| In the context of the frequent occurrence of global extreme weather events and continuous expansion of urban scale in China,the sensitivity and vulnerability of cities to flood disasters have become more and more obvious.According to this situation,the state clearly put forward the construction concept of sponge City,and launched the upsurge of sponge city construction,especially the construction of source control measures throughout the country.Although there is a lot of research on source control measures such as LID,few people have been involved in the evaluation of the effects of different measures and their combination,and further research is needed.(1)Combined with the maximum ponding depth and runoff coefficient method,the SWMM model in the study area is constructed;Through field surveys,rainwater buckets,permeable paving,rainwater gardens and grass-planting ditches were selected as LID measures suitable for typical areas.Based on the upstream and downstream relationship of the drainage network and land use types,a refined LID layout plan was designed and formulated.(2)The single LID measure can reflect the control effect of rainfall runoff from three aspects: infiltration amount,reducing runoff peak value and lag peak time,and the three effects of each measure decrease with the increase of return period.Under different return periods,the runoff reduction and control effect of the same measure installed upstream and downstream at the same time is equivalent to the superimposed effect of the measure when it is deployed separately upstream and downstream.Among them,in terms of the total runoff reduction and control effect,the permeable paving is the best,between 19% and 52%;the grass-planting ditch is better,between 6% and 15%;the rain garden is weak,between 2% and 9%;and the rain bucket is the weakest,between 2% and 8%;and the ranking of the above measures is also consistent in the runoff peak reduction and peak time lag effect.(3)The runoff reduction and control effect of the LID combination measures also decreases with the increase of the return period.In terms of the reduction and control effect of total runoff,the ones with permeable pavement are better,reducing control effect between 22% and 39%;those with grass ditch are better,reducing control effect between 7% and 39%;those with rain gardens are better,reducing control effect between 6% and 35%;and those with rain buckets are weaker,reducing control effect between 6% and 26%;.Among them,the upstream and downstream combined measures of permeable pavement and grass planting ditch are the most effective,while the combined upstream and downstream measures of rainwater bucket and rainwater garden are the least effective.(4)By comparing the runoff reduction effect of single and combined measures under different return periods,it is found that the effect of combined measures is the same as the cumulative effect of the effects of two single measures.That is,in this study,the offset or gain effect of the two single lid measures arranged upstream and downstream in runoff reduction and control is not significant.This study verifies the feasibility of the construction of low impact development measures in the main urban area of Handan,provides a basis for solving the problem of urban waterlogging in heavy rains,and also provides a reference for the construction of low-impact development measures in northern cities. |
