Broadscale Coastal Inundation Modelling
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To understand the implications of changes to marine climates and the impact on people, analysis is required of the spatial extent and depths of flooding in urban and rural areas. Over extended timescales, the uncertainties related to possible sea-level rise and changes in storminess increase significantly. As such, there is no certainty regarding when and if a major storm or breach will occur. The increasing availability of some details of changing wave climate (described in Chaps. 2 and 3) and full range of beach evolutionary behaviours (given in Chap. 7) offer an opportunity to improve the implications of these uncertainties on flood extents.
Uncertainties in beach level in front of flood defences, future sea level, extremes of wave height and water level and breach location(s) require that a wide range of current and potential future conditions are considered to fully understand flood risk. It is therefore crucial to capture and model a wide range of possible future inundation events. We simulated shallow flow hydrodynamics and validated this with a comparison of the recorded inundation extent from a flood event in 1938. Subsequently, with 1,344 simulations for each breaching scenario, we analyzed the full range of hydraulic loadings, beach morphologies, coastal defence structural responses (overtopping and breaching) and coastal management policy in order to understand the full range of uncertainties that influence long-term changes in flood impacts.
Initially, LISFLOOD-FP was used to simulate inundation over the full extent of the floodplain. Later in the case study development, we benefitted from increased desktop computing power and were able to use the more advanced NewChan model for the more detailed analysis of flooding in the Norfolk Broads. Flood depth and extent in the Norfolk Broads are dominated by extreme water levels and to a lesser extent wave heights. Rising sea levels will notably increase the area at risk of flooding, posing substantial challenges for coastal managers in this region. The results of these simulations are integrated with information on damages to quantify flood risk in Chap. 9.
KeywordsInundation modelling Flood depth and extent Overtopping Defence breach Sea-level rise
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