Document Type : Special Issue: New Approaches to Water and Soil Management and Modeling
Authors
1
Ph.D. student of Watershed Management Sciences and Engineering, Department of Range and Watershed Management, Faculty of Natural Resources, Urmia University, Urmia, Iran
2
Associate Professor, Department of Range and Watershed Management, Faculty of Natural Resources, Urmia University, Urmia, Iran
Abstract
Cross-sectional geometry has a fundamental impact on the hydraulic behavior of the Shatt al-Arab River, an important waterway providing the water life supply to almost 4.5 million people in Basra City, southern Iraq. Using 200 cross sections at 1-km spacing through a 200-km hydrodynamic modeling framework that is employed in HEC-RAS, the analysis combines Sentinel-2 and Landsat-9 satellite imagery, 30-m DEM datasets, and in situ discharge measurements to quantify the impact of channel width on flow velocity, tidal intrusion, and sediment dynamics. Here, we find an inverse relationship between channel width and flow velocity (R² = 0.92). In this way, expansion of 150 to 350 m of channel increases discharge capacity by 125% but at the same time, flow velocity decreases by 57%, increasing tidal penetration by half while increasing the sediment deposition by 50%. In contrast, channel narrowing results in high water levels with a rise in flood risk of up to 1.8 m. An optimal width range of 280–300 m is determined which provides a balanced hydraulic performance in terms of discharge capacity, approximately 5,900 m³/s capacity, seawater intrusion by ~25 km, and sediment build-up by nearly 35% as opposed to the wide channel segments. The results suggest that this width of channel should be considered an optimal width range for river rehabilitation and management, with dredging of high-sedimentation reaches (100–150 km; >12 cm/year) be in the priority mode. The continued and real-time hydrological monitoring application is further recommended in order to assure sustainable water security, with long-term river operation.
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