Simulating the Hydrological Impact of Green Roof Use and an Increase in Green Areas in an Urban Catchment with i-Tree: A Case Study with the Town of Fontibón in Bogotá, Colombia

Abstract

Urbanization has produced various social, environmental, and hydrological impacts, such as reduced biodiversity, increased urban temperatures, ecosystem degradation, air and water pollution, changes to hydrological processes, groundwater recharge alterations, increased prevalence of floods, vegetation removal, and potential increases in unstable soils. Finding solutions to mitigate the impacts of urbanization is of vital importance in the development and planning of cities, and particularly so for developing countries. One strategy gaining momentum is the use of green roofs and larger green areas (greater green cover under trees, with the purpose of increasing the permeable area) for runoff control. In this study, a simulation was carried out using the i-Tree Hydro software that involved the urban basin in the Fontibón area of Bogotá, Colombia, with the aim of observing the hydrological benefits of trees, green areas, and permeable zones. Five scenarios were proposed in which green roof coverage was implemented (20% and 50% increases in green areas in Scenarios 1 and 2), coverage under existing trees was enhanced (50% and 100% increase in Scenarios 4 and 5), and finally a complete removal of green zones in Fontibón was simulated (Scenario 3). The town is relatively susceptible to a reduction in its existing green areas, with an increase in total flow of more than 50% for one scenario considered. Thus, an increase in the permeable coverage under trees (50% and 100% increased coverage under existing trees) provided the best strategy for mitigating the impacts of urbanization by reducing the total, maximum, and average impervious flow by 3%, 4%, and 8%, respectively. Finally, an increase in permeable zones corresponding to plants was proposed via the implementation of green roofs. However, this strategy showed a response to the reduction in the lowest total flow at 1%.