Integrated assessment of the impacts of climate and land-use changes on future flooding and effective adaptation in the Gin River Basin, Sri Lanka

Abstract

Study regionGin River Basin, Sri Lanka. Study focusThe individual and combined effects of climate and land-use changes on flood flow and inundation in the Gin River basin, Sri Lanka, were assessed. Downscaled, bias-corrected future precipitation projected by an ensemble of general circulation models (GCMs) under the Representative Concentration Pathway (RCP) 4.5 emissions scenario was input into a flood model developed using the Rainfall Runoff Inundation (RRI) model. Possible flood mitigation measures were identified based on flood simulations through the integrated assessment incorporating future climate and land-use projections. New hydrological insights for the regionThe basin is projected to receive increased rainfall during the southwest monsoon (9.7 %) and second inter-monsoon (15.7 %) seasons, excluding March and April, in the future. Human settlements will expand in the downstream areas of the basin, while a significant share of agricultural land (27 %) in the basin will be converted into shrublands by 2050. High flows are predicted to increase by 16 % and 4 % at the upstream and downstream gauging stations, respectively, while mean river flow is expected to decrease by 25 % (upstream) and 34 % (downstream). In addition, a 3.5 % increase in annual maximum inundation extent is projected. However, the total inundation extent in the basin can be reduced by 1.3 % by regulating land-use changes, particularly the conversion of agricultural land into riparian forests.