Experimental Investigation of the Partial Vegetation Effect on the Flood Wave Propagation Resulted from Dam Failure in Urkmez Residential Area by means of Distorted Physical Model

Abstract

The purpose of this study is to investigate the effect of partial vegetation on the wave propagation resulted from sudden dam failure in a residential area. Temporal variations of water depths and flood wave propagation velocities were determined and compared with those obtained from the experiments performed without vegetation. The experiments were performed on the distorted physical model of Urkmez Dam and its downstream region. The distorted physical model with horizontal scale of 1/150 and vertical scale of 1/30 contains the dam reservoir, the dam body, the residential area of Urkmez coastal town until the sea and the partial vegetation. In the model, the reservoir has an active volume of 11.222 m3, the dam body has a length of 2.84 m and a height of 1.07 m, and the downstream area is nearly 200 m2. Water depths were measured by e+ WATER L level sensors placed at various locations of the downstream region. Velocities were measured by ultrasonic velocity profilers (UVP) located near the level sensors. Flood wave propagation was recorded by the high definition digital camera. Experimental findings obtained from the physical model were converted to the prototype values, in nature. The changes in water depths and elapsed times, also the changes in velocities and their occurrence times were determined for different zones of the downstream area in the presence of vegetation. The experimental results revealed that in such a dam failure, the flood arrives at the sea in 6 s in the absence of vegetation, while in 10 s in the presence of vegetation. These values correspond to 2.74 min and 4.57 min, respectively in the prototype. The existence of vegetation resulted in decrease in flood propagation velocities mainly in the dense residential area, as expected. It was observed that the maximum water depths were increased at the left bank and decreased at the right bank, except at level sensor S6 which is very close to the creek. It was observed that the maximum depth averaged velocities were decreased in the sparse and dense residential areas. The existence of the vegetation changed considerably the local velocities during rising and recession stages of the water depth. It was found that the order of magnitude of the prototype velocities was high and such velocities can cause serious damage mainly in the buildings close to the dam body. Because the presence of vegetation caused a decrease in flood propagation velocities in the sparse and dense residential areas, it would reduce the damages on the buildings in these areas.