Pre-event failure analyses of Kestel dam for disaster management

Abstract

The present study [1] was undertaken for the State Hydraulics Works of Turkey (DSİ) within the framework of the program (TUR/94/006) for the Improvement of the Disaster Management of Turkey, executed by the General Directorate of Disaster Works under the Ministry of Constructions and Settlement. In this study, numerical failure simulations of Kestel dam were performed under different scenarios. Kestel dam is located on the Kestel creek near the Bergama County within the province of İzmir in the western part of Turkey. This location was selected as the pilot region by DSI for the present study, which may be used later as a basis within more comprehensive disaster management programs at a larger scale. The required data for the study were provided by DSI. Next, the numerical failure simulations were carried out under different scenarios. The numerical model employed in the present study was the one developed by Pread, D.L. at the National Weather Service, the U.S.A. and it is called the NWS DAMBREAK Model. In the simulations, it was assumed that a breaching started within the dam body soon after the maximum possible flood hydrograph entered the dam reservoir and caused the water to spill over the dam crest due to the insufficient capacity of the spillway. Other assumptions were made as to the formation characteristics of the breaching of the dam, such as the breaching shape, final breach width and breach formation time. For the worst scenario case the final breach width was taken as 190 m (about 3 times the dam height) and the failure time was assumed to be 30 minutes. The peak flood discharges, peak flood elevations and flood arrival times at preselected six cross-sections downstream of the dam were determined. The flood discharge hydrographs indicated that the regions affected adversely were those closest to the dam site. At the end, it was recommended that DSI establish a new department, namely, Department of Dam Safety at its headquarters in Ankara supported by auxiliary units to be set up in the regional directorates of the DSİ. The engineers working for this department should prepare emergency action plans (EAP) for a potential dam-break disaster in coordination with the local public authorities. The EAP's are outlined in detail in the present study.