| Summary: | 碩士 === 國立臺灣大學 === 生物環境系統工程學研究所 === 106 === With the development of the social economy, the building and impervious paving in urban are dramatically increased. However, in recent years short duration rain and typhoon events frequently occur in urban area, which rainfall is more than the drainage capacity of storm sewer systems. Therefore, flooding in urban areas has been occurring more and brings damage to the public and the economy on various aspect. In order to reduce losses, the government has stipulated that the entrance and exit of the building must sets floodgates. Because the size and position of buildings’ gateways are different, we must set the specific size of floodgates for buildings’ gateways. Therefore, we use the idea which street as a short drain system, we can set floodgates at the edge of street to reduce losses.
The study explores that floodgates effects on the improvement of drainage and inundation in urban areas. Therefore, the study selected two floodgates set modes, which are full set mode and partial set mode and three floodgates set heights, which are 60, 90, 120 centimeters. Two floodgates set modes and three floodgates heights combined into six kinds of floodgates set strategy. Six floodgates set strategies and return periods rainfalls are inputted into flood model to simulate. Next, annual loss, annual benefit of the strategies were calculated by flooding loss and probability of excess. Finally, we used the annual average loss, annual average benefit and benefit ratio to evaluate what kind of set strategies is the best economic feasibility of set strategy in the study area.
In the study, Muzha drainage basin in Wenshan District, Taipei, is selected as the study area. In same height, the annual average benefit of partial set mode is better. In same set mode, the annual average benefit of floodgates set height 120 centimeters is better. The result of benefit-cost ratio analysis is that the partial set mode with set height 90 centimeters means the best economic feasibility of set strategy, and the full set mode with any set height is not economic feasibility.
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