Recently, flood inundation due to dam/reservoir failure can be occurred everywhere by climate change. Most of irrigation reservoirs in Korea are aging facilities, that the undesirable accident such as overtopping, piping can frequently occurred. In addition, it is expected to increase these disasters due to the rapidly changing weather and heavy rainfall over the past rainfall records. Reservoir failure tends to collapse abruptly, thus it will cause damage to residents, who cannot evacuate from dangerous area. The appropriate combination strategies of structural measures and non-structural measures are strongly needed to mitigate such kind of accidents. Structural measures is to strengthen the embankment and on the facility itself, including measures to increase the safety factor for the collapse of the reservoir through the maintenance. Non-structural measures include continuous monitoring for reservoir safety and education for the evacuation routes and shelters. Establishment of EAP(Emergency Action Plan) shows the one of the an effective response system.
This study analyzes the limitation of existing methodology used for establishing EAP of reservoir failure and supplements the methodology by suggesting two-dimensional model, which can provide the more sophisticated information such as flood depth, velocity and flooded area. When the inundation area of the downstream of dam is widely located, and many people can be situated at risk in the downstream of reservoir, one-dimensional numerical modeling cannot provide the detail information of inundation and it is difficult to consider the topography such as buildings and roads. To compensate for these problems, the new methodology suggested by performing an analysis of the reservoir failure applying the two-dimensional finite volume method based on HLLC and MUSCL methods.
Two-dimensional numerical models are applied for the flood simulation of Sandae reservoir in Gyeongju, which occurred, in 2013. The Cartesian mesh and unstructured mesh are used to consider the topography of study area. The predictions are verified by comparing with measured flooded area and depth. This study also includes a comparison of simulation results with a set of scenarios between finite differential model, FLO-2D, and finite volume model. As a result, two-dimensional numerical model revealed that it can be more applicable of establishing EAP because it can take into account a variety of factors including flood risk index and evacuation routes.
Accordingly, this study can contribute to not only calculate a more accurate inundation range for reservoir failure but also provide risk information by applying two-dimensional numerical model for establishment of EAP.