Detailing of flood-detention reservoirs for resilience

Abstract

There are currently around four new flood-detention reservoirs (FDRs) built each year in the UK, which although only being modest structures with a median height of 4 m and reservoir capacity of 300 000 m3, can pose a significant risk to the community as they are located immediately upstream of the community they are protecting. These communities range from around five to several thousand households. The authors have designed and supervised over 30 new FDRs in the UK in the last 20 years, together with inspections of a similar number designed by others. This paper describes the emerging issues regarding risk of failure of these dams. Examples of measures to manage risk are described, with discussion of when selection of the options to increase resilience against a particular failure mode should be mandatory, and when it may be more appropriate to consider it on a case-by-case risk-based approach. The paper also discusses more strategic issues of design standards for design of spillways at FDRs, comparing the hazard introduced by construction of the reservoirs with the annual benefits of flood risk reduction.