Green Values(R)
Green infrastructure can be an affordable and sustainable approach to storm water management. However, it is sometimes not given serious consideration because decision makers lack a method for quickly evaluating alternatives prior to investing in detailed feasibility studies. In 2005 CNT developed the Green Infrastructure Calculator as a means of overcoming this barrier. The calculator is designed for users with various levels of interests. Users range from advocates seeking evidence of the potential benefits of green infrastructure to developers considering whether to invest in engineering studies.
A user first identifies the characteristics of a site, including acreage, number of lots, rooftop sizes, the extent of other impermeable surfaces, and soil type and slope. The calculator estimates stormwater volumes and peak rates from a typical lot and from the site as a whole. It calculates detention volume requirements and annual groundwater recharge volumes for the site based on conventional infrastructure. It also estimates the costs of each major component of the stormwater infrastructure. The user is then encouraged to select one or more green infrastructure interventions like roof drains to rain gardens; half of lawns replaced with native vegetation; porous pavement; green roofs; additional tree cover; drainage swales instead of stormwater pipes. The calculator then estimates the resulting changes in runoff volumes and flow rates, the costs of infrastructure by component, and both the financial and intangible benefits resulting from the selections.
Use the Calculator at http://greenvalues.cnt.org/calculator.
The Joyce Foundation funded the development of the Calculator.
