山区多沙河流漂石河段洲滩发育特征试验研究

山区多沙河流漂石河段受水沙条件影响，洲滩发育丰富，改变了漂石河段的水沙运动规律及洲滩演变特征。基于野外调查与室内物理模型试验，探讨了漂石对多沙河段水动力特征及洲滩发育过程的影响。通过都江堰市岷江支流白沙河与龙溪河的野外调查，分析了典型漂石河段床沙组成及漂石河床形态特征。由于山区河流暴雨洪水及挟带的泥沙及河道地形多变等因素，大量上游来沙在漂石河段落淤，河床内洲滩的大量发育。通过系列室内物理模型试验，分析不同泥沙补给条件下漂石河床的洲滩形成过程及河床形态变化与水位响应过程。研究结果表明：暴雨山洪产生丰富的泥沙补给，导致白沙河与龙溪河的粗颗粒平均粒径粗大，存在大量漂石，形成漂石河段。漂石河段水力要素多变，河床形态剧烈调整。当上游泥沙补给时，受漂石周围水流变化影响，漂石河床局部以横向带状溯源淤积为主，下游段两侧淤积突出，极易形成漂石洲滩，从而增大局部河床比降，减缓河道下切。上游来沙不均匀过程显著改变了漂石河床局部水位及泥沙淤积规模。因此，通过野外调查与室内物理模型试验，揭示了水沙条件下的漂石河床形态变化特征，山区河流上游来沙与漂石共同影响洲滩发育过程，表明漂石对山区多沙河流的水沙运动产生突出影响。

Experimental Study on Characteristics of Bouder Bars Evolution in Mountainous Sediment-laden River

The water and sediment conditions influence the channel evolution around the river boulder regions in mountainous sediment-laden river, which significantly changes the characteristics of water and sediment movement and riverbed deformation. Through field investigation of Baisha River and Longxi River, the tributaries of Minjiang River in Dujiangyan City, this paper analyzes the bed sand composition and morphological characteristics of the typical boulder reaches. Field investigations found that due to the torrential rains and floods of mountain rivers and the sediment carried by them, as well as the changing terrain of the river, a large amount of upstream sand was silted in the section of the boulder river, resulting in the development of large number of beaches in the riverbed. Based on field investigation of typical riverbed and physical model experiments, this study analyzed the effects of boulder and sediment supply on hydrodynamic characteristics and beach development in river reach. According to the experimental results, it can be concluded that the heavy rain and flash floods produced abundant sediment supply including boulders, resulting in the coarse average particle size of the Baisha River and the Longxi River, forming a large number of boulder reaches. The hydraulic factors around boulder abruptly, lead to the considerable changes of the water level and riverbed forms. Under the sediment supply, the upstream sediment is mainly lateral banded source deposition, while the downstream sediment deposition is prominent on both sides, which is easy to form a drift stone beach. The development of boulder beach can increase the local riverbed gradient and slow down the river channel cutting. While, the non-uniformity of upstream sediment supply changes the local water level and sediment deposition scale around the boulder. Therefore, this paper reveals that the morphological characteristics of the boulder riverbed under the condition of water and sediment are revealed. It shows that the sediment and boulders from the upper reaches of the mountainous rivers jointly affect the development process of the beach, and the boulders have a prominent impact on the movement of water and sediment in mountainous sediment-laden river.