入湖河流三角洲形成发展规律

Formation and Development Law of Rivers Into the Lake Delta

通过概化水槽试验对水流泥沙从河流进入浅水湖泊层后的三角洲堆积体形成发展过程进行研究,得到如下规律.平面形态变化:第一阶段,三角洲堆积体在初期按水下舌状、扇状和树枝状形态形成发展,其表面有明显的主河槽且两侧区域有较多串沟;第二阶段,三角洲堆积体表面依次形成顺直河槽、分汊河槽和微弯河槽,水流泥沙沿不同河槽的主流方向以不同方式向前推进.纵向推进速率变化:第一阶段初始较大,受横向展宽影响纵向推进逐渐减弱;第二阶段以相对稳定的速率推进.垂向变化:堆积体的淤积抬高速率初始较大,随历时增加逐渐减小并保持稳定,整体上不断淤积抬高.横向变化:受河槽底部泥沙淤积抬高的影响,水流泥沙向两侧区域漫流;随堆积体纵向推进长度变长,水流泥沙在河槽主流中出现横向泥沙输移现象.

This paper used the flume generalized experiment to investigate the formation and development of delta deposition,after the water flow and sediment was transport into the shallow water lake from the rivers. The results show the changes of delta deposition’s plane configuration can be divided into two stages. First stage,the delta deposition developed follows the morphogenetic of tongue,fan and branching shape,with mainly channel on the surface of the deposition and more string ditch on both sides. Second stage,river channel gradually formed on the surface of deposition,as the morphogenetic of straight,branching,slightly curved,in order,water flow and sediment goes along way,different with the main channel and moves forward with a different style. Delta deposition’s longitudinal launching rate changes is in consistent with two stages,the initial rate is larger and gradually decreasing affected by the lateral broadening. The second stage,delta depositions move forward as relative stabilization rate. The change of vertical deposition,the rate of the deposition’s silting up is big at first,as time goes on,the rate tends to small to keep constant,the deposition keep silting up development as a whole finally. The change of lateral broadening,water and sediment moved to the sides because of the influence of sediment at the bottom silting,lateral sediment transport occurred along the river channel mainstream due to the longer of deposition’s longitudinal launching length.