WSD approaches ultimately provide a suite of benefits in addition to stormwater management.
The following section looks at broader economic and community values associated with WSD approaches, from direct or indirect use.
The land developer
A clustered development form promoted by WSD directs land development to the most appropriate location irrespective of zoning provisions. This can potentially increase a developer's yield while lowering unit costs by reducing infrastructure requirements, as previously discussed.
The marketability of a WSD development is greatly enhanced through additional natural areas and increased open space. This often represents less time in the marketplace and a premium price. Clustered housing has been selling in the US at over US$5,000 more on average than housing on conventional subdivisions (Powell et al., 2005). Communities with increased levels of open space, and properties that abut a park or wetland area, are reported as having a significant increase in property value (Natural Economy Northwest, 2008; Crompton, 2005; Emmerling-Dinovo, 1995).
WSD developments are generally associated with more open space and enhanced landscape amenity. Buildings may be clustered in areas with good relative aspect and access to infrastructure. The clustered form also provides for a dynamic community structure with positive social aspects.
Communities with increased amenity are likely to retain their market value. In Seattle the retrofit of streets as 'green streets' with WSD treatments increased property values by up to 6% (North Carolina State University, as cited in Shaver, 2010a). As an indication, a study in Portland, Oregon found that street trees added an average value of $8,870 to the sale price of residential properties, and reduced time on the market by an average of 1.7 days (Donovan & Butry, 2009).
The protection of contact recreation in our rivers and harbours is a significant issue in Auckland. The retrofit of our communities to WSD can enhance water quality through stormwater treatment practices, and through attenuating the peak flows that can be responsible for CSOs (where they exist). WSD approaches can also reduce water supply demand (i.e. if raintanks are used), sewer/stormwater pumping and associated energy demands.
WSD promotes connected open spaces associated with natural drainage patterns. This connectivity supports The Auckland Plan's visions for a 'blue-green network' of open spaces in the city, and for making freshwater an identifying feature of Auckland (Auckland Plan Directives 7.0, 7.8, 7.10). Studies of connected park systems in Boston and Philadelphia found direct use value up to $100,000 per acre of parkland (Harnick & Welle, 2009). The location of public open space in stream corridors also improves public awareness around water conservation and natural heritage issues.