| Summary: | 碩士 === 國立成功大學 === 自然災害減災及管理國際碩士學位學程 === 104 === The heavy rainfall of Typhoons usually causes nationwide floods, in turn, yielding huge loss of human lives and economics. Taiwan is located in the zone where active tropical cyclone frequently forms in the western Pacific Ocean, so rainfall intensity is typically high yet with very short the concentration time of flow. The growth rate of the population has also increased rapidly in the urban area. The economic loss caused by flood disaster would be higher in the urban area compared to rural area. Therefore, to reduce the loss casing by flood is the main issue for disaster prevention policymakers. There are different measures in flood preventing. Building detention ponds is one of the common counter-measure to reduce the damage of flood, but most of them cost time, land and budget to construct. Fish ponds or fallow land are also known to be used as a temporary detention pond with relatively low cost.
In order to examine the economic benefit of using fish ponds as a temporary detention pond under different water depth remain in the fish ponds, this study uses the PHD model (Physiographic Drainage-Inundation Model) and the TLAS (Taiwan Typhoon Loss Assessment System) to simulate the property loss due to flood in different return period events. This study choose part of the Chia-Nan plain as an illustrative sample of an area that which is a flood potential area during typhoon and heavy rainfall events. The study area includes Zengwun River watershed and Yanshui River watershed. The study area is about 1,138 km^2.
The results indicate that with higher return period of the rainfall events, the more flood-containing space in the fish ponds is beneficial to reduce the economic loss. Under different return period of rainfall period, there will be a suitable amount of water should be adjusted before the events occur. Results also show that the benefit of pre-drainage operation in fish ponds decreases when the rainfall intensity increases. From the results, we can provide a reference for better prevention and mitigation operation before and during heavy rainfalls in the future.
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