Stormwater Attenuation and Green Roof Retrofit

This chapter describes research demonstrating how to assess whether to retrofit with a green roof to attenuate stormwater runoff. Pluvial flooding causes substantial financial costs, disruption and impact on our urban settlements. A range of technical specifications for stormwater roofs and critical issues to consider in retrofitting existing buildings are evaluated. Theoretical frameworks of the distributed benefits of green roofs are presented, and a methodology to estimate potential for stormwater attenuation of green roof retrofit at the city-scale level is described in detail. Recent empirical research undertaken in two cities with very different climatic conditions – Melbourne, Australia and Newcastle, UK – at city-scale level is evaluated. Having examined the city-scale level, a second illustrative case study at an individual building scale outlines stormwater performance and the assessment process in Portland, OR. A summary of the potential benefits of green roof retrofit for stormwater attenuation is made