Cost Implications of Adapting Stormwater Management Devices to Climate Change

Low impact stormwater management devices for stormwater treatment are increasingly common elements in the urban landscape around the world. Their use has been suggested as a means of adaptation in areas with projected increases in the intensity and frequency of extreme rainfall. However, there is little advice on how to design these devices for climate change and the costs involved. This point is important as the perceived cost is often a barrier to device installation. This paper investigates the costs of adapting ponds and raingardens for climate change. The work builds on an investigation of the impacts of adaptation on the sizing of wet detention ponds and raingardens where hypothetical examples of such devices were sized using TP 10 for a range of climate projections and levels of imperviousness. The COSTnz life cycle costing tool is used to determine the associated costs of design adaptation. Along with a baseline (no change) scenario, two adaptation strategies to the end-of-the-century were investigated for ponds (proactive and incremental adaptation) and one for raingardens (proactive adaptation). For the ponds, the increase in total life cycle cost is between 8.7 – 12.3 %, and there is an increase of 8.5 % for raingardens.