Abstract:Climate change contributes to enhanced flood damage that has been increasing for the last several decades. Understanding climate uncertainties improves adaptation strategies used for investment in flood control facilities. This paper proposes an investment decision framework for one flood zone to cope with future severe climate impacts. This framework can help policy-makers investigate the cost of future damage and conduct an economic assessment using real options under future climate change scenarios. The proposed methodology provides local municipalities with an adaptation strategy for flood control facilities in a flood zone. Using the proposed framework, the flood prevention facilities in the Nakdong River Basin of South Korea was selected as a case study site to analyze the economic assessment of the investments for flood control facilities. Using representative concentration pathway (RCP) climate scenarios, the cost of future flood damage to 23 local municipalities was calculated, and investment strategies for adaptation were analyzed. The project option value was determined by executing an option to invest in an expansion that would adapt to floods under climate change. The results of the case study showed that the proposed flood facilities are economically feasible under both scenarios used. The framework is anticipated to present guidance for establishing investment strategies for flood control facilities of a flood zone in multiple municipalities' settings.

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In recent years, sudden and local downpours in Korea have become more frequent. These rainfall patterns increase load on drainage system and reduce ability to exclude inland water, leading to flooding. If such rainfall patterns lead to flash floods especially in dense urban areas, sudden submergence of underground spaces by floods can be a fatal threat to life. Therefore, it is very important to secure evacuation routes in case of inundated underground spaces. In this study, we tried to determine evacuation safety by understanding hydraulic characteristics of inundated stairs that could become evacuation routes in underground spaces. For this purpose, water depth and volume flow rate were measured at each point of inundated stairs, and data obtained from results were used to evaluate evacuation safety at each step.

Hahoe, a historical village, is famous for two large nonvegetated sandbars. These sandbars have become covered with vegetation after construction of the two upstream dams. To identify the contributing factors to vegetation recruitment, flow regime, soil moisture, flood intensity and climate conditions before and after two dams were investigated. The occurrence of drought caused flow change and significant encroachment of riparian vegetation in just 3 years after the second dam was in place. Numerical results show that the dimensionless shear stress was a useful factor for predicting vegetation recruitment. Decrease in peak flows and aggradation of the sandbars resulted in more of the sandbar area experiencing low shear stress, hence facilitating vegetation colonization. In conclusion, the development of optimal dam operation rule to increase the difference of peak release flows between germination and flood season may be required to manage the riparian vegetation sustainably and economically in the regulated river.