河道形态改造对城市河流生态水力性能的影响

Influence of river course form transformation on ecological hydraulic performance of urban rivers

为探究城市河道形态改造的有效性,根据河道自然修复理念,采用正弦函数对典型城市渠化河道的河宽、水深和蜿蜒度等地形几何变量进行振荡波动,并借助数字河道合成技术生成6种河道数字地形模型,在此基础上采用二维水动力模型考察不同河道形态改造对河床干扰度、水力形态多样性指数和浅滩缓流生境面积等生态水力指标的影响。结果表明:研究河段城市渠化河道生态水力性能随地形几何变量的振荡波动而变化,且河道空间形态越复杂,河道生态水力性能越好;在高流量(8~12 m 3/s)下,“深潭浅滩”形态构造下河床干扰度平均减少88.2%,水力形态多样性指数平均提高37.4%,而浅滩缓流生境面积增加24.9倍,表明河流生态水力性能得到显著改善;城市河道近自然形态重构能大幅降低河道对于流量变化的敏感性,并显著提高河道生态结构稳定性,有助于河流生态系统的恢复。

In order to explore the effectiveness of urban river course form transformation,sine function was used to oscillate the topographic geometric variables such as river width,water depth and meandering degree of typical urban channelized river according to the concept of natural river course restoration.Six kinds of digital terrain models of river course were generated with the help of digital river course synthesis technology.On this basis,a two-dimensional hydrodynamic model was used to investigate the influence of different river course forms on the river bed disturbance,hydro-morphological index of diversity,shallow slow-water habitat area and other ecological hydraulic indicators.The results show that the ecological hydraulic performance of urban channelized river in the study changes with the fluctuation of topographic geometric variables,and the more complex the spatial shape of the river course,the better the ecological hydraulic performance of the river.Under high discharge(8~12 m 3/s),the river bed disturbance under the“deep pool-shoal”morphology structure is reduced by 88.2%on average,the hydro-morphological index of diversity is increased by 37.4%on average,and the shallow slow-water habitat area is increased by 24.9 times,indicating that the ecological hydraulic performance of the river has been significantly improved.The reconstruction of near natural form of urban rivers can significantly reduce the sensitivity of rivers to discharge changes,and significantly improve the stability of river ecological structure,which is conducive to the restoration of river ecosystems.