二維都市漫地流之分析研究

Abstract

因極端氣候的發生，近年來洪災頻傳，都市淹水成為非常熱門的議題。起初，由於資料不足，再加上對都市漫地流的運作模式沒有完全性的了解，人們使用一維模式模擬都市漫地流。一維模式將整個集水區做子集水區切割，每一個子集水區中的漫地流則透過計算矩形斜板流的方式計算。近年來，電腦科技的進步帶動二維模式快速發展。透過二維模式模擬，我們可以更清楚的了解都市漫地流在二維空間中的流動方式，以及造成的影響。然而，越精細的二維模擬就需耗費越多的計算資源、模擬時間，以及非常多的資料量需求，因此這次研究主要探討二維模式的必要性。 這次研究使用了兩種不同的水文模式，第一個是一維模式EPA SWMM，它的控制方程式為運動波方程式。在使用一維模式時，我們使用集水區轉換法將自然集水區轉換為一維模式中的集水區。第二個是二維模式GSSHA，它的控制方程式為擴散波方程式。研究中有許多不同的模式測試，透過測試結果了解建物及不透水面積對漫地流流況的影響，以及兩種模式結果的差異。如若建物對漫地流的影響很大，那麼在都市漫地流模擬中二維模式的使用則非常重要，因為一維模擬較難表現建物造成的影響。

In the past, the overland flow in urban watershed is always simulated in a very simplified manner. Currently, most models for urban flood planning and management simulate flood transform based on lumped concept. One reason is the lack of enough data, the other is we do not fully understand its behavior. However, with the development of fully-distributed model, we can more carefully examine the two-dimensional movement of urban flood. However, on the other side, it would consume more time due to large amount of calculation. With the help of fully-distributed hydraulic model, the study would like to examine whether a lumped model can take the effect of building and impervious area into account well with some factors. By this way, will lumped model be precious enough to represent urban flooding? In this study, the results are compared by two models. The first model is SWMM, a lumped model, which uses kinematic-wave equation as governing equation. The second one is GSSHA, a distributed model, which uses diffusive-wave equation. By comparing the result of SWMM and GSSHA, we will be able to examine whether the result of the currently wide-used KW approach is appropriate for modeling urban flooding or any further improvement is required.