Abstract
The development with filling method might increase the flood risk and damage in the surrounding areas, especially in low-lying areas. The objective of this study was to develop a methodology to assess the damage of flood risk transfer effect on surrounding areas. We studied a development located in Tainan, Taiwan and applied a SOBEK model to analyze the transfer effect of flood risk, and calculated the amount of loss in the surrounding land. After land development, the risk of flooding in the development zone declined. However, the risk of flooding in the southern area of the development zone increased. The development of land changed the original decentralized drainage system to centralized drainage system. The peak outflow discharge of surface runoff increased so much that it was more than the flow capacity of the downstream channel. This resulted in transferring the flood risk to the surrounding areas. Direct losses due to floods for industrial, commercial, residential, and agricultural lands as well as public facilities were calculated by the flood damage curves. Indirect losses were estimated using the industry-related model. The expected annual damages before and after land development in the southern area of the development zone were NT$ 6.38 million and NT$ 7.39 million, showing that the expected annual damage was increased by NT$ 1.01 million after land development.
Highlights
Many researchers have studied the relationship between the urbanization in the watershed and the hydrological regime in the river
Because the elevation in the development zone was raised by adopting a filling method, and a complete drainage system and a detention basin were built in the development zone, flood risk in the southern area of the development zone increased
The methodology developed in this study can assess the damage of flood risk transfer effect on surrounding areas arising from land development
Summary
Many researchers have studied the relationship between the urbanization in the watershed and the hydrological regime in the river. In the process of urbanization, human interference in the natural hydrological cycle often increases the proportion of surface impermeable area and, as a result, there has been a decrease in the amount of infiltration and an increase in the amount of surface runoff [1,2,3]. The flood risk downstream increases due to the urbanization in the watershed [8]. Du et al indicated that the land-use changes in the Pearl River Delta (PRD), China, has markedly increased direct runoff over the past 20 years. Urbanization in PRD increased the area of impervious surfaces in the central plain, and displaced farmland to the hilly peripheral areas [9]
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