Assessing flood inundation mapping through estimated discharge using GIS and HEC-RAS model |
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| Authors: | Ernieza Suhana Mokhtar Biswajeet Pradhan Abd Halim Ghazali Helmi Zulhaidi Mohd Shafri |
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| Institution: | 1.Department of Civil Engineering, Faculty of Engineering, Geospatial Information Science Research Centre (GISRC),University Putra Malaysia,Serdang,Malaysia;2.Department of Surveying Science & Geomatics, Faculty of Architecture, Planning and Surveying,Universiti Teknologi MARA Perlis,Arau,Malaysia;3.Centre for Advanced Modelling and Geospatial Information Systems (CAMGIS), Faculty of Engineering and Information Technology,University of Technology Sydney,Sydney,Australia |
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| Abstract: | Water discharge is the main parameter in hydraulic modeling for flood hazard assessment. However, the unavailability of data on discharge and observed river morphologies resulted in erroneous calculations and irregularities in flood inundation mapping. The objectives of this study are (i) to investigate uncertainties of hydraulic parameters (width, cross-sectional depth, and channel slope) used in discharge equation and (ii) to examine the influence of estimate discharge on water extent and flood depth with different boundary conditions on interferometric synthetic aperture radar (IFSAR) and modified IFSAR DEMs. Sensitivity analysis was conducted with the Monte Carlo simulation method to generate random data combinations. Bjerklie’s equation was used to calculate discharge based on the three variables, and Manning’s n was substituted into the Hydrologic Engineering Center River Analysis System (HEC-RAS) model. TerraSAR-X was used to distinguish existing flood water bodies and normal water extent. The uncertainty of the combined variables was assessed with the likelihood measures such as F-statistic, mean absolute error, root mean square error, and Nash–Sutcliffe efficiency which compares observed and predicted inundated area as well as flood water depth simulated using the HEC-RAS model. |
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