A coupled hydrological-hydrodynamic modelling approach for assessing the impacts of multiple natural flood management interventions on downstream flooding

This study used a coupled hydrological-hydrodynamic model to evaluate the effectiveness of multiple natural flood management interventions, including woodland planting, hedge planting, soil aeration, riparian buffer strips and leaky dams and their influence on flood peak delay, discharge reduction and inundation extents and depths for high flow events in a large-scale catchment (81.4 km2).

The coupling approach between SD-TOPMODEL and Flood Modeller 2D demonstrated a good fit and reliable performance for both peak discharge and timing simulations. The study also revealed that leaky dams are more effective in delaying flood peaks than in reducing peak discharge in the tributary catchments and their impacts at the larger catchment scale are similar to that provided by the combination of all NFM interventions. While NFM scenarios consistently showed positive flood mitigation impacts with reductions in peak discharge, inundation extent and depth, the maximum woodland scenario across the catchment unexpectedly increased inundation extent and depth due to the potential synchronisation of flood wave arrivals downstream and increased surface roughness on floodplains.