Mathematical Modeling of the Effect of Meanders Removal on Changes in Erosion Rate: A Case Study in Karun River's Gangieh Meander

Abstract

One of the nonstructural methods of increasing aqueduct and decreasing flood balance in rivers is to create a shortcut to remove steeped arches. With regard to the dynamic system of river, any type of change in the stable structure of the river may lead to possible changes in the river morphology and creates new problems. In this study, after removing Ganjieh meander in downstream Ahvaz with the aim of organizing and increasing Karun River's aqueduct around Ahvaz city, hydraulic changes of flow and erosion and sediment level after removing meander were modeled using Hec-Ras4 mathematic model. This model was conducted in Karun River in an interval of 16 kilometers around Zargan – Farsiat for 25 years. Results of this research showed that, in the first 16 kilometers, in low to medium discharges of Karun in upstream meander, the water surface balance was high and decreases over time and in high water, discharge does not change significantly over time. In downstream meanders, in medium to high water, discharges, after removing meander water level balance increase compared to conditions before remove. Overall, before and after removing meander, in 16 to 18 kilometer as well as 35 to 40 kilometers, the cumulative weight of erosion and or sedimentation has the maximum value and their density increases over time.