Quantifying the reduction in flood risk using natural flood management measures

Natural Flood Management (NFM) measures are being implemented on the Littlestock Brook, a tributary of the River Evenlode in the Thames catchment, in order to reduce flood risk in the village of Milton-under-Wychwood. The measures include woody dams, riparian vegetation, hedges, field corner bunds, sedimentation ponds, off-line storage, woodland creation and combinations of these measures. In order to assess the effectiveness of the measures to reduce flood risk, hydraulic modelling of the catchment has been carried out in which the measures have been discretely represented within a 2D model. The modelling has been used to identify the effect of the measures on flooding for a range of flood frequencies and provides the opportunity for economic appraisal of the measures. The modelling has also been used to plan additional measures in order to further reduce flood risk and manage projected increases in flood flows due to climate change. The presentation will discuss the problems associated with this type of modelling, particularly the method for rainfall-runoff modelling. Early findings of research to upscale the results to the wider catchment will also be discussed