Urban stormwater runoff is nonpoint source (NPS) pollution, which remains thenation largest source of water quality problems. Through comparative case studies,this dissertation examines the environmental implications of different urbandevelopment, models in different geographical locations and then, studied bestmanagement practices (BMPs) benefits for urban stormwater runoff problems, whichcan be the guideline to protect the urban water bodies and human health. Thefeasibility, advantages and effectiveness of various stormwater runoff approaches areinvestigated through urban land-use and surface types. Results show that:
(1) The sources of the different contaminants in Shanghai and Bamako are typicallycommon to most urban environments, the contaminants are organic type and thepartial pollution is serious.
(2) With additional differences between the two cities in terms of demographics,land-use, climate, urban development and existing approaches, substantial differencesare noted for pollutant concentration levels and their pattern distribution in each city.
(3) The results revealed that stormwater quality is mostly affected by the humanactivities such as industrial production, traffic transportation, commercial activities,construction works, etc. Higher levels of impervious surfaces like roads, parking lotsand rooftops result in higher volume of runoff with higher peak discharge, shortertravel time are generally toxicity organic compounds, sediment, heavy metals,nitrogen, phosphorus and more severe pollutant loadings. Thus, they become thepollution sources, which ultimately declined the water quality and hold a threat tohuman health. For this reason, it has significantly realistic and scientific meaning tostudy stormwater runoff BMPs benefits in such busy urban watersheds like Bamakoand Shanghai.
(4) The objective of this dissertation is to develop urban stormwater runoff BMPs andto demonstrate the potential benefits of such practices in urban stormwater runoffquantity and quality control. The basic characters of stormwater NPS pollution aresummarized. Major advances in fields of land-use, rainfall/runoff, spatial distributionof contaminants, site assessment and any subsequent risk assessment, application ofthe new technologies and the management are discussed. The comparative case studyof Bamako city (Mali) and Shanghai city (China) included different BMPS and othersmeasurements strategies for urban stormwater runoff.
(5) The study was based on the sampling of 4 storm events from roads (traffic,industrial, commercial, residential areas) and from 4 roof materials in Shanghai,versus 1 storm event on roads (traffic, industrial, commercial, residential areas) andfrom 2 roof materials samples in Bamako as well as the analysis of effective data. Thecontents of nitrogen, total phosphorus, heavy metals etc. and their spatial/temporaldistribution in stormwater runoff are studied and compared. The method of estimatingevent mean concentration (EMC) is used to calculate the contamination levels fromdata analysis. Results show that the concentration of pollutants varied strongly amongsurface types and time.
(6) Average EMCs of pollutants such as TP and NH_4~+-N from the two urbancatchments can be described and ranked in descending order of magnitude:commercial, traffic, industrial, and residential areas. TP concentration levels forShanghai city exceeded the fifth class value for surface water guidelines from allsurface types and were 4.39; 4.34; 5.81 and 7.1 times those measured in Bamako city.NH_4~+-N pollution in Bamako commercial area is more serious exceeding by 2.38times the fifth class value for surface water standards of China and 1.36-timeconcentration from Shanghai commercial area.
NO_3~--N and NO_2~--N order of magnitude slightly varies from one to another city.NO_3~--N pollution was a high environmental issue from all surface types of Bamako(e.g. concentrations were 4.94 and 2.79 times the fifth class value of surface waterguideline for industrial and commercial areas respectively. Similarly, these values were 10, 8, 5, and 3 times the values calculated in Shanghai industrial, commercial,residential and traffic areas respectively. NO_2~--N pollutions are weaker everywhere.
The study also demonstrates that roofs could be a serious source of nonpointwater pollution. Stormwater from old concrete roof is identified as the mostcontaminated of the four roof types. Then, good care and maintenance of concreteroofs is critical in reducing pollution in roof runoff.
The average EMCs of heavy metals such as Cr, Pb, Zn and Cu, were measuredand compared. Cr contamination level is of concern from all surface types in the twocities. Respectively, Cr and Pb pollution in Shanghai were 10 and 14 times greaterthan the values measured in Bamako industrial area. Zn values of Shanghai were 6.77and 3 times those of Bamako in industrial and traffic area respectively. Given metalsconcentration levels and the water quality criteria, treatment is required for Cr fromall investigated land-uses of this study and for Pb to all-Shanghai surface types.Likewise, treatment is required for Zn in Shanghai industrial and traffic areas.(7) Inaddition to those impacts, the policy and the populations' behavior lead to importantimplications for stormwater runoff management. Then, the results put forward theneed for new form of governance facilitating integrated solutions and knowledgepartnerships.
The study estimated the magnitude of such impacts and demonstrated theenormous potential of using BMPs for monitoring these regional scale environmentalprocesses. Theses measures need to be implemented in conjunction with an integratedwater resources environmental management system, involving informationdissemination to the public and public education. These results cannot themselvesonly fill up the blank in the research of NPS pollution of Shanghai and Bamako, theyoffer however reliable and scientific basis for the urban stormwater runoff pollutioncontrol.If the benefits of stormwater runoff can be shown to compare favorably withthe benefits of BMPs, this will provide an incentive to overcome other obstacles towidespread adoption of stormwater management.