Effect of Grid Size of the Digital Terrain Model on Hydrologic Simulation

數值地形模型有助於地景展現、空間分析及水文模擬等，近年來，它已廣泛應用於土木、地理及自然資源等領域。雖然數值地形模型甚為有用，但它的網格結構常影響到水文模擬，故本研究旨在瞭解數值地形模型的網格大小對水文模式TOPMODEL反應之影響，包括地形指標、模式參數值及逕流模擬等，並探討地形指標與最佳水力傳導性參數之關係。研究區域為福山二號集水區(94ha)，水文資料取自1995年7月至10月間，含流量、雨量及氣溫等，透過五種不同網格邊長(10,20,30,40,50m)的數值地形模型求取地形指標，供水文模式TOPMODEL模擬所需，並應用Rosenbrock最佳化演算法找出模式最佳參數值。結果顯示，地形指標平均值隨網格大小增加而增加，當網格邊長為10m的模式最佳參數組套用於其他不同網格大小上時，模式有效率將隨網格大小增加而略為減少，不過當每一不同網格大小的模式參數值被最佳化後，其模式有效率則趨近相同，此時最佳水力傳導參數值卻團網格大小增加而增加，此乃為了補償網格大小的改變對地形指標之影響；此外，地形指標平均值則與最佳水力傳導參數值成正相關。考慮水文模擬、地景展現及資料處理需求等條件，此五種不同網格邊長之數值地形模型，以10m邊長之數值地形模型較為適宜，但爾後研究區域若有更精細之數值地形模型資料，則應作進一步之探討。

關鍵字

數值地形模型；水文模擬；水力傳導性

並列摘要

Digital Terrain Model (DTM) data are helpful for landscape representation, spatial analysis, and hydrologic modeling. In recent decades, DTM data have been widely applied in many fields, such as civil engineering, geography, and natural resources. Although DTM data are useful, their grid-based structures affect hydrologic simulation. Thus this paper attempts to understand the effects of grid sizes on the responses of the hydrologic model, TOPMODEL, including topographic indices, model parameter values, and streamflow simulation in Fushan watershed no. 2(94 ha). The relationship between the topographic index and optimized parameter values of hydraulic conductivity in TOPMODEL was also examined. Five different grid size DTM data, at 10, 20, 30, 40, and 50m, were applied to calculate topographic indices. The hydrologic data, including precipitation, streamflow, and air temperature from July to October 1995 in the study area, were selected. The Rosenbrock optimization algorithm was used to find optimal parameters within their reasonable ranges. Results show that the mean of topographic indices increases as grid size increases. When optimal parameters of TOPMODEL for 10-m DTM data are fixed and then applied to other grid sizes, model efficiencies slightly decrease with increase of grid size. However, model efficiencies can become virtually identical if parameters are properly optimized for different DTM data. The optimized parameter value of hydraulic conductivity increases as grid size increases. This is due to compensation for the effects of changing DTM grid size on topographic indices. In addition, there is a positive relationship between optimized parameter values of hydraulic conductivity and means of topographic indices. Based on the hydrologic simulation, landscape representation, and data handling requirements for these 5 different gird sizes, the 10-m grid size is recommended for DTM-based applications of geomorphologic and hydrologic modeling in the study area. However, we should check our results again if there are finer DTM grid sizes in Fushan watershed no. 2 in the future.

並列關鍵字

digital terrain model ； hydrologic simulation ； hydraulic conductivity

國際替代計量

Effect of Grid Size of the Digital Terrain Model on Hydrologic Simulation

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