09/18/03
Evaluating Rooftop and Vertical Gardens as an Adaptation Strategy for Urban Areas
FINAL
3.1 Introduction A simulation model of a green roof was developed in order to assess the potential reductions of stormwater runoff from different buildings, in different cities across a range of climates. As a green roof is a special type of catchment in terms of soil type, depth and vegetation, the model was based on the simulation of major hydrological processes. The research was designed so as to use observations from a field roofing facility to calibrate the model, and then use the other data to validate the model’s performance. Due to the delays in constructing the field roofing facility, stormwater runoff data were not available. Instead, various components of the model were tested individually with other data sets. The model was developed primarily as a research tool. Beyond this specific research, it is hoped this model could be used for future research and for educational purposes. However, the philosophy from the start has been to build it using a visual programming language so that it could provide the basis for a tool that could be used by other stakeholders to assess the capacity of any particular green roof design. In addition, the evapotranspiration component of the model will hopefully be used to estimate the impact of evaporative cooling on the summer energy consumption for cooling, which is missing from all available energy models. 3.2 The Green Roof Hydrology Model 3.2.1 Modelling Approach Various approaches are available for simulating precipitation and runoff processes. These software range from the simple water balance to more complicated processes based on distributed hydrologic models. They cover hydrologic processes involving vegetation and single to multi-layer soil processes. In a hydrological simulation, each of these models has advantages and disadvantages over the others with regard to data requirements, computing time and resources. Application of any particular model  empirical, water balance, conceptual-lumped and physically based models  often depends on the specific objectives of the exercise, the need for analytical, future scenario and geographic flexibility and the requirements for precision in the estimates. The choice of models in this research was highly dependent on the need for future flexibility in terms of climate scenarios and geographic region, the differing needs of various stakeholders and the nature of a green roof.
CCAF Report B1046
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