Planning Research For Urbanized Region Stormwater Drainage System Based On Low Impact Development

The rapid development of urbanization disturbed original hydrological cycle ofthe area, and increased the number of flood disaster in the urbanized areas, and manycities have suffered serious urban waterlogging disasters. This research in view ofrainfall and runoff characteristics in north China and the characteristics ofurbanization region, a sustainable urbanization region stormwater drainage systemplanning methodology based on LID (Low impact development) was developed, andstudied in a case region.First of all, the LID concept was combined with the region planning, and theplanning principles planning procedures and planning framework of urbanizationsustainable rainwater drainage system were established. This study used SUSTAIN asthe assistive tool for planning the layout of region stormwater managementmeasurements, and combining with the planning framework the region rainwaterdrainage system was planned and designed.A teaching and living region of an university in Tianjin is took as the study area,and the rainfall and runoff characteristics were monitored and analyzed. Analysisresults show that the sum probability of the heavy rain, torrential rain and heavydownpours was about19.5%in the study area, and in the case of this kind of rainfall,different degree of waterlogging would generally occur. The Event MeanConcentration (EMC) of COD, NH3-N, TP and SS in runoff exceeded the relevantenvironmental quality standards for surface water, which illustrated that the non-pointsource pollution of study area would cause pollution to the receiving waters.The runoff control abilities of several mature rainwater best managementpractices and LID practices were analyzed and summarized in the BMP database. TheBMPs were divided into on-site interception/treatment practices, runoff processingand treatment practices and regional storage/treatment practices, and according to theplanning principles the primary choosing principles were established, and the primaryLID practices and BMP practices were chose. Then the BMPs classification andevaluation system were established based on analytic hierarchy process (AHP) andMonte Carlo simulation. The performance equation of the evaluating indexes were setup, the weight of each criterion was calculated, and finally comprehensive score distribution of the practices were calculated. At last, green roof, rain barrel, vegetatedfilter strip, biorentention and wet detention pond were chose.According to the study area data, the LID and BMP practices layout and runoffmodel was established based on SUSTAIN. The practices were combined anddesigned in the study area. According to the different layout ways, four scenarios wereestablished, modeled and evaluated. The modeling results showed that theperformance of the layout which combined the LID and BMP practices was betterthan the layout of LID practices or BMP practices, especially the combination layoutwith BMP practices at the end of the catchment was the optimal combination layout.Combining the runoff characteristics of the study area and the runoff control targets,the optimal combination layout was optimized, and finally the optimal cost-benefitLID and BMP practices layout scheme was obtained.