Search Results (2)

After the breach of a landslide dam, the sediment in the breach opening will be carried downstream by the breach flood. The river channel will also be eroded by the flood, resulting in bed load transport. Three large-scale dam breach tests were conducted to investigate the sediment transport behavior after a dam breach. The topography data of the creek channel were measured before and after the dam breach tests to understand the sediment transport behavior. The sediment transport simulations of the dam breach tests were conducted using the iRIC Nays2DH software. The simulations focused on three types of test setups: the single dam, single dam with a spur dike, and double dam models. The terrain (DEM) for the numerical model input was designated based on the LiDAR results, and a flow hydrograph during the dam breach tests was applied. The accuracy of the simulations was assessed using the “coverage index” and “mean absolute percentage error”. A numerical parametrical study was performed to find the major parameters that influenced the simulations. The results showed that the dynamic behavior of water flow and sediment during the dam breach processes were effectively captured by the iRIC Nays2DH simulation, but with limitations. The average flow velocity of the flood in the single dam case was the fastest among the three types of dam breaches. Due to the contraction of the creek channel caused by the spur dike, severe erosion occurred locally, and the flow rate increased in the narrowed section. Water impoundment between the two dams after the first dam breach and the consequent breach of the second dam were also well-simulated for the double dam breach. The findings and simulations in this study help explain dam breaches better and can guide researchers working on sediment transport during dam-breach floods. Full article

This study investigated riverbank protection strategies along the dynamic Jamuna River in Bangladesh, a braided river prone to erosion and sedimentation. It reviews past countermeasures and emphasizes the effectiveness of groyne-type structures in redirecting flow and preventing erosion. Notably, the left bank exhibited greater stability than the right bank, emphasizing the need for effective groyne installations. A systematic methodology utilizing numerical modeling using International River Interface Cooperation (iRIC Nays2DH) ensured accuracy in assessing morphological impacts. This research presents novel countermeasures incorporating groyne installations along the right bank of the Jamuna River. Simulations are undertaken to assess the effectiveness of these measures under a range of flood scenarios, identifying a zone highly prone to erosion that exhibits the utmost vulnerability. The simulation scenarios comprised a base condition without groynes, two series of groynes separately placed in two selected zones, and a combined approach for both areas. Analysis of the four simulation cases, each encompassing three flood conditions, revealed that implementing two ‘I’-shaped perpendicular groynes in series within the erosion-prone area effectively diverted oblique flow. This approach proved optimal, mitigating erosion risk by redirecting flow and shaping sandbars along the Jamuna River’s riverbank. This study enhances Jamuna River protection, emphasizing groyne-type structures’ importance and promoting a holistic understanding of morphological dynamics for future river management and effective countermeasures. Full article