Extensive Green Roof Curve Number

Effective cns for extensive green roofs roof thickness in.

Extensive green roof curve number.

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. 2 3 4 6 8. 5 42 since 2009 the number of different green roof systems on the market has expanded greatly. 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.

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. Reduced curve number based on the available water capacity of the growing medium growing medium must meet the design criteria specifications. The curve number for green roofs for large rainfall events is given as 84 fassman beck et al 2015.

Have much shallower growing media 2 to 6 inches which is planted with carefully selected drought tolerant vegetation. Extensive green roofs are typically constructed from a number oflayers asshowninfig 1 fromtherooftopup thefirsthydrauli. Nevertheless a 2007 study developed a runoff curve number for an extensive green roof for use in tr 55 calculations. 94 92 88 85 77 reprinted from the 2000 maryland stormwater design manual mde 2000 2009 chapter 5 p.

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. 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. 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 green roof systems.

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. Extensive vegetated roofs are much lighter and less expensive than intensive vegetated roofs and are recommended for use on most development and redevelopment sites. 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.