Document Type : Research Paper
School of Civil Engineering, College of Engineering, University of Tehran, Tehran, Iran.
There have been many dam removals around the world in recent decades due to safety issues, reservoir volume loss, and other factors. Sediments are deposited in dam reservoirs after years of operation, and sediment transfer downstream following dam removal requires further investigation. The aim of this research is to analyze and predict the effects of removing the dam on sediment transport, especially fine sediment transport on steep slopes. A case study of the Zonouz Dam in East Azerbaijan Province is used to demonstrate this. Sediment transport is predicted using a one-dimensional numerical model called DREAM1. Three sediment transport equations were considered for this grain size and slope to choose the most appropriate one. These equations include Brownlie, Smart and Rickenmann. Next, their results were collected for 350 laboratory experiments with conditions similar to modeling and the results were compared with each other. The calculations revealed a lower error in the Brownlie equation results. Sediment transport following the removal of the Zonouz Dam was modeled numerically for wet, dry, average, and recorded discharges. Based on the modeling results, erosion rates were high in the early years but decreased over time. Moreover, the dispersion mechanism is dominant over translation in the evolution of the pulse, resulting in sediments being transported downstream up to 11 kilometers. According to the results, approximately 82% of the sediments will be eroded after seven years under the hydrological conditions present at the Zonouz Dam.