Document Type : Research Paper
Department of Civil Engineering, Guilan University, Rasht, Iran
Department of Watershed Management Engineering, Faculty of Natural Resources, Sari Agricultural Science and Natural Resources University, Sari, Iran
School of the Built Environment, Heriot-Watt University, Edinburgh, UK
Department of Geography, Texas State University, San Marcos, Texas, USA
This study examines the relations of structures and shapes of streambed evolution after dam break floods. A flume was used to simulate dam-break floods with variations of initial upstream water levels and variance, from uniform to graded, of the bed sediments. Detailed measurements of the evolution and composition were made during these experiments. The data indicate that intense scour occurred immediately downstream of the “dam break” in both uniform and graded sediments. The resulting bed surfaces of graded sediments showed coarse-fine-coarse structures in the areas with the lowest scour and highest deposition and various type of cluster (i.e. line and heap). This pattern was not observed in beds of uniform sediment. The scour hole changes from circular to oval-shaped in both uniform and graded sediments with increasing bed slopes.
Keywords: Dam break, Experimental, Bed-surface composition, Graded and uniform sediment, Scour.