Abstract
In an existing urban environment, retrofitting low impact development (LID) solutions can provide an opportunity to address flooding and water quality problems. Taking into account the need to effectively estimate the impact of vegetated LIDs, particular attention has recently been given on the evapotranspiration (ET) process that is responsible for the restoring of green roof water-holding capacity. The present study aims to develop a methodological approach to estimate the actual ET as climate input data in the United States Environmental Protection Agency (EPA) Storm Water Management Model (SWMM) continuous simulation. The proposed approach is calibrated on a single green roof installation based on one-minute continuous simulations over 26 years of climate records. Then the calibrated methodological approach has been implemented to perform continuous simulation of a small urban catchment retrofitted with green roofs. Based on simulation results, the peak and volume reduction rate evaluated for the 1433 rainfall events are equal to 0.3 on average (with maximum values of 0.96 for peak and 0.86 for volume). In general, the adopted methodology indicates that the actual ET estimate is needed to suitably assess the hydrologic performance of vegetated LIDs mainly concerning the volume reduction index; furthermore, the methodology can be easily replicated for other vegetated LID applications.
Highlights
In the last few decades, water quality and quantity issues related to the urban environment pose multiple challenges involving many actors such as researchers, local and regional public authorities, and citizens
The main objective of this paper is to investigate the role of vegetated low impact development (LID) in storm water runoff mitigation at the urban catchment scale by analysing the continuous simulation results
Reference impervious roof; green roof according to the potential evapotranspiration (PET); green roof according to the calibrated actual ET; Two simulations for the catchment scale:
Summary
In the last few decades, water quality and quantity issues related to the urban environment pose multiple challenges involving many actors such as researchers, local and regional public authorities, and citizens. In order to address the need to control and limit storm water runoff, low impact development (LID) principles and applications represent the new approach to storm water management. LID solutions are designed to mimic pre-development hydrologic conditions promoting storage, infiltration and evapotranspiration (ET) processes. Rain gardens, green roofs and permeable pavements are included among LIDs. Referring to the single installation scale, the performance of LIDs as runoff source control measures is well documented in the literature (e.g., [1]). Several experimental studies, carried out at both the pilot and full scales, demonstrate that LIDs contribute to reducing the runoff volume and peak flow rate. The storm water volume retention observed for green roofs varies between 12%
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