Leaky dams augment afforestation to mitigate catchment scale flooding

Abstract Despite calls for large‐scale afforestation to alleviate flooding, the effectiveness of such action remains unclear. Simulations with SHETRAN hydrological model are therefore carried out 335‐km 2 Irthing catchment and its 1‐10‐km headwater catchments in northwest England determine: (a) whether forests can reduce flood peak discharges a large catchment; (b) proportion that requires be effective; (c) extent which combination natural management features (leaky dams) improves upon on own. Four‐year simulations were run range forest covers extents leaky dam installation, latter modelled as channel hydraulic resistance. Hydrograph, frequency discharge magnitude responses cover simulated (and observed) replicated at full scale. Afforestation own given magnitudes but has variable impact individual magnitudes. For Irthing, 76% reduces mean 20 peaks partial duration series by 10% relative current 21% largest only 2.5%. Accompanying adverse effects include 17.5% reduction long‐term runoff loss agricultural land. By contrast, dams mitigate frequencies effectively, over magnitudes, no annual runoff. The installation required 22%. flow resistance increases have still translated into specific designs. Nevertheless, considering figures indicatively, 20% streams Strahler orders 1–3 achieves 35% 7.5% reduction. study illustrates potential dense network augment mitigation, especially discharges, while minimizing impacts water resources food security.