工程方式對淹水減災效益之數值模擬評估

A NUMERICAL STUDY ON PLUVIAL FLOODS MITIGATION USING TWO STRUCTURAL MEASURES

10.6149/JDM.202109_10(2).0003

葉森海(Sen-Hai Yeh)；郭文達(Wen-Dar Guo)；江申(Shen Chiang)；張志新(Chih-Hsin Chang)；陳偉柏(Wei-Bo Chen)

內水淹水 ； 二維零慣性水動力模式 ； 工程方式 ； 排水改善方案 ； 路基抬升方案 ； pluvial flood ； 2-D model ； structural measure ； drainage improvement project ； road raising project

災害防救科技與管理學刊

10卷2期（2021 / 09 / 01）

43 - 58

繁體中文

短延時強降雨所造成的內水淹水為臺灣最嚴重的天然災害之一。當排水系統因強降雨而飽和時，內水淹水經常就發生在平坦或低窪地區。本研究應用二維零慣性水動力模式評估兩種工程方式對減緩淹水災情的成效。第一種方式簡稱P1，為排水系統的改善；第二種方式簡稱P2，為結合排水系統的改善與道路基底提升。二維零慣性水動力模式使用最新取得的土地利用資料為曼寧係數的使用依據。5年、25年、100年及500年重現期24小時累積雨量被採用為氣象條件，用以驅動二維零慣性水動力模式。透過數值模式分析結果顯示，當使用5年重現期24小時雨量作為內水淹水條件時，P1在降低淹水範圍的成效相當顯著，最大可降低63%的淹水面積。至於減少淹水人口衝擊方面，當使用5年重現期24小時雨量作為內水淹水條件時，P2可減少約69%受到衝擊的人口。然而，當100年及500年重現期24小時累積雨量發生時，P1對降低影響人口的效能比P2高。以整體分析結果而言，工程方式對淹水面積及受影響人口的改善效能會隨高24小時累積雨量重現期出現而降低。

Pluvial flood is one of the severest natural disasters in Taiwan. A pluvial flood usually occurs in the flat or low-lying areas when the drainage system is saturated with intense rainfall. This study applied a two-dimensional (2-D) zero-inertia (diffusive wave) model to evaluate the flood mitigation performance of two structural measures, one is a drainage improvement project (P1) and the other is a combination of drainage improvement and road raising project (P2). The Manning coefficients in the two-dimensional model were determined through the latest land-use data of the study area. The 24-hour cumulative precipitation for 5-, 25-, 100-, 500-year return periods were served as meteorological boundary conditions to drive the 2-D model. The results indicate that the utilization of the P1 was more significant in mitigating the flooding extent, the maximum reduced rate of the flooded area can reach 63% when the 24-hour cumulative precipitation of 5-year return period was imposed on the 2-D model. Regarding the decrease in the number of people impacted by flood, the P2 only performed better with a reduced rate of 69% for excreting the 24-hour cumulative precipitation of 5-year return period on the 2-D model. However, the P1 is superior to P2 in reducing the number of affected people under the conditions for 24-hour cumulative precipitation of 100-, 500-year return period. The overall ability of the structural measures for flood mitigation decreases as the return period increases.

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