A specific module dedicated to simulate green roof behaviour has been added in Multi-Hydro.
It is inspired from a model presented in details in Versini et al. (2014a).
Integrated among “resilience measures” Multi-Hydro options (already comprising basin and
barrier), this module is applied on each cell previously identified as green roof during the
land use analysis. Using a reservoir model structure, it produces for each time step a modified
rainfall field representing the green roof response for green roof cells and conserving the
original rainfall for the remaining cells. These new rainfall fields are then used as input data
for the complete Multi-Hydro cycle. Within these loops, green roof cells are considered as
standard roof; i.e. impervious pixels whose water is directly routed to the nearest gully.
An application of this Multi-Hydro version at the basin scale is presented in Versini et al.,
Choose the Land cover code
If green roof option has been selected, cells where green roof are implemented have to be
identified. For this purpose, a window ask for the land cover code characterizing green roof
(=8 by default).
Choose Green Roof properties
Green roof properties have then to be defined. They regroup:
Soil thickness (in meters);
Hydraulic conductivity (in meters per hour);
Porosity (ranging 0 to 1);
Field capacity (ranging 0 to 1);
Initial substrate saturation (ranging 0 to 1).
Based on this information, the Green Roof module is theoretically able to represent a wide
range of green roof configurations. Initial substrate saturation appears to be a very important
parameter characterizing the substrate capacity to store water.
Versini, P.-A, Ramier, D., Berthier, E. and de Gouvello, B. 2014a. Assessment of
the hydrological impacts of green roof: from roof scale to basin scale. Journal of hydrology,
Versini, P.-A., Gires, A., Abbes, J.-B., Giangola-Murzyn, A., Tchinguirinskaia, I. and
Schertzer, D. 2014b. Simulation of green roof impact at the basin scale by using a distributed
rainfall-runoff model. 13th International Conference on Urban Drainage, Sarawak, Malaysia,
7-12 September 2014.