Bioretention and Green Roof Systems in Semi-arid and Arid Climates: Evaluating and Optimizing the Retention and Pollutant Removal Utility

Implementation of low impact development (LID) techniques is becoming increasingly important as a means of reducing stormwater runoff volumes and treating deteriorated water quality resulting from climate change and urbanization. Although stormwater management is difficult under all climate conditions, in semi-arid and arid climates increased erosion, flooding, and pollutant buildup occur due to long dry periods broken by monsoonal events. Furthermore, long periods of drought reduce vegetation survival in these climates. Through an examination of existing literature on the performances of green roofs and bioretention systems in semi-arid and arid climates, this review has identified both the utility of these technologies and potential limitations. With some modifications involving strategic design decisions and vegetation selection, bioretention and green roof technologies can be utilized as effective LID technologies to reduce runoff volume and remove potentially hazardous contaminants from these environments. Ultimately, semi-arid and arid bioretention basins have utility in both retaining runoff and reducing pollutants in effluent. However, green roofs fail to consistently improve stormwater quality. Both technologies have limited utility individually in large or high-intensity storm events. Therefore, combined systems referred to as “treatment trains” should be utilized as a means to better mitigate increased runoff volumes while simultaneously treating stormwater for potential reuse in irrigation.