| Summary: | 碩士 === 逢甲大學 === 水利工程與資源保育學系 === 107 === Due to the imperviousness area increases rapidly because of rapid urban development in the recent several decades and extreme rainfall events occur frequently, the original flooding-control structures will be unable to meet the actual flooding events. The Water Resources Agency and the Soil and Water Conservation Bureau are looking for locations where flooding can be saved and converted into flood storage and detention. This study proposes the search methods and the evaluation forms of potential farmland areas by using Geographic Information System software and field investigation. The research also proposes the usable priority of 30 potential farmland areas with the areas over 6000 m2 by field investigation. The research searches the potential concave terrain by using ArcGIS hydrology module and 5m Digital Elevation Model. The study area is the Dali river watershed in Taichung City. There are 12,033 potential concave terrain locations with the elevation over 100 m based on the calculation result from hydrology module. The maximum area of the 12,033 potential concave terrain locations is around 2.5 ha. The account of potential concave terrain locations with the area over 100 m2 is around 2,963. The research selects 31 potential concave terrain locations with the area over 6000 m2 to proceed field investigation. The research sets three steps to assess whether the potential concave terrain locations can be the usable farmlands. The first step is the analysis before the field investigation, including the location, area, land use type of the potential concave terrain and assess whether the potential concave terrain locations located in the flooding susceptibility area. The second step is field investigation, including the depth measurement of the concave terrain location and the investigation of waterways, water-stored and hydrology-related engineering. The third step is the assessment of potential development susceptibility in the future, including the investigation of land use type in the neighborhood, the need of water resource, and a brief description of this potential concave terrain location. The score of each assessment or investigation in the above-mentioned steps ranges 1 to 5, and the research sums the score of each assessment or investigation and ranks the score summation as the usable priority of the potential concave terrain locations. There are 20 potential concave terrain locations which can be usable in the future based on the field investigation on 31 potential concave terrain locations with area over 6000 m2. If the 20 potential concave terrain locations are transferred to farmlands in the future, the water storage volume of the 20 potential concave terrain locations is estimated as 369,875 m3.
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