Coastal Trends Report Essex (Subcell 3d - Harwich to Canvey Island) RP008/E/2008 July 2008 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 2008 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 © Environment Agency copyright and/or database rights 2008. All rights reserved. Fishtail breakwaters at West Clacton golf course Glossary Accretion The accumulation of sediment on a beach by the action of natural forces or as a result of man-made artificial structures Bathymetry The topographic relief of the seabed Chainage The distance along a topographic survey transect line, measured in metres Chart Datum The level to which all soundings on a marine navigational chart are based Erosion The loss of material from a beach by the action of natural forces or the result of man-made artificial structures interfering with coastal processes FCP Foreshore Change Parameter Foreshore The area of beach lying between high water and low water Foreshore rotation Foreshore steepening or flattening resulting in the convergence or divergence of high and low water marks Longshore drift Movement of sediment along the shoreline MHWS level of Mean High Water Spring tides MHWN level of Mean High Water Neap tides MLWN level of Mean Low Water Neap tides MLWS level of Mean Low Water Spring tides MSL Mean Sea Level Ordnance Datum The mean sea level ( as derived from 6 years of observation at Newlyn, Cornwall) used as a datum for calculating the absolute height of land on official British maps. Recharge A management practise of adding to the natural amount of sediment on a beach with material from elsewhere. This is also known as beach replenishment, nourishment or feeding SMP Shoreline Management Plan Coastal Trends Analysis…………………………………………………….......... 1.0 INTRODUCTION 1.1 PURPOSE AND APPLICATION 1.2 BACKGROUND 1.3 BEACH TOPOGRAPHIC PROFILE DATA 1.4 ANALYSIS METHODOLOGY 1.5 FUTURE OUTPUTS 2.0 ESSEX (SUB-CELL 3d) COASTAL TRENDS 2.1 INTRODUCTION 2.2 GENERAL DESCRIPTION – HARWICH TO CANVEY ISLAND 2.3 OUTLINE OBSERVATIONS 2.3.1 Harwich to Hamford Water 2.3.2 The Naze (Stone Point) to Lee-over-Sands (Colne Point) 2.3.3 Mersea Island 2.3.4 Dengie Flat (Bradwell Peninsular to Ray Sand) 2.3.5 Maplin Sands (Foulness Point to Havengore Head) 2.3.6 Southend-on-Sea (Haven Point to Leigh-on-Sea) 3.0 GRAPHICAL VIEW OF RESULTS APPENDIX 1 – DETAILED RESULTS APPENDIX 2 - REFERENCES © © Crown copyright and database rights 2008 Ordnance Survey 100024198. © Environment Agency copyright and/or database rights 2008. All rights reserved. Map 1 – The Anglian Coast 1.0 Introduction 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 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 Canvey Island on the northern side of the outer Thames estuary (Map 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 major 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 rationale 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; x Annual aerial photographs x Annual topographic beach surveys (winter and summer) at 1km intervals x Bathymetric surveys (extension of beach survey lines out to approximately 10 metre depth offshore) x 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 twenty 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 sixteen 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 sixteen 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 increasingly difficult and expensive to maintain. 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 (SMPs) 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 into 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+b 1 * 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. 1.4 Analysis methodology The profile data presented in this report is in the form of beach level 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. In this report the area between the MHWN (Mean High Water Neaps) and MLWN (Mean Low Water Neaps) level is used 2 **. * 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.