Temporal variations in the potential hydrological performance of extensive green roof systems

Abstract

Existing literature provides contradictory information about variation in potential green roof hydrological performance over time. This study has evaluated a long-term hydrological monitoring record from a series of extensive green roof test beds to identify long-term evolutions and sub-annual (seasonal) variations in potential hydrological performance. Monitoring of nine differently-configured extensive green roof test beds took place over a period of 6 years in Sheffield, UK. Long-term evolutions and sub-annual trends in maximum potential retention performance were identified through physical monitoring of substrate field capacity over time. An independent evaluation of temporal variations in detention performance was undertaken through the fitting of reservoirrouting model parameters. Aggregation of the resulting retention and detention variations permitted the prediction of extensive green roof hydrological

A Longitudinal Microcosm Study on the Effects of Ageing on Potential Green Roof Hydrological Performance

“…The finding that seasonal changes far exceed long-term changes was unexpected but may relate to annual cycles in the green roof's living components (flora and fauna). However, whilst De-Ville et al [11] utilized a longitudinal study which included both vegetated and unvegetated systems, changes in physical characteristics could not be directly visualized or measured; instead, they were inferred from monitored rainfall, runoff, and moisture content data. The aim of the work reported in the present paper was to undertake a controlled longitudinal study of green roof microcosms using non-invasive XMT visualization techniques and laboratory measurements of field capacity and detention to directly link these fundamental hydrological characteristics with any changes in physical properties occurring over time.…”

“…The longitudinal microcosm study was undertaken in parallel with the long-term monitoring and the cored microcosm studies presented in De-Ville et al [11] and De-Ville et al [10], respectively. In this paper, we will present the new findings from the longitudinal microcosm study and draw together findings from the three parallel investigations to reach overall conclusions on the impact of substrate ageing on green roof potential hydrological performance.…”

“…Saturated hydraulic conductivity was determined from the 3D XMT image using a Lattice-Boltzmann CFD model (DigiUtility [18]). Full details of the image-processing protocol are provided in De-Ville et al [10] and De-Ville [12]. The root networks of the ageing cores were analysed where sufficient contrast between the roots and surrounding substrate existed, using the root tracking software RooTrak [19].…”

“…To overcome the limitations of discrete temporal sampling De-Ville et al [11] utilized long term rainfall, runoff, and moisture content records from nine differently configured extensive green roof test beds to determine whether significant changes in potential hydrological performance occurred over time. New methods were proposed to use monitored data to estimate how two of the roof's fundamental physical properties (field capacity and detention control) varied over time.…”

“…In this paper, we will present the new findings from the longitudinal microcosm study and draw together findings from the three parallel investigations to reach overall conclusions on the impact of substrate ageing on green roof potential hydrological performance. Further details of the complete research program may be found in De-Ville [12].…”