Comparison between hard-engineered and nature-based solutions for flood risk management: A case study of Bin Brook

Flood risk management systems have traditionally relied on hard-engineered measures to improve conveyance and local hydraulic capacity, while nature-based solutions that slow, store, or desynchronise flows are increasingly being promoted for their capabilities in adapting to changing climate conditions and wider environmental benefits. However, the comparative effectiveness of these approaches and the extent to which they can complement one another as an integrated approach remains to be explored further and better characterised. This study evaluates and compares hard-engineered, nature-based solutions (NbS), and their integration for flood risk management using a one-dimensional unsteady flow hydraulic model of the Bin Brook catchment in the UK, where recurrent property flooding is driven by an undersized culvert. Modelled results show that hard-engineered scenarios are most effective in lowering water surface elevations, whereas NbS produce greater delays in peak flow arrival times and desynchronise runoff from rural upstream sub-catchments. When combined, these approaches produce complementary effects and achieve greater flood risk reduction than either approach could accomplish alone.