| Small rivers in rural areas is an important part of river system, and in recent years,the governance of large and medium-sized rivers have had a certain effect. But problems like water pollution,environment damage and sediment deposition about rural rivers are still grim.Comprehensive management of the rural small rivers can not only enhance the flood control capacity of river but also promote the building of a new countryside. Ecological management of rivers has become the development trend of domestic and abroad. But most of the domestic research mainly focuses on the engineering measures,research focused on economic,society and ecological environment benefit coordination is rare. There are not many contents about the differences between small rural rivers and large and medium-sized rivers.Based on the characteristics of rural small rivers,this paper mainly studied the following contents:Firstly,the related theories were elaborated and studied.Characteristics of rural small rivers,differences between large and medium-sized rivers, both harnessing principles and methods and other parts were all incuded.Secondly, engineering including dredging, slope protection and embankments for ZhangCun torrent ditch in LiChuan county were all studied.Thirdly, based on practical engineering and economic rationality,compound section was optimized using the best hydraulic conditions.Fourthly, advance of freshet in meandering river between WuLi Bridge and HongWei Bridge was analyzed aimed at ZhangCun torrent ditch.The main conclusions of the study are as follows and partly innovative:(1) Small river basins management should be consistent with the reguirements of the whole river basin planning.Taking appropriate flood risk and avoiding one-sided management, local interests should serve the overall intrests of rivers at the necessary key moment. Perfecting corresponding legal system, framing people′s behavior,reducing water pollution and protecting water environment are all needed; People involved should insisting the harmony between human and water; Single engineering method should be avoided.Protection and prevention are all mainstay. Engineering management is secondary and biological measures shoud be insisted at the same time.(2) Small rivers should be dredged regularly;The rivers should be avoid cutoff,retaining the meandering natural form. Constructing hydrophilic landscape, ecological embankment,nature waterfall as well as creating a good aquatic environment should be focused.Giving priority to the use of ecological compound section,strengthening the construction of hydropower and functioning quantitative assessment of environment impact are all needed.(3) The ZhangCun torrent ditch in LiChuan conty where the flood was poor venting should be dredging.Natural materials and ecological advanced composite materials can be used to protect the cross slope. Ecological compound section is used in river course. The main channel part of the section adopts optimal hydraulic conditions to solve.The slope height and beach width were calculated according to the optimal formula of the overall cross section.The obtained cross section vertificated by the model should satisfy the requirements of releasing flood waters and ensuring flood safety.(4) The cut-off river speeds up the process of flood, lead to the lower water level and sharply increasing flow velocity which is not conducive for the stability of cross-strait slope and anti scour.A winding river can store more flood,reduce velocity and increase the flowing time compared to the straight channel which can regulate flood effectively. Maintaining the nature shape of the winding river has important significance to alleviate flood pressure of downstream outlet and the main river.(5) The valves of flow velocity of windering river are different in different position.Compared with straight river,it helps to form living environment rich of diversity which is beneficial to the growth of aquatic animals and plants.River morphology has important hydraulic and ecology significance.The river′s natural form should be ensured and the artificial cutoff should be avoided when dredging small rural rivers. |
