簡易一維土石流型堰塞湖潰決演算及運動波洪水傳遞模型：以荖濃溪為例

Simple One-Dimensional Dam Breach and Flood Route Models for Tributary-Dammed Lake: A Case Study of the Laonong River in Southern Taiwan

陳慈愔(Tzu-Yin Chen) ； 洪啟耀(Chi-Yao Hung)

《中華水土保持學報》 50卷4期 (2019/12) Pp. 131-142

https://doi.org/10.29417/JCSWC.201912_50(4).0001

摘要

2009莫拉克風災造成大量崩塌土砂堆積於台灣山區支流集水區，形成後續土石流事件之料源。大規模之土石流將擴大主支流匯流口處之沖積扇，並可能進一步淤塞主流形成堰塞湖，進而對下游村落產生威脅。本研究以土砂連續方程式與水流連續方程式為基礎的潰壩模式模擬堰塞湖之形成與潰決過程，再以一維非均勻河道運動波模型進行洪水演算，探討堰塞湖潰壩對下游保全對象之影響。本研究所提出之演算模型僅需少量可由現地資料率定之參數即可進行高效率且可靠之模擬，可同時將主流上游流量與潰壩所產生的洪峰流量一併納入計算，亦可在精簡的計算中模擬出河道寬度與坡度變化對洪水傳遞速率與洪峰削減之影響。本研究以荖濃溪與其支流布唐布納斯溪交會口之堰塞湖做為案例，採用蒙地卡羅法配合現地歷史降雨資料和率定完成之降雨逕流模式生成大量洪水事件作為堰塞湖潰決模式之上游邊界條件，再以系列模式模擬之結果進行分析，得到不同情境下此區域兩百年重現期之堰塞湖潰壩洪水水位預測值。最後，根據分析結果，提出針對台灣山區洪水事件之危害性評估建議。

關鍵字

堰塞湖 ； 蒙地卡羅法 ； 潰壩模式 ； 運動波輸送理論

並列摘要

Due to numerous landslides caused by Typhoon Morakot in 2009, much loose sediment was deposited in the upper reach of the tributary of Laonong River. Loose material was transported into the main stream during the heavy rainfall of the typhoon and formed a tributary-dammed lake. If the dam were to fail, this would pose a significant threat to downstream villages. In this research, we present a diffusion equation-based one-dimensional semianalytical model of a tributary-dammed lake breach. To estimate the most dangerous scenario, the model incorporates the intense discharge caused by torrential precipitation during typhoons. To assess the security of downstream villages, the floods are routed by a one-dimensional kinematic wave solution for a nonuniform valley. The solution can simulate areas impacted by flooding with much reduced computational cost and topographical data requirements. Finally, the research applies combined methods to the tributary-dammed lake at the confluence of the Putunpunas tributary river with the Laonong River. The maximum flood elevation of the dam was estimated for breach floods under different scenarios.

並列關鍵字

tributary-dammed lake ； breaching model ； kinematic wave model