963 11 1 2 Christchurch Quay, Redbridge (Southampton), Wareham Quay Portsmouth, Bognor Regis, Bournemouth, Christchurch, Wareham

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City, Town, Village Outside SCOPAC Area Road names

Day

Year

Month

Severity Event No. Event Southampton, Milford-on- 83 1963 11 18 2 Folkestone, Hastings Sea, Keyhaven The Rise, Burley and Milford Beach, Hurst Spit, Rhineford Road, 84 1963 11 23 2 Keyhaven, Lymington Waterloo Road, Broad Lane, Mayflower Hotel 85 1965 1 20 1 Bournemouth Dymchurch, Hull 86 1965 1 21 3 Ryde, Cowes, Gurnard 87 1965 10 17 1 Selsey Southampton, Mudeford, 88 1966 10 15 2 Portswood Hythe, Lymington 89 1966 10 18 1 Lymington, Keyhaven Hythe, Southampton, 90 1966 10 24 2 Portsmouth Southampton, Hythe, 91 1967 10 4 1 Cowes, Esplanade Road Beaulieu,Weymouth Cowes, Ryde, Newport, Bournemouth seafront, Portsmouth, Southampton, Wareham Causeway, 92 1967 11 2 3 Hayling Island, Fareham, Mudeford Quay, Bognor Regis, Selsey, Dovercourt seawall Lymington, Hythe Limmer Lane, Davenport Road, West Felpham, Bognor Regis, 93 1967 11 10 2 Sands Caravan Park, Medmerry, Selsey, Arundel River Road, Sussex River Authority Gloucester Road, York 94 1967 12 27 1 Bognor Regis Road Hythe, Lymington, Ryde, Cowes, Newport, Poole Quay, Wareham Yarmouth, Portsmouth Causeway, Mudeford 95 1968 12 20 3 (Eastney), Netley, Beaulieu, Quay, Weston Shore Woodmill Lane Road, Cobden Bridge (Southampton) Southsea (Portsmouth), Bournemouth seafront, Hayling Island, Emsworth, Christchurch Quay, 96 1969 1 17 2 Havant, Cowes, Yarmouth, Southsea Esplanade, St Southampton, Hayling George's Road to South Island Parade Pier Lymington, Milford, 97 1969 1 18 1 Lower Woodside Keyhaven Southampton, Portsmouth, 98 1969 11 9 1 Cowes, Chichester Harbour Portsmouth, Fareham, 99 1969 11 12 2 Emsworth, Portchester, Cowes, Southampton 153 SCOPAC Storm Analysis Study

City, Town, Village Outside SCOPAC Area Road names

Day

Year

Month

Severity Event No. Event Southampton, Portsmouth, 100 1974 1 12 4 Hayling Island, Ryde 101 1974 1 19 1 Freshwater Bay, Ryde Quay Road Severn Valley, Dawlish, Millbrook, Southampton, Uckfield, Hailsham, Fareham, Southsea Lewes, Folkestone, (Portsmouth), Cowes, Ryde Poole Quay, Stanley 102 1974 2 10 3 Southampton, St Blazey, (Isle of Wight), Hayling Road Par, Plymouth, Fareham, Island, Christchurch, Avonmouth, Walton Bay, Millbrook, Pill Lower Westhill Road, Simeon Street, Spencer Ryde, Seaview, Ventnor, Road, East Street, 103 1974 2 16 3 Cowes, Lymington Appley Rise, Quay Road, Castle Street, Link Road, Bridge Road Portsmouth, Old Portsmouth, Langstone, 104 1975 1 28 1 Cowes, Newport, Ryde, Hayling Island, Southsea, Fareham Bridge Street, 105 1975 1 31 1 Christchurch Weymouth Quay, Commercial Road Isle of Portland, Hythe, 106 1976 10 14 1 Torquay Beaulieu, Marchwood Portsmouth, Eastoke 107 1976 10 23 1 (Hayling Island) 108 1977 12 17 1 Lymington, Gosport Lane Gosport Lane Sandgate, Fenland, Margate iron jetty, The Wisbech, Wells-next- Parade, West Coast the-Sea, The Wash, bars, Dreamland, Buckie, Sandend, Golden Garter Saloon Grampian coast, Bar, Old Boundary Findhorn, Shelly Head Road, Harbour Street, Bothy, Portgordon, Gladstone Road, Marina Hayling Island, Cowes, King's Lynn, Esplanade, Ramsgate Bembridge, Ryde, Isle of Cleethorpes, Sandilands, and Sandwich Road, 109 1978 1 11 2 Wight, Southampton, Marblethorpe, Golf Road, Sandown Portsmouth, Gurnard Ingoldmells, Walcott, Castle, Athelstan Place, Deal, Alnmouth, Amble Royal Cinque Ports Golf Harbour, Berwick-upon- Club, Deal Pier, Beach Tweed, Blyth, Isle of Street, Pfizer factory, Thanet, Ramsgate, Quay Cottage, Toll Broadstairs, Sandwich, Bridge, Sandown Road, Lido, Minnis Bay, Sloane Street, Harnet Birchington, Deal, Street, Delf Street,

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City, Town, Village Outside SCOPAC Area Road names

Day

Year

Month

Severity Event No. Event Sandhills, Kingsdown, Jarvist Place, North Isle of Sheppey, Road, South Road, Leysdown, Sheerness, Richmond Street- Warden Bay, Garrison Point, Short Whitstable, Herne Bay, Street, Railway Road, Swalecliffe Alma Road, Marine Parade, Cross Street, Granville Road, Hope Street, Beach Street, Rose Street, Island Wall, Marien Crescent, Nelson Road, 110 1978 2 18 1 Isle of Portland Preston Beach, Southampton, Portsmouth, 111 1978 2 26 3 Portland Beach, Chesil Hayling Island, Eastney Beach, Esplanade Road Thorn Cross, Sutton, Ryde, Seaview, Ventnor, 112 1978 3 4 2 St Helens Bridge Road, Steephill Yarmouth, Hurst Spit Road, The Strand Southampton, Hythe, 113 1978 11 15 1 Weston Shore Calshot Isle of Portland, Southampton, Gosport, 114 1978 12 12 2 Weston Shore Calshot, Warsash, Portchester Chesil Beach (Isle of 115 1979 2 13 1 Portland), Hurst Spit, Hayling Island 116 1979 12 13 1 Isle of Portland Portsmouth, Gosport, 117 1980 1 21 2 Bexhill (Brighton) Hayling Island, Eastbourne 118 1980 1 26 1 Cowes Anchor Inn, High Street Portsmouth, Wotton 119 1980 10 25 1 Findhorn, Burghead Bay Bridge (Isle of Wight) 120 1981 3 9 1 Swanage, Bridport Bridgend, Cardiff Corfe Castle Gosport, Eastoke, Hayling Avon, Burnham-on-Sea, Island, Old Portsmouth, Brean, Weston Super Portsmouth, Langstone, Mare, Uphill, Sand Bay, Emsworth, Fareham, Ryde, Eastern Road, Clarence 121 1981 12 13 4 Wick St Lawrence, Cowes, Yarmouth, Shanklin Esplanade Kingston Seymour, (Isle of Wight), Weston, Clevedon, Pawlett, Southampton, Milford-on- Avonmouth Sea 122 1981 12 18 1 Cowes, Seaview

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City, Town, Village Outside SCOPAC Area Road names

Day

Year

Month

Severity Event No. Event Weston Super Mare, Burnham-on-Sea, Hayling Island, Cowes, 123 1981 12 30 1 Minehead, Clevedon, Mudeford Bay, Yarmouth Porlock, Watchet, Hythe, Sandgate Portsmouth, Hayling 124 1982 10 16 2 Island, Milford Lowestoft, Great Yarmouth, Redcar, Morecambe, Filey, Scarborough, Mablethorpe, Oban, Castle Street, York Stratchlyde Region, Avenue, Harwich Quay, Whitby, Lossiemouth, West Street, Church Cowes, Bembridge, Findhorn, Buckie, 125 1983 2 2 4 Street, Alms and Angel Southampton Portgordon, Kingston, pub, Tiberius Casio, Garmouth, Bembridge, Strand Street, Hunt's Brighton, Harwich, Gallery Cliffsend, Pavillion, Sally Lines, Birchington-on- Sea, Southend, Minnis Bay, Sandwich, Ramsgate Commercial Road, Hope Square (Weymouth), Eastern Road, Hythe, Hayling Island, Southsea's St Helen's Emsworth, Fareham, playing field, Weston Portsmouth, Old Shore Road, parks and Portsmouth, Copnor, gardens along River Lymington, Ryde, Cowes, 126 1983 12 19 4 Penzance, Fowey, Looe Itchen, The Strand, Newport, Seaview, Ferry Road, Castle Sandown, Yarmouth (Isle Street, York Avenue, of Wight), Southampton, Link Road, Well Road, Felpham, Christchurch, Seaview Road, Sea Eastney Road, Upper Bognor Road, Lymington Quay, Bridge Street Portsmouth, Ryde, Cowes, 127 1984 9 26 1 Thames at Putney Hythe, Fareham Warsash (River Hamble), Fareham, Cowes, Polmorla, Wadebridge, 128 1984 10 24 2 Weston Shore Road Southampton, Portsmouth, Padstow, Chapel Amble Christchurch Quay

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City, Town, Village Outside SCOPAC Area Road names

Day

Year

Month

Severity Event No. Event Mudeford Quay, Commercial Road, Havant Road, Weston Parade, Yeo Vale Road, Fowey, Padstow, Bideford Quay, East- Wadebridge, The-Water, Crow Point, Lymington, Portsmouth, Sladesbridge, Horsey Island Bank, Southampton, Cowes, Perranporth, Farlington, Rolle Quay, Mill Road, Gurnard, Ryde (Isle of 129 1984 11 23 3 Hilsea, Bideford, Fair View, Harbour and Wight), Fareham, Hythe, Ilfracombe, Instow, Wilder Road, old Ice Hayling Island, Langstone, Appledore Fremington, Factory Barnstaple, Fawley, Shoreham, Selsey Lee Bay, Weare Giffard, Danefield Road, Clayton Barnstaple, Pilton Road, Warner Road, High Street, Vectors Tavern, Bell Inn, Medina Road, The Strand Elmer, Wadebridge, Padstow, Newquay, Weston Shore Road, Southampton, Portsmouth, Hayle, Mousehole, A27 at Emsworth, Hayling Island, Eastney, Flushing, Mevagissey, St Selsey's West Sands 130 1985 4 7 3 Hythe, Cowes, Emsworth, Blazey, Fowey, caravan park, Birdham Bosham, Portchester, Lostwithiel, Looe, pool car park, Anchor Selsey Torpoint, Calstock, Bleu pub Dartmouth 131 1986 11 19 1 Southampton Weston Shore Road Southsea (Portsmouth), 132 1986 11 21 1 Cowes Weymouth Harbourside, West Bay, Weston Shore Road, Lymington, Hamble-le- Town Quay, Test Lane, Boscastle, Chapel Amble, Rice, Southampton, Cowes, Union Streed, Queens Polmorla (Wadebridge, 133 1987 10 7 3 Ryde, Shanklin (Isle of Road, The Strand, River Camel), Brighton, Wight), Fareham, New Vectis Bar, High Street, Redbridge Forest Vernon Square, Monkton Street, Muggleton Lane, Sharewell 134 1988 1 5 1 Ryde 135 1988 1 21 2 Ryde

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City, Town, Village Outside SCOPAC Area Road names

Day

Year

Month

Severity Event No. Event Bath Road, Bridge Street, Wick Lane, Springvale Road, Quay Street, Mudeford Quay, Ancasta Marina, Birmingham Road, Samuel Whites Inductria Estate, Bridge Road, Weymouth Harbourside, West Bay, Southampton, Gosport, Weymouth Quayside, Newport, Cowes, Ryde, Cove Row, Commercial Yarmouth, Seaview, Road, Weymouth, Gurnard, (Isle of Wight), Preston Beach, Poole Fareham, Emsworth, Old Quay, Green Road, Portsmouth, Eastney Stanley Road, Poole (Portsmouth), Selsey Bill, Park, Sandbanks Road, Hythe, Warsash, Keyhaven, 136 1989 12 13 5 Plymouth, Isles of Scilly Shore Road, Weston Pennington, Hurst Spit, Shore Road, Cowes Lymington, Mudeford, Parade, Castle Street, Hayling Island, Lepe, Lower York Avenue, Portchester, Christchurch, Well Roas, Gasworks Isle of Portland, Poole, Lane, Saltern Wook Sandbanks, Yarmouth, Quay, Town Quay, Freshwater, Elmer, Bognor Bracklesham Bay Regis, Walhampton caravan park, Eastside and West Sands caravan park, Clayton Road, Waterloo Road, Kings Saltern Road, Solent Cottage, Lymington Town Sailing Club, Nelson Place, Quay Road, The Gun Inn, Prospect Place Sidmouth, Dawlish, 137 1989 12 20 1 Southampton Budleigh Salterton, Lympstone Weymouth Quayside, 138 1992 8 30 1 Weymouth Brighton Preston Bach Road, Charmouth beach huts 139 1992 12 5 1 Lymington, Ringwood Road

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City, Town, Village Outside SCOPAC Area Road names

Day

Year

Month

Severity Event No. Event Broad Street, Bath Portsmouth, Old Square, Royal Oak, Portsmouth, Hayling Commercial Road, Island, Fareham, Warsash, Broad Street, Bath Portchester, Gosport, Square, Weston Shore, Cowes, Ryde, Wootton Royal Victoria Country Bridge, Newport (Isle of Park, Quay Arts Centre, 140 1993 1 10 4 Brighton Wight), Hythe, Romsey, The Strand, Slope Inn, Southampton, Lymington, Weston Bridge, High Langstone, Titchfield, Street, Princess and Selsey Bill, Netley, Lepe, Cowes Esplanades, Hamble, Weymouth, Newport Road, Chichester Lymington Quarry, Wallington Road 141 1994 1 8 1 Medmerry, Selsey Severn Valley, Avonmouth, Pill, Portsmouth, Cowes, Shirhampton, Hinkle 142 1994 12 4 1 Hamble-le-Rice, Old Broad Street Point, Stolford, Newport, Portsmouth Boverton, Llantwit- Major Southampton, Old Portsmouth, Langstone, Sandbanks Road, Fareham, Gosport, Evening Hill, London Emsworth, Hayling Island, Road, Broad Street, 143 1994 12 7 2 Botley, Sandbanks, Medina Car Park, Cosham, Bognor Regis, Alverstone Road, East Southsea, Copnor, Hilsea, Cowes Road Langstone, Hamble-le-Rice, Chichester, Ryde Langstone, Gosport, Portsmouth Eastern Portsmouth, Southsea, 144 1995 1 19 3 Road, Southsea Parade, Hayling Island, Clarence Parade Southampton Quay Road, Stoney Lane, Bridge Street, St Christchurch, Chichester, 145 1995 1 20 1 Margaret's Avenue, Selsey Manor Lane, Chichester Road 146 1995 2 1 1 Weymouth Commercial Road Portsmouth, Wootton Weymouth Quayside, 147 1995 12 23 1 Bridge, Hythe, Dibden Commercial Road Porlock Bay, Dover, Seafront Collingwood Portsmouth, Langstone, Avonmouth, Portishead, hotel, Marine Parade, 148 1996 10 28 2 Emsworth, Gosport, Pill, Newport, Barry, The quay instow, the Hayling Island, Chichester Cardiff, Appledore, Basket Shop Lynmouth, Bideford, Ilfracombe, Barricane Beach

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City, Town, Village Outside SCOPAC Area Road names

Day

Year

Month

Severity Event No. Event instow, Combe Martin, Woolacombe, Bideford Cheyne Beach, Hartland, Quay, Lee Bay Clovelly, Westgate-on- Sea, Westgate, Dover, Northney, Brighton Sefton coast, Avonmouth, Cumberland Road, Town Bridge, 149 1997 2 9 1 Weymouth Hinkley Point, Clevedon, Commercial Road Weston-super-mare, Newport Southsea, Sandbanks, Mudeford, Portsmouth, Shore Road, Chichester 150 1998 1 4 2 Selsey, Hayling Island, Brighton Way Gosport, Fareham, Chichester Portsmouth, Selsey, Ryde, 151 1998 1 13 3 East Beach Chichester Southampton, Old 152 1998 3 4 1 Portsmouth (Portsmouth) Hinkley Point, Walton Weymouth Quayside, Bay, Avonmouth, Wood Portsmouth, Selsey, Town Bridge, Bideford 153 1998 9 9 1 Hill Bay, Newport, Langstone, Emsworth quay, West Sands Portishead, Barry, caravan park Rhoose Shore Road, Quay Sandbanks, Christchurch, Avonmouth, Pill, Hinkley Road, Chichester Way, 154 1999 1 3 1 Mudeford, Selsey, Point, Brean, Newport, Weymouth quayside, Chichester, Portland Island Penarth Town Bridge Selsey, Chichester, 155 1999 10 24 1 Southsea (Portsmouth) West Sands caravan 156 1999 11 28 3 Medmerry, Selsey park, East Beach Road, Drift Road, Bognor Pier Portsmouth, Totton, Southampton, Selsey, 157 1999 12 25 3 Newport, Cardiff, Barry Weston Shore Lymington, Chichester, Northam, Warsash, Ryde 158 2000 9 29 1 Chichester 159 2000 10 29 1 Selsey Bill 160 2000 12 12 2 Brighton, Christchurch 161 2001 3 10 1 Portsmouth, Emsworth Lumley Road 162 2002 1 29 1 Portsmouth, Hayling Island

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City, Town, Village Outside SCOPAC Area Road names

Day

Year

Month

Severity Event No. Event Barrow-in-Furness, Langstone, Southsea, Old Sladebridge, Mevagissey, Portsmouth (Portsmouth), 163 2002 2 1 2 Polkerris, Fowey, Golant, Shore Road Hayling Island, Lerryn, Lostwithiel, Southampton, Sandbanks Cremyll, Calstock Commercial Road, 164 2003 1 20 1 Weymouth, Christchurch Town Bridge, Quay Road Chichester way, Shore Mudeford, Sandbanks, 165 2004 10 27 1 Road, Poole Park, Parstone, Swanage Victoria Avenue Chesil Beach (Isle of Chichester Way, Portland), Millbrook Commercial Road, (Southampton), Millbrook Road, Stokes 166 2005 11 3 4 Portsmouth, Weymouth, bay Road, Wheatlands Lyme Regis, Mudeford, Avenue, Weston Shore Eastoke, Hamble, Gosport Road 167 2005 12 2 1 Christchurch, Swanage Quay Road, High Street 168 2007 11 25 1 Chichester Brightlingsea St Denys, Woodmill, Coastal roads between Lyme Regis and Weymouth, Banks Beaulieu, Totton, St Denys, Road, Sandbanks Woodmill Lane, Weston terminal, The Quay, (Southampton), Southsea, Hamworthy Park, Old Portsmouth, Sterte Avenue, Church Portsmouth, Cowes, Green, Quay Road, The Yarmouth, Gurnard, Quomps Park, Teignmouth, Flushing, Newport (Isle of Wight), Chichester Way, English Channel, Bosham, Emsworth, Selsey Undercliff Drive, East Avonmouth, Portishead, 169 2008 3 10 3 Bill, Lymington, Lee, Street, Camber Quay, Hinkley Point, Clevedon, Calshot, Hythe, Warsash, Southsea Rock Gardens, Weston-super-Mare, Hamble-le-Rice, Eastoke Clarence Esplanade, Burnham-on-sea (Hayling Island), South Parade, Priory Langstone, Poole, Road, Riverside Park, Chichester, Weymouth, Weston Shore, West Portland, Poole, Sands caravan park, Christchurch, Bosham Lane, Bosham Bournemouth, Wareham Walk, Bleu Anchor pub, Pagham Close, Ragland Pub, Queen Street, High Street, Terminus Road, Yarmouth Harbour 170 2010 11 11 1 Isle of Wight

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City, Town, Village Outside SCOPAC Area Road names

Day

Year

Month

Severity Event No. Event Banks Road, The Quay, Broadstone Way, Waterloo, Rockley Studland, Brighton, Sands, A399, Lower Lymouth, Bideford, Gaydon Street, A386 Exmouth, Shirwell, 171 2012 10 11 1 Poole, Sandbanks Bideford, Bideford Long Sheepwash, Woolsery, Bridge, A388, Southcott Crediton, Barnstaple, Garage, Holsworthy Great Torrington Road, road between South Molton and Umberleigh Wedgewood Drive, Weymouth, Sandbanks, Whiteclliff Road, Sterte Poole, Wareham, Avenue, Church Green, 172 2012 12 14 1 Looe, Lossiemouth Christchurch, Mudeford, Quay Road, Chichester Swanage Way, High Street, Commercial Road 173 2013 1 12 1 Sandbanks Shore Road 174 2013 10 28 1 Yarmouth A27, A259, Priory Road, Shore Road, The Chichester, Eastbourne, Parade, Queens Road, Bognor Regis, St Denys, Town Quay, East Cowes 175 2013 11 3 1 Hythe, Eling, Southampton, Brighton Esplanade, Yarmouth Cowes, Yarmouth, Havant, Harbour, Langstone Beaulieu High Street, Bosham High Street, Palace Lane Queen Street, South Sunderland, Hull, Street, Langstone High Boston, Great Yarmouth, Street, East St, Blundell Havant, Yarmouth, Cowes, Lowestoft, North Road, Palace Street, Southampton, Chichester, Berwick, Laywick, Northney Road, Bench St Denys, Emsworth, Blackpool, Cleveleys, 176 2013 12 6 1 Street, Channel View Havant, Portsmouth, Walcott, Cromer, Road, Cambridge Road, Bursledon, Beaulieu, Whitstable, Portgordon, Gazen Salts, Quay Park, Hayling Island New Brighton, Rhyl, Secret Gardens, Sandwich, Deal, Knightrider Street, Broadstairs Ranelagh Road Chichester, Sandbanks, Shore Road, Quay Road, 177 2013 12 31 1 Christchurch, Cowes The Parade

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City, Town, Village Outside SCOPAC Area Road names

Day

Year

Month

Severity Event No. Event Shore Road, The Quay, Hamworthy Park, Poole Park, B3074, The Quomps park, Christchurch Highstreet, Mudeford Lifeboat House, Isle of Man, Newquay, Chichester Way, Minsterworth, Preston Beach, Chichester, Hinkley Point, Maisemore, Elmore, Commercial Road, Sandbanks, Poole, Newnham-on-Severn, Portland Beach Road, Wareham, Christchurch, Hastings, Hinkley Point, Baiter Park, Quay Road, Mudeford, Havant, Parrett, Burnham-on- Ilford Lane, B3075, Emsworth, Fareham, 178 2014 1 2 2 sea, Parkstone, Langstone High Street, Portsmouth, Cowes, Axemouth, Westward Queen Street, Lower Yarmouth, St Denys, Ho!, Northam Burrows, Quay, Bath Square, The Southampton, Gosport, Chivenor, Barnstaple, Parade, Esplanade East Lymington, Hamble, Instow, Torridge Cowes, Riverside Park, Warsash, Lyme Regis Estuary, Cheyne Beach, Weston Parade, Lepe Brighton Road, Stokes Bay, Town Quay, The Quay, Hurst Spit, Pyramids Centre Esplanade, Canoe Lake, Ilfracombe sea wall, Pebbleridge Road, Pilton Park, Marine Parade in Instow 179 2014 1 6 1 Christchurch Aberystwyth 180 2014 1 31 1 Bournemouth, Westbourne B3065 Aberystwyth, Newgale, Looe, Newlyn, Hinkley The Quomps Park, Quay Point, Burnham-on-sea, Road, Chichester Way, Northam Burrows, Hele, Beach Side Café, The Ilfracombe, Lynton, Foscle Inn, Pilton Park, 181 2014 2 2 1 Christchurch, Mudeford Bideford, Westward Ho!, Combe Martin pub, Fowey, Newlyn, Bucks Mills slipway, Porthleven, Mevagissey, Saunton Beach hut, Plymouth, Salcombe, Quay Road, Chichester Exmouth, Kingsbridge Way, Sawmill Inn, A399 (Estuary) Shore Road, Lilliput Sandbanks, Poole, Lyme Dawlish, Hamworth Road, The Quay, 182 2014 2 5 4 Regis, Chiswell, Chichester Park, West Bay Preston Beach Road, Portland Beach Road

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City, Town, Village Outside SCOPAC Area Road names

Day

Year

Month

Severity Event No. Event Hurst Spit, Shore Road, Sandbanks, Banks Chesil Beach (Isle of Road, Branksea Portland), Milford on Sea, Avenue, Avon beach, Mudeford, Lymington, Friars Cliff, Bistro on Sandbanks, Poole, the beach, Urban Reef, Christchurch, Newlyn, Plymouth, Preston Beach, Hamm 183 2014 2 14 3 Bournemouth, Weymouth, Egham, Surrey Beach, Priory Road, Chiswell, St Denys High Street, Bridge (Southampton), Cowes, Road, Beldornie Yarmouth, Ryde, Hayling Towers, The Parade, Island, Southsea Bandstand Park, Pier Road, Hurst Spit, Quay Road Chichester, Bognor Regis, 184 2014 10 9 1 Selsey Bill 185 2015 10 28 1 Christchurch Poole, Southsea Porthcrawl, 186 2016 2 8 1 (Portsmouth) Aberystwyth Swanage, Southsea A20, A2, Mill on the 187 2016 11 19 1 (Portsmouth) Mole

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APPENDIX G – MILFORD-ON-SEA WAVE DATA

Background – severe recent erosion

Early in 2020 and an ongoing problem that is being managed at the time of writing has been the stability of a 75-metre stretch of the wall on the New Forest coastline at Milford-on-Sea. This preceded major erosion during 2018/19 nearby and has been seen to be as a result of the ongoing winter storm and extreme wave conditions along with possible depletion of sediment feed in recent years.

This has been a problematic situation for all involved from beach hut owners and coastal engineers – particularly given the pressures and rules with funding.

What has been missing for the coastal engineers/managers involved has been understanding and communicating to the public of the observed hydrodynamic data sets. This can explain how unusual certain conditions are and the role that natural (prevailing and recent) conditions could have played in these events. Therefore, a quick additional price of analysis was done under the pretext of this project for the Milford WaveRider Buoy (the oldest in the region, installed following the Hurst Spit scheme in 1996).

Figure G.1: Green dot shows the Milford buoy location owned by the Channel Coastal Observatory.

Wave data analysis

Using 17 years of Milford buoy data (with some gaps / missing data filled by an interpolation with data from the nearby Boscombe buoy) this provided wave height back to 1996/97 and up to June 2020. Storms were selected by 16hr peaks in the 30-minute time series with counts of events in the bar plots (Figure G.2) from July to July (as in this report this captures ‘storm seasons’).

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Also, we summarised monthly averages for wave height, period and direction from CCO data sets and produced table of events ranked by wave power peak and wave height (HS) peak.

Results

Taking the top 50 most powerful wave events over a span of 17 years, assuming a very basic “frequentist” representation of statistics, we would expect about 3 events to have been in the top 50 from 2019/20. However, we see 8 events in the top 50 so plenty of powerful events this recent winter. The same philosophy applied to ranking events by HS, we have had 5 events in the top 50 during 2019/20, so an anomalously higher count for one winter (Table G.1).

There are upward trends in monthly significant wave height and period 2005-2020 (Figures G.2 and G.3) and a more southerly migrating trend in wave direction (Figure G.4). As noted earlier in the report there is also an upward trend (slight and not statistically certain) in annual bimodality probably related to the slight increase in wave period.

Figure G.2: Monthly wave heights and linear trend at Milford (plotted from CCO data)

Figure G.3: Monthly wave period (TZ) and linear trend at Milford (plotted from CCO data)

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Figure G.4: Monthly wave direction and linear trend at Milford (plotted from CCO data)

Figure G.5: Storm season counts of wave events above thresholds at Milford.

Initial interpretation

These changes and patterns in wave could explain some the changes seen on the beach; which have been seen within the recent decade where there has been heightened and subtly changing (e.g. bimodality and direction) wave activity. We also know that mean sea level is changing, and scientific literature dating back decades (e.g. Bruun, 1962) and others suggests how these changes alone will be expected to be manifested sometime in terms of beach response. Beyond sea level, the changes could be multifaceted in their origin: larger, longer (more powerful) waves are approaching less obliquely so will be more powerful inshore for the south facing beaches. Any

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recent change in prevailing direction itself could cause instability which along with increasing wave heights disturbing sediment in deeper areas and increasing transport away from the shoreline. For example, waves impacting the shore more less obliquely could increase the energy expended on the shoreline whilst also changing the dynamics of longshore drift. Any resulting net sediment transport change and subsequent instability could also have depleted nearshore sediment sinks over the past few years, which exacerbate the storm and recovery effects, with accelerated erosion every time a big swell comes in.

These hypotheses should form part of future research. This roughly coincides with heavily eroding beach (to the basal layer) at Solent Beach about 1km west of the Hengistbury Head Long Groyne (at the eastern extent of Poole Bay). These areas have not been replenished with coarse material for some time (Solent beach in 1988/9) and an ongoing change to hydrodynamics and/or specific impacts of 2013/14 may all be contributing to what is being seen on the ground.

Brief follow up – January 2021

Following emergency works in late 2020 by NFDC to protect the coast from eroding further, there was interest in what the impact of further winter storms would have been without them,

It had already been noted prior to the works how closely Storms Ciara and Dennis had impacted in February 2020, 1 in 2-year and 1 in 1-year wave height events clustered a week apart (and only a few weeks after another 1 in 1-year event in January 2020). In the winter of 2020/21 Storm Aiden saw 2.76m and 2.6m wave peaks on spring tides between the 31th October and 2nd

November, then on the 27th December 2020 a 1 in 5-year wave height storm (HS 3.79m), the 11th highest peak in 24 years of data. This highlighted the recent ongoing hydrodynamic loading to defences in the region.

Reference: Bruun, P. (1962). "Sea-Level Rise as a Cause of Shore Erosion". American Society of Civil Engineers Journal of the Waterways and Harbours Division. 88: 117–130.

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