Flood Risk Assessment
Worthing Eirene Road
Keywords: Feasibility Studies, Flood Risk Assessment, Coastal Modelling Wave Overtopping.
Client, Architect & Other Organisations
Bayview Developments Ltd
Terrance O'Rourke & Partners
KPP Planning Ltd
Description
Bayview's Eirene Road development site is located in West Worthing directly behind a large barrier beach which affords a high degree of protection against tidal inundation to the low lying land to the rear of the beach. Bayview intend to replace the existing housing with an apartment block. The Environment Agency indicated that a study should be carried out to evaluate the risk of flooding due to wave overtopping of the barrier beach for a 1 in 200 year return period .
Scope of Work
Edenvale Young Associates was appointed to undertake a detailed Flood Risk Assessment for the Eirene Road site which principally involved the development of a wave overtopping model in conjunction with an assessment of morphological changes to the beach profile during storm conditions.Historical cross sectional beach profile data was obtained from the Environment Agency which indicated that the beach profile was generally stable with some fluctuation to the front profile on a year to year basis but with no signs of recession to the face within the data record.
A 1D model including the effects of wave breaking, shoaling and wave set-up was constructed to transform nearshore wave data to the toe of the barrier beach. The model was run for the eight joint probability combinations of peak water level and wave climate identified in the Coastal Defence Strategy for Worthing. The results of the 1D model was applied to a wave overtopping model based upon the Hedges & Reis and Besley empirical methodologies to identify the combination of water level and wave climate producing the worst wave overtopping condition. Powell's method for evaluating cross sectional morphological changes to the beach was then applied to the results of the 1D wave transformation model to evaluate possible changes to the cross sectional profile of the beach.
A synthetic time series of extreme water levels was also derived for the site based upon the gauge record at Dover using water level records from 1923 to the present day. The 1D wave transformation and wave overtopping model was applied over the synthetic time series of water levels to the existing and projected beach cross sectional profiles to give a total wave overtopping volume during the tidal cycle.