Research On Water System Construction Of Urban Rivers In Xiong’an New Distric

The formation,construction and development of cities are carried out relying on rivers.Good river ecological environment can promote the better development of cities to a certain extent.As the theory of harmony between man and nature gains popularity,people are increasingly concerned about whether the water environment of the city is good and whether the structure of the river system is reasonable.Especially when the new urban area begins to be planned,how to construct a reasonable water system structure to support its future production and living needs becomes particularly important.Based on the national key research and development project "technology and demonstration of wetland restoration and ecological function improvement in xiong’an New Area"(Project No.:2018yfc0506904)topic 4 "construction technology of ecological infrastructure and ecological security pattern in xiong’an New Area",and on the basis of summarizing domestic and foreign research on urban river system structure,this paper takes the river network construction in the starting area of xiong’an New Area as an example,Based on the planning outline of xiong’an new area,this paper analyzes the water system structure of urban river wetland which has similar hydrological and underlying surface conditions with the study area,and plans a reasonable water system structure for the study area.Using SWMM model and river ecological water demand,this paper analyzes the water system structure from two aspects of water safety and water environment safety,Finally,a water system structure suitable for the study area is planned.The main research work and achievements are as follows:(1)By analyzing the hydrological characteristics of the study area and the underlying surface scenario after planning,it is determined that the hydrogeological conditions of Suzhou Gusu district and Dongying Dongcheng District are similar to those of the study area,and the water system of the study area can be determined by referring to the urban water system structure of the two areas.Through the analysis of the urban water system of the two cities,the water surface rate of the river system in the study area is about 5.5%,the river network density is 1.66,and the river network development coefficient at all levels is about 1.The outer layer of the water system is the water system around the city,and the inner water system is distributed in a dendritic structure.(2)SWMM model is used to model the river system in the study area.Taking P=2 rainfall as an example,the comprehensive runoff coefficient method is used to calibrate the parameters of the model,and other frequency rainfall is used to verify the model.The simulated runoff coefficients of the calibrated model are between 0.6 and 0.8 in the main urban area,and between 0.15 and 0.45 in the urban wetland area,which is in line with the actual situation.(3)By analyzing the simulation results of the model under different return period rainfall scenarios,the overflow situation and discharge of the river under each rainfall scenario are obtained。Under the rainfall of P=1 and P=2,the river does not overflow.Under the rainfall of P=1 and P=2,the river does not overflow.Under the rainfall of P=5,P=10 and P=20,the number of overflow nodes is 2,8 and 13 respectively,and the overflow duration is controlled within 15 minutes.Under the extreme design rainfall of P=50 and P=100,the number of overflow nodes increased to 14 and 15.According to the distribution of overflow nodes,it is identified that the river section prone to overflow is the third grade river near dafenggudian.(4)Based on the hydrological data of Baoding and Xiongxian County in 19612019,the annual precipitation frequency curve is drawn.The year 2012 is the year of abundant water(p=25%),that of 2016 is the year of flat water(p=50%)and that of 2006 is the dry year(75%).The ecological water demand of rivers in the three representative years is calculated.The results show that the total ecological water demand in the year of abundant water is 170.015 million cubic meters,that in the flat water year is 170.4846 million cubic meters,the total ecological water demand in the dry year is 175.5873 million cubic meters,and the difference between the three levels of water demand is no more than 6million cubic meters.