Application of Hec-Ras Model to Analyze of Sediment Transport Dynamic Pre and Post Construction of Fall Structures at Lower Nara Canal Off-Taking From Upper Nara Canal, Sukkur Barrage, Indus River, Sindh, Pakistan

Abstract

This paper presents the research study using the HEC-RAS model to evaluate sediment dynamic problems in lower Nara canal pre and post-construction of fall structures at RD-77 and 101 respectively which is a major tributary of upper Nara canal that off-takes from Sukkur barrage on the left bank of Indus River. As a result, the hydraulic model has computed longitudinal and cross-section, velocity, water surface profiles, and sedimentation dynamics. Sediment transportation without fall structure is aggradation (5.75 ft and degradation (4.50 ft) and with fall structure aggradation (4.25 ft) and degradation (2.75 ft) respectively. Sediment transportation without fall structure is aggradation 500,000 tons and degradation 225,000 tons and with fall structure aggradation 155,000 tons and degradation 125,000 tons. Sediment transportation without fall structure is degradation 600,000 tons and with fall structure is aggradation 110,000 Tons and degradation 165,000 Tons. Sediment transportation without fall structure is aggradation 1,750,000 Tons and with fall structure is aggradation 1,300,000 Tons. Hence the results of the model revealed that aggradation at u/s and degradation at d/s of fall structures that is a true representation of the behavior of fall structures. Whereas, the section is wider than aggradation occurred and degradation is experienced in narrow sections in both scenarios (with and without fall structures). The positive impact of constructed fall structures was analyzed on the morphology of the canal. Hence, the construction of fall structures are essential at the change of country/steeper slope to avoid unnecessary erosion.