| Summary: | 碩士 === 逢甲大學 === 水利工程與資源保育學系 === 102 === Due to the over development of urban area, the soil’s water permeability has been ignored for a long time, which leads to the increase of urban water impermeability area that prevents rain from entering the ground to supplement water for soil. This not only results in urban heat island effect but draining off underground water resources. If the drainage system could not let out the surface runoff caused by heavy rain a serious flood may therefore occurs.
Based on the Low Impact Development (LID) concept developed by the USA as well as European Green Infrastructure(GI), the facilities for storage, permeation and surface runoff reduction are required in order to relieve surface runoff, expand flood retention and permeating space in urban area and simultaneously to share urban surface runoff volume.
The geological structure of the Taichung Basin is mainly gravel stratum of which permeability is fine. However, the urban development has affected its good permeability; hence, in this research, it combines permeable pavement with vertical infiltration pipes into the parking lot in Feng Chia University and penetrated through the soil surface having poor permeability. Those are in order to facilitate vertical and side permeation, provide the water storage, as well as reduce surface runoff.
Refer to the current parking lot condition as the basis, by adding vertical infiltration pipes beneath the permeable pavement of the parking lot, the saturated conductivity of double-ring test could be increased 18~35 times. The experimental results show that the vertical infiltration pipes is applicable to be one LID component for increasing permeability with regard to Taichung basin’s geological condition.
The related parameters and field-test results collected from the study site (60m×15m) were utilized for simulation by Storm Water Management Model (SWMM). Firstly, all simulation situations were based on current conditions. For the conditions changed to the parking lot built with water impermeable pavement, the surface runoff volume would increase 15% and the peak discharge would increase 10%; If the pavement changed from the current interlock brick to grass brick the surface runoff volume and the peak discharge volume could be decreased by 12.5% and 5.4%, respectively.
Next we simulated the study-site watershed and pavement rebuilt situation and added into LID module. With regard to installed area and runoff reduction percentage, the optimum reduction benefit occurred when the installed area is 10% of the total, which effectively reduced surface runoff volume and peak discharge; while the installed area of pavement rebuilding situation reached over 20%, the peak discharge occurring time could be delayed by 10 minutes. By rebuilding interlock brick with grass brick to install the LID module 10% and compared with the original condition, it showed that the rainfall pattern design for one, two, and five years’ recurrence interval could all reduce surface runoff volume over 15%. The LID module of one year recurrence interval of rain design could reduce more percentage of surface runoff volume and peak discharge volume than the five years recurrence interval, which explains that the LID setting has relatively larger benefit on small rain.
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