Study On The Effect Of Green Space Vegetation On Rainwater Interception In Buildings And Communities In Beijing’s Old City

Green space vegetation is a basic constituent element of various rainwater reduction facilities,and plays an important role in rainwater interception and purification.The protection of the style and features of the old city has attracted more and more attention in recent years.At present,most of the old cities are facing problems such as insufficient greening rate,old infrastructure,unreasonable utilization of rain water resources and high cost of renovation in the process of renovation or renewal.How to use the green space vegetation to reduce the loss of the old urban style due to the problems of waterlogging and water pollution caused by rainfall?How much effect can green space vegetation play in rainfall?What kind of plant design and configuration can maximize the effect of plant retention?This series of questions is the core question to be answered in this article.This study firstly sorted out and analyzed the relevant research on the effect of urban green space vegetation on the interception effect of rainwater,and expounded the principles of vegetation interception of rainwater from the three aspects of plant canopy,stem and litter,and in the canopy interception part It is divided into three parts:arbor canopy interception,shrub canopy interception and herb canopy interception.At the same time,the evaluation indexes and research methods of plant interception capacity are summarized.The choice provides the basis.Through field research on the green space vegetation characteristics of 6buildings and communities in the old city of Beijing,the selected vegetation types,plant height,breast diameter and crown width,configuration mode,ecological habits,ornamental characteristics,and canopy covering other underlying surfaces Relationship and existing problems,a detailed analysis of the green area vegetation characteristics of the old city buildings and communities.In order to evaluate the ability of the plant canopy to intercept rainwater,in this paper,21 plant leaves from 6 research sites in the old city of Beijing were selected as the experimental samples.The leaf water absorption,canopy interception volume,canopy interception volume,plant community field rainfall interception rate and community multi-year average rainfall interception rate were calculated.Research showed that:(1)the relationship between water absorption and immersion time was logarithmic;(2)the water absorption process of plant leaves can be divided into three stages.The water absorption process of trees and shrubs is similar.The mean water absorption of leaves at 20 min is 0.17 g and 0.05 g,respectively;the mean water absorption of leaves at 80 min is 0.18 g and 0.06 g,respectively;and the mean water absorption of leaves at 120 min is 0.18 g and 0.06 g,respectively.The average water absorption of herb leaves was 0.13 g at 20 min,0.27 g at 40min,and 0.21 g at 120 min.(3)The canopy rainfall interception of 11 species of arbors was between 71.30 and 738.72 g/m~2,and the canopy rainfall interception of the 6 shrubs was between 41.79 and 275.28 g/m~2,the canopy rainfall interception of the 4 herbs ranged from57.82 to 217.49 g/m~2,and the canopy interception of evergreen conifers was significantly higher than that of deciduous broad-leaved plants;(4)canopy interception of some shrubs and herbs was higher than that of some arbors,such as Buxus sinica and Iris tectorum.(5)the plant canopy interception volume is positively correlated with canopy cover area and plant canopy interception quantity,the evergreen coniferous tree+evergreen shrub+herb combination has the largest canopy interception volume.(6)The ratio of the average annual rainfall interception of the Cedrus deodara+Buxus sinica+Iris tectorum community canopy to the total rainfall is 11.57%,which has a significant interception effect on small and medium rainfall events.Based on the experimental data of plant canopy interception and annual rainfall historical data,the i-Tree Hydro model was used to simulate the historical scenario,current situation scenario,and total annual runoff,basic watershed flow,and permeable surface runoff in the site.Compare with the impervious surface runoff,and analyze the changes of the above four types of runoff in the multi-situation according to the simulation results,summarize the reasons for the changes and the main influencing factors,analyze their correlations,and find out their laws of action.Finally,based on the above research results,this paper proposes the principles of vegetation selection and configuration optimization in the old city,and discusses the detailed optimization design strategy from the two aspects of the plant community plane structure and vertical structure,and summarizes the main measures of the old city plant maintenance optimization.The green space vegetation has the best effect on rainwater interception,which provides a certain reference for the construction of sponge city green space.