The suspended load in rivers affects the survival and growth of animals and plants, and causes ecological pollution as well, threatening the health of river ecosystem. The aquatic vegetation can mitigate the ecological threat caused by suspended load. In order to explore the mechanism of environmental and ecological effect of aquatic vegetation and make full use of it, we carried out laboratory experiments in a flume; the principles of sediment incipient motion inhibition, sediment transport slow-down, and sediment stop acceleration by submerged vegetation were explained from the aspects of time-average velocity, turbu-lence intensity and shear stress, etc. . The experimental results showed that in the range of plant density in the experiments, the relationship between plant density and suspended sediment settling rate was non-linear. Therefore, when the submerged vegeta-tion ( tape grass) is applied in the regulation of suspended sediment flow, appropriate plant density should be adopted so as to fully realize its effect and save the cost.%河流悬沙可影响水体中动、植物生存和生长，并造成生态污染，威胁河道生态系统的健康。水生植被可以减缓悬沙带来的生态危害。为了探求水生植被环境和生态效应的产生机理，并使其更有效地发挥作用，开展了室内水槽试验，从时均流速、紊动强度、切应力等方面，科学解释了沉水植被抑制泥沙起动、减缓泥沙运输、加快泥沙止动的原理。试验表明，在所研究的植株密度范围内，植株密度与对悬沙沉降并不成线性比例。因此，沉水植被(苦草)用于治理水流悬沙时，可适度选取植株密度，使其既发挥治理成效，又节约经济成本。
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