Modelling future flood events under climate change scenarios in the Pungwe River Basin

Abstract

This study sought to project future changes in hydroclimatic variables and to establish how climate change affects flood inundation extent in the Pungwe River Basin. Climate ensembles of 10 Regional Climate Models from the CORDEX project were selected. The historical rainfall and temperature time series and the downscaled climate data were input into the HBV model to generate streamflow for the 2022–2099 period. Flood extents for 50-, 100-and 1,000-year return periods were predicted using the HEC-RAS hydraulic model. By 2070, annual rainfall at all nine studied meteorological stations is predicted to reduce by a maximum of 61%. Temperature is expected to increase up to 1.5% over the same period. By the 2070s, simulations from HBV revealed that the peak flows for the Pungwe River Basin will increase by up to 100% and decrease by approximately 57% as projected by the model ensemble. The analyses also show that by 2070 climate change may cause a minimum of 2,784.4 km2 and a maximum of 8,235.6 km2 of flood extension. These results are essential for decision-making on flood hazard mapping and early warning systems, prompting a pathway for sustainable development. HIGHLIGHTS Satellite rainfall estimates, RCMs, hydrological, and hydraulic models for flood inundation extent mapping.; By 2070, the future projections show increasing temperature and decreasing rainfall.; Climate change will, however, increase peak flows and inundation extent by the 2070s.; Significantly affected places in the Pungwe River Basin include cropland, built-up areas, roads, schools, hospitals, and business infrastructure.;

Keywords

• inundation extent
• regional circulation models
• return period
• streamflow simulation
• flood mapping