Abstract
Recently, an increase in impervious area induced by the process of urbanization has significantly affected the quantity and quality of urban surface runoff. Among the pollutants of the storm flow, total suspended solids (TSS) are an extremely important cause of water quality deterioration. This paper aims to use the integrated nondominated sorting genetic algorithm (NSGA II)–Storm Water Management Model (SWMM) method to find optimal Low-Impact Development (LID) plans which ensure maximum TSS load reduction and minimum total relative cost. Green roofs, permeable pavements, and tree boxes with fixed parameters and unit costs were considered for seeking optimal planning alternatives in the Cau Bay river basin. The optimization process yielded a cost–effectiveness curve, which relates cost of LID implementation with its corresponding TSS reduction efficiencies. The advantage of the optimization approach was clarified when, with a defined cost of LID implementation, there was a significant difference in TSS reduction efficiencies between the optimal and non-optimal alternatives. The increase in return periods of rainfall patterns not only resulted in a reduction in the TSS removal efficiencies of LID practices at the outfall of the study area, but also spatially changed in terms of the TSS removal efficiencies of the sub-catchments. The return period of the rainfall patterns utilized for LID design should not exceed 2 years. The simulation–multi-optimization approach facilitates integration of LID practice plans into the urban infrastructure master plans in Vietnam.
Highlights
In recent decades, an increase in impervious area induced by the process of urbanization has significantly affected the quantity and quality of urban surface runoff
Low-Impact Development (LID) practices for water quality improvement have not yet been considered at either the site or the basin scale. To fill in these gaps, this paper aims to (1) develop the integrated NSGA II-Storm Water Management Model (SWMM) model to find optimal LID planning alternatives in urban basins that ensure maximum Total Suspended Solids (TSS) load reduction and minimum total relative cost; and (2) evaluate optimal planning alternatives for the TSS control of a wide range of designed storm events for the Cau Bay river basin
An alternative consists of a combination of green roofs, permeable pavements, and tree boxes, which is implemented for sub-catchments in the upper area of the Cau Bay River basin
Summary
An increase in impervious area induced by the process of urbanization has significantly affected the quantity and quality of urban surface runoff. The increased impervious area results in increased peak flow and reduced concentration time. The surface runoff washes off a significant amount of the pollutant loads from impervious areas, deteriorating the receiving water body at local and regional scales. Most of the pollutant load from urban areas is carried from events with a return period of less than 2 years [1]. Among the pollutants of the storm flow, Total Suspended Solids (TSS) are an extremely important cause of water quality deterioration, leading to esthetic issues, higher costs of water treatment, a decline in fishery resources, and serious ecological degradation of aquatic environments [2]
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