MODELLING THE POTENTIAL FOR SPATIALLY DISTRIBUTED, NATURAL FLOOD-RISK MANAGEMENT TECHNIQUES TO MITIGATE FLOOD RISK AT THE CATCHMENT SCALE FOR A UK AGRICULTURAL CATCHMENT

Abstract

impact of flooding throughout the UK is significant and the financial burden felt by individuals, communities and the government. Many flood alleviation schemes are delivered using hard-engineered approaches that can provide high standards of protection, but do not address the root cause of flooding. Delivering civil engineering schemes cannot always be justified using the current cost-benefit criteria or due to difficulties of in working within a settlement. This justifies the need to investigate sustainable, lower-cost initiatives that can be delivered more holistically and remotely from the receptor settlement. Natural Flood-Risk Management (NFM) is an area of great interest that has had several comprehensive reviews and a Defra release of £15 million in flood and coastal erosion risk management research and development funding. The aim of NFM is to work with natural hydrological processes and restore the natural water holding capacity of catchments. Currently, there is a lack of evidence on the benefits of this approach and whether or not they can be delivered efficiently to the same standard of protection for the same design life.
This research thesis used two complementary approaches to assessing NFM potential: (1) rapid connectivity risk mapping assessment (SCIMAP-Flood); and (2) detailed, physically based, fully spatially distributed simulation of catchment hydrology (CRUM3). These methods have been combined to provide a powerful toolkit to effectively target mitigation of flood risk and to simulate potential impact on flood peak through a variety of NFM interventions. These methods were applied to the study area (Tutta Beck), a 7.06km2 agricultural catchment that flooded twice in 2012.
A variety of flood mitigation strategies were investigated in the Tutta Beck catchment, including spatially distributed land cover change to intercept and resist overland flow, woody debris dams to slow the flow of water through the channel network and spatially targeted depressions to attenuate overland flow. It was established for this catchment that the most effective technique for reducing peak discharge was the use of in channel large woody debris spatially targeted using SCIMAP-Flood, particularly when combined with spatially distributed attenuation.