Abstract
This study aims to monitor the flash flood response of Vidor/Wadore hill torrent in Pakistan by the integration of Personal Computer Storm Water Management Model PCSWMM (hydrologic) and HEC-RAS 5.x (hydraulic) models. The method leverages remote sensing and GIS derive estimates of measured and inferred parameters of Vidor rural catchment to quantify the flash flood events of the last four years: 2014–2017. The calibration of the PCSWMM is performed using the sensitivity-based radio tuning calibration (SRTC) tool. The Nash–Sutcliffe efficiency (NSE), coefficient of determination (R2), and relative error (RE) values were found between 0.75–0.97, 0.94–0.98, and −0.22–−0.09 respectively. The statistical indicators prove the accuracy of PCSWMM for rural catchments. The runoff response of Vidor torrent is also analyzed for 0.5/12.7, 1.5/38.1, and 2.0/50.8-inch/mm rainfall hyetographs. The generated hydrographs are used to simulate 2D-module in HEC-RAS 5.x for floodplain demarcation in the piedmont area. The accuracy of the flood extent is analyzed using spatial overlay analogy in the ArcGIS environment by comparing simulated and historically available flood extents. The simulated flood extent shows 76% accuracy with historic flood extent. The impact of flash flood events shows wheat, maize, and fruit orchards are the most effected agriculture in piedmont area. The results revealed that the integration of hydrological, hydraulic, and geospatial modeling approaches can be used to model a full picture of catchment response during flash flood events.
Highlights
Flash floods are considered one of the most disastrous natural hazards because of their sudden and severe impact [1]
The generated hydrographs were tested for piedmont plain to analyze the simulated flood extents and depth distributions using 2D hydraulic modeling domain of HEC-RAS 5.x
The integrated approach of hydrological, 2D-hydraulic modeling, and GIS-RS approach is used to identify the potential disaster of Vidor torrent
Summary
Flash floods are considered one of the most disastrous natural hazards because of their sudden and severe impact [1]. Intense rainfall on steep slopes of hill torrents engenders flash flooding with a short lag time that causes an unbearable economic loss. Human intrusion and variability in climate have modified the prevailing natural conditions and rainfall-runoff processes in mountainous catchments, ensuing an increase in the frequency of flash flood events. The rainfall-runoff behavior in steep mountainous catchment is a complex process solely depends upon the physical parameters (shape, size, type of stream, etc.) of catchment [9]. Among the different methods (Green Ampt, Hortons, Holton, etc.), Soil Conservation Service Curve Number (SCS-CN) has proven to be an enduring technique to quantify the flash flood discharge volumes in catchments [9,16]
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