The Role of Green Roofs in Climate Change Mitigation and Adaptation: Analyzing Performance During Extreme Rainfall Events

Abstract

This study evaluated the water storage and runoff capacities of an extensive green roof simulator in Bahía Blanca, Argentina, during the region's most extreme precipitation event in 47 years. The analysis involved a time series of daily precipitation from 1961 to 2022. A Green Roof model was applied using daily precipitation data, potential evapotranspiration, and field-measured water storage capacity data from 2022. The model was based on a 1 m² green roof simulator, with 50% of its surface covered by native species. The substrate depth was set at 15 cm, with a soil water storage capacity of 58.7 mm. Precipitation in Bahía Blanca showed considerable variability across temporal scales. The most frequent events (89%) involved less than 20 mm of rainfall, followed by events between 20.1 mm and 40 mm (8%). Eight events with precipitation between 80.1 mm and 100 mm were recorded, with March 24, 2022, marking the highest daily rainfall in 15 years (90.3 mm). However, when examining three-day accumulated rainfall, the period from March 23 to 25, 2022, accumulated 150.3 mm, making it the most extreme event in the last 47 years and the second highest in the 62 years analyzed. During this event, total runoff amounted to 83.4 mm, indicating a substantial water storage of 44.6% by the green roof simulator. Given the projected increase in the frequency and intensity of extreme rainfall events, green roofs offer a sustainable and innovative solution for mitigating and adapting to climate change impacts. Additionally, they serve as crucial urban green infrastructures for managing runoff, particularly in regions prone to intense precipitation events like Bahía Blanca.

This study evaluated the water storage and runoff capacities of an extensive green roof simulator in Bahía Blanca, Argentina, during the region's most extreme precipitation event in 47 years. The analysis involved a time series of daily precipitation from 1961 to 2022. A Green Roof model was applied using daily precipitation data, potential evapotranspiration, and field-measured water storage capacity data from 2022. The model was based on a 1 m² green roof simulator, with 50 % of its surface covered by native species. The substrate depth was set at 15 cm, with a soil water storage capacity of 58.7 mm. Precipitation in Bahía Blanca showed considerable variability across temporal scales. The most frequent events (89 %) involved less than 20 mm of rainfall, followed by events between 20.1 mm and 40 mm (8 %). Eight events with precipitation between 80.1 mm and 100 mm were recorded, with March 24, 2022, marking the highest daily rainfall in 15 years (90.3 mm). However, when examining three-day accumulated rainfall, the period from March 23 to 25, 2022, accumulated 150.3 mm, making it the most extreme event in the last 47 years and the second highest in the 62 years analyzed. During this event, total runoff amounted to 83.4 mm, indicating a substantial water storage of 44.6 % by the green roof simulator. Given the projected increase in the frequency and intensity of extreme rainfall events, green roofs offer a sustainable and innovative solution for mitigating and adapting to climate change impacts. Additionally, they serve as crucial urban green infrastructures for managing runoff, particularly in regions prone to intense precipitation events like Bahía Blanca.