Marie-Curie IAPP ‘Green Roof Systems’ Project
The Green Roof Research Conference 18-19 March 2013, Sheffield
Modeling and monitoring the hydrologic response of green roofs in the Mediterranean climate Anna Palla Dept. of Civil, Chemical and Environmental Engineering, Univeristy of Genova. anna.palla@unige.it
Introduction Since 2007, the University of Genova has carried on a monitoring programme to investigate the hydrologic response of green roofs in the Mediterranean climate by installing a green roof experimental site. The objectives of this contribution are to provide detailed information about green roof hydrologic performances in the Mediterranean climate (retained volume, peak flow reduction, runoff delay) and to describe a complete modelling approach for describing the associated hydrologic response. Furthermore aiming at the assessment of the impact of green roofs on the storm water runoff quality, in 2010, water chemistry data are included in the monitoring programme. Preliminary results concerning green roof impact on water quality are also presented.
Overview of Methodology The hydrologic performances are analyzed on an event basis and for the whole monitoring campaign (in terms of average, median and standard deviation values); in order to assess the impact of the mediterranean pluviometric regime on the green roof response. A mechanistic approach is here described to simulate the hydrologic response of a green roof. The SWMS_2D model (Šimunek et al., 1994) is employed to simulate the infiltration process and water content profiles in 2D variably saturated porous media. The governing flow equation is the two-dimensional form of the Richards’ equation. The numerical model was calibrated and validated using eight rainfall events observed at the green roof experimental site from September to December 2008.
Key Findings The mechanistic modelling approach properly reproduces the infiltration process which plays a crucial role in the prediction of green roof response at the event-scale.
Marie-Curie IAPP ‘Green Roof Systems’ Project
The Green Roof Research Conference 18-19 March 2013, Sheffield 28 October 2008
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Figure 2 – Measured and simulated hydrographs for the 28 October 2008 rainfall event.
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Figure 3 –Predicted vertical profile of the soil water content (continuous line) and the th corresponding observed values (dots) for the 28 October 2008 rainfall event.
Further Reading Gnecco, I., Palla A., Lanza, L.G. and La Barbera P. 2012. A green roof experimental site in the th Mediterranean climate: the storm water quality issue. 9 International Conference on Urban Drainage Modelling (9UDM), 3-7 September, Belgrade, Serbia. Palla, A., Gnecco, I. and Lanza, L.G. 2012. Compared performance of a conceptual and a mechanistic hydrologic model of a green roof. Hydrol. Proc., 26(1), 73-84. Palla A., Gnecco I. and Lanza, L.G. 2009. Unsaturated 2-D modelling of subsurface water flow in the coarse-grained porous matrix of a green roof. J. Hydrol. 379(1-2), 193-204.