Regional Rainfall Zoning guidelines especially for Metropolis are generally expressed via 1) Reference rainfall criteria: Precipitation-Duration-Return Period (P, D, T) values, and 2) Discharge rules: the rate at which storm-water from reference rainfall events can be discharged into the sewer network, to avoid flooding. Therefore, to design green roofs that can comply with the aforementioned discharge rules, it is critically important to use realistic reference rainfall scenarios as input to hydrological models that simulate green roof discharge. The Universal Multifractal framework, is utilized here for simulating region-specific reference rainfall scenarios since it incorporates properties such as intermittency, scale invariance and non-Gaussian statistics. The hydrological model used here is made up of 1) the Nonlinear Reservoir model that takes care of the substrate layer’s hydrological behavior, and 2) a simple Pulsating Outlet model that takes care of the drainage layer’s hydrological behavior. A new Metric (Zero Emission Metric - ZEM) is defined here to quantify the compliance of green roof designs with the zoning regulations. This procedure is used to propose zone-specific base-design configurations of zero emission green roofs for Paris, Strasbourg, Brest and La Reunion.