都會區內澇淹水警戒值之研究

Abstract

目前為符合各級政府淹水防救災的需求，水利署制定了一套系統及運作機制，針對臺灣地區積淹水災害進行預警作業，以降雨量訂定各地淹水之警戒標準，並配合全臺灣各地自動雨量站之即時觀測資訊發布即時預警資訊，並提供縣、市政府及ㄧ般民眾盡早做防淹準備。然而水利署現行的淹水警戒係以觀測降雨量進行淹水預警，尚未多加考量地形、水利設施與河川水位等因素。為發展更為完善的淹水警戒機制，本研究以新北市中、永和區之瓦磘溝流域為研究區域，考量完整之現地實際情況，以各延時之設計降雨量及不同外水條件進行淹水模擬之評估。模擬結果發現都市地區周邊之區域排水外水位對都市地區排洪影響頗大，藉此建立都市周邊之區域排水外水位與可能造成淹水之各延時累積雨量的關聯性，訂定出適合瓦磘溝流域之內澇淹水警戒雨量，得到更完整且有效之警戒雨量，以提升淹水警戒之品質，可供都市地區洪水災害防制之用。

In this study, a new flood warning standard (FWS) is proposed to fulfill the flood prevention demand of the government. The sizes of flood inundation areas are determined by rainfall durations, terrain, water conservancy facilities and river levels. For the purpose of investigating the effect of river levels at the outflow boundaries and rainfall durations on the flood inundation area, the Wayaogou drainage channel basin is adopted as a study region which is located in the Zhonghe and Yonghe Districts in Taiwan. Various river levels at the outflow boundaries and various rainfall durations are used to conduct the flood inundation simulations to find flood inundation areas of the study region. The ratio of the flood inundation area and the total area of the study region exceeding 5% is viewed as a warning criterion. Based on the criterion, different combinations of river levels at the outflow boundaries and rainfall durations are provided in the new FWS. Comparing with the original FWS established by the Water Resources Agency (WRA), the new FWS involving the factor of river levels at the outflow boundaries in addition to the factor of rainfall durations is more reliable on preventing the occurrence of disaster.