Study On The Effect Of The Ladder Configuration Modification Of The Upper Convex Green Space On The Total Runoff Control

With the rapid development of the economy and the continuous advancement of urbanization,a large number of natural grounds have been replaced by hard paved ground,resulting in an ever-increasing proportion of urban impervious areas.At the same time as water shortage in many areas of China,rainwater floods and sewage spread The problems related to rainwater control and management such as flood disasters,runoff pollution,and groundwater level reduction are becoming more and more serious.Rainwater is an important link in the water circulation system.It plays a key role in the regulation and supplement of water resources and the change of ecological environment.As an ecological urban rainwater treatment facility,green space can effectively maintain and protect the natural hydrological functions of the site and alleviate imperviousness.Increased flood peak flow caused by increased area,increased runoff coefficient,and increased pollution load.However,the existing forms of uplifted green space are mostly determined according to the purpose of landscaping and the specific functional requirements of some cities.The actual seepage effect of green space does not meet the peaking and flood detention,source runoff pollution control and stormwater control.The requirements for utilization are not conducive to the construction of the sponge city.In this study,the traditional slope-upward green space is taken as the research object.Through the water balance principle,the green real estate infiltration theory and the artificial simulated rainfall test,the stepwise reformation of the slope green space is studied on the silo-type seepage bed to the green space seepage effect and the total runoff.The impact of quantity.The scale of the test model is expanded.By studying the flow generation process of the stepped green ground pilot plant,it is further verified that the stepped configuration of the green space has a good improvement effect on the total runoff control,and from the perspective of the total amount of sponge urban runoff control.Evaluation.The main results are as follows:1.The runoff process of slope green land mainly consists of three stages,namely initial infiltration stage,initial stage of production and stable stage of production.Rainfall intensity and slope will have a certain degree of impact on the greenfield runoff process,mainly reflected in the initial runoff time,stable runoff intensity and total runoff.When the rainfall intensity increases to a certain extent,the rainfall intensity exceeds the slope and becomes the impact of greenfield runoff.The most important factor in the process.The infiltration intensity of the soil decreases exponentially with the duration of the rainfall process.The decline process conforms to the Horton model and eventually stabilizes.2.In order to facilitate the description of the influence of the step-by-step transformation on the hydrological process of the upper slope slope green space,this study proposes the concept of“the ratio of ladder and slope”?ie,the ratio of stepped green area to total area of convex slope green area?.When the rain intensity is constant,the initial runoff time lags with the increase of the slope ratio S,and the stable runoff intensity decreases with the increase of the slope ratio.This difference caused by the stepped terrain reconstruction It is more obvious under the condition that the slope is steep and the rainfall intensity is small.The slope can be adjusted to make the rain water fully accumulate and infiltrate,and increase the infiltration strength of the soil.In the rainfall range of40⁷0mm/h,the stable infiltration strength f_c and the slope ratio S exist as follows:Relationship:f_c=a?1-sina+Ssi na?^1.3192+b In type:ais the slope of the green space,the values range of a and b are related to the rainfall intensity.The value of a ranges from 0.162 to 0.301,and the range of b ranges from 0.266 to 0.320.3.In order to make the test results closer to the actual project,the scale of the test site was expanded,and the pilot test was carried out on the stepped green space.The effect of the ladder configuration on the total runoff control was further studied.The model of the seepage effect of the green space was carried out.The actual application verification shows that when the rainfall intensity is 29.7mm/h,the stepped green space with an area of 2.7m×2.2m can not only absorb its own rainwater,but also can undertake40.89⁶1.77m³ concrete.The water supply on the impervious road surface does not occur in the outer row,which can meet the requirements of the sponge city on the total runoff control rate.