Study On Combination Screening And Application Effect Of Plant-artificial Matrix Based On Heavy Rainfall Control

With the rapid development of urbanization,the increase of impervious area has caused a major change in the hydrological cycle,leading to the accelerated collection speed of falling rainwater,and gradually prominent rainfall-runoff problem in the city,which has a great impact on people’s life.In this paper,the eigenvalues of the combination of plant and artificial substrate were quantified according to the German Institute for Research in Development Landscape Architecture(FLL)code through the selection of artificial substrate materials and plant growth monitoring experiments.Solute penetration and staining tracer experiments under different rainfall conditions were carried out in the laboratory.According to the solute penetration curves and staining tracer images,the flow migration rule of plant-artificial matrix combination in heavy rainfall events was analyzed,and the plant-artificial matrix combination with the lowest degree of preferential flow migration was obtained.Taking the dormitory in the East District of Hubei University of Technology as the research object,the parameters of the optimal combination of plant and artificial matrix were selected as the input parameters of the LID-green roof module in SWMM.The SWMM model was used to control the Green roof in the study area,and the reduction effect of rainfall and runoff before and after the control was analyzed.The main conclusions of this study are as follows:(1)The specification of perlite had no significant effect on dry density,specific gravity,porosity,saturation load and permeability of the matrix assemblage(P BBB 00.05),but had significant effect on the maximum water holding capacity of the matrix assemblage(P <0.05),which showed that the maximum water holding capacity of perlite(3-6 mm)was higher than that of perlite(4-8 mm).The addition rate of two types of perlite had significant effects on the permeability,dry density,porosity,maximum water holding capacity and saturation load of the respective pearlite matrix(P <0.05).However,vermiculite supplemental rate had no significant effects on dry density,porosity,maximum water holding capacity and saturation load of vermiculite matrix(P bb0 0.05).The aggregate types had significant effects on dry density,porosity,maximum water holding capacity,saturation load and permeability of the matrix(P<0.05).(2)During the observation period of 50 days,the type of substrate had no significant effect on the number of leaves(P BBB 0 0.05),but had significant effect on the length and width of leaves at 30-40 days(P <0.05),and had significant effect on the height of plants at 30-50 days(P <0.05).The leaf length,leaf width and plant height of perlite group were lower than those of vermiculite group.The substrate thickness had no significant effect on the number of leaves(P BBB 0 0.05),but had significant effect on leaf length and leaf width at 30-40 days(P <0.05),and had significant effect on plant height at 30-50 days(P <0.05).With the increase of substrate thickness,the leaf length,leaf width and plant height of plants increased.(3)In the plant-free artificial matrix group,the skewness of solute penetration curves in the 10 a-6 cm group was greater than 0.1 under the two substrates,indicating preferential flow migration.In the plant-artificial matrix group,only the vermiculite group(10 a 14 cm)did not have current preferential migration,while the other groups had current preferential migration.The staining tracer experiment showed that there were different sizes of unstained area and number of staining pathways in the plant-perlite formation,so the preferential flow migration occurred in the plant-perlite formation.Based on the results of solute penetration experiment and staining tracer experiment,as well as data analysis of orthogonal test table,combined with plant growth,the optimal combination with the lowest degree of water flow priority migration was selected as Vermiculite group of 14 cm.(4)After LID control,in the rainfall event that occurs once every two years,the total runoff in the study area decreases from 390 m~3 to 250 m~3,with a peak reduction rate of 35.90%,and the peak runoff in the study area decreases from 0.253 m~3/s to 0.186m~3/s,with a reduction rate of 26.48%.The runoff coefficient in the study area decreased from 0.65 to 0.38.During the 5-year rainfall event,the total runoff in the study area decreased from 630 m~3 to 420 m~3,with a peak reduction rate of 33.33%,the peak runoff in the study area decreased from 0.361 m~3/s to 0.254 m~3/s,with a reduction rate of29.64%,and the runoff coefficient in the study area decreased from 0.69 to 0.45.In the rainfall event that occurs once in a decade,the total runoff in the study area decreases from 830 m~3 to 570 m~3,with a peak reduction rate of 31.33%;the peak runoff in the study area decreases from 0.467 m~3/s to 0.309 m~3/s,with a reduction rate of 33.83%;and the runoff coefficient in the study area decreases from 0.73 to 0.50.