The Interaction Between Flow & Sediment Process And Riverine Environment

River, as the source of the social development, is the most active part of the topographic process and ecosystem. Flow & sediment process, river boundary, water environment and river ecosystem constitute the whole river system, and they interact and constraint each other. As to the incomprehensive understanding of the integrity of the river system, especially lack of acquaintance of the interaction between flow & sediment process and riverine environment, the river resources have been used without long-time consideration, which leads to the degradation of the river health. Whether aims to release the contradiction between river development and riverine environment or to maintain the sustainable development of river health, it is necessary and significant to carry out the deeply researches on riverine environment.Riverine environment is an important part of the river system, and also it is the most interested part of river health. For a long time, aquatic environmentalist and ecologist have done comprehensive and intensive researches on it, but most of them were specialized in a single field. The deeply researches on the interaction of the various aspects of the whole river system and specially the interaction between riverine environment, sediment movement and river evolution are deficit, which, in a certain extent, constraints the development of the researches on it.Based on the low of the sediment transportation and river bed deformation, the flow & sediment process and its variation are taken as the main clue in this paper. Several aspects are considered: The low of river pollutant transportation and transform are discussed for micro-scale; The characters of the river ecosystem and its adjustments are summarized for macro-scale; The relationship between flow & sediment process, river evolution and riverine environment are built up; Predict the trend of riverine environment adjustment and bring forward the corresponding assessment method and protect countermeasure.The key issues discussed in this paper are shown as follows:(l)Analyze the causes that lead to the disease of river environment and illustrate the significance of the researches on the riverine environment. Summarize the previous researches on it and suggest that the integrity and intrinsic relationship of the river system must be emphasized and the multi-subject method must be used.(2)Based on the summarizing and analyzing on the characters of sediment transportation and river evolution, it is concluded that flow and flood of Nature River show a certain regulation, and the combination of water and sediment can reflect the longtime effect of river bed erosion and sediment deposition under the action of flow & sediment. Analyze the low of reservoir operation, and get the result that the variation of hydrology process and water & sediment combination will generally impact the downstream bed form and river environment.Analyze the characteristic of downstream river bed erosion and sediment concentration recover, put forward the method that calculate the scour distance and conclude that the scour will decrease the water level in the low water period and increase the elevation difference of floodplain and channel. Summarize the characteristic of downstream river evolution, and point out the evolution characters: thewinding reaches will decantation the bend and cut the beach; the straight reaches will increase its stability; channel bar change to side-bar; small bar change to big bar and so on.(3)Due to the complex interaction between pollutant transportation and flow and sediment transportation in the river, previous researches have lack of considering on the influence of the sediment and its transportation.In this article, the interaction of pollutant and sediment is deeply studied. The amount of pollutant transportation during the course of sediment deposition and re-suspension are confirmed, and the computed pattern, which can reflect the dynamic course of bed mud release, is established.According to the characteristic of the pollutant, two models are established ,and compared with previous models these two models can do better to offset the deficiencies in considering the influence of sediment. By structure and case analysis on the models, the result shows that the established models can reflect all kind of processes of pollutant transportation on the sediment, and have a good simulation precision.Analyzing the water quality response to flow and sediment regime variation, it is concluded that the decrease of sediment concentration and the coarseness of grain size are disadvantageous to the pollutant adsorption and degradation, river bed form change leads to the decrease of flow velocity and weaken of the ability of river auto purification, and at the same time, scour in the pollutants deposition regions do harm to the water quality.(4)The river ecosystem is closely related to the fluvial dynamics and river morphology, but this was insufficiently recognized in previous researches. Based on the low of sediment transportation and river evolution, the research on river ecosystem is conducted. It is concluded that natural variations of flow & sediment process are significant whether to maintain the successive of the river or to constitute the diversity of function process, and protect the habitat succession and biodiversity.The ecological response of flow & sediment process can be simply divided into two kinds: short-time response and long-time response. Previous studies are mostly carried on the short-time responses that always are obvious. But these long-time responses are deeply impact but lack of study, which are the disturbance of flow & sediment process, the diversity and natural succession of long-time formed habitats.By analyzing the rive ecosystem response to flow and sediment regime variation, put forward the probably adverse impacts token by hydrological variation, sediment trapping and downstream channel erosion.Based on the relationship between ecosystem response downstream reservoir and hydrological variation and bed erosion, we build up the relational graph about the reservoir operation, water and sediment arrangement and ecosystem response, which is the base of predicting river ecosystem response and ecology health regulation.(5)Based on the analysis on the interaction between the river aquatic environment and ecosystem, the secondary environment effects by water and sediment variety are shown as:The variety of water quality of reservoir may lead to the ecosystem deteriorate phenomena, such as water body eutrophication and algal bloom. And the decrease of thewetland area, water amount entering in the wetland, and the broken of wetland function and succession, will weaken the eco- and environment function of wetland.And the feedbacks of river ecosystem are shown as:Riparian vegetation affects on flow structure and riverbed roughness; impacts the riverbed deformation by changing the trapping efficiency and the ability of bank anti-scour. The riparian vegetation variation will increase band stability and at the same time, increase the flow resistance of flood flow.(6)Presently, the definition of river health is not unified, the assessment formwork of river health lacks of its integrity and predictable, and the countermeasure of maintain river health are searching for. This paper points out the dualism functions in the nature river and exploited river. Base on this understanding, the river health is defined and the connotation of healthy river put forward as: the flow and sediment varies at their limit range.In this paper the elementarily river health index system and assessment method are put forward. The method generally reflects the healthy condition of river environment and rives service function, and at the same time, it emphasizes the unification of exterior embodiment and internal factors and is satisfied with its predictability.It is concluded that the primarily principle to maintain the sustainable development of rive health is to maintain a certain water and sediment process in order to satisfy the requirements of river environment and service function. And the special countermeasures are brought forward to maintain the river health: control the river resources exploit, realize the reasonable and orderly exploitation, as well as build up the regulation of reservoir operation which gives attention to river environment.