The Research On The Influence Of Pervious/Impervious Pattern On Runoff And Pollution In Pacel-based Catchment

In the process of rapid urbanization,the urban land use types and underlying surface conditions have changed greatly,which makes the urban hydrological cycle a great change,resulting in the urban waterlogging and non-point source pollution.Many studies have shown that the proportion of impervious surface in the catchment is the main factor affecting the quantity and quality of urban surface runoff.In recent years,many scholars try to explore the influence of impervious area threshold on hydrological response of watershed or catchment.However,the research on how the spatial pattern of pervious/impervious surface affects the process of urban non-point source pollution(conflux and pollutant transport)is still lacking.In view of the above,the study learns ideas from the landscape ecology to address the problems of spatial patterns and ecological processes.The influence of spatial distribution and configuration of pervious patches on hydrological process and pollution output in parcel-based catchment was analyzed by selecting appropriate landscape pattern metrics.The study revealed the relationship between the static spatial pattern of pervious/impervious patches and the dynamic process of runoff pollution output in the parcel-based catchment,which to identify and evaluate the effects of pervious/impervious surface spatial configurations(patch areas,distance and shape,etc.)on total runoff and pollutant cumulative loads.The main conclusions are as follows:(1)For the metrics of fragmentation,the patch density(PD)was positively correlated with Q and Ld.and largest patch index(LPI)was negatively correlated with them.Especially,PD was significantly positively correlated with Ld(r=0.59,P<0.05,calculated in COD).LPI was significantly and negatively correlated with L_d(r=-0.60,P<0.05,calculated in COD).(2)For the metrics of complexity,landscape shape index(LSI)was positively correlated with Q and Lp,and mean shape index(MSI)was negatively correlated with them.Especially,LSI was significantly positively correlated with L_p(r=0.61,P<0.05,calculated in TP).MSI was highly significantly and negatively correlated with Lp(r=-0.62,P<0.01,calculated in TP).(3)For the metrics of vergence,the split index(SPLIT)was positively correlated with Q and Ld,and the cohesion index(COHESION)was negatively correlated with them.While the COHESION was significantly negatively correlated with Ld(r=-0.59,P<0.05,calculated in COD)and positively correlated with L_d(r=0.6,P<0.05,calculated in COD).(4)In the planning on the distribution and pattern of pervious surface under small-scale catchment,it is suggested that the scattered small-regular patches should be transformed to large-irregular patches or patch group.