A.D. Swan and V.R. Stovin (UK)
Design methods & aids; rehabilitation, reclamation and renovation; sewers and drains; sustainability
This paper explores the relationship between increased urbanisation and subsequent capacity problems within drainage infrastructure. The respective merits of resolving these problems using: i.) ‘quick fix’ engineered solutions; and ii.) long-term ‘planning-based’ remedial measures are investigated. The ‘quick fix’ approach would typically involve the provision of in-sewer storage (e.g. a storage chamber or oversized sewer pipes) to store excess flows, releasing them back into the sewer later for subsequent conveyance to an outfall. SUDS retrofitting appears to represent an attractive alternative to this ‘hard engineering’ approach, but has proved to be difficult to implement within the current UK regulatory environment. The ‘planning-based’ approach, on the other hand, might involve the imposition of ‘green-field’, or stricter, runoff restrictions to all new planning proposals submitted for urban sites (both new-build and brown-field redevelopment) – with a view to incrementally reducing the storm-water runoff entering the system over time. These issues are illustrated in relation to a UK case study that contains known ‘surface water’ flooding problems. Historical maps are used to demonstrate how the catchment has become increasingly urbanised over the last 50 years; and a simple modelling exercise demonstrates how this process has been directly responsible for exacerbating the catchment’s flooding problems. The case study also demonstrates practical opportunities for reducing/resolving the flooding problems with both ‘quick fix’ engineered solutions, retrofit options, and long-term ‘planning-based’ remedial measures.
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