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Research and Monitoring on the Coast - Coastal ProcessesArticle by Graham Lymbery, Technical Services, Sefton Council
Coastal Processes Defn - Collective term covering the action of natural forces on the shoreline, and nearshore seabed.
If we are to ensure that our environmental legacy is better than our environmental inheritance then we need to know what is going on. Research and monitoring of coastal processes enables us to improve our overall understanding of this complex and changing environment, and to assist with management decisions which are based on the best available knowledge at any given time.
Monitoring of coastal processes on the Sefton Coast is primarily carried out by the Council in conjunction with the Environment Agency and partners in the Liverpool Bay Coastal Group. There are other sources of data such as that gathered by wind farm operators, aggregate extraction companies and ports. However, this information only tells us what is happening at a point in time under a certain set of conditions. Whilst we can measure what is happening now we need to understand what will happen in the future so that we can try and accommodate these changes. This is where the research element comes in; by looking in more detail at the available information we can develop our understanding of the processes and develop predictions for the future evolution of the coast.
Research can occur at a number of spatial levels, it can be very local such as that being looked at as part of the PhD, or it can be national and trans-national such as that looking at climate change. On the Sefton Coast we are participating in regional research that is looking at three main areas:
Sediment movement - to identify and define the movement of sediment within the area from Llandudno to Solway Firth. This information can be used when designing schemes and also to inform decisions in relation to proposals such as aggregate extraction.
Tidal flows - this is closely linked with the above study and aims to provide a better understanding of tidal currents within the area from Llandudno to Solway Firth.
Wave and water level joint probability - when designing schemes and looking at risk we need to understand the chances of extreme storm events occurring within the area from Llandudno to Solway Firth. The worst storms are associated with high tides occurring at the same time as surges and large waves, this study will aim to provide a better definition of the probability of these extreme events occurring.
What do we monitor?
One way to look at what we monitor is to use a conceptual model referred to as the Source-Pathway-Receptor-Consequence (SPRC) Model (HR Wallingford, 2002). This model provides a simple conceptual tool for representing, in this case, the overall process/shoreline/hinterland system associated with the provision of coastal defence.
Sources in the model are the magnitude of the coastal forcing parameters on the coast - wind, waves, tides etc (wave climate and storm typicality)
Pathways are the routes which the waves and tides travel over and are transformed by (also hydrographic surveys, aerial photography)
Receptors are the hinterland areas and the different defence types, topography, land use and development status applying in particular areas. (Shoreline and Defence Inspections, Monitoring of behaviour and performance of sand dunes)
Consequences are the effects that flooding and erosion has on the receptors.
Why is the coast is not static? Some of the changes come about as a result of geological processes, these tend to be slow but operate over a long time period such as the gradual infilling of the Ribble estuary. Some processes are cyclical in nature such as weather patterns that repeat over a period of years or decades. Then there are human influences such as aggregate extraction, dredging, land reclamation and climate change.
Example Research - PhD being undertaken by Vanessa Holden
"Past, present and future sea-level change: an integrated management approach to modelling the geomorphology and sediment dynamics of the north Sefton coast".
Sefton Metropolitan Borough Council regularly surveys the area at fixed points on the marshes, and has done so for many years. This research will use the same points for data collection, to allow a comparison with historical data. Samples collected from the surface of the marsh will be analysed to provide evidence of the present day sediment.
Monitoring sites will be established to investigate how much sediment is being deposited onto, or eroded away from, the marsh surface. Cores of sediment will also be analysed to investigate the historical nature of the sediments making up the marsh. The use of historical photographs (especially aerial photographs) will provide further evidence to determine precisely the nature of coastal changes in the area, and will provide indications and evidence for the causes of the changes.
A major aim of this project is to provide a permanent record and database of the current and past status of the northern Sefton coast salt marshes. This will allow future changes to be assessed in comparison with this baseline information.
Once all the data has been collected and analysed, it is hoped that it will be possible to evaluate and model likely future changes, so as to contribute to the strategic planning of coastal management.
Sefton has carried out monitoring on the coast for a number of years and the corporations carried out monitoring prior to this with measurements of the beach going back to the early part of the twentieth century. This data has been used for specific research in the past but with the increasing power of computers it has been possible to transfer significant amounts to computers and carry out relatively complex analysis of the data. Following a workshop at the last Sefton Coast Forum that looked at how best to disseminate this data the Council are in the process of developing a report on coastal processes and supporting information. The report will include summary sheets that describe the historical and current evolution of individual areas and provide an indication of the predicted evolution. It is also hoped to provide briefing sheets on items such as climate change that will be located on the web site in the near future (www.seftoncoast.org.uk) so as to make the hard copy report brief and accessible whilst providing all the background information to those who are interested. (Access to the internet is available at any Sefton Council library).