東門溪防砂壩調降對河床沖淤變化之影響

Fluvial Bed Variation of Dongmen Creek After Cutting Down the Check Dam

劉宜君(Yi-Jun Liu) ； 許詠晴(Yung-Ching Hsu) ； 邱渝方(Yu-Fang Chiu) ； 李正鈞(Zheng-Jun Li) ； 廖雯慧(Wen-Huil Liao) ； 陳樹群(Su-Chin Chen)

《中華水土保持學報》 50卷2期 (2019/06) Pp. 63-72

https://doi.org/10.29417/JCSWC.201906_50(2).0003

摘要

為穩定台灣恆春東門溪下游滯洪池庫容，本研究針對上游兩座可調式防砂壩提供操作建議。為達此目的乃採用室內渠槽試驗探討各種調降防砂壩方式，對東門溪上下游河床變化及土砂運移量之影響。試驗結果顯示，隨著二號壩溢口橫桿調降，其上游高程呈現等速下降、遷急點呈現等速上移趨勢，而下游會受到一號壩的影響產生回淤情形，其高程及遷急點變化無固定趨勢。在調降壩體初期時有較大的土砂運移量，使得壩體上下游河床坡度變化亦較大，而隨著二號壩溢口調降一半橫桿，土砂運移量及上下游河床坡度已趨近不變，達到上下游河床之平整化。逐次調降可使遷急點緩慢變化並避免土砂量一次性下移所造成之危害。

關鍵字

可調式防砂壩 ； 壩體調降 ； 河床演變 ； 遷急點 ； 土砂運移

並列摘要

To stabilize the capacity of the downstream detention pond, the recommendations of upstream two adjusted check dams in Dongmen Creek, Hengchun, Taiwan are provided. Moreover, to investigate the effects of various types of check dams on sediment transport and fluvial bed variations, the flume experiments were used. The results show that as the horizontal bars in the second dam are gradually removed, the elevation decreases and the knick points move upstream at a constant velocity. However, the first dam causes sediment deposit that flushed from second dam, and the changes in elevation and knick points do not significantly affect the trend between two dams. In addition, large amounts of sediment transport causes substantial slope change during the initial stages of adjusting a check dam. The sediment transport and slope stabilize when half the number of horizontal bars are removed from the second dam. Therefore, gradually cutting down the check dam can slow the change in knick points and prevent the disaster caused by large amounts of sediment being suddenly deposited in the river.

並列關鍵字

adjusted check dam ； cutting down ； fluvial bed variation ； knick point ； sediment transport