Assessing the efficacy of hydro-ecological based wetland management approach for flood resilience of a large river catchment

Riverine flooding is a widespread global challenge and is predicted to worsen with climate change. Wetlands have been recognised as a potential nature-based solution (NbS) to riverine flooding, but are rapidly degrading globally, reducing their capacity to store water. Furthermore, in monsoon climates, natural wetlands can prove inadequate during peak flows, reaching their capacity early in the monsoon season. Management and rejuvenation of these wetlands provides a potential method to overcome the limitations and ensure the efficacy of wetlands as nature-based solutions for flood risk reduction. In this study, a hydro-ecological based management approach is adopted that formulates a storage release policy by considering threshold precipitation and wetland ecological requirements for assessing the flood resilience of both existing and rejuvenated wetlands. The approach is applied over a large river catchment, the Brahmaputra River, to explore the efficiency of the proposed release policy under different wetland rejuvenation scenarios and to assess the influence of wetland location on flood risk reduction. Additionally, the influence of rainfall distribution and the number of wetlands present in different zones of the catchment, and their operationality on streamflow response is analysed. The proposed wetland management approach showed peak streamflow reduction at the catchment outlet of 1–2 % for existing wetlands and up to 8 % for maximum rejuvenation of wetlands. At the sub-catchment scale, one of the major tributaries observed streamflow reductions of ∼ 6 % in the existing scenario and ∼ 30 % in the rejuvenation scenario. The occurrence of flood threat level events at prominent cities was reduced up to 60 % with wetland rejuvenation. The findings of this study demonstrate the potential impact of wetlands as NbS and provide guidance to help develop strategies for sustainable catchment-scale wetland management practices to enhance flood resilience.