河道水流、泥沙与植被耦合作用机理及应用研究

Soil erosion in the watershed and the sediment deposition in the estuary and the river channel had brought disarsters to the flood control and the environmental engineering. Based on the site investigations and the river channel morphoelogy in the estaury regions, Both the sudden expansion channels and the vegetated islands are selected to observe how the vegetation affects the water flow and the sediment erosion-deposition . When the vegetations are submerged, the water flow has three dimensional characteristics, the recirculation regiones and the vortex structures depend on the water level and the density of the vegetation. By considering the variation of the water level near the river mouth, the water level and the density of the vegetation are chosen as the main factors in the comparision study. Not only the effect of the vegetation on the water flow is considered, but also the impact of water flow on the vegetations will be also observed. The water flow model will be built by considering the resistance force from the vegetation, and the convection-diffusion model will be established for the pollutant transportation in the gaps between the vegetations. The mechanism of the vegetation affecting the recirculation region and sediment transportation will be revealed. It is the first time to reveal the following phenomenon: .1) the influnence of the vegetation on the recirculation regiones and sediment .erosion-deposition of the sudden expansion channel; .2) the influnence of vegetation on the vortex shedding and sediment . transportation behind the vegaetated islands; .The above results would enhance the original innovation.The new mathematical model will be proposed, the impact of the water flow on the vegetations will be also evaluated by considering the bending displacement of the vegetations and the erosion of the river bed. By integrating the turbulent flow model, suspended sidement transportation model, bed-load model and river morphorlogy reshaping model, the water flow and the sediment transport in Hengshui lake and its river channels will be predicted.

河口及内陆河道泥沙冲淤问题，给防洪和生态环境工程带来灾害。本立项在野外调查的基础上，针对入湖河口地区的特点，选取具有植被的突扩和渐扩河道、具有植被的岛屿等，分别研究植被对河道水流运动及泥沙冲淤的影响。植物被水淹没后，河道回流区范围和漩涡形态受水位升降和植被密度变化支配。试验针对入湖河口地区水位变化频繁的特点，选取典型河道，以水位升降和植被密度变化为参数，不仅观测植被对水流的影响，也观测水流对植被的冲击影响。建立水流运动模型和通过植被间隙的物质对流扩散模型。探讨滩地植被对河道回流区、漩涡结构、泥沙沉积及地形冲刷的影响机理。本立项在以下两个方面具有创新性，1）植被对突扩河道回流区及河道冲淤的影响机理；2）植被对岛屿尾流及地形冲淤的影响机理。上述研究尚属首次。集成水流运动模型、悬移质和推移质泥沙输移模型、河床变形模型，结合衡水湖及周边河道的实际模拟河口水沙运动，研究具有理论意义和实际应用价值。

针对植被对河道水流及泥沙淤积影响问题，在植被对水流影响的研究方面开展了多个物理模型试验。如在平底矩形河道的全断面长距离布置植被，完成了挺水植被及淹没植被对水流流速分布及流动阻力影响试验，揭示了有植被情况下流速垂向分布的特征，包括流速垂向分布的极值点及拐点位置；开展了复式断面河道情况下植被对流速分布的影响研究，获得不同复式断面河道情况下的流速分布规律，并通过理论分析的方法获得复式断面流速分布的解析解。 完成了斑块植被对水流流态影响研究，揭示了斑块植被尾流区水动力特征，包括尾流区流速分布随植被密度的变化规律；在斑块淹没植被的情况下，流速具有三维分布特征，如流速分布在斑块后侧的尾流区及立面回流区，揭示了尾流区及立面回流区流速分布特征随植被密度的变化规律。. 在植被对水流影响研究的基础上，开展了植被对河道泥沙淤积试验观测，在水槽一侧及水槽中间部位布置矩形斑块植被，观测植被区、尾流区及植被两侧无植被区的泥沙沉降规律。在物理模型试验的基础上，建立了包括植被、水流及泥沙淤积耦合的数学模型，预测植被对河道泥沙淤积的影响。研究结果应用于北京市平谷区的泃河整治，研究为河道生态整治提供科学依据,. 本项目执行期间为2013年1月至2016年12月，目前在国际学术期刊上发表标明本资助号的SCI论文6篇，中文期刊及会议论文11篇， 合计发表论文16篇。完成面上基金项目对发表论文的要求，在国际本领域高质量的学术期刊上发表论文多篇，证明本研究结果的创新性。