STATISTICAL ANALYSIS FOR FLOOD HAZARD ASSESSMENT UNDER CLIMATE CHANGE IN THE NIGER RIVER BASIN: CASE STUDY OF MEKROU RIVER SUB-BASIN (BENIN)
GBAGUIDI, Sewanou Juferlin
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ABSTRACT Literally, West Africa has experienced climate change and variability in terms of frequency, intensity, and persistence of extreme changes, such as floods and droughts as well. The occurrence of rainfall deficits and excess has meaningfully increased in recent years. Yet, these events have had serious impacts on the environment, economy and human lives. Niger River basin also experienced some negative effects of climate change. However, there is lack of knowledge on flood hazard potential in the basin and mostly in its sub-basins. The main objective of this study was to assess the flood hazard occurrence under climate change in the Mekrou basin. Daily rainfall and stream flow data recorded over a 30-year period, 30-meter grid of digital elevation model (DEM) dataset, land use/land cover datasets to create curve number (CN) values of the river catchment were used for hydrological modelling using ArcGIS. The SCS Curve Number method was used to perform Loss model, then SCS Unit Hydrograph for Transform model and Lag method for Routing model to compute the input basin and river reach parameter values for each sub-basin, for instance initial abstraction, curve number, imperviousness and lag time for both basin and river reach, in HEC-HMS to compute a 5-year, 10-year, 20-year, 30-year, 50-year and 100-year flood for the entire catchment. The result reveals an increase in future quantile change compared to the historical quantiles. The change ranges between 9.09% and 57.29% for the period (2026-2055) and 21.12% to 75% for 2070-2099. Therefore, it is clearly indicated that flood frequency will increase in the middle and by the end of 21st century due to the climate change, in the Mekrou River basin. It has been noticed that when the return period increase, the discharge quantiles increase too. That’s mean higher discharge will be recorded by 2100 compared to 2050 as well as the historical period (1983-2005) based on the result of the study.
- Nexus: Water-Climate