Applications and risks associated with a low cost flood defence barrier

An innovative low cost self erecting flood barrier is described (patent pending) and its applications discussed. The flood defence is provided by a geomembrane embedded in a backfilled trench and attached to rigid covers that rise with the flood waters. The covers are restrained by ties attached to the membrane. It is considered particularly appropriate for protection against floods up to 1 m in depth where a permanent defence barrier would intrude into the landscape or require the import of expensive fill material to create impermeable bunds. It is also relevant on more permeable ground where foundation cut off walls might otherwise be required to reduce ground water flow. The risks associated with the use of such a self erecting membrane are assessed in comparison with traditional permanent walls or banks and the temporary demountable barriers employed in the Severn valley region in recent months. It is demonstrated that the self erecting barrier is cost effective particularly where the visual amenities of a waterside area would otherwise be lost.