中永和地區都市排洪系統最佳管理措施之探討

Abstract

台灣都市人口密度逐年增加，迫使都市快速開發，導致都市地表不透水率大幅提升，造成地表逕流大量增加，因此都市地區發生洪災的機率及程度也隨之加劇，舉凡梅姬颱風、凡那比颱風、0612豪雨…等皆為近年發生嚴重洪災之降雨事件。然而，在高密度開發的都市中，要藉由增建或加大雨水下水道管線來改善內水氾濫問題的效果有限， 因此，近年來經濟部水利署與內政部營建署積極參考國外之經驗，希望可以藉由於美國推廣十幾年的低衝擊開發(LID，low impact development)技術，來減少都市受洪水威脅之機率。LID技術主要是透過源頭管理，並利用分散式、並聯、小規模的透水、保水設施來增加雨水入滲潛勢及基地保水能力，期望能維持或回復基地開發前的水文狀況。而常見的LID設施包括了雨水花園、植生草溝、綠屋頂、透水性鋪面…等。 本研究以新北市中永和區為例，透過SWMM模式建立該區域的排水系統模型，並設定數種治水策略分別對颱風雨、暴雨、設計降雨進行模擬，策略包括了LID設施策略、滯洪池策略、雨水下水道策略與綜合策略，本研究以模擬結果之地表逕流與超量溢流來評估策略的效果，並對各種策略進行成本估算，最後比較各策略的成本效益，以作為最佳管理措施之參考依據。 研究結果顯示，在相同建造成本之下，最佳管理措施應採滯洪池及雨水下水道為主，採透水性鋪面與生態滯留池為輔，在相互搭配之下，其效果不但優於傳統採建置大量雨水下水道的方式，還具有景觀、生態、綠美化、減緩熱島效應…等附加價值。

Due to the raising population and extreme rainfall, urban flood becomes a severer problem. In Taiwan, the rapid increase of impervious surface area raise the probability of occurrence of urban flooding and enlarge its influenced area. For example, Typhoon Megi, Typhoon Fanapi and 0612 strom events all caused severe floods in recent years. In high-density urban, building more storm sewers has limited effects on improving flooding conditions .Therefore, in recent years, the Water Resources Agency and the Ministry of Interior try to use low-impact development techniques to reduce the chance of flooding. LID emphasizes on maintaining or restoring the site hydrological conditions back to predevelopment. And its strategy is combining distributed, parallel connection and small-scale devices functioning as infiltration, interception, rainwater storage or detention facilities to increaseinfiltration chances for runoff. The common LID facilities include rain gardens, vegetative swales, green roofs, permeable pavement ... and so on. Study area was chosen as Chung Ho and Yong he District, New Taipei City. Through the SWMM model to establish the drainage system model, and set several scenarios that include the LID facilities strategy, detention pond strategy, storm sewer strategy and integrated strategy. Then use the results of surface runoff and excess overflow to evaluate the effectiveness of strategies, and estimate the project's cost .Finally, compare the cost-effectiveness of each strategy as a best management measures reference. The results show that under the same cost, best management practices should be adopted detention ponds, storm sewers, permeable pavement, bio-retention cell with each other. The effect is not only superior to the traditional approach to build a large storm sewer, but also has benefit of landscape, ecology, green, slowing the urban heat island effect ... etc.