Martello lakes breach analysis Keywords Waterside Development Flood Risk Breach Analysis TUFLOW Client, Architect & Other Organisations Cameron Taylor Consulting Engineers Cofton Ltd

Martello Lakes Typical TUFLOW Output Click on Image to Enlarge

Description The Martello Lakes project involves the development of an existing quarry site for housing in Kent.  The site which is approximately 400m from the coast is generally low lying sited with ground levels significantly less than extreme tidal levels . Inundation from the sea of and existing residential estates and the quarry is prevented by a shingle barrier beach adjacent to the coast.   In order to reduce the risk of flooding to the housing development Cameron Taylor Consulting Engineers recommended to the developer that the building platform for the site be rasied to a level in excess of the 1 in 200 extreme water level including an allowance for climate change for sea level rise. However, the proximity of the development adjacent to an existing housing estate meant that the there was uncertainty in the impact of the new construction on flooding to third party properties. In addition, it was also felt that the existing shingle barrier could be vulnerable to damage during an extreme event. The Environment Agency advised the developer that it would only remove its planning objections if a detailed breach analysis  was carried out and that there was no significant increase in flood risk to third party properties.

Scope of Work Edenvale Young were approached to undertake the breach analysis by Cameron Taylor using the TUFLOW software. The project included:- An analysis of extreme water levels at Hythe ranges in order to produce a time series of water levels covering three tidal cycles An assessment of breach development during the tidal cycle. The development of a ground model of the area with a cell size of 5m based upon LiDAR data obtained from the Channel Coast Observatory. The creation of a TUFLOW model including variable geometry relating to the development of the breach. Key reference points were established around the estates which included threshold levels for a number of  properties on the estate.  The TUFLOW model was initiall run for a number of breach development scenarios with and without the development platform so that the impact of development could be assessed. Flood levels and depths were compared for each reference point to establish the impact of the development on flooding. A second series of TUFLOW runs were undertaken to evaluate the impact of including a preferential flood route to exploit the existing lake for flood storage.  The result od both stage of work were presented to the EA.