Can a ‘green roof’ strategy could reduce the impact of excess rainfall?

A green roof strategy could help cut the negative impact caused by severe storms and flooding, studies have shown.

Effective Protection Against Excess Rainfall

A study by the United States Environmental Protection Agency has taken a closer look at the way green roofs can effectively combat the threat posed by annual rainfall.

“Results indicate that the green roofs are capable of removing 50% of the annual rainfall volume from a roof through retention and evapotranspiration. Rainfall not retained by green roofs is detained, effectively increasing the time to peak, and slowing peak flows for a watershed.”

“There are seasonal considerations as more runoff is generated during winter and for many summer storms, there was no runoff. Green roof runoff does contain concentrations of some nutrients and other parameters, but values are in line with other planted systems. Due to the volume reduction, actual nutrient loadings from green roofs are less than asphalt roofing runoff or otherwise manageable at the downspout.”

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Amazing Results

Researchers at Newcastle University compared the effectiveness of urban green infrastructures such as green roofs, ponds, and water channels with traditional engineering measures such as culverts or flood walls in reducing disruption during extreme rainfall events such as ‘Thunder Thursday’. They found that greening every roof in the city could reduce travel disruption by over 25%.

Green infrastructure uses natural processes to store rainwater and decrease the amount released on roads and pavements.

As a result, the depth of flooding is reduced which can make its impact more manageable.

Richard Dawson, professor of earth systems engineering at Newcastle University, said: “We saw on Thunder Thursday the massive amount of damage and disruption that flooding can have on our transport networks.”

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Additional Benefits of Green Roof

Along with this huge benefit, the installation of a green roof also offers the following benefits to the property and the surrounding area.

The benefits of constructing a green roof include:

• Improving the local environment by providing wildlife habitats
• Absorbing CO2, pollution and particulates from the atmosphere
• Improving sound and vibration insulation
• Improving thermal insulation
• Reducing the amount and speed of rainwater run-off by around 50% and forming part of a SUDS design
• Reducing the “heat island” effect in built-up areas and helping to improve air quality and environment
• Protecting the structure and waterproofing membrane from:
  • UV light and heat from the sun
  • impact and abrasion
  • environmental elements including extremes of temperature
  • plant and bird infestation
• Ballasting inverted waterproofing systems
• Optimising the structural footprint by:
  • Increasing space – providing new and attractive natural amenity areas
  • Adding floor space in often high-density developments
  • Adding focal points
  • Decreasing energy costs
  • The increasing value of the development
  • Properties with green roofs sell/rent faster rate than naked buildings
• Making the planning process easier
• Money-saving

Innovation in Green Roofing Systems

Wallbarn has developed a new, improved design for the M-Tray® modular green roof system for 2019. This pre-grown sedum green roof product is supplied in easy-to-handle plastic tray units.

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