Hydrologic and Nutrient Removal Performance of Rain Gardens: A Review

Author(s): Ly, P.; Ramirez-Avila, J.

As the intensity of hydrologic events and concerns of pollutants in stormwater runoff increase, it is critical to recognize the importance of stormwater management. Thus, best management practices (BMPs) have been developed as control measures against the potentially detrimental effects caused by excess runoff. Structural or institutional BMPs have been proven to successfully manage stormwater runoff, improve runoff quality, and mitigate effects of erosion. Rain gardens or bioretention facilities have been used as a structural BMP to filter pollutants from runoff and mitigate erosion by slowing runoff volume and velocity. However, because of the great variability in soil type, vegetation, rainfall conditions, and many other parameters, it is difficult to assess the hydrologic efficiency of a given rain garden. Past research has quantified rain garden's performance in terms of volume of the system's inflow, outflow, and removal of nutrients and heavy metals. Because a good understanding of design configurations, climate conditions, and temporal relationships are crucial for the efficient performance of a rain garden, a study aimed to compare and contrast results on previous rain garden research, in order to determine correlations between design configurations and their potential to both, flow and pollutant loads. From these compiled studies, it was found that hydraulic conductivity is a major design parameter to be considered as high infiltration leads to greater hydraulic performance, but poor nutrient removal. Inherent soil properties such as the soil test phosphorus are also indicative of how well the rain garden will perform in terms of water quality.

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