Use and performance of timber bunds as a natural flood management (NFM) technique at local and catchment scales

Natural flood management (NFM) is a sustainable and increasingly popular approach for riverine flooding mitigation, often used in conjunction with traditional flood protection solutions. This investigation focuses on timber bunds, a relatively novel NFM technique. Timber bunds are designed large in-stream dams made of wood sourced on site. Having been installed in only two trial locations in the United Kingdom so far, there is still a limited understanding of their performance at local and catchment scales. In this study, the timber bunds effectiveness in reducing flood peak magnitude and delaying flood arrival, when deployed as individual assets or in a network, is quantified for rainfall events of different return periods. Modelling results indicate positive effects in reducing peak flows, with more favourable results for large return period events and when timber bunds are deployed individually at the sub-basin scale. When deployed in a network, benefits may decrease due to peak synchronisation and the larger runoff volumes. The remarkable cost-effectiveness of timber bunds adds to their potential for successful wider use.