Study On The Effectiveness Of Runoff Reducing And Control Through Concave Greenbelt Measures

With the continuous development of social and economy in China,the process of urbanization is becoming faster and faster.All kinds of "urban diseases" have also come into people’s attention,among which urban waterlogging has become a major persistent disease affecting people’s work and life.In order to alleviate urban waterlogging,the theory of "sponge city" came into being and was implemented in many places.However,at present,the research on sponge measures is not comprehensive and detailed,some measures are still in the construction form,feasibility analysis and other aspects,and the reduction and control effect of surface runoff needs to be further studied.In this study,a certain area in the east of Handan is taken as the research area.According to the data of drainage pipe network and underlying surface type,the current SWMM model of the research area is constructed by manual precise generalization method.The maximum water depth verification method is used to select the typical rainfall runoff process on August 2,2019 for model parameter calibration,and the typical rainfall runoff process on August 4,2019 and August 25,2019 for model verification.And the results meet the requirements.Based on SWMM,this paper proposes a new technique to realize the simulation of the concave greenbelt.By using this method,the constructed model is transformed and the "LID mode" of the research area is constructed.In different typical rainfall scenarios,the runoff response process of the model is analyzed and the runoff reduction and control effect of the concave greenbelt is evaluated.The results are as follows:(1)under the actual rainfall scenario,the characteristics of waterlogging in the study area are simulated and analyzed,and it is found that the waterlogging in the south side of Xunzi street is the most serious.(2)based on Chicago rainfall pattern,the design rainfall with different return periods is constructed according to the regional characteristics,and the runoff response process of the current mode and LID mode are compared and analyzed.Due to the long duration and large amount of rainfall,and the limited area of greenbelt,the measures of concave greenbelt can reduce and control runoff to a certain extent,and with the rainfall return period Increase and decrease.(3)under the actual rainfall scenario,the runoff response process of the current mode and LID mode is compared and analyzed,and it is found that the concave green belt measures have the effect of peak cutting and emission reduction,lag peak time and reduce the depth of regional waterlogging.At the same time,it was found that the measure is better in the case of small rainfall.This study expands the research of sponge measure effect evaluation in the northern region,provides a certain technical reference for the construction of sponge city in Handan area,and provides a strong support for the promotion and construction of sponge city.