多重尺度網格配置結合建物效應模擬街道淹水之研究

Abstract

由於台灣都市發展迅速，建築物大量興建與不透水面積的比例上升，因而多數降雨無法滲入地下，使得地表逕流量增大，且地表水流受建築物阻隔影響，提高街道淹水之機率。為重現淹水情況之發生，透過淹水模式進行水理計算，而隨著遙測技術的進步，提供更高解析度之數值地形模型，亦提升淹水模式模擬之準確性，更能夠掌握真實淹水情況。 欲有效利用計算機資源，運用多重尺度網格之模擬可減少運算網格數量及節省計算時間。多重尺度網格於運算過程中，其邊界導致的誤差將影響到細網格內模擬之精度。因此，本研究主要探討SOBEK模式結合不同尺度之粗網格搭配細網格，並在局部細化區域考慮建物效應，模擬高解析度之街道淹水情形且找出最佳的搭配組合，以達到較佳之演算效率及精度。 以測試案例評估SOBEK模式運用多重尺度網格之可行性，使用三種解析度之粗網格(20m×20m、40m×40m、100m×100m)與細網格(10m×10m)相互搭配。將多重尺度網格與全區細化網格(10m×10m)模擬淹水結果作一比較，分析三種多重網格配置之差異。再應用SOBEK模式加入雨水下水道並結合建物效應，模擬典寶溪流域內梓官市區2010年凡那比颱風街道淹水之情況。使用兩種多重尺度網格(5m×5m搭配10m×10m、5m×5m搭配20m×20m)並與全區細化網格(5m×5m)比較之，模擬結果以5m×5m搭配10m×10m之組合最佳。研究發現利用SOBEK模式以多重尺度網格並結合建物效應之模擬，可增加演算效率也顧及其精確度。

Due to the rapid development in recent years, surface runoff has considerably increased and accompanied with a higher flood risk since infiltration has been blocked by more and more impervious municipal area in Taiwan. Flood forecast and simulation has been improved with the advances of flood models, remote sensing technologies, and the application of multi-scale grid for reducing the number of computational grids and computer time. However, multi-scale grid makes procedural error that influences the accuracy of down-scale inundation simulation. To achieve the optimal multi-scale grid configuration for pursuing higher efficiency and accuracy, this study is to investigate the simulation of the street flooding in high resolution which combines different scales of coarse grids and fine grids in SOBEK model with the building effect applied to the fine grids. A test case was used to assess the feasibility of SOBEK model using three multi-scale grid combinations, including three kinds of coarse grids (20m×20m, 40m×40m and 100m×100m) with a fine grid (10m×10m). The simulation results in applying each kind of multi-scale grid combinations were compared with the result by using full fine grid. SOBEK model was applied with sewer and building effects to simulate the flood in the Ziguan District in Dianbao River watershed during Typhoon Fanapi (2010). The results of two configurations using multi-scale grid combinations (5m×5m with 10m×10m、5m×5m with 20m×20m) were compared with the result with only fine grid (5m×5m) and showed that the optimal configuration is 5m×5m with 10m×10m. It can be concluded the simulation of the street flood which combines the multi-scale grid configuration and building effect in SOBEK model are more efficient and accurate.