Towards a generic rainfall-runoff model for green roofs

Abstract

A simple conceptual model for green roof hydrological processes is shown to reproduce monitored data, both during a storm event, and over a longer continuous simulation period. The model comprises a substrate moisture storage component and a transient storage component. Storage within the substrate represents the roof's overall stormwater retention capacity (or initial losses). Following a storm event the retention capacity is restored by evapotranspiration (ET). However, standard methods for quantifying ET do not exist. Monthly ET values are identified using four different approaches: analysis of storm event antecedent dry weather period and initial losses data; calibration of the ET parameter in a continuous simulation model; use of the Thornthwaite ET formula; and direct laboratory measurement of evaporation. There appears to be potential to adapt the Thornthwaite ET formula to provide monthly ET estimates from local temperature data. The development of a standardized laboratory test for ET will enable differences resulting from substrate characteristics to be quantified.

Application of a Conceptual Hydrological Model to Identify the Impacts of Green Roof Substrate Ageing on Detention Performance

“…1 for event 7. Overall values of k ranged from 0.003 to 0.065; such results are similar in magnitude to other published outcomes [1,4]. The mean values of k for each year of study showed a year-on-year increase.…”

“…A generic conceptual hydrological green roof model was first proposed by Kasmin et al [1] and has since been developed and validated by Stovin et al [2]. This model includes both retention and detention processes to accurately indicate green roof runoff for rainfall input data.…”

“…DATA ANALYSIS For each of the 25 events a fixed value of n=2 was used [1,2], k was then optimised using a least squares regression technique. The 25 events were then divided into groups by their year of study.…”

A modelling study of long term green roof retention performance

“…Miller, 2003;Bengtsson et al, 2005;Jarrett and Berghage, 2008;Palla et al, 2010;. Furthermore, Jarrett and Berghage (2008) and Kasmin et al (2010) attention is paid to the ET rate, which is considered to by the key parameter in green roof retention performance modelling.…”

“…It should be noted that the focus here is specifically on retention performance (i.e. volumetric control); detention (temporal delay) is addressed separately (see for example, Jarrett and Berghage, 2008; Kasmin et al, 2010;Yio et al, 2012;Vesuviano et al, 2012).…”