Distorted Physical Model to Study Sudden Partial Dam Break Flows in an Urban Area

A distorted physical model, based on Urkmez Dam in Izmir, Turkey, was built to study sudden partial dam break flows. The distorted model had a horizontal scale of 1/150 and a vertical scale of 1/30, containing dam reservoir, dam body, and downstream area-from dam body to Urkmez urban area until the sea coast. In the model, the reservoir is approximately 12 m(3), the dam body has a width of 2.84 m and a height of 1.07 m, and the downstream area is nearly 200 m(2). The Urkmez Dam was chosen because Urkmez Town is located right at its downstream area, allowing the study of dam break flows in an urban area. Furthermore, the dimensions were suitable such that it allowed the construction of a physical model (dam reservoir, dam body, and downstream area) having a horizontal scale of 1/150 in the available space of 300 m(2). The features creating roughness such as buildings, bridge, and roads were also reflected in the physical model. The dam break flow was investigated for sudden partial collapse, which was simulated by a trapezoidal breach on the dam body. The water depths at downstream area were measured at eight different locations by using e+ WATER L (level) sensors. The velocities were measured at four different locations by ultrasonic velocity profiler (UVP) transducers. The propagation of the flood was recorded by a high-defnition camera. The experimental results show that the Urkmez area can be flooded in a matter of minutes, at depths reaching up to 3 m in residential areas in 4 min. The flood wave front can reach the residential areas in 2 min and to the sea coast in 4 min. Flow velocities can reach 70.9 km/h in sparse residential areas, close to dam body. Away from the dam body in the sparse buildings part of the town, the velocities can reach 27.7 km/h. In dense residential areas of the town, the velocities are too low (2.8 km/h) but flow depths can reach 3 m. Velocity profiles show similar behavior like unsteady and nonuniform open channel flow in nonresidential areas close to the dam body. In residential areas away from the dam body, the velocity profiles are more uniform, having lower velocity values. Vertical variations of velocities show markedly different behavior during rising and recession stages. The profiles are smooth during the rising stage in sparse residential area, yet it shows fluctuating behavior during the recession stage. (C) 2014 American Society of Civil Engineers.