NUMERICAL INVESTIGATION OF 2D DAM-BREAK FAILURES BY USING GIS APPLICATIONS

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2021-7-12
Ashraf, Ammar
In this study, the dam-break analysis of Ondokuz Mayıs Dam, İhsaniye Dam, and Avcıdere Dam is performed using full momentum HEC-RAS and dynamic wave FLO-2D model. The breach hydrograph for each dam was obtained by modeling the reservoir with dynamic wave routing in HEC-RAS. Three breach hydrographs (S1, S2, and S3) were calculated for each dam using a different set of breach parameters. The breach hydrographs were routed over the floodplain using both HEC-RAS and FLO-2D models. For Ondokuz Mayıs Dam, an accuracy check is performed for elevation data by comparing the Land Registry (Tapu Kadastro) and DSI data, and a new Digital Elevation Model (DEM) is developed using both datasets which is used in flood modeling later. Model calibration is done for Ondokuz Mayıs Dam; by using the flow depth of 2.735 m observed in the Engiz Creek in the year 2010. The calibration was done by varying the roughness values using the trial-and-error method. The calibrated model is then used for the breach hydrograph routing simulations. For Ihsaniye Dam and Avcıdere Dam, roughness values were selected based on the land use Google Earth images. The results of the routing analysis are presented in terms of inundation maps of maximum flow depth, maximum velocity and arrival time of maximum depth. For each dam, comparison of flow depth is presented at selected sections in populated areas. Moreover, the effect of sensitivity of grid resolution, roughness values, and breach hydrograph on the results are also presented. Flood hazard maps are prepared for each breach hydrograph to identify the risk-prone areas in the three dam sites. It was observed that in case of Ondokuz Mayıs Dam breach, Ondokuz Mayıs District will be at high hazard level, for İhsaniye Dam breach, Yalakdere Town will be at a high hazard level, and for Avcıdere Dam breach, Yalakdere town and southern part of Avcıköy town will be at a high hazard level. Flood damages caused by dam breach were also calculated in terms of losses to buildings and agriculture for the relevant areas. From the dam breach modeling results, it was concluded that there is a need to develop emergency action plans for the relevant areas, and the population in the affected areas should be educated about it, so that loss of lives and property can be avoided.

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Citation Formats
A. Ashraf, “NUMERICAL INVESTIGATION OF 2D DAM-BREAK FAILURES BY USING GIS APPLICATIONS,” Ph.D. - Doctoral Program, Middle East Technical University, 2021.