Simulation Of Total Rainwater Runoff Before And After The Sponge City Pilot Construction In Wanzhou City Based On Infoworks ICM Model

The fundamental purpose of sponge city construction is to improve the environmental quality of people’s lives.It needs to be carried out in a targeted manner in conjunction with the city’s development plan.Its main objectives include total runoff control,runoff peak control,and runoff.Pollution control and rainwater resource utilization,annual runoff total control rate is the primary control target of sponge city construction.Therefore,the construction of the sponge city must be suitable to local conditions.Through the simulation of the total amount of rainwater runoff based on local geographical,reasonable transformation plan can be drawn and which is conducive to the realize the construction goals.To this end,the experimental area for sponge city construction in Wanzhou District was selected to carry out this study.Based on online monitoring of rainfall and runoff data,and by using the rainwater management model(Infoworks ICM)to study the runoff characteristics and sponge city constrction stragegy,including the optimal combination of rainwater garden,grass-growing and permeable pavemen,etc.And the variation of hydrological conditions and runoff characteristics in Tianzi Lake and Longbao River before and after sponge city construction of the under different rainfall intensities were analyzed And the main research results are as follows.1)The historical rainfall characteristics of the study area are consistent with the current rainfall characteristics.According to rainfall and runoff,the current annual total runoff control rate target of Wanzhou District is 60.24%.Sensitivity of ICM parameters:Under drizzle conditions,the fixed runoff coefficient is a highly sensitive parameter,the sensitivity to the total runoff is greater than the peak flow,and the impervious flow parameters are only moderately sensitive to the peak flow.under moderate rain conditions,the fixed runoff coefficient The permeable and confluent parameters and the initial infiltration rate are more sensitive to the total amount of runoff than the peak flow.The Manning coefficient of the pipeline is only moderately sensitive to the peak flow,and the steady permeability is the sensitive parameter for the total runoff.Under heavy rain conditions,the Manning coefficient of the pipeline is highly sensitive to the peak flow,and the fixed runoff coefficient is the total of the runoff.Sensitivity;under heavy rain conditions,the Manning coefficient of the pipeline is highly sensitive to the peak flow,the fixed runoff coefficient is moderately sensitive to the total runoff,the initial infiltration rate parameter is the sensitive parameter for the total runoff,and the steadyflow rate is the total runoff.The amount is moderately sensitive.2)There are more existing pipe networks in the Tianzi Lake and Longbaohe sub-districts,and the design scale of the rainwater drainage pipe network is mostly less than once every two years.At the same time,some upstream pipe bottom elevation is lower than the downstream pipe bottom elevations areower than the downstream ones.The simulation results show that in the Tianzi Lake and Longbaohe areas,the overload rate of the pipe at P=2a were 22% and 47.6%,respectively,and the node overflow rates were 7.1% and 15.8%,respectively.3)The total amount of runoff control effect in the ICM model were sorted into rain garden > permeable paving > green roof > planting ditch,scale permeable paving =green roof > rain garden.The total runoff and dynamic reserve peaks are sensitive to LID size.At the same ranoff control rate,the LID scale required for dynamic reserve peaks is larger than the total runoff.The factors that affect total runoff and dynamic reserve peaks are follow the oreder of Rain Garden > Permeable Pavement > Green Roof.Construction scale follow the order of Permeable Pavement = Green Roof > Rain Garden.4)According to the measured data,ICM model and SPSS software are used to analyze the runoff.It was shown that the extent of impact on runoff follows rainfall >rainfall peaks > average rainfall intensity > previous sunny days > rainfall duration.The construction scale of Tianzi Lake area were: 11.196 ha of green roof、21.370 ha of permeable pavement、 2.140 ha of rain garden.The construction scale of the Longbao River area were 97.272 ha of green roof、 36.990 ha of permeable pavement and 85.224 ha of rain garden.After the Sponge city construction,the total rainwater runoff control rate of the Tianzi Lake area can reach to 88%,and the Longbao River area can reach to78%,which will totally meet the reqired goal which proposed by the local sponge city Planning of 75%.Based on the measured rainfall and runoff data,this study analyzes the storage effect of LID technologies in the Infoworks ICM model.The sponge city construction strategy of the experimental area in Wanzhou District was also proposed.This study can provide certain data support for effectively promoting the mountain sponge city construction.