A contribution towards the analysis of the effect of climate change and sea level rise on hydrodynamic conditions and sediment transport off East Anglian coast
PublisherUniversity of Manchester
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Coastal management accounting for shoreline erosion and coastal flooding requires information about various physical processes that take place over a range of temporal and spatial scales. Field measurements provide information on the past and current coastal environment and statistical tools are used to determine extreme conditions that can lead to damage. However, in a changing climate, these conditions cease to be statistically stationary, making predictions problematic. To assess future conditions, a set of scenarios for greenhouse gas emissions has been defined to project impacts on global oceanographic conditions and sea level rise. This thesis estimates the effect of these global projections on coastal processes off the North Norfolk coast of the UK. A model system is set up to downscale global conditions on to nearshore conditions (wave climate, water level and beach profile), which influence coastal stability and coastal flood risk. The system is based on coupling numerical models for different temporal and spatial scales. The area contains large tidal sandbanks and shore-connected sand ridges. The downscaling procedure accounts for interactions that take place on the upper part of the continental shelf where these large-scale seabed features affect wave propagation, tidal flows and sediment transport. The modelling system is then validated against historical data and then used to compute long-term inshore hydrodynamic characteristics and sediment transport resulting from future projections of climate change and sea level rise. This enables an assessment of extreme inshore wave heights, overtopping discharge rates and their occurrence at a sea defence through extreme joint probability analysis. This modelling assumes a fixed seabed. However, the system includes a sub model for the release of sediment from the cliff erosion, which provides a source of sediment for the maintenance of the offshore sandbanks. The link between the cliff and the sandbanks is demonstrated by computing the residual sediment transport. The model system is also used to assess the impact of offshore sand extraction on coastline erosion. Finally, the system is used to analyse an overtopping and flood inundation event at Walcott in 2007 enabling uncertainties in the predictions to be assessed.