Performance of flood embankments in England and Wales

Abstract

There are some 35 000 km of estuarine and river flood defence embankments in England and Wales with an annual budget of approximately £450 million spent on maintenance and new construction. The effective performance of these embankments during extreme flood events is critical for the provision of sustainable flood defences. However flood embankments can become less effective over a period of time for a number of reasons such as (a) increased frequency of flooding due to climate change, (b) an increase in the required standard of service or other functional requirements and (c) long-term deterioration from the intended condition—as constructed or maintained. The tendency for earth embankments to deteriorate with time is of particular concern because climate change and the increasing rate of occurrence of extreme events are leading to an increase in loading. This paper reviews the geotechnical factors that can affect the performance of fluvial and estuarine flood defence embankments in the short and long term. The review considers the traditional methods used to construct flood embankments compared with modern techniques, the type of local materials used for construction, the range of possible geotechnical factors that can lead to a loss of performance and finally case histories of embankment breaches.