عنوان مقاله [English]
نویسندگان [English]چکیده [English]
Dams have many essential benefits to serve the increasing demand of human population in making world a better place for living. Dams are purposely built for irrigation, power generation, flood mitigation, water supply and even for recreation and fishing activities. However, substantially huge amount of water body stored behind the standing dam structure could seriously pose severe risks to many. Great level of energy stored in the impounded reservoir will cause unbearable impacts if it be released suddenly to the downstream area. Therefore, it is important to conduct a dam break study to determine the outflow resulted from break event.
The art of dam break modeling lies primarily in the prediction of the outflow hydrograph as a result of dam failure. This can be done via physical models and laboratory experiments and numerical modeling techniques. Physical models are not always financially viable therefore, the numerical modeling is often taken as a better alternative. Numerical modeling techniques estimate the outflow hydrograph via four methods;
physically based methods; parametric models; predictor equations and comparative analysis
This study has used the MIKE modeling software to simulate the dam break event, determine the outflow hydrograph to be routed to the downstream area, and to obtain the flood maps. Furthermore, animation tools available in MIKE software offer better appreciation of the dam break event, added with enhanced graphics of inundation maps to visualize the flood wave movement in variation of time and space.
In the present study, the simulation of the dam break in Golpayegan and Kucherei earth dams in Isfahan Province was investigated using MikeFlood software. The MikeFlood is a software that creates a relationship between the one-dimensional model Mike11 and two-dimensional model Mike21. The way it operates is when the Mike11 is activated at times before the flow section fills in the main river and conducts flood routing in the main waterway. As the discharge increases and the cross-section fills in the main river and the stream enters the floodplain, the Mike21 model is activated and begins to simulate a two-dimensional flow in the floodplain. Due to different boundary conditions, different scenarios occur, which need to be introduced into the model. In this research, there are three possible scenarios including: 1) break of the both Golpayegan and Kucherei dams due to the overpass; 2) the break of the Golpayegan dam due to the piping, and the Kucherei dam due to the overpass, 3) no break in the Golpayegan dam, and the Kucherei dam break due to the piping, have been tested and compared.
In the first scenario, 53 minutes after the Kucherei dam breakdown, the maximum flow rate of 118727 m3/s was perdicted. In the second scenario, the maximum flow rate of 110717 m3/s, 51 minutes after the Kucherei dam breakdown was perdicted, and in the third scenario, the maximum discharge of 50208 m3/s was perdicted, 43 minutes after the Kocherei dam breakdown. The flood alert time and zone division have also been compared in different scenarios. In the first scenario, the floodplain has more area and the advance rate was faster. In the third scenario, the flow rate was lower than the others. Also, the Alvand town will not be flooded due to its location in a higher area than Golpayegan city, and also, Saeed Abad industrial town will not be flooded. The alert, peak arrival and flood recession times in the sections increase and are directly related to the increase ofthe distance from the sections to the dam. The results showed that due to the dam breakdown in all three different scenarios, Alvand town and Saeed Abad industrial town, which are among the important areas below the dam will not be flooded.