Abstract
Levee breaches are some of the most common hazards in the world and cause the loss of lives, livelihoods, and property destruction. During the 2010 flood in Pakistan, the most devastating breach occurred at Tori Levee on the right bank of the Indus River, downstream of the Guddu Barrage, which caused residual floods in northern Sindh and the adjoining regions of the Balochistan province. In this study, 2D unsteady flow modeling performed for Tori Levee breach computed residual flood inundation by coupling a HEC-RAS (Hydrological Engineering Centre—River Analysis System) 2D hydraulic model with remote sensing and Geographic Information System techniques. The model performance was judged by comparing the observed and simulated water levels (stage) during peak flow at seven different gauging stations located within the Indus River reach and daily flood extents and multi-day composites. The quantitative values for the calibration and validation of the HEC-RAS model showed good performance with a range of difference from 0.13 to −0.54 m between the simulated and observed water levels (stage), 84% match for the maximum flood inundation area, and 73.2% for the measure of fit. The overall averages of these values for the daily flood comparison were 57.12 and 75%, respectively. Furthermore, the simulated maximum flow passed through the Tori Levee breach, which was found to be 4994.47 cumecs (about 15% of peak flow) with a head water stage of 71.56 m. By using the simulated flows through the Tori Levee breach, the flood risk maps for the 2010 flood identified hazard zones according to the flood characteristics (depth, velocity, depth times velocity, arrival time, and duration). All the flood risk maps concluded the fact that the active flood plain was uninhabitable under flood conditions.
Highlights
Floods are among the most common natural disasters around the world, claiming a substantial loss of life and property in the vicinity of rivers
The sensitivity of the model for ALOS, ASTER and SRTM was evaluated for maximum depth (m), velocity (m/s) and flood extent
The results showed that the HEC-RAS model performed fairly well to simulate water levels during peak floods in comparison to the observed
Summary
Floods are among the most common natural disasters around the world, claiming a substantial loss of life and property in the vicinity of rivers. Pakistan is one of the most vulnerable countries in the world in terms of exposure to different natural calamities [3]. Global Climate Risk Index (CRI) 1991–2011, Pakistan ranked as the eight most disasterprone country in the world; after the 2010 floods, Pakistan ranked at the top of the list of countries most affected by weather-related disasters [4]. Flood Forecasting Commission [5] classifies floods as low (river flowing within deep channel), medium (partly inundating river), high (river almost fully submerging and flowing up to high banks/levees), very high (river flowing between high banks/bunds with encroachment on the freeboard) and exceptionally very high flood (imminent danger of overtopping/breaching). For the Indus River, low flood discharge ranges from 7000 to
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