Flood mitigation analysis for abnormal flood

Abstract

Rainfall characteristics are changing due to climate change in Korea, as they are across the rest of the world. While the average annual rainfall is increasing, the number of rainy days is decreasing and that results in the increase of rainfall intensity. Because of the increase in rainfall intensity, the frequency of abnormal rainfall and floods is also increasing and can lead to extensive damage. It is necessary to establish reasonable alternatives to mitigate flood damage. In order to establish suitable disaster mitigation alternatives to overcome abnormal flooding, the following methods are used. Firstly, a test basin which has a big city in downstream vulnerable to flood damage is selected. Secondly, flood vulnerability is evaluated by a variety of scenarios and flood mitigation alternatives. Finally, the goal is to find out the best flood mitigation alternative that can protect the city located downstream. Since the Namhangang River basin selected for the test basin has only one reservoir, Chungju Reservoir, the flood control capability is relatively small considering the basin area. Therefore, in the case of flood occurrence which exceeds the flood control capacity of Chungju Reservoir, Yeoju which is located downstream of Chungju Reservoir, may have flood damage. In July of 2006, the flood was close to the design flood that actually occurred in Yeoju. The July of 2006 flood event is first analyzed, and the rainfall which is 1.2, 1.3, 1.4, 1.5 times greater than the actual rainfall is generated and analyzed for the safety of Yeoju. On the basis of the analyzed flood vulnerability of Chungju Reservoir, five alternatives are considered to reduce the flood damage in Yeoju. As a result, the alternative of constructing a new reservoir is found to be the most efficient alternative to mitigate the flood damage in Yeoju. © 2010 WIT Press.