Screening and construction of runoff-allocation hotspot in a watershed
逕流分擔 ； 最大保水量 ； 大肚台地 ； Runoff allocation ； Maximum potential retention ； Dadu terrace
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2018年水利法之「逕流分擔」與「出流管制」專章通過，政府期藉由降雨妥適分配於邊坡，提升土地耐淹能力，降低河道承受之洪水，減少人居地淹水風險及生命財產損失。然目前逕流分擔之量體以滯洪考量而非蓄洪，遂此，利用最大蓄水量差值為指標，篩選超滲逕流重點區位，並萃取逕流分擔熱點區位加以營造，供新法於技術執行與管理之參考。 大肚台地隨著臺中都會區發展，不透水鋪面增加，加上高發生頻度野火產生大面積草地，草地斥水層降低集水區水源涵養能力，導致暴雨時台地周圍水患頻傳。利用SCS之曲線值法，計算現況及開發前之最大蓄水量差值，萃取超滲逕流之重點集水分區，此外，採窪蓄區位、土地利用、權屬、坡度等因子，篩選逕流分擔熱點區位，最後，除解決下游之淹水問題外，亦採可食地景手法營造多功能之保水空間。 結果顯示大肚台地以沙鹿區之超滲逕流量2,789,539 m3為最高，但逕流分擔區位僅可承受16%之逕流體積，除可透過加深既有漥蓄區位外，另以道路邊溝串聯漥蓄區位，以異地補償方式分擔逕流量體。在逕流分擔熱點區位營造部份，從北勢溪集水區可篩選出約5.1公頃之公有草生地，規劃具滯(蓄)洪、生態保育及景觀遊憩等功能之滯洪保水設施，基地營造後之最大蓄水量為12,326 m3，結合新增之滯(蓄)洪量39,900 m3共計52,226 m3為逕流分擔量體，對下游淹水區位將可減少4公分之淹水。
In 2018, the special chapter of runoff-allocation and outflow-control in Water Law was promulgated. The purpose of the Act was upgrading flood resistant ability on the land, reducing the flood volume in the river and decreasing the flood risk and loss of life and property by runoff-allocation on the slopeland. However, the runoff-allocation volume was regarded as detention not retention. Therefore, the difference of maximum potential retention through land use change was applied as the index to screen the hotspot of excessive runoff. The hotspot of runoff-allocation can be screened and constructed for the reference of execution and management of the new Law. With the development of Taichung Metropolitan Area at the Dadu terrace, the impervious pavement has increased. In addition, the high frequency of wildfires increase grassland area and decrease the capacity of water conservation. In this study, the Curve Number method is applied to extract the hotspots of the excessive runoff. The coverages of depression storage, land use, ownership and slope were applied to screen and construct the hotspots of runoff-allocation using edible landscaping measure for solving the inundation issue of the downstream. Results show that the highest excessive runoff is 2,789,539 m3 in Sha-lu District but the sites of runoff-allocation can only afford 16% of the excessive runoff. In addition to adjusting the depth of depression site, the method of string the depression sites using roadside ditch can compensate the excessive runoff. For the construction of runoff-allocation hotspot, there is a 5.1ha-public grassland can be planned with the multi-purpose of disaster prevention and reduction, ecology conservation and landscape recreation in the Bei-shi Creek watershed. The total volume of the runoff-allocation hotspot is 52,226m3 including 12,326m3 in water storage and 39,900m3 in retention/detention. The planned allocation volume can reduce about 4cm flooding depth of the downstream denudation area.
生物農學 > 生物環境與多樣性