應用二維水理輸砂模式評估野溪清疏成效之研究

Using a 2D Hydrodynamic Model to Assess the Dredging Efficiency in an Upstream Creek

詹勳全(Hsun-Chuan Chan) ； 邱亮鈞(Liang-Jyun Ciou) ； 彭振捷(Chen-Chieh Peng) ； 張承遠(Chern-Yuan Chang) ； 郭炳榮(Ping-Jung Kuo)

《中華水土保持學報》 48卷3期 (2017/09) Pp. 113-126

https://doi.org/10.29417/JCSWC.201709_48(3).0002

摘要

本研究藉由CCHE-2D 水理模式評估野溪河道清疏方案之成效，選定宜蘭縣碼崙溪為研究區域，擬定未清疏 (零方案)、河道清疏為複式斷面及蘭陽溪匯流口附近河道疏濬等方案，搭配不同疏濬深度，共6 組方案進行模擬分析，以洪水事件後底床回淤情況評估不同方案之成效。模式之檢定項目選定輸砂公式及調適長度，結果顯示當輸砂公式採用Modified Engelund and Hansen 輸砂公式，並搭載調適長度為1,000 公尺進行模擬時，於碼崙溪下游靠近蘭陽溪匯流口附近之河段有良好的模擬成效。採用完成檢定後之水理模式，評估不同清疏方案經過芭瑪颱風後之底床高程變化，針對保全對象碼崙橋橫斷面之模擬結果進行探討，研究發現零方案洪水後之平均回淤高度為1.5 公尺；主流清疏方案因主斷面處通水斷面積增加，形成囚砂區，平均回淤高度上升為1.7 公尺；蘭陽溪匯流口附近河道疏濬後，使溪水流速增快、泥砂輸送能力提高，平均回淤高度隨疏濬深度增加而降低，當疏濬深度介於1.5~2.0 公尺時，對應之平均回淤高度小於1.0 公尺。模擬結果分析顯示，碼崙溪河道清疏為複式斷面後，初期雖可提供碼崙橋下足夠之通洪斷面，但後續遭遇洪水會有快速回淤之現象；藉由匯流口底床疏濬後，可提高碼崙橋附近之水流流速，進而增加洪水自身挾砂能力，持續有效維持通洪斷面。

關鍵字

水理輸砂模式 ； 清疏 ； 成效 ； 碼崙溪

並列摘要

This paper aims to evaluate the efficiency of dredging scenarios in Malun Stream by using a CCHE- 2D hydrodynamic model. The dredging scenarios were: do-nothing, dredge at the main stream with a compound cross-section, and dredge at the confluence of the Malun Stream and Lanyang River. Considering the different depths of dredge at the confluence, there were six dredging scenarios investigated in the present study. Through the simulation of the bed changes in a flood event, the aggregation of the dredging areas was used to evaluate the efficiency of dredging scenarios. The verification of the CCHE-2D model showed the Modified Engelund & Hansen formula with the adaptation length equal to 1000 meters successfully represented the bed changes in the study areas. The simulation results showed the average height of aggregation was about 1.5 meters near the Malun Bridge in the do-nothing scenario. The corresponding value of the dredge at the main stream increased to 1.7 meters, because the sediment was trapped in the dredging areas. Near the Malun Bridge, this resulted in a decrease of the area of the cross-section and a corresponding decrease of ability to pass flood level. However, the dredge at the confluence showed an increase of flow velocity and ability of sediment transport. Moreover, the height of aggregation decreased with the increase of dredging depth. With the dredging depth ranging from 1.5~2.0 meters, the height of aggregation was less than 1.0 meters. The dredging at the confluence of the Malun Stream and Lanyang River was found to be the most effective dredging scenarios among the one studied here.

並列關鍵字

Hydrodynamic model ； dredge ； efficiency ； Malun stream