Extensive Green Roof Curve Number

Nevertheless a 2007 study developed a runoff curve number for an extensive green roof for use in tr 55 calculations.

Extensive green roof curve number.

Of the rooftop systems available extensivegreen roofs are thinnest up to 15 cm usually the most lightweight and the cheapest and are therefore most likely to be deployed in retrofit scenarios oberndorfer 2007. Effective cns for extensive green roofs roof thickness in. The green roof used to establish the curve number was composed of a 3 deep soil 55 expanded slate 30 sand and 15 organic matter. Extensive green roof systems.

In addition green roof curve numbers were shown to be much lower than traditional roofing materials which are typically assigned a curve number of 98. The soil had a total porosity of 50 6. To quantify the effect that roof slope has on green roof stormwater retention runoff was analyzed from 12 extensive green roof platforms constructed at four slopes 2 7 15 and 25. In this study curve numbers ranged from 84 to 90 resulting in a potential retention s ranging from 28 2 mm to 48 4 mm 1 1 1 9 in.

Green roof technologies which entail growing plants on rooftops are increasingly being used to alleviate stormwater runoff problems. The curve number for infiltration trench is adapted to be 61 in accordance with the. In this study rainfall runoff data of four green roofs with varying structural configurations under dry and wet substrates were analyzed to acquire the effective estimation for runoff coefficient c v and curve number cn parameters results showed that for the dry and wet substrates averaged runoff retention of vegetated green roofs varied from 34 7 to 48 5 and from 14 7 to 30 6 that. 5 42 since 2009 the number of different green roof systems on the market has expanded greatly.

The curve number for green roofs for large rainfall events is given as 84 fassman beck et al 2015. 2 3 4 6 8. Reduced curve number based on the available water capacity of the growing medium growing medium must meet the design criteria specifications. Paired rainfall runoff data were analyzed for up to 21 living roofs with varying.

See pages 6 and 7 plus either page 9 for extensive green roofs or page 10 for intensive green roofs as appropriate maximum roof slope 20 evapotranspiration appropriate species selection see pages 5 and 6. Despite substantial performance evidence in the literature the lack of a curve number cn or volumetric runoff coefficient c v to apply to prescribed methodologies for planning and regulatory submissions may be perceived as a barrier for implementation. Extensive vegetated roofs are much lighter and less expensive than intensive vegetated roofs and are recommended for use on most development and redevelopment sites.