Simulation Research On Urban Surface Runoff And Non-point Source Pollution And LID Control Effect Based On Remote Sensing And HYSWMM

The current imperfect urban wading infrastructure has led to many problems in the rapid development of the city.The flow generation and convergence process in the natural state will be interfered to a large extent by humans.The increase in impervious area and the lagging of urban pipeline networks have caused cities to face greater pressure from waterlogging and water pollution during rainfall.At present,the research on surface runoff hydrology and water quality at the small-scale,especially at the level of the building community,has made great progress,but there are few researches at the level of urban areas.Therefore,it is of great significance to conduct research on surface runoff and non-point source pollution in a larger urban area.This article takes an old town in Qingdao as the research object,and combines remote sensing technology with hydrology on the basis of reference to the current domestic and foreign rain and flood research.Using remote sensing software ENVI 5.3and Hongye storm drainage and the low-impact development simulation system(HYSWMM),the surface runoff and non-point source pollution models in the area were constructed and simulated research:First,based on remote sensing(RS)and geographic information technology(GIS),the medium-resolution remote sensing satellite image Landsat 8 OLI is used as the data source.After pre-processing operations such as correction and cutting,according to the actual situation of the study area,the main underlying surface type of the study area is selected.Using ENVI 5.3 and Arc GIS 10.7,the types and proportions of the underlying surfaces in the study area were extracted,which were 42.71% for building roofs,30.02%for roads,14.83% for green areas,and 12.45% for bare land.The confusion matrix method is used to evaluate the accuracy of the extraction results,and the total classification accuracy obtained is 89.14%,and the Kappa coefficient is 0.85,which shows that the classification result is more accurate.Secondly,use HYSWMM to construct surface runoff and non-point source pollution models in the study area,and select appropriate hydrological and water quality parameters.Under the conditions of the return period P=1a,2a,5a,10 a and 20 a,with SS,COD,TN and TP as runoff pollutants,a simulation study was carried out on the surface runoff and water pollution in the current study area.The results show that the surface runoff presents a trend of first increasing and then decreasing during the whole rainfall process.The total amount of runoff and the total pollution load are increasing with the increase of the return period.The peak concentration of pollutants SS and COD decrease with the increase of rain intensity,while the peak concentration of TN and TP show the opposite law.In addition,the peak concentration time of pollutants will appear 4 to 8 minutes earlier as the return period increases.It can be seen that the greater the return period,the greater the impact on surface runoff and non-point source pollution in the study area.Finally,a low-impact development facility(LID)scheme was designed for the study area.Determine 4 types of plans suitable for the actual underlying surface type of the study area,namely 5% recessed green space(LID 1),3% green roof(LID 2),15%permeable pavement(LID 3)and 3 types of LID facilities Combined facilities(LID 4).Add LID facility parameters on the basis of the established model.The models of different LID facilities are simulated in terms of discharge runoff,peak discharge,total pollutant load,and pollutant concentration.The results show that the control effect on surface runoff is LID 4> LID 2> LID 1> LID 3.The reduction rate of runoff can reach 34.83% at the highest point,and the reduction rate of peak flow is greater than 6.23%.In terms of non-point source pollution control,the ability to reduce the total pollutant load is shown as LID 4> LID 1> LID 2> LID 3.For discharge port Y244,the control ability of pollutant concentration is LID 4> LID 3> LID 1> LID 2.On the whole,the combined facilities can show excellent control effects in both surface runoff and non-point source pollution,and the control effect in the low return period is better than that in the high return period.At this time,the control effect can be improved by increasing the area of the LID facility or adding other facilities together.