Thursday, November 17, 2011

Green roofs and rainfall, nature's best irrigation

Green Roofs love rain
Rain is always welcomed by Florida green roofs.  Problem is for years now we haven't been receiving as much rain from the sky as we historically used to receive.

In fact, the Jacksonville and other areas of Florida and the Southeastern US, such as Houston and others are experiencing long term serious drought.

So when rain visits here, the green roof systems and plants must take advantage of every precious drop of water.

Last night we received about 15mm of rainfall, a little over one half inch.  Since all of our green roof systems are shallow in depth, I was confident the plant roots had an opportunity to adsorb a good amount of water.

Curious though to just how much water some our potted plants received, I ventured out into the nursery and selected a plant potted up in a one gallon container and removed the plant, examining the rootball for moisture.

Green Roof plants, Florida's rainfall events do not allow for much water adsorption anymore
As the photo shows, the top ten to twenty millimeters was wet.  Beyond fifty millimeters or so the roots were bone dry.

Horizontal roof architecture for green roofs has advantages, particularly if the green roof lies in the hot and dry climates of the world.  Horizontal root architecture is discussed here.

So though shallow roofs may not be the answer for all green roof applications, they have established themselves as viable alternatives in hot and dry climates, providing lightweight potential, lower cost, beauty, habitat and stormwater attenuation.

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