The Research About The Check Dam System Optimization In Small Watershed On The Loess Plateau

The check dam, as an important engineering measures of soil and water conservation onthe loess plateau, plays an irreplaceable role in reducing sediment into the Yellow River,improving the ecological enviroment and promoting local development and so on. As ourcountry paying more attention to the problem of water loss and soil erosion and stronglyinvesting on the soil and water conservation, the comprehensive management of smallwatershed on the loess plateau becomes the focus of the control of water loss and soil erosion.The check dam,especially the check dam system in the channels of small watershed plays akey role in the comprehensive management of small watershed. Therefore, the research aboutthe check dam system optimization in small watershed has important practical significanceand application value.The author of this article consulted lots of references in this field and did fieldinvestigation of comprehensive management of small watershed on the loess plateau, on thebasis of the existing research results, combined with the actual situation of the construction ofthe check dam system in small watershed on the loess plateau and the future direction ofdevelopment, combining theoretical analysis and practical application, mainly research on theoptimization of the check dam system in small watershed, main archievements are as follows:（1）The dam site selection is crucial to the construction of the check dam. When weselect the check dam site, we must take into consideration various factors such as economy,society and ecology.Among them,some facters can be quantitatively analyzed, some facterscan only be qualitatively analyzed. By using the analytic hierarchy process, combinequalitative analysis with quantitative analysis, select broadly representative factors as thetarget layer, criterion layer and index layer, set up the comprehensive evaluation system ofoptimal choice of the check dam site. By adopting the expert evaluation method, grade thecorresponding indexs of qualified dam sites, multiply the average of expert evaluation and thecorresponding weights of index, then sum them up, draw a final score of every dam site,select the optimum dam site from a number of dam sites.（2）In the comprehensive management of small watershed, as a result of the limitationof factors such as funds, manpower and material resources, several check dams of planningand construction in channels of small watershed often can’t be built by once, usually adopt the construction method of phased implementation. How to scientifically construct the checkdams of system by stage, make its maximum comprehensive benefits. Therefore,it need tostudy on the construction sequence optimization of the check dam system. By analyzing thebenefits of sediment blocking, production, flood control and irrigation which made by checkdam construction as well as the construction cost, considering the social discount rate, whenthe benefit cost rate is maximum, the construction sequence of the check dam system of smallwatershed is best.（3）At present, in practical engineering, a lot of check dams adopt the constructionmethod of that design by once, increase height by stage, finally meet the design height of thecheck dam. By using this method of increasing height of the check dam by stage, can makefull use of alluvial soil in the front of the check dam to serve as part of the volume ofearthwork of dam body. However, how to determine the number of times of increasing heightby stage and how to confirm the height to heighten every time is the problem must be firstsolved of increasing height by stage of check dam. Establish mathematical model which takesthe present value of total cost of increasing height by stage of the check dam as objectivefunction, when the present value of total cost is minimum, then the method of increasingheight by stage of check dam is optimal.All in all, along with our country increasing the intensity on the control of water loss andsoil erosion, as the focus of the control of water loss and soil erosion, the comprehensivemanagement in small watershed on loess plateau attracts great attention. The check dam playsa more and more important role in soil and water conservation as an important engineeringmeasure of the comprehensive management of small watershed. Through the construction ofcheck dam systems in small watershed, give overall consideration to both upstream anddownstream, main and branch channels, play integrate function of the system and thenachieve comprehensive management of small watershed. Therefore, it is necessary and urgentto research on the check dam system optimization of small watershed. Based on systematicresearch on optimal choice of check dam site, construction sequence and increasing height bystage, get a series of research findings which are of practical significance and reference value,have positive effects on planning, construction and management of the check dam system insmall watershed on loess plateau, meanwhile, have important significance in futher enrichingand improving the theoretical system of check dam system construction and comprehensivemanagement of small watershed.