Study On Stormwater Runoff Control Method And Application Simulation Based On Runoff Sharing

The risk of urban waterlogging increases with the rapid urbanization process and the increase of impervious surface,which has become a great threat to urban water security.Since2013,under the strong support of national policies,urban drainage system upgrading project,waterlogging control project,sponge city construction project and other works have been carried out in an all-round way,and related theoretical research and scientific practice are also constantly explored and improved.At present,the research of urban drainage system is mostly confined to the discharge problem,and there is still a lack of effective absorption and control methods of excess runoff.In addition,traditional drainage systems directly discharge rainwater under non-exceeding rainfall events,leading to the waste of rainwater resources.Based on the research trend and national demand of waterlogging control,focusing on the frequent occurrence of urban waterlogging,this paper uses the Infoworks ICM,takes Shiqingya River basin in the Sponge City pilot zone of Jinan as the research object,and uses the model to clarify the current situation of the production and confluence of urban underlying surface under the background of sponge city construction.The concept of"flow sharing"is introduced into the urban flood control and drainage construction system,and the rainwater runoff control method and application simulation research based on"flow sharing"are proposed.The control method of time-sharing utilization of rainwater storage facilities is discussed from the perspective of"time scale",and the flow sharing mode of different rainwater facilities from the perspective of watershed is discussed from the perspective of"space scale".The rainwater runoff control method and control mode with"flow sharing"as the core are obtained to avoid or reduce the intensification of waterlogging risk caused by rapid urbanization,so as to provide research ideas and practical approaches for urban stormwater management and waterlogging disaster risk prevention.The main research results of this paper are as follows:（1）Three kinds of enable rules for rainwater storage tanks are proposed,including:ruleⅠis enabled when rainfall occurs;ruleⅡis enabled when the rainfall intensity reaches the set threshold;ruleⅢis enabled when the accumulated rainfall reaches the set threshold,through real-time control in the Infoworks ICM.The system implements the above control rules.Under the"time scale",each of the three enable rules of rainwater regulation and storage pool has corresponding thresholds.（2）The reduction capacity of total effluent,peak flow and velocity under the optimal control effect of enable ruleⅠ,ⅡandⅢwere compared and analyzed.The unit volume of rainwater storage tank set with three kinds of enable rules was 300 m³·ha^-1.The optimal start-up thresholds corresponding to ruleⅠ,ⅡandⅢare 300 m³·ha^-1,1 mm·min-1 and 20 mm respectively.The results show that ruleⅢhas the best control effect on the total outgoing flow,while ruleⅡhas the best control effect on the peak flow and velocity.Under the simulation of two actual rainfall events in Jinan,it is verified that ruleⅢhas the best control effect on the total outflow,and ruleⅡhas the best control effect on the peak flow and velocity.Therefore,different starting rules can be selected according to the actual demand to control the total runoff discharge,peak flow and velocity.（3）Based on domestic and international stormwater management experience,it puts forward the flow sharing mode and construction approach from the perspective of watershed.By systematically sorting out the research results and practical experience of outflow control and runoff sharing in typical cities at home and abroad,it summarizes the waterlogging prevention and control mode based on outflow control and runoff sharing applicable to Chinese urban watershed scale.The construction method includes drainage unit division-determination of outflow control threshold-assessment of current status control ability-calculation of runoff sharing demand-formulation of runoff sharing scheme-evaluation and optimization of effect.The feasibility and reliability of the flow sharing model are verified by taking the study basin as an example.（4）Based on the spatial difference of flow sharing,two flow sharing schemes,"inter-regional flow transfer"and"intra-regional flow absorption",were proposed under the"spatial scale".The research watershed was selected for application analysis.The results showed that the peak flow of watershed control points met the control threshold requirements under the 50-year return period."Regional discharge absorption"can effectively reduce the risk of waterlogging disaster in the inner basin and downstream cities.At the watershed scale,the characteristics of the natural water cycle system are fully considered and the control threshold is scientifically determined.At the drainage unit scale,reasonable and feasible runoff sharing schemes are formulated according to local conditions.By constructing a multi-scale and multi-level whole process runoff control system of"drainage infiltration,source emission reduction,pipe network storage and terminal regulation and storage",It can reach the target of watershed and downstream runoff peak and total amount control and meet the requirements of urban waterlogging control.