| Accelerated urbanization, the impact of urban development on aquatic ecosystemsis gradually emerging. Rising the rate of hardcourt blocked rainwater infiltration,increased stormwater runoff, shorten the time rainwater catchment, the impact of thenatural cycle of urban water systems, increased water pollution, triggering floods.In thepresent work, as taking Qinghu district in Shenzhen as an experimental area, learn fromthe concept of low-impact development （LID）, the comprehensive investigation on themutual interaction among climate characteristics, topographic and hydrologic propertieswas carried out by means of in-site survey. After then, a comparative investigation onthe LID techniques’ functions was conducted in laboratory-scale. Based on theparameters and relationships determined in-and out-site, SWMM model was adopted tosimulate, for looking for a sustainable strom water control and utilization strategy.The survey and monitoring results in the studied area displayed that: first, the solidparticle with a fine average size （<0.6mm） on the land surface dominated on the landsurface, while the smaller size solid particles that have rather high adsorption capacityof pollutants only have limited proportion; second, the pollutants concentration inrunoffs from municipal road and conventional roof were quit high in the beginning ofrainfall, and the concentration has apparently decline trend with the progress of rainfall,finally arrives at a stable; last, the non-point pollution source mainly comes from themunicipal roads, rather than conventional rood, owing to that the pollutants on the roadprefer to be washed away and therein carried by the initial runoff. The road surface ismuch easier to be affected by the initial runoff flushing compared with roof, as that itsEMC value of TSS, COD, TP, TN is more than30、4、13、1.5times of those of roof.The experimental studies on the LID techniques showed that the compositepermeable brick have a higher permeability coefficient than those of sand foundationbrick and terra cotta tiles. However, the permeable brick is quit easy to be clogged,reflected by the sharp decreasing of permeability coefficient after50min filtration study.Sunken grass space has a better capability for runoff control, not only in retention ofoutflow, but also in pollutants interception and removal, compared with permeablebricks, through series runoff tests under simulated and natual rainfall. Notwithstanding,its capabilities of runoff control highly depended on the sunken green vegetation、thereturn period、the soil thickness、and the ratio of green space. Considering theefficiency of runoff control and pollutants removal, as well as cost-effectiveness, therecommended sunken grass space were vegetation of Baixicao、return period of1year、soil thickness of60cm、green rate of1/2. Improved gullies having a good clipping decontamination capabilities, retention of water0.79m3and removal of54%SS,66%COD,46%ammonia,72%of TP. In addition, artificial wetlands suitable forhandling stormwater runoff, which have stable operation effect. Pollutants of COD,BOD5, ammonia, TP removal efficiency is more than62%.Based on these experimental results, the SWMM model was constructed tosimulate the hydrological effects and improvement of LID techniques used in the studyarea. When the land use progessed without LID technical regulation, the runoff volumeafter development （the impervious area of70%） would be increase to more than0.84times than before（the impervious area of20%）, while the infiltration capacity declinedby67%. In constract, after once more than35%area employed a combined LIDtechnical that includes green space, permeable pavement, gullies, constructed wetlandsand so on, for the case of return period of10years, the discharge opening of the outflowtime deferred more than34min, the runoff and peak flow reduced by63%and57%,respectively. Moreover, the pollutants removal would also be improved to some extent,as that more than49%of TN, TSS, TP and COD are removed. |
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