入湖浅水三角洲形成过程实验模拟分析

本文基于自然模型法,对入湖浅水三角洲的形成发展过程进行实验模拟,从河型和流场变化的角度,分析其河道演变过程规律。通过改变上游来沙和下游水位,研究不同边界条件对三角洲形成过程中河道摆动及河型发育的影响。实验结果表明:(1)河槽在顺直、分汊及无河槽的形态间交替演变,下游淤积的河坝会导致地形抬高、反水压力以及溯源淤积现象,促进河道发生周期性横向摆动。(2)三角洲表面流场形态及流速大小随河型变化,且与演变阶段有关。(3)上游多沙和下游高水位,都能使河型周期历时变短,主流摆动角度变大,摆动点位置向上游移动,较多来沙可以使河道形态由鸟足状向辐射状发育。在这一演化过程中,来沙影响占主导而水位影响居次要,水位变化条件不会从根本上改变河道形态的类型。

Experimental analysis of the formation process of lacustrine shallow-water delta

Based on the natural model method, a set of experiments were conducted to study the formation and development process of shallow water delta. The evolution process of the channel was analyzed accord-ing to the change of channel patterns and flow field. By changing the upstream sediment concentration and the downstream water level, the influence of different boundary factors on the channel lateral movement and the channel patterns was studied. The results show that:(1) the channel changes among straight, dis-tributed and no channel patterns, and downstream deposition leads to the raise of topography, anti-water pressure and upstream deposition phenomenon, which promote the channel to move laterally with a certain period;(2) the flow pattern and velocity of the surface flow of the delta vary with the channel patterns and the evolution stages, and (3) more upstream sediment concentration and lower downstream water level result in shorter evolution cycles of the channel and larger movement angle, which leads the movement point moves to the upstream. Moreover, the shapes of the channel change from bird-foot to radial shape. In this evolution process,the upstream sediment concentration plays the dominant role comparing to the wa-ter level,which cannot affect the river channel patterns fundamentally.