Hydraulics & Hydrology Fall 2023 Seminar Series
Hydrological Modelling for Flood Risk Assessment on the Indus River, Pakistan
Saeed Ur Rehman Aziz
Lyles School of Civil Engineering, Purdue University
Tuesday, September 19, 2023
Floods are destructive natural phenomena with profound socio-economic impacts, particularly in large river basins like the Indus River basin. This study focused on a 438-kilometer stretch of the Indus River, divided into two areas: Chashma to Taunsa and downstream of Taunsa to Kotmithon (238 and 194 kilometers, respectively). Utilizing the Hydrologic Engineering Center–River Analysis System (HEC–RAS v6.0.3) for 1D and 2D flood hydraulic modeling and floodplain mapping, the study-initiated risk assessment and emergency planning. GLO-30 with 30-meter resolution DEM was used for this study. Dem Verification was done by using Google Earth Image. To create river bathymetry, a physical survey and DEM extracted cross sections are used. Different statistical distributions were used for frequency analysis to find flood peak estimates for extreme events. KS, Chi, and Anderson tests were used to get the best distribution to create IDF curves with different return periods. A Flood Hydrograph was used as an unsteady inflow boundary condition, In the 1D model, optimized Manning's values for the river channel, left bank, and right bank closely matched statistical parameters, indicating close alignment between simulated and observed flood extents. Sentinal-2 Land Use Land Cover (LULC-2022) data set is used in 2D modeling for assigning "n" values. Calibration and validation of the HEC–RAS v6.0.3 model for the 2010 and 2006 floods demonstrated strong agreement with real-world events. The Nash and Sutcliffe coefficients were 0.94 and 0.95, the Correlation coefficients were 0.96 and 0.97 and the PBIAS was 1.55 and 1.13. The study compared flood extents predicted by the model with MODIS satellite images for the 2010 and 2006 floods, revealing significant alignment. Flood mitigation strategies were developed to safeguard the Indus River basin from rare 200-year floods, promoting proactive planning and resource allocation for community protection.
Saeed Ur Rehman Aziz is a visiting research scholar in Prof. Venkatesh Merwade’s group at the Lyles School of Civil Engineering at Purdue University. He holds an M.Sc in Irrigation and Drainage Engineering and is currently enrolled as Ph.D student at the University of Agriculture, Faisalabad, Pakistan. His research focuses on hydrological modeling, river bathymetry generation, and large-scale flood assessment framework.