Hydrological Effectiveness of an Extensive Green Roof in Mediterranean Climate

In urban water management, green roofs provide a sustainable solution for flood risk mitigation. Numerous studies have investigated green roof hydrologic effectiveness and the parameters that influence their operation; many have been conducted on the pilot scale, whereas only some of these have been executed on full-scale rooftop installations. Several models have been developed, but only a few have investigated the influence of green roof physical parameters on performance. From this broader context, this paper presents the results of a monitoring analysis of an extensive green roof located at the University of Calabria, Italy, in the Mediterranean climate region. To obtain this goal, the subsurface runoff coefficient, peak flow reduction, peak flow lag-time, and time to the start of runoff were evaluated at an event scale by considering a set of data collected between October 2015 and September 2016 consisting of 62 storm events. The mean value of subsurface runoff was 32.0% when considering the whole dataset, and 50.4% for 35 rainfall events (principally major than 8.0 mm); these results indicate the good hydraulic performance of this specific green roof in a Mediterranean climate, which is in agreement with other studies. A modeling approach was used to evaluate the influence of the substrate depth on green roof retention. The soil hydraulics features were first measured using a simplified evaporation method, and then modeled using HYDRUS-1D software (PC-Progress s.r.o., Prague, Czech Republic) by considering different values of soil depth (6 cm, 9 cm, 12 cm, and 15 cm) for six months under Mediterranean climate conditions. The results showed how the specific soil substrate was able to achieve a runoff volume reduction ranging from 22% to 24% by increasing the soil depth.

[1]  J. Šimůnek,et al.  On the use of global sensitivity analysis for the numerical analysis of permeable pavements , 2018 .

[2]  K. Soulis,et al.  Runoff reduction from extensive green roofs having different substrate depth and plant cover , 2017 .

[3]  盧熙明,et al.  Pressure-Plate Extractor 內 土壤水分含量 變化로부터 不飽和水理傳導度의 計算 , 1984 .

[4]  Kuppusamy Vijayaraghavan,et al.  Green roofs: A critical review on the role of components, benefits, limitations and trends , 2016 .

[5]  Michele Turco,et al.  MODELLING THE HYDRAULIC BEHAVIOUR OF PERMEABLE PAVEMENTS THROUGH A RESERVOIR ELEMENT MODEL , 2018, 18th International Multidisciplinary Scientific GeoConference SGEM2018, Water Resources. Forest, Marine and Ocean Ecosystems.

[6]  V. Stovin,et al.  Independent Validation of the SWMM Green Roof Module , 2017 .

[7]  Uwe Schindler,et al.  Evaporation Method for Measuring Unsaturated Hydraulic Properties of Soils: Extending the Measurement Range , 2010 .

[8]  Uwe Schindler,et al.  The evaporation method: Extending the measurement range of soil hydraulic properties using the air-entry pressure of the ceramic cup , 2010 .

[9]  Hong-Seok Yang,et al.  Acoustic effects of green roof systems on a low-profiled structure at street level , 2012 .

[10]  M. Maglionico,et al.  A long-term hydrological modelling of an extensive green roof by means of SWMM , 2016 .

[11]  M. Santamouris.  Cooling the cities – A review of reflective and green roof mitigation technologies to fight heat island and improve comfort in urban environments , 2014 .

[12]  R. Lazzarin,et al.  Experimental measurements and numerical modelling of a green roof , 2005 .

[13]  G. P. Wind,et al.  Capillary conductivity data estimated by a simple method , 1966 .

[14]  Emily Voyde,et al.  4 Living roofs in 3 locations: Does configuration affect runoff mitigation? , 2013 .

[15]  R. Żmuda,et al.  Hydrological Performance and Runoff Water Quality of Experimental Green Roofs , 2018, Water.

[16]  E. Tollner,et al.  Modeling stormwater runoff from green roofs with HYDRUS-1D , 2008 .

[17]  S. Kordana.  The identification of key factors determining the sustainability of stormwater systems , 2018 .

[18]  D. Pumo,et al.  Potential implications of climate change and urbanization on watershed hydrology , 2017 .

[19]  R. Feddes,et al.  Simulation of field water use and crop yield , 1978 .

[20]  S. Archfield,et al.  Urban base flow with low impact development , 2016 .

[21]  Patrizia Piro,et al.  A Comprehensive Approach to Stormwater Management Problems in the Next Generation Drainage Networks , 2018, The Internet of Things for Smart Urban Ecosystems.

[22]  Patrizia Piro,et al.  A Comprehensive Analysis of the Variably Saturated Hydraulic Behavior of a Green Roof in a Mediterranean Climate , 2016 .

[23]  P. Bevilacqua,et al.  Thermal inertia assessment of an experimental extensive green roof in summer conditions , 2017 .

[24]  P. Piro,et al.  Simple flowmeter device for LID systems: From laboratory procedure to full-scale implementation , 2019, Flow Measurement and Instrumentation.

[25]  Miroslav Šejna,et al.  Recent Developments and Applications of the HYDRUS Computer Software Packages , 2016 .

[26]  Van Genuchten,et al.  A closed-form equation for predicting the hydraulic conductivity of unsaturated soils , 1980 .

[27]  Emily Voyde,et al.  Hydrology of an extensive living roof under sub-tropical climate conditions in Auckland, New Zealand , 2010 .

[28]  A. Palla,et al.  Compared performance of a conceptual and a mechanistic hydrologic models of a green roof , 2012 .

[29]  D. Rowe,et al.  Green roofs as a means of pollution abatement. , 2011, Environmental pollution.

[30]  Yanling Li,et al.  Modeling Hydrologic Performance of a Green Roof System with HYDRUS-2D , 2015 .

[31]  V. Stovin,et al.  The hydrological performance of a green roof test bed under UK climatic conditions , 2012 .

[32]  Xinhua Zhao,et al.  The influence of dual-substrate-layer extensive green roofs on rainwater runoff quantity and quality. , 2017, The Science of the total environment.

[33]  W. Durner,et al.  Simplified evaporation method for determining soil hydraulic properties: a reinvestigation of linearization errors , 2008 .

[34]  Graig Spolek,et al.  A Pilot-Scale Evaluation of Greenroof Runoff Retention, Detention, and Quality , 2011 .

[35]  S. Wilkinson,et al.  Modelling green roof stormwater response for different soil depths , 2016 .

[36]  Kristin L. Getter,et al.  Quantifying the effect of slope on extensive green roof stormwater retention , 2007 .

[37]  P. Piro,et al.  The Influence of Hydrologic Parameters on the Hydraulic Efficiency of an Extensive Green Roof in Mediterranean Area , 2016 .

[38]  Daniel E. Marasco,et al.  Hydrological performance of extensive green roofs in New York City: observations and multi-year modeling of three full-scale systems , 2013 .

[39]  Jenq-Tzong Shiau,et al.  Return period of bivariate distributed extreme hydrological events , 2003 .

[40]  Wolfgang Rauch,et al.  Parameter Sensitivity of a Microscale Hydrodynamic Model , 2018, New Trends in Urban Drainage Modelling.

[41]  Ruifen Liu,et al.  Hydrologic response of engineered media in living roofs and bioretention to large rainfalls: experiments and modeling , 2017 .

[42]  H. Koivusalo,et al.  Simulation of green roof test bed runoff , 2016 .

[43]  K. Metselaar.  Water retention and evapotranspiration of green roofs and possible natural vegetation types , 2012 .

[44]  Kamil Pochwat,et al.  Dimensioning of Required Volumes of Interconnected Detention Tanks Taking into Account the Direction and Speed of Rain Movement , 2018, Water.