Coastal Trends Report Lincolnshire (Subcells 2b-c - Grimsby to Gibraltar Point) RP007/L/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 Beach at Skegness (Photo: Environment Agency) 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 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. Renourishment 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, recharge or feeding. SMP Shoreline Management Plan ii Coastal Trends Analysis…………………………………………………….......... 1. Introduction...............................................................................................2 1.1 Purpose and application ....................................................................2 1.2 Background .......................................................................................2 1.3 Beach topographic profile data ..........................................................3 1.4 Future outputs ...................................................................................3 1.5 Study area .........................................................................................4 2. Lincolnshire (sub-cells 2 b-c) coastal trends.............................................6 2.1 Foreshore change analysis................................................................6 2.2 Foreshore change analysis results ..................................................10 2.2.1 Outline observations.................................................................10 2.2.2 Graphical view of results ..........................................................13 3. Lincshore analysis ..................................................................................24 3.1 Lincshore nourishment ....................................................................24 3. 2 Lincshore Volumetric analysis .........................................................25 3. 3 Lincshore topographic survey and profile analysis ..........................28 3.3.1 Graphical view of profiles (Topographic survey profile analysis results) 31 4. Description of results ..............................................................................38 4.1 Description of results, North Lincolnshire ........................................38 4.2 Description of results, South Lincolnshire and the Lincshore coast.44 5. Discussion & summary ...........................................................................52 6. References .............................................................................................53 7. Appendix.................................................................................................55 iii © © Crown copyright and database rights 2008 Ordnance Survey 100024198. © Environment Agency copyright and/or database rights 2008. All rights reserved. Figure 1.1 – The Anglian Coast 1 1. 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 (Figure 1.1). 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 large 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 is 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 1 km intervals • Bathymetric surveys (extension of beach survey lines out to approximately 10 m 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, phase VII of the Anglian Coastal Monitoring Programme is underway, 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. 2 However, the Agency now possesses 16 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 Topographic surveys are elevation measurements taken along a defined transect line. The transect line runs from an established marker along a bearing relative to Grid North. The Strategic & Development Planning (Shoreline Management Group) in Anglia has carried out bi-annual topographic surveys since 1991 at 1 km intervals along the Anglian coast. The most recent set of available data means that there is now a continuous record of beach levels spanning 16 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 Anglian coast is dynamic and responds to changes in wave, current and wind action that shape beach profiles and morphological characteristics. Understanding the response of the Lincolnshire shoreline to external forces, both anthropogenic and natural is vital to successful management decisions. Artificially defended beaches that