山坡地開發程度對於下游洪患影響之研究

Influence on the Flood Disasters in the River Downstream by the Degree of Hillside Development

為有效降低流域中、下游洪水災害，近年各水利主管單位已建立堤防、排水設施與抽水站系統等防洪水利工程，但隨集水區土地開發與利用，導致原先設計之防洪相關設施可能已不足因應土地開發後增加之流量，本文目的在於研究流域中上游之山坡地開發，對中、下游洪水災害之影響。以 25 年、50 年、100 年及200 年重現期評估開發現況 （增加土地開發為0%） 及非都市計畫地區增加土地開發10% 、20% 、40% 、60% 時之淹水災害情形。以200 年重現期為例，依據淹水模擬結果比較得知，在高度開發（60 ％）情況下，整體淹水面積增加4.8 公頃，其中下游敏感地區增加3.2 公頃，佔66.67 ％。而在相同重現期，增加上游土地開發程度時，整體淹水面積與淹水深度會增加，雖淹水面積增加比例不大，但主要集中於下游地區，造成淹水風險增加。因此流域中上游之山坡地未能妥適開發與管理，中下游地區洪患風險將增加，本文研究結果因此可供政府相關單位進行山坡地開發之參酌。

In recent years, the Taiwanese government has established a number of flood water prevention systems, including dikes, pumping stations and drainage systems to effectively reduce the downstream flooding. At the same time, with the catchment area of land development and utilization, the result was that the original design of flood control facilities might be less relevant in the light of land development. So, it has become increasingly necessary to effectively control of the upper and middle reaches of the river basin development of hillside land to non-engineering methods in river basin management, downstream flooding. The main purpose of this project is to simulate the inundation area within different status of non-urban planning areas of land to increase the degree of development, such as 0%, 10%, 20%, 40%, 60%, and under 4 different return periods, such as 25 years, 50 years, 100 years and 200 years, for intensive rainfall events. The simulation results can be employed to assess the flooding impact in the downstream lowland and to establish the policy analysis tools for the hillside land development .