Stormwater Attenuation And Green Roof Retrofit

This chapter describes research demonstrating how to make an assessment of whether to retrofit with green roofs as a mean of attenuating stormwater run-off as a means of contributing to urban flood risk management. The problem of pluvial flooding in terms of financial costs and the impact on our urban settlements is the starting point for a discussion on the potential of retrofitted green roofs as a mitigation measure. A range of technical specifications for stormwater roofs and critical issues to consider in retrofitting existing buildings is 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. The chapter reports on recent empirical research undertaken in two cities with very different climatic conditions; Melbourne Australia and Newcastle UK, at city scale level. 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 USA. The chapter concludes by describing how the stormwater effectiveness of green roof may be limited in certain conditions by the availability of suitable buildings and the source of floodwater. A summary of the potential benefits of green roof retrofit for stormwater attenuation is made