格網局部細化之淹水平行演算模式

Parallel Algorithm for Down-scale Inundation Simulations

黃成甲(Chen-Jia Huang) ； 許銘熙(Ming-Hsi Hsu) ； 李懿軒(Yi-Xuan Li)

《農業工程學報》 60卷2期 (2014/06) Pp. 85-100

https://doi.org/10.29974/JTAE.201406_60(2).0008

摘要

台灣地理與氣候特殊，每遭颱風暴雨，往往造成中下游地區淹水氾濫，導致生命財產損失，應用二維淹水模式模擬淹水潛勢圖供決策單位及民眾因應預警，有助於減輕洪患之損失。隨著遙測技術發展、資料解析度提高，淹水模式精度大幅提升。但若使用高精度的數值地形資料，卻也使演算時間過於冗長。此外，隨著電腦科技發展，程式開發已普遍朝向平行化發展，本研究主要目的為平行化多重格網局部細化之二維淹水模式。本研究於多重格網方法中加入平行演算法，將全區粗網格與數個局部細化網格區域，進行多重尺度模擬，可減少網格計算量，並將各區域之計算獨立交由多執行緒進行平行演算，以期提高模式之演算效率。本文研究案例為曾文溪流域，以2009年8月重創台灣南部之莫拉克颱風事件進行模式精度及效度分析探討。經由案例模擬，搭配平行演算法，成功使演算效率大幅提升。本研究在兼顧準確性的同時，能快速演算有效地提供即時淹水資訊，作為防災管理決策支援達到減災之效果。

關鍵字

多重格網淹水模擬 ； 平行演算法 ； 多執行緒

並列摘要

In Taiwan, due to the special physiographic and climatic conditions, typhoon or rainstorm event occurs frequently. Besides, it usually causes disastrous inundation in the midstream and downstream floodplain, and takes losses of lives and property. The two-dimensional inundation model can simulate flood risk map in advance to predict the potential flood depth and velocity, enabling informed government improve emergency planning and policy to reduce the losses. The multi-scale inundation simulation model using local fine grid at the dense population areas could reduce the time of calculation. The method is a feasible solution to provide a much higher resolution mesh with less computational time. The quick growth of remote sensing technology has obviously promoted the quality, in both resolution and precision respects, of topographic data. The demand for high resolution of 2D inundation simulations will cause the extraordinary requirement of computational resources for simulations. Recently, the developments in computer hardware have greatly advanced, therefore computational time can be reduced by running in parallel over multiple threads. The main purpose of this study focuses on parallelizing the multi-scale inundation model. In multi-scale inundation model, this research parallelizes global domain and all the local regions to multi-threads by parallel algorithm. The method makes the flood inundation model would be reduced computational time and speedup the efficiency. The parallel method was applied to the simulation of typhoon Morakot event of 2009 in Tseng-Wen river basin. This study compares both accuracy and efficiency by the error correction and speedup ratio. The results show that it is not only improving the accuracy of simulation, but also raising the efficiency of computational time. The method of parallel for multi-scale inundation simulation strikes a good balance between accuracy and efficiency. The significant result of this high efficiency model will greatly improve the real-time inundation early-warning system, and provide inundation information to authority for the disaster reduction.

並列關鍵字

Multi-scale inundation simulation ； parallel algorithm ； multi-thread