| Rapid urbanization has led to continued conversion from natural ecological space to urban space,resulting in the great changes of original natural state of hydrologicaly response,aggravating risks of urban floods and endangering urban residents' life and security.So far,the new urban storm water management concept based on the low impact development(LID)controls has been promoted and developed at home and abroad.However,most pervious studies are mainly carried out in the field scale(lot scale),and the new urban storm water management based on LID controls enhances the resilience of urban storm water management for the purpose,rather than improvements of storm water regulation effects confined to a single site.Therefore,how to apply new urban storm water management concepts,how to optimize the spatial pattern of LID controls in the city(watershed)scales,and construct modes of urban growth scenarios that could reduce the flood disaster risks effectively are the problems expected to be solved at present.The study utilized GIS and Storm Water Management Model(SWMM)to be loosely-coupled,and chose a new growing area of southern Bazhong as the study area to analyze different LID controls and it's optimized spatial pattern under the mechanism of urban storm water regulation with different rainfall intensities by using the Low Impact Development(LID)module of SWMM;then the study constructed and simulated hydrological characteristics under 4 different scenarios:the pre-development state(current situation)(SO),a traditional urban development plan(S1),an urban development plan with LID controls(S1),and an urban development plan in which LID controls were specially located to decrease the DCIA(S3),in order to reveal potential impacts of the study area's storm water regulation under 4 different scenarios in urban district scale and provide suggestions for the sponge city's constructions of the new growing area of southern Bazhong.The main conclusions of this paper are as follows:(1)Under the same percentage of impervious area,the proportion raise of DCIA which directly connected to the outlet could lead to the reduce of infiltration volume and increase of runoff,however,the storm water regulation could raise with the increasing of rainfalls under certain rainfall intensities,and graduated dropped off when over certain rainfall intensities.(2)LID controls have different effects on the storm water regulation due to the diversities of their own types and empirical parameters,and these differences are mainly reflected in their sensitivities to the rainfall intensity and the way to deal with rainfalls(infiltration or storage).The analysis found that runoff volume control effects of permeable pavements and rain gardens tended to be higher than green roofs and infiltration trenches in a unit area after determining empirical parameters according to characteristics of the study area,and stronger effects when in strong rainfalls;but green roofs and rain gardens were mainly on rainwater collections and storages rather than had the storm water regulation of increasing infiltration capacity.The regulation of four LID controls on peak flows are related to rainfall intensities and rain types.When the rain peak flow appeared,if storm water regulation capacity of four LID controls had not reached saturation,all had effects of peak flow reduction;but if had reached saturation,the decreasing effect would disappear and even the peak flow would increase.(3)Optimized pattern of LID controls will directly affect the DCIA,and then influence storm water regulation effects.The study found that optimized spatial patterns by Seepage canals and permeable pavements could reduce the DCIA significantly and realize the storm water regulation effectively according to four LID controls(Seepage canals,permeable pavements,green roofs,rain gardens)determined by types and construction ways.(4)With the rainfall intensity purpose of the sponge City(the control rate of 85%),runoff volume,outflow volume,peak flow,and runoff coefficients of urban growth scenarios(S1,S2,S3)had different degrees of increase effects compared to SO.Among them,compared S2 with S1,the runoff volume,outflow volume,and peak flow of S2 decreased respectively by 17%,16.8%,27.1%while the control rate of total runoff had increased by 11 percentage points to 77%;but compared S2 with S3,peak flow of S3 decreased respectively by 22.4%,30%,16.3%while the total the control rate of total runoff had increased by 7 percentage points(up to 84%).It showed that the two schemes of LID controls could achieve the sponge city control target(annual runoff control rates from 75%to 85%),but if optimized spatial pattern of LID controls were considered,the urban storm water regulation effects would be better.(5)Under the ten-year rainfall intensity,runoff volume,outflow volume and peak flow of the four scenarios were obviously improved but significantly different.Researches showed that compared S1 with S0,S1 had a very significant urban hydrological effect,runoff volume,outflow volume and peak flow of SI increased respectively by 32%,38%and 37.2%while the control rate of total runoff had increased by 11 percentage points to 32%;compared S2 with S1,S2 could reduce the runoff and increase the total runoff control rate of effects significantly(the runoff decreased by 17%,the total runoff control rate increased to 44%);however,compared with S2,the storm water regulation effects of S3 were weaker.It indicated that LID controls still had effects of storm water regulation in heavy rainfalls,but the reception was weak by storm water regulation effects of LID controls' optimized spatial pattern.This paper analyzed the impacts from changes of DCIA,LID controls and optimized spatial pattern to urban hydrology and storm water regulation characteristics based on the construction of SWMM of the study area and GIS in different rainfall intensities.The study not only provided guidance for the sponge city's construction in Bazhong,but also loosely coupled GIS data and SWMM data,realizing the abutment of urban planning data(CAD format),GIS data,SWMM parameters and data,and providing a good idea and method to plan and design the city(watershed)pattern and land use layout(including LID controls)and evaluate effects of storm water regulation on the sponge city's construction,and finally realize urban sustainable and flexible storm water regulation.The whole thesis contains about 42 000 words,67 pictures and charts. |
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