Coastal Trends Report, the Wash, 2007

Coastal Trends Report

The Wash (Gibraltar Point to Old Hunstanton)

RP002/W/2007 March 2007

Title here in 8pt Arial (change text colour to black) i We are the Environment Agency. We protect and improve the environment and make it a better place for people and wildlife. We operate at the place where environmental change has its greatest impact on people’s lives. We reduce the risks to people and properties from flooding; make sure there is enough water for people and wildlife; protect and improve air, land and water quality and apply the environmental standards within which industry can operate. Acting to reduce climate change and helping people and wildlife adapt to its consequences are at the heart of all that we do. We cannot do this alone. We work closely with a wide range of partners including government, business, local authorities, other agencies, civil society groups and the communities we serve.

Published by:

Shoreline Management Group Environment Agency Kingfisher House, Goldhay Way Orton goldhay, Peterborough PE2 5ZR Email: [email protected] www.environment-agency.gov.uk

© Environment Agency 2007 Further copies of this report are available from our publications catalogue: All rights reserved. This document may be http://publications.environment-agency.gov.uk reproduced with prior permission of or our National Customer Contact Centre: T: the Environment Agency. 03708 506506 Email: [email protected].

ii The Wash from the mouth of the River Witham (Photo: Environment Agency) Contents

1.0 THE ANGLIAN COASTAL MONITORING PROGRAMME......

1.1 PURPOSE AND APPLICATION ......

1.2 BACKGROUND......

1.3 BEACH TOPOGRAPHIC PROFILE DATA ......

1.4 ANALYSIS METHODOLOGY......

1.5 FUTURE OUTPUTS ......

2.0 THE WASH (SUB-CELL 2D) COASTAL TRENDS ......

2.1 INTRODUCTION ......

2.2 ANALYSIS OF WASH SALTMARSHES ......

2.3 OUTLINE OBSERVATIONS ......

2.3.1 Western shore of The Wash (mouth of River Witham to Gibraltar Point)......

2.3.2 Southern Shore (Snettisham Scalp to River Welland)......

2.3.3 Eastern Shore (Snettisham Scalp to Old Hunstanton) ......

2.4 GENERAL CONCLUSIONS ......

Figure 1 – The Anglian Coast 1.0 The Anglian Coastal Monitoring Programme

1.1 Purpose and application

This report is intended as a tool to assist coastal managers in a variety of their functions including; strategic planning, capital engineering works and maintenance programmes. In addition to this the report will be of assistance with general education and awareness raising of coastal issues. The outputs also will also aid the determination of beach health parameters within NFCDD (National Flood and Coastal Defence Database).

1.2 Background

The Anglian coastline stretches from Grimsby near the mouth of the River Humber to Southend-on-Sea on the northern side of the outer Thames estuary (figure 1). With a total length of approximately 470km the coast is a diverse mixture of dune fronted flood plains, shingle barrier beaches, saltmarsh and soft cliffs. There are no significant geological ‘hard rock’ coastal areas and thus significant proportions of the coast are vulnerable to marine flooding and erosion. This is likely to be compounded by climatic change and sea level rise in the future. In order to reduce the impacts of this upon the built and natural coastal environment much investment has been made in both hard and soft engineering solutions over the last century. This has resulted in significant proportions of the coast being artificially held to prevent the loss of development and infrastructure located in vulnerable areas.

The Environment Agency has undertaken regular strategic coastal monitoring of the Anglian coast since 1991. The rational behind the programme is to assist the implementation of appropriate and sustainable works on the coast whether this be works undertaken by the Agency for the purpose of flood risk management or works undertaken by various maritime district council partners for erosion reduction purposes. An additional output from the monitoring programme is the assessment of coastal dynamics to inform long term strategic plans for the coastline. The vehicle for this is the Shoreline Management Plan (SMP) process, which is currently being reviewed along the entire Anglian coast.

The Anglian Coastal Monitoring Programme collects a variety of data including;

• Annual aerial photographs • Annual topographic beach surveys (winter and summer) at 1km intervals • Bathymetric surveys (extension of beach survey lines out to approximately 10 metre depth offshore) • Continuous wave and tide recording (nearshore and offshore)

In addition to this, in-depth monitoring addresses specific sea defence scheme requirements at a variety of locations along the coast. At the time of writing, the Anglian monitoring programme has begun phase VII, which includes a suite of five offshore, and nineteen nearshore continuous wave and tide recorders. Various reports based upon the data collected over the years have been produced. Until now the work undertaken has been unable to assess any significant trends in the data due to the insufficient length of time over which the data has been collected. However the Agency now possesses 15 years of beach topographic data and it is therefore possible to analyse these to determine initial indicators of longer-term trends. Data collected in the future can be readily added to this analysis to further ascertain the validity of the trends.

1.3 Beach topographic profile data

The Environment Agency has collected beach topographic profile data at 1km intervals along the coast since 1991. Profiles are taken twice yearly in summer and in winter. The most recent set of available data means that there is now a continuous record of beach levels spanning fifteen years. Generally the area of interest is the average rate of beach erosion or accretion along the coast. In addition to this, gradual change to the gradient or steepness of the beach is of particular interest to coastal managers.

The analysis of trends in beach morphological behaviour may have significant impacts upon coastal management decisions in the future. Artificially defended beaches that are experiencing erosion and steepening trends may prove to be difficult and expensive to maintain structures. Even with maintenance the structures may fail because of inadequate structural support or ground movements from diminishing quantities of beach material and subsequent beach platform loss. However it is not the intention of this report to ascertain such issues at a local scale. The ongoing revisions of the Shoreline Management Plans (SMP) and Coastal Strategic Studies, which are currently being compiled along the Anglian coast, are the appropriate vehicle for this assessment.

The length of the Anglian coast means that there are over 400 topographic profiles that have been collected over the years. For the purposes of regional strategic coastal management, the entire UK coast has been divided up sediment cells and sub-cells (HR Wallingford, 1994 & Defra, 2006). These are individual discrete sections of the coast that are considered to be independent from each other in terms of coastal processes. The relevant sections on the coast are: -

Flamborough Head to Donna Nook Sub-cell 2a+b1 Donna Nook to Gibraltar Point Sub-cell 2c Gibraltar Point to Old Hunstanton Sub-cell 2d Old Hunstanton to Kelling Sub-cell 3a Kelling to Lowestoft Ness Sub-cell 3b Lowestoft Ness to Felixstowe Sub-cell 3c Harwich to Canvey Island Sub-cell 3d

These boundaries are convenient divisions for the separation and publication of the results of the trends analysis reports.

1 The first SMP review for this section of coast will encapsulate the coast from Flamborough Head to Gibraltar Point. Only that part of the coast south of the Humber is within the Anglian region. 1.4 Analysis methodology

The profile data presented in this report is in the form of beach level and where appropriate, beach volume analysis. The data was analysed using a function of ‘SANDS’ software (1). Tidal levels and conversions from Chart Datum to Ordnance Datum were kindly supplied by Proudman Oceanographic Laboratory from their ‘POLTIPS’ software (2). Generally, the accepted definition of the foreshore is the intertidal region between the highest and lowest tide level. Here the area between the MHWS and MLWS level is used.

The Wash coastline has two distinct type of foreshore. On the western and southern shore there are sea defence banks fronted by, sometimes extensive, lengths of saltmarsh. In front of this are expanses of mudflat leading down to the low water mark. On the eastern shoreline, from Heacham to Old Hunstanton and beyond, the coast reverts to a sand/shingle ridge on the upper foreshore with extensive sand and mud flats revealed at low water.

The two types of foreshore in the Wash area require slightly different analysis methodologies. Figure 2 shows two typical profiles from the saltmarsh fronted coastline. The upper saltmarsh shows variability on the scale of cm’s per year whereas the lower mudflat shows much a much greater degree of movement. The individual profiles were analysed by assessing the vertical level of the data at 20m intervals from the landward edge of the saltmarsh. This gave a suite of height measurements for each 20m section from every profile, from which a trend of movement was obtained by linear regression. Figure 3 demonstrates a typical output from this method. Here the saltmarsh and the upper mudflats can be seen to be accreting at a rate of up to approximately 10mm per year, however there as a sharp boundary where the lower mudflat reverts to a variable and sometimes erosional trend.

On the eastern shore the sand/shingle ridge was analysed by obtaining the position of the beach at specific heights (i.e. MHWS) for each profile. From this data a trend of movement of the upper beach could be obtained. The sand/shingle ridge south of Heacham has been modified over recent years and has been subject to reprofiling/recycling of beach material. In 2006 a significant beach renourishmant scheme was undertaken.

Saltmarsh to mudflat boundary change throughout the Wash region was ascertained by a comparison of the digitally orthorectified aerial photography. A comparison was made between the 1992 and the 2006 surveys and the areas of saltmarsh/mudflat accretion and erosion are shown. Figure 2. Two typical profiles from The Wash saltmarsh area

L3B6 - marsh/mudflat boundary @ approx 680m

Yearly rate 0.015 4 Height

3.5 0.01

0.005 2.5

0 2 Height (mOD) Trend (m yr-1) 1.5 -0.005

-0.01 0.5

-0.015 0

m m 60m 120m 180m 240m 300m 360m 420m 480m 540 600m 660m 940 600m 780m 1000m1060m1120m1180m1240m1300m1360m1420m1480m1540m1 1660m1720m1 Chainage (m)

Figure 3. Suite of annual trends from coastal profiles after analysis. 1.5 Future outputs

Future updates of this report will include updated information on beach trends using the latest available profile data. In addition to this the report may include extended analysis utilising other data sets collected by the Shoreline Management Group. Bathymetric surveys have been undertaken at 5 year intervals and this will be enhanced as part of the phase VII (2006-2011) monitoring programme. In addition to this output from the wave and tide recording buoy deployments will be included. These reports will support and inform the move towards a ‘risk-based’ monitoring programme for 2011 and beyond. © © Crown copyright and database rights 2007 Ordnance Survey 100024198. © Environment Agency copyright and/or database rights 2007. All rights reserved.

Figure 4 – The Wash 2.0 The Wash (sub-cell 2d) coastal trends

2.1 Introduction

The Wash coastline is entirely located within the 2d coastal sub-cell. This report analyses the profile data collected along the coast from Gibraltar Point in Lincolnshire to Old Hunstanton in Norfolk.

The Wash is a macrotidal rectangular embayment open at its northern end to the North Sea. It has a surface area of 615km2 and possesses approximately 10% of the UK saltmarsh and mudflat designated habitat. The western and southern shores consist of low-lying farmland protected by earth embankments, which are fronted by a sequence of saltmarsh then mudflats leading to the main channels. In some places the saltmarsh is extensive stretching several km’s in a seaward direction beyond the sea defences. The eastern shore, however, possesses different characteristics. The coast here is cliffed to the north near Hunstanton with wide sandy beaches. To the south of Heacham the ground level of the hinterland lowers and the coast returns to saltmarsh and mudflat with extensive off shore sandbanks near the delta system of the River Great Ouse, which enters The Wash near Kings Lynn. With the exception of the shoreline north of Heacham the entire stretch of coast is of artificial origin having been subject to progressive land claim projects over the centuries.

Generally, when compared to other coastal defences on the Anglian coast, the Wash embankments are relatively modest structures. The presence of broad expanses of saltmarsh and mudflats offer significant protection to the defences from wave attack. Exposure and wave attack can only occur during more extreme high water levels, especially during storm surge events. For this reason any trend in the reduction of the width and the height of the saltmarsh is of critical concern to coastal managers along with any landward movement trend in the main channel along the eastern side of the bay.

Four highly modified rivers drain into The Wash. On the western shore the Welland and Witham (both trained into a common outfall) and on the southern shore the Nene and Great Ouse. For the purposes of this report The Wash shoreline is divided into three sections; the western shore between the mouth of the River Witham to Gibraltar Point, the southern shore between the River Witham and the River Ingol and the eastern shore between the River Ingol and Old Hunstanton.

The Wash coastal monitoring campaign began two years after the other Anglian coastal monitoring programmes started in 1991. This study deals only with the coastline and does not analyse any data that has been collected further inland beyond the mouths of the rivers. 2.2 Analysis of Wash Saltmarshes

The following pages show the results of the analysis. The detailed plans show the results overlaid over the 2006 aerial survey photographs. Each profile location is numbered.

The vertical trend is represented by lines at 20m intervals along each profile where the length of the line is representative of the trend rate. Green lines represent a vertical accretion trend and red lines are indicative of vertical lowering or erosion.

The hatched areas represent areas of horizontal saltmarsh/mudflat boundary change between 1992 and 2006. The yellow hatch shows areas where the saltmarsh has accreted and the areas where saltmarsh have been lost are hatched in blue.

On the eastern shoreline the analysis of data collected on the shingle/sand upper beach is shown. Horizontal erosion/accretion trends are represented by red/blue triangles. Yellow circle’s as shown where the beach has remained stable throughout the data collection period.

The final A3 plan shows a large scale overview of the results over the whole Wash area. Anglian Coastal Monitoring Programme 2007 - The Wash Profile Locations

01.25 2.5 5 7.5 10 Km

L L 3D 3D 4 ¯ L3 3 L D2 3D L 1 3C L 6 L 3C 3C 5 L 4 3C 3 L3 L C2 3C L3 1 L B7 3B L 6 3B L 5 3B L3 4 B3 L3 West B2 L3 B1 L N 3A 1 L 7 D 3 3 A6 L3 A5 L3 N1 A4 D2 L3 N1D A3 1 L N0A 3A East 8 2 N L3 0A7 A1 N0 6 A6 C 5 N 4 C 0A5 L 4 4 3 L C 2 4 C C N0A L 4 4 4 L 1 L C N0 4 7 South A3 L B 4 6 N0A L B 2 4 L 5 B 4 4 N0B1 L B 4 3 L B 4 N0B2 L N N0B3

0 3 N 3 C

2 0 4

5 N0B 2 D N 1

A 2 C 1

B A 0

0 4

D 2 4 D 1 C

L 0 L N 0 N 3

1 L D 4

B N N 0 0 4 L C L N N 4 0 C 5

© © Crown copyright and database rights 2007 Ordnance Survey 100024198. © Environment Agency copyright and/or database rights 2007. All rights reserved. Anglian Coastal Monitoring Programme 2007 - The Wash Plan 1

L3A4

L3A3

L3A2

L3A1 ¯

00.05 0.1 0.2 0.3 0.4 0.5 Km

Vertical Change Rate (m) Red = erosion

Green = accretion 0.02 0.01

Hatched Areas

Yellow = marsh formed between 1992-2006 0.01 Blue = marsh lost between 1992-2006

0.02

L3B1

L3A7

L3A6

L3A5 ¯

0 0.25 0.5 Km

Vertical Change Rate (m) Red = erosion Green = accretion 0.02 0.01

Hatched Areas

Yellow = marsh formed between 1992-2006 0.01 Blue = marsh lost between 1992-2006

0.02

L3B5

L3B4

L3B3

L3B2 ¯

0 0.25 0.5 Km

Vertical Change Rate (m) Red = erosion Green = accretion 0.02 0.01

Hatched Areas

Yellow = marsh formed between 1992-2006 0.01 Blue = marsh lost between 1992-2006

0.02

Km 00.05 0.1 0.2 0.3 0.4 0.5 ¯ L3C1

L3B7

L3B6

L3B5

Vertical Change Rate (m) Red = erosion Green = accretion 0.02 0.01

L3B4 Hatched Areas

Yellow = marsh formed between 1992-2006 0.01 Blue = marsh lost between 1992-2006

0.02

L3C4

L3C3

L3C2 ¯

Km 00.05 0.1 0.2 0.3 0.4 0.5

Vertical Change Rate (m) L3C1 Red = erosion Green = accretion 0.02 0.01

Hatched Areas

Yellow = marsh formed between 1992-2006 0.01 Blue = marsh lost between 1992-2006

0.02

L3D1

L3C6

L3C5 ¯

Km 00.05 0.1 0.2 0.3 0.4 0.5 L3C4 Vertical Change Rate (m) Red = erosion Green = accretion 0.02 0.01

Hatched Areas

Yellow = marsh formed between 1992-2006 0.01 Blue = marsh lost between 1992-2006

0.02

L3D4

L3D3

L3D2 ¯

Km 00.05 0.1 0.2 0.3 0.4 0.5

Vertical Change Rate (m) Red = erosion Green = accretion 0.02 0.01

Hatched Areas

Yellow = marsh formed between 1992-2006 0.01 Blue = marsh lost between 1992-2006

0.02

Km 00.05 0.1 0.2 0.3 0.4 0.5 ¯ N0B4

N0C1

N0C2

Vertical Change Rate (m) Red = erosion Green = accretion 0.02 0.01

N0C3

Hatched Areas

Yellow = marsh formed between 1992-2006 0.01 Blue = marsh lost between 1992-2006

0.02

Km 00.05 0.1 0.2 0.3 0.4 0.5

¯ N0C3

N0C4

N0C5

Vertical Change Rate (m) Red = erosion Green = accretion 0.02 0.01

Hatched Areas

Yellow = marsh formed between 1992-2006 0.01 Blue = marsh lost between 1992-2006

0.02

© © Crown copyright and database rights 2007 Ordnance Survey 100024198. © Environment Agency copyright and/or database rights 2007. All rights reserved. © rw oyih n aaaergt 07Odac uvy10218 Environment Agency copyright and/or database rights 2007. © Crown copyright and database rights 2007 Ordnance Survey 100024198.

N0D5 Anglian Coastal Monitoring Programme 2007 - The Wash - The 2007 Programme Monitoring Coastal Anglian . . . . 0.5 0.4 0.3 0.2 0.1 0 0.05 ¯ Km

N0D4

N0D3 Blue = marsh lost between 1992-2006 between lost marsh Blue = 1992-2006 between formed marsh = Yellow Areas Hatched

N0D1

0.01 0.01 Plan 10

0.02 0.02 © rw oyih n aaaergt 07Odac uvy10218 Environment Agency copyright and/or database rights 2007. © Crown copyright and database rights 2007 Ordnance Survey 100024198. Anglian Coastal Monitoring Programme 2007 - The Wash - The 2007 Programme Monitoring Coastal Anglian Green = accretion = Green = erosion Red (m) Rate Change Vertical

L4A3 0.01 0.01

0.02 0.02 Blue = marsh lost between 1992-2006 between lost marsh Blue = 1992-2006 between formed marsh = Yellow Areas Hatched

L4A1 ¯ Km Plan 11

N0D5 Anglian Coastal Monitoring Programme 2007 - The Wash Plan 12

Km 0 0.1 0.2 0.3 0.4 0.5

L4B4

L4B3

L4B2

Vertical Change Rate (m) Red = erosion Green = accretion 0.02 0.01 0.01

0.02 L4B1

Hatched Areas Yellow = marsh formed between 1992-2006 Blue = marsh lost between 1992-2006

Km 0 0.1 0.2 0.3 0.4 0.5

L4B7

L4B6

Vertical Change Rate (m) Red = erosion Green = accretion 0.02 0.01 0.01 L4B5

0.02

Hatched Areas Yellow = marsh formed between 1992-2006 Blue = marsh lost between 1992-2006

Km 00.05 0.1 0.2 0.3 0.4 0.5 ¯

L4C4

L4C3

L4C2

Vertical Change Rate (m) L4C1 Red = erosion Green = accretion 0.02 0.01

Hatched Areas

0.01 Yellow = marsh formed between 1992-2006 L4B7 Blue = marsh lost between 1992-2006

0.02

Km 00.05 0.1 0.2 0.3 0.4 0.5 ¯

L4C6

Vertical Change Rate (m) Red = erosion Green = accretion 0.02 0.01 L4C5

Hatched Areas

0.01 Yellow = marsh formed between 1992-2006 Blue = marsh lost between 1992-2006

0.02

Vertical Change Rate (m) Red = erosion Green = accretion 0.02 0.01

0.01 N0B1

0.02

Hatched Areas Yellow = marsh formed between 1992-2006 Blue = marsh lost between 1992-2006

Km 0 0.1 0.2 0.3 0.4 0.5 ¯

N0B2

N0B3 #

Upper sand/shingle beach # = Erosion ! = Stable = Accretion #

N0B4

Vertical Change Rate (m) N0A6 # Red = erosion Green = accretion 0.02 0.01 0.01

0.02

Upper sand/shingle beach # = Erosion N0A5 ! = Stable = Accretion # ¯

0 0.1 0.2 0.3 0.4 0.5 N0A4 #

N0A3

N0B1

Vertical Change Rate (m) Red = erosion Green = accretion 0.02 0.01 0.01

0.02 N1D1

Upper sand/shingle beach # = Erosion ! = Stable = Accretion # ¯

Km 0 0.1 0.2 0.3 0.4 0.5 N0A8

N0A7 # N0A6 #

Vertical Change Rate (m) Red = erosion Green = accretion 0.02 0.01 0.01

0.02

Upper sand/shingle beach # = Erosion ! = Stable = Accretion # ¯

Km N1D3 0 0.1 0.2 0.3 0.4 0.5 #

N1D2

N1D1

N0A8

This following section offers a description of the results to accompany the plans on previous pages.

BC = boundary change. This refers to saltmarsh/mudflat boundary difference from comparison of the 1991 and 2006 orthorectified aerial photography surveys. The values refer to the change observed at each profile location. Positive values indicate seaward accretion and negative values indicate landward erosion of the boundary .

2.3.1 Western shore of The Wash (mouth of River Witham to Gibraltar Point)

L3A1, BC + 120m. Located close to the northern training wall of the Tabs Head, adjacent to the mouth of the River Witham. Relatively short profile shows a consistant average vertical accretion trend of ~15mm year with a max marsh height of ~3.1 mOD.

L3A2, BC + 200m. Borstal Banks, profiles shows a consistent average vertical marsh accretion trend of ~18mm year with a max marsh height of 3.0mOD. Mudflat shows accretion along entire length of profile with a large ‘bulge’ of increased annual trends between 1100m and 1500m chainage. This is likely to be a shift in the deep channel serving the Rivers Witham and Welland (see aerial photo).

L2A3, BC + 260m. 100m south of Frieston realignment site. Marsh shows very slight vertical accretion trend with a max marsh height of 3.2mOD. The lower mudflat shows variability with significant accretion at the lower end.

L3A4, BC + 220m. profile located in front of the Frieston managed realignment site. Marsh shows a moderate average vertical accretion trend of ~5mm with a max marsh height of 3.0mOD. The lower mudflat generally shows accretion trends with marsh drainage channel movements accounting for isolated erosion.

L3A5, BC -90m. Butterwick Low, the marsh shows an average vertical accretion trend of 10mm year with a max marsh height of 3.3mOD. The upper mudflat shows high variability that is likely to be related to movements of the drainage channels at this location. The lower mudflat beyond ~1000m generally shows an accretion trend.

L3A6, BC + 60m. The marsh shows an average vertical accretion trend of 5mm year with a max marsh height of 3.2mOD. The mudflat shows general accretion trends out to ~1300m beyond this erosion is apparent. This is likely to be a result of the shifting mudflat drainage channel.

L3A7, BC + 80m. The marsh shows an average vertical accretion trend of 5mm year with a max marsh height of 3.1mOD. The mudflat shows an vertical erosion trend of variable rates. No drainage channels dissect the profile.

L3B1, BC + 80m. Leverton Pumping Station, the marsh shows an average vertical accretion trend of 10mm year with a max marsh height of 3.2mOD. The upper mudflat shows some vertical erosion trends at ~1.5mOD with significant accretion at levels lower than this.

L3B2, BC no change. The marsh shows an average vertical accretion trend of 10mm year with a max marsh height of 3.4mOD. The upper mudflat shows vertical accretion trends with a reversion to significant erosion beyond ~900m.

L2B3, BC + 70m. the upper (older) saltmarsh shows relative stability at around 3.5mOD. The lower saltmarsh shows steady vertical accretion trends. The mudflat shows continuous vertical erosion along its entire length with the exception of a channel at ~1800m.

L2B4, BC + 30m. The upper (older) saltmarsh shows some minor vertical erosion trend of several mm’s year at a height of around 3.5mOD. The mudflat shows almost continuous vertical erosion along its entire length.

L2B5, BC no change. Profile shows clear vertical height shift at saltmarsh/mudflat boundary. Saltmarsh shows variability/erosion at higher levels (above 3.5mOD) with accretion at levels below this. Majority of lower mudflat shows a modest vertical accretion trend of ~5-10mm year.

L3B6, BC no change. The Horseshoe (data gap 700-900m). Some vertical accretion at the seaward end of the saltmarsh, however, much of the remainder of the data shows a minor erosion trend.

L3B7, BC no change. Jubilee Bank (a), the saltmarsh at this location is narrow. The average height of the upper saltmarsh is lower than marsh to the south with a max height of ~2.9mOD. The trends show significant variability along the mudflat with consistent vertical erosion immediately beyond the marsh/mudflat boundary for a distance of ~300m.

L3C1, BC + 50m. Jubilee Bank (b), a narrow saltmarsh that has shown some vertical accretion since 1992. The whole profile shows a general vertical accretion trend (except drainage channels).

L3C2, BC + 150m. Jubilee Bank (c), at 300m width, a narrow saltmarsh. Whole profile shows general vertical accretion trend.

L3C3, BC + 160m. Jubilee Bank (d), the higher marsh at ~3.3mOD shows some vertical erosion with the remainder of the marsh and mudflat showing an vertical accretion trend.

L3C4, BC + 150m. Jubilee Bank (e), saltmarsh shows vertical accretion trends and the mudflat generally shows vertical accretion along its entire length.

L3C5, BC + 150m. Jubilee Bank (f), general stability of upper mature marsh at ~3.2mOD. Whole mudflat profile shows vertical accretion.

L3C6, BC no change. Jubilee Bank (g), general stability of upper mature marsh at ~3.2mOD. Profile crosses network of drainage channels and shows a general trend of vertical erosion along most of its length. L3D1, BC + 100m. Wainfleet Sand (a), general trend of vertical accretion along majority of profile. Saltmarsh/mudflat boundary has accreted by ~100m since 1992.

L3D2, BC + 100m. Wainfleet Sand (b), strong vertical accretion trend of ~15-20mm along entire length of profile.

L3D3, BC + 350m. Stable marsh with vertical accretion trends along entire profile.

L3D4, BC -120m. Relatively stable profile over saltmarsh. Sandy ridge at marsh edge retreating landward. Short (~200m) length of monitored mudflat shows strong vertical erosion trends.

2.3.2 Southern Shore (Snettisham Scalp to River Welland)

Generally profiles taken on the southern shore of The Wash do not extend any significant distance over the mudflat.

N0B4, BC + 100m. Actual profile shows 100m saltmarsh boundary accretion but adjacent to area with no boundary changes recorded. Profile shows strong vertical accretion trends over entire length.

N0C1 to N0C5. East of Great River Ouse. All profiles show strong marsh/mudflat boundary accretion of between 160-320m. Profiles all show high vertical accretion trends up to a level of ~3.5mOD.

N0D1 to N0D3. Breast Sands, east of Great River Ouse. All profiles shown marsh/mudflat boundary accretion of ~150-200m and vertical accretion trends.

N0D4, BC No change. Strong vertical accretion trend over whole profile except the higher marsh at the landward edge of the profile ~3.5mOD.

N0D5, BC +260m. Strong vertical accretion trend over whole profile.

L4A1, BC –130m. Isolated saltmarsh/mudflat boundary erosion at this location (see plan). Vertical accretion trend along entire profile.

L4A2 & L4A3. East of River Nene Mouth. Profiles show BC accretion of 160 and 220m. Both show vertical accretion trend except the higher marsh at the landward edge of the profile ~3.5mOD.

L4B1, BC +180m. Vertical accretion trends of ~ 5-15mm year.

L4B2, BC +140m. Modest vertical accretion trend >5mm year.

L4B3, BC no change. Vertical accretion trend of marsh with short length (~200m) of mudflat showing general stability.

L4B4, BC no change. First 600m of profile above 3.5mOD and shows relative vertical stability. Remainder of profile variable due to drainage channels. L4B5, BC no change. High level marsh at ~3.5mOD shows variable trends, lower marsh shows vertical accretion.

L4B6 & L4B7, BC +100m and 300m. At both locations the high level marsh at ~3.5mOD shows variable trends, lower marsh shows vertical accretion.

L4C1 to L4C4, BC L4C1 no change, L4C2-4 +220-260m. All profiles show variability at landward high level marsh ~3.5mOD. Vertical accretion showing at seaward extents of marsh.

L4C5 & L4C6, BC no change. No change to saltmarsh boundary position at profile locations but general saltmarsh accretion in the vicinity of these profiles. Both profiles have lower marshes at ~3.1mOD and show vertical accretion.

2.3.3 Eastern Shore (Snettisham Scalp to Old Hunstanton)

This length of coast has extensive sand/mudflats extending in places several km’s from approximately the MSL-MHWN position. Along much of this coast there is a sand/shingle ridge on the upper beach above MSL-MHWN mark. At various locations this ridge is reinforced with groynes, gabions and other structures. The coast from Heacham northwards has a flexible blockwork revetment leading on to a concrete seawall up to the main Hunstanton frontage. No defences are present Between Hunstanton and Old Hunstanton.

Two separate analysis methodologies are utilised on this frontage. The lower sand/mudflats are analysed in a fashion similar to the saltmarsh analysis undertaken along the southern and western shores of The Wash. For the sand/shingle ridge the position of the ridge at specific heights (i.e. MHWS in mOD) is obtained from each profile and the distance from the common base point . The result is a trend of horizontal movement for each specified height.

N0B3, River Ingol mouth. The seaward face of the shingle ridge has shown stability over the monitoring period with a modest horizontal accretion trend of ~0.3m year towards the base of the ridge. The sand/mudflat shows an vertical accretion trend of ~ 20-30mm year along much of it’s length. This accretion reduces at the lower end of the profile beyond 2000m but no vertical erosion trend is apparent.

N0B2, Snettisham Scalp south. The shingle ridge at this location has demonstrated an horizontal erosion trend of ~0.5-0.6m year. The lower mudflat shows a general vertical accretion trend and which reduces where the profile is bisected by the channels of Wolferton Creek and the River Ingol.

N0B1 and N0A2, both N0B1 and N0A2 profiles originate from adjacent points near Snettisham Scalp car park. Both profiles show relative horizontal stability of the shingle ridge with little movement. The reason for this is that the ridge provides flood defence for an extensive caravan park and has been subject to shingle recycling and re-profiling. In 2006 and extensive beach renourshment scheme was undertaken. Both profiles show similar behaviour along the sand/mudflat section although the southern profile (N0B1) is considerably shorter. Generally both profiles show vertical accretion trend of the flats with a section between 300-700m showing a modest erosion trend of ~5mm year. N0A3, Snettisham Coastal Park. Flexible armoured concrete revetment installed 2002. Overall beach shows a horizontal erosion trend of ~0.5m year. Sand/mudflat profile shows a general trend of vertical erosion although the rates are very modest at <5mm year.

N0A4, Snettisham Coastal Park. Shingle ridge shows general stability. Lower sand/mudflat demonstrates a vertical erosion trend along its entire length although the rate is modest at 2-6mm year.

N0A5, Heacham southern beach access point. Lower shingle ridge shows stability prior to renourshment in 2006. Upper shingle ridge has been modified to provide access to the beach. Lower mudflat shows modest (~5mm year) vertical erosion trend <750m and accretion thereafter.

N0A6, Heacham north. Solid concrete stepwork and crest with a wavewall on upper beach installed 2003. Sand/gravel upper foreshore shows strong horizontal erosion trends of ~1.6m year and associated foreshore steepening. Lower sand/mudflat shows vertical accretion trend with recorded rates ~6-20mm year.

N0A7, between Heacham and Hunstanton. Solid concrete stepwork and crest with a wavewall on upper beach throughout monitoring period. Sand/gravel upper foreshore shows modest horizontal erosion trends of ~ 0.5m year. Lower sand/mudflat shows modest vertical accretion trend of ~5mm year.

N0A8, Hunstanton south. Solid concrete stepwork and crest with a wavewall on upper beach in place throughout monitoring period (wavewall improved 2004) with timber groyne field. Survey data inconclusive on upper beach due to presence of structures. Lower sand/mudflat shows modest vertical erosion trends increasing to severe erosion at approx. the MLWS level.

N1D3, Hunstanton Pier. Upper sand beach shows horizontal erosion trends of ~1.5m year on the upper foreshore with horizontal accretion at approx. MSL, giving a beach flattening trend. Lower sand/mudflat is generally showing a strong vertical accretion trend of ~0.4m year, along most of its length although erosion trends are apparent at its nearshore edge.

N1D2, Hunstanton Cliffs. The upper sandy beach shows general stability although the lower beach shows high horizontal variability near MSL. The lower sand/mudflat shows a vertical erosion trend along its entire length although the rate is modest at ~5- 10mm year.

N1D1, Old Hunstanton. Upper sandy beach shows some horizontal erosion trend near the MHWS mark of ~ 0.5m year and MSL mark shows modest advance giving a flattening profile. Lower beach shows vertical accretion trend inshore (<100m) with general stability further offshore. 2.4 General conclusions

Studies undertaken by the Coastal Geomorphology Partnership (1998 & 2002) have indicated that the areas of geomorphological interest are;

• vertical accretion/erosion of the upper saltmarsh and the lower mudflat,

• advance or retreat of the saltmarsh-mudflat boundary,

• movement of deepwater channels at the lower end of the profiles.

This report summarises the data collected by the Environment Agency in The Wash since the early 1990’s. Two separate types of analysis were undertaken, vertical changes were measured on the saltmarshes and mudflats and horizontal changes were measured along the sand/shingle ridge on the eastern shore. All recorded measurements were analysed to obtain trends in the data. In addition to this orthorectified aerial photographs we analysed to establish the extent of saltmarsh horizontal growth or loss between 1992 and 2006. Due to safety concerns the surveyors are unable to walk over several Km’s of mudflat to reach the LWM. Therefore it has not been possible to analyse trends in deepwater channel movement with the profile data alone.

The analysis of the orthorectified aerial photography revealed that the total area of established saltmarsh has increased by 1021 Ha between the aerial photography campaigns of 1992 and 2006. The total area in 2006 was 4378 Ha. The majority of new marsh, 734 Ha, has formed on the southern shoreline of The Wash.

Generally most of the profiles taken on the saltmarshes have shown some degree of vertical accretion over the last 13 years. Accretion trends are highest where new marsh has formed after the first surveys were undertaken in 1993. Accretion appears to cease or become variable on more mature marsh where the vertical level approaches approximately 3.5 mOD. This is particularly apparent at the coast adjacent to Holbeach St Matthew (L4B5 to L4C3) where the landward extents of the profiles show minor erosion trends.

On the western shore of the area of new horizontal saltmarsh growth was significantly less than the southern shore. The profiles from north of Butterwick Low across the Wrangle Flats to The Horseshoe at the southern end of the Jubilee Bank nearly all show an erosion trend across the entire profile length. New horizontal saltmarsh growth recorded at this location has been minimal.

On the eastern shore the profiles between Shepherd’s Port and Heacham all show an erosion trend (N0B1 to N0A5) on the lower sand flats. The sand/shingle ridge on the upper beach at these locations all show a trend of stability with the exception of N0A4 which has an erosion trend. However, the upper beach along this frontage has been modified by sediment reprofiling and recycling. In addition to this a major renourishment campaign was undertaken in 2006. Appendix - References

(1). SANDS software by Halcrow Group PLC. http://www.halcrow.com/sands

(2). POLTIPS software by Proudman Oceanographic Laboratory. http://www.pol.ac.uk/appl/poltipsw.html

Coastal Geomorphology Partnership 1998. Monitoring in The Wash: Issues Paper. Report to Environment Agency (STCG21). Centre for Coastal Management, University of Newcastle.

Coastal Geomorphology Partnership 2002. Coastal Data Analysis: The Wash. Study 3: Long-term inter-tidal profile evolution modelling. Report to Environment Agency (STCG/2000/49). Centre for Coastal Management, University of Newcastle.

Defra, 2006. ‘Shoreline Management Plan Guidance: Volume 2, Appendix E – Open coast SMP management boundaries’. http://www.defra.gov.uk/environ/fcd/policy/smp.htm

HR Wallingford 1994. ‘Coastal Management: Mapping of Littoral Cells’, report SR328

Hunstanton/Heacham Sea Defences. Strategy/Project Appraisal Report. Angency Scheme Number: LMB 12058. Posford Duvivier, April 2001

Hunstanton/Heacham Sea Defence: Beach Management Manual. Environment Agency, October 2002.

Taylor, JA, Murdock, AP & Pontee, NI, 2004. A macroscale analysis of coastal steepening around the coast of England and Wales. The Geog. Journal, Vol 170, No. 3, Sept 2001, pp. 179-188.

Wash Banks: Gibraltar Point to Hobhole. Strategy Study – Project Number 9139670. Halcrow, July 1997