A study of screening the priority sites for water storage at Dadu terrace using environmental index

• Main Authors: Hsueh-Fen Tseng, 曾雪芬
• Other Authors: 林昭遠
• Format: Others
• Language: zh-TW
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/92499357560365444318

碩士 === 國立中興大學 === 水土保持學系所 === 103 === Dadu Terrace belongs to laterite with the characteristics of infiltration difficulty. Large-scale developments expand rapidly due to gentle slope at the top of the Terrace, and the increasing of impervious pavement causes large amount of surface runoff during the torrential rain. Under the condition of extreme rainfall event frequent occurrence, the Terrace is vulnerable to disasters of slope collapse and debris flow, and the downstream urban areas are easily suffering floods. Hence, it is important to find out the potential landslide and/or flood areas for the disaster prevention of the Terrace. Management units were delineated using the roads of Tai-No1, Tai-No1-2, County-125 and Taichung-77, and the vulnerability of each management unit can be estimated from the indices of extreme rainfall, road development and inverted Normalized Difference Vegetation. Landslide scale potential for the units can be extracted from the indices of soil depth and river concave. In addition, the curve number of pre- and/or post- development in a management unit can be evaluated using maps of land-use and soil, and then the hotspot units with the obvious difference in potential maximum retention could be filtered out. Finally, the depression storage sites extracted from the Digital Elevation Model in the hotspot units are recommended to propose the environmental creation strategies. Results show that southern terrace has the highest vulnerability because of having higher index value extreme rainfall and road development. The southern protection forest can be regarded as the areas with higher potential landslide. There are 7 hotspot sub-watersheds selected according to the changes of CN derived from land-use coverage. The hotspot sub-watershed, Cheng-gong hill, also locates on the southern terrace and is the highest changes of CN. In order to prevent landslide and flood due to excess runoff, the depression storage sites need to be filtered out from the hotspot sub-watershed for water resources conservation. The priority depression storage sites are strongly recommended to create the multipurpose ponds with the function of sedimentation and flood detention, landscape and leisure, microclimate adjusted, firefighting, irrigation and groundwater recharge.