Abstract
Flood is a natural process generated by the interaction of various driving factors. Flood peak flows, flood frequency at different return periods, and potential driving forces are analyzed in this study. The peak flow of six gauging stations, with a catchment area ranging from 169 - 124,108 km2 and sufficient observed streamflow data, was selected to develop threshold (3rd quartile) magnitude and frequency (POTF) that occurred over ten years of records. Sixteen Potential climatic, watershed and human driving factors of floods in the study area were identified and analyzed with GIS, Pearson’s correlation, and Principal Correlation Analysis (PCA) to select the most influential factors. Eight of them (MAR, DA, BE, VS, sand, forest AGR, PD) are identified as the most significant variables in the flood formation of the basin. Moreover, mean annual rainfall (MAR), drainage area (DA), and lack of forest cover are explored as the principal driving factors for flood peak discharge in Wabi-Shebele River Basin. Finally, the study resulted in regression equations that helped plan and design different infrastructure works in the basin as ungauged catchment empirical equations to compute QMPF, Q5, Q10, Q50, and Q100 using influential climate, watershed, and human driving factors. The results of these empirical equations are also statistically accepted with a high significance correlation (R2 > 0.9).
Highlights
IntroductionNied et al [4] describe physical controlling factors of flood include: hydrological pre-conditions (e.g., soil saturation, snow cover), meteorological conditions (e.g., amount, intensity, and spatial and temporal distribution of precipitation), runoff generation processes as well as river routing (e.g., superposition of flood waves in the main river and its tributaries)
Mean annual rainfall (MAR), drainage area (DA), and lack of forest cover are explored as the principal driving factors for flood peak discharge in Wabi-Shebele River Basin
The analysis indicates that mean annual rainfall (MAR) has a strong relation with the flood indices (QMPF) and variables of both other factors, which push it to be one of the candidates for flood drivers in the basin
Summary
Nied et al [4] describe physical controlling factors of flood include: hydrological pre-conditions (e.g., soil saturation, snow cover), meteorological conditions (e.g., amount, intensity, and spatial and temporal distribution of precipitation), runoff generation processes as well as river routing (e.g., superposition of flood waves in the main river and its tributaries) These multidimensional causes of the flood made it less predictable and aggravated its impacts worldwide [5]. Climate is a critical driver on the fluvial flood hazard It is highly affected by various features of atmospheric systems, including water content of the atmosphere, different precipitation characteristics (intensity, duration, total amount, timing, or phase), the antecedent precipitation index (API), large-scale circulation patterns [7].
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