Coastal Flood Risk

 Background

The value of the UK’s assets at risk from flooding by the sea have significantly increased in recent years, and currently stands at a value of £132.2bn, with some 4 million properties in England and Wales alone under threat (Office of Science and Technology, 2004). Currently, there is a lack of robust and integrated “clouds-to-coast” frameworks for coastal flood risk. The interactions between atmospheric, oceanic and coastal processes are poorly understood, resulting in large uncertainties in the performance of sea defences in extreme conditions.

EPIRUS is a joint research proposal between the Universities of Plymouth, Swansea and Liverpool. The primary objective is to develop an integrated 'clouds-to-coast' modelling framework which captures the complex interactions between the atmosphere, ocean and coastal flood and erosion, in order to accurately quantify the flood risk. The main aims of the project include;

• Development of an integrated modelling methodology for a 'clouds-to-coast' prediction of flooding and erosion
• Link a high resolution mesoscale meteorological model to regional and local scale models for wave transformation, and local coastal models for predicting wave overtopping and scour near coastal defence structures.
• Modelling methodology validation with field datasets
• Application of modelling methodology to investigate uncertainties by creating ensembles of possible storm events

 The 'clouds-to-coast' modelling system

Meteorological models that are routinely run for the UK domain in national weather centres have such a coarse spatial resolution that coastal models have difficulty utilising their output as an effective input. Therefore, a downscaling procedure is required to bridge the scale gap between the large-scale meteorological modelling domains and coastal modelling domains.

The WRF modelling system is utilised to resolve the dynamics over high resolution (~1km) grids. High resolution wind and pressure fields generated by WRF are subsequently used in the following hydrodynamical models:

• North East Atlantic WAM model (continental scale, ~1000s km) - provides wave forcing for regional model.

• POLCOMS-WAM model (regional scale, ~100s km) - takes the regional meteorological information to produce wave, tide and surge conditions for local models. The model, developed at the Proudman Oceanographic Laboratory (POL), is comprised of a baroclinic three-dimensional current model and a third-generation spectral wave model with coverage of both the deep ocean and the continental shelf

• COAST2D model (coastal zone scale, ~10s km) - produces further detailed hydrodynamics in the coastal zone, and provides information for coastal flooding and erosion studies. Included within the model are the main coastal processes, such as wave refraction/diffraction, breaking, reflection, tides and wave-current interaction.

• Surf zone models (2D RANS-VOF and 3D LES-VOF-LES ) determine wave overtopping, breaking, turbulence and streaming in the surf zone.