Assessment of the hydrological impacts of green roof: From building scale to basin scale

Abstract

International audienceAt the building scale, the use of green roof has shown a positive impact on urban runoff (decrease and slowdown in peak discharge, decrease in runoff volume). The present work aims to study whether similar effects are possible at the basin scale and what is the minimum spreading of green runoff needed to observe significant impacts. It is particularly focused on the circumstances of such impacts and how they can contribute to storm water management in urban environment. Based on observations on experimental green roofs, a conceptual model has been developed and integrated into the SWMM urban rainfall-runoff model to reproduce the hydrological behaviour of two different types of green roof. It has been combined with a method defining green roofing scenarios by estimating the maximum roof area that can be covered. This methodology has been applied on a long time series (18 years) to the Châtillon urban basin (Haut-de-Seine county, France) frequently affected by urban flooding. For comparison, the same methodology has been applied at the building scale and a complementary analysis has been conducted to study which hydrometeorological variables may affect the magnitude of these hydrological impacts at both scales. The results show green roofs, when they are widely implemented, can affect urban runoff in terms of peak discharge and volume, and avoid flooding in several cases. Both precipitation – generally accumulated during the whole event-and the initial substrate saturation are likely to have an impact on green roof effects. In this context, the studied green roofs seem useful to mitigate the effects of usual rainfall events but turn out being less helpful for the more severe ones. We conclude that, combined with other infrastructures, green roofs represent an interesting contribution to urban water management in the future

Improvement to the Huff Curve for Design Storms and Urban Flooding Simulations in Guangzhou, China

“…SWMM is developed by the American Environmental Protection Agency [46]. It has been widely applied in urban drainage management, flood-control facility design, water quality modeling, and so on [47][48][49][50][51][52]. In order to verify the Improved Huff curve at the rainfall depth-runoff calculation, SWMM is established in the Shiqiao Street, in the downtown area of Panyu District in the south of Guangzhou (Figure 1c).…”

“…Thus, the flooding volumes simulated by SWMM using different design storm hyetographs could represent the real situations to some extent. Of course, more storm events data could provide better model parameters and simulations [47].…”

A Simplified Model for Modular Green Roof Hydrologic Analyses and Design

“…HYDRUS has difficulties modeling open water storage, experiences convergence issues when dealing with extremely dry or wet conditions, and requires advanced skills in simulating precipitation events with variable recurrence intervals, durations, and depths [2]. Other modeling efforts are either case specific [3], statistics based [4,5], or limited in capability to simulate the actual physical processes involved [6][7][8][9][10]. Some physical-process-based models, such as the conceptual model [11] by Locatelli et al are good for evaluating large-scale impacts of green roofs when integrated in the urban drainage model; the hydrological flux model [12] by Stovin et al is successful in predicting the long-term water content and runoff retention performance; and the two-stage storage routing model [13] by Vesuviano et al uses a semi-empirical model to simulate runoff responses.…”

İstanbul’un Yağmur Suyu Taşkınlarına Karşı Yeşil Teras Çatıların Önleyici Rolü

“…Bu sayede şiddetli yağmurlarda yeşil çatılara gelen yağmur suları tutulur ve belli bir süre sonra şebekeye gönderilir. Böylelikle şebekelerdeki yağmur yükü hafiflemekte, debi pikleri düşmekte ve taşkın riski azalmaktadır [17][18].…”

“…Bu bağlamda İstanbul kentinin yoğun ve hızlı şehirleşme bölgelerinde coğrafi bilgi sistemi ile çatıların yüzey alanlarının tespit edilerek, yeşil çatıya dönüştürülme potansiyeline sahip çatı oranları belirlenir ve sayısal modelleme ile bunun yağmur suyu şebekesi üzerindeki etkileri araştırılır. Bu araştırmaların sonucuna göre yeşil çatıların şehir hidrolojisi bakımından pozitif etkisi böylelikle sayısal ortamda gösterilmiş olunur [30].…”