Green roof runoff modelling in Dublin for climate resilience : runoff reduction performance of a single green roof for stormwater management using hydrological modelling with climate change projections

Abstract

This thesis aims to show the runoff reduction performance of green roofs based on climate change projection scenarios using hydrological simulation tools for mitigating and adapting to flooding events in a flood prone city, Dublin. Green roofs like other sustainable urban drainage systems are able to reduce and delay runoff but the reduction performance depend on many design features as well as external factors. Simulation methods can be used to tailor and enhance the design of green roofs to create a more sustainable urban drainage system while adapting future weather conditions that depend on climate change and mitigate the risk of flooding. Currently, hydrological simulation methods are more frequently used to assess the design, deployment and the impact of sustainable drainage solutions but more studies are needed that includes that are based on simulations validated with real life data and climate change projection models. This study is based on a model validated with real life data and uses climate change projetion model to assess the future implications of climate change and the impact of a green roof could have in stormwater management in Dublin. The model is created using Soil and Water Assessment Tool (SWAT) and calibrated according to a green roof deployed in Dublin based on observed runoff from the green roof. The model is later used with weather parameters taken from a climate change projection model. The runoff obtained from this model is bias corrected using the runoff from the model that uses the historical weather parameters. A further analysis of the urbanization trends of Dublin which will affect the future of the city and its stormwater management strategies and flooding problems. The runoff reduction is assessed compared to the foreseen changes in the land use of the city. Main findings show the green roof is able to reduce %26-%55 of the runoff while the performance drops in more frequent and intense rain events. It is observed that climate change models are subjected to significant biases for weather parameters, especially for precipitation and bias correction on input variables or outputs is strongly advised. The urbanization trend shows Dublin, like many other cities will be more impervious in the future which will add to the effects of climate change. Multiple green roofs together with other sustainable drainage systems can create a cascading effect on overall runoff of the city, alleviating risk of flooding