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.

Green Roofs - many times the last line of defense for water quality

Green and living roofs are so very important to our water quality, sometimes being the last line of defense for removing pollutants before runoff enters our waterways.

Green roofs slow down stormwater, cleaning and sequestering pollutants 

Even small green roofs can provide a significant benefit to reducing peak runoff amounts and reducing loadings on creeks, rivers and ponds.

Blue Hole, Ichetucknee Springs

Once stormwater hits a roof and flows to the street below it may only be a matter of minutes before the water and any contaminants picked up as the volume flows across streets, drives and roads enters Florida's drinking water supply.

Floating wetlands, Gainesville, Florida - greenroof on a pond

Storm drain allows pollutants to enter waterways

Florida has a unique geology across many parts of the state called Karst.  Karst formations are typified by limerock with caves, tunnels and holes throughout the  formation.  Once stormwater runoff enters the limerock above drinking aquifers the flow to the pools of underground water can be very quick.

Many times storm drains are a direct connect to water supply aquifers

Green roofs, living walls, floating wetlands and other best management practices can help keep water clean by slowing the runoff and removing contaminants from the water.

Wekiwa Springs, Florida - higher in nitrogen and algae

 Wekiwa Springs, located just north of Orlando, Florida and shown above is surrounded by houses, streets, roads and commercial development.  Though many good best management practices are in place to contain nutrients and runoff, the springs still suffer from high nutrient contents such as nitrogen and phosphorous.

Salt Springs, Ocala National Forest, not as impacted by development

Salt Springs in the Ocala National Forest on the other hand, though threatened by development, does not have all the septic tanks, stormwater runoff and as you can see, the water is much clearer, contains less nitrogen and other nutrients and is so much more healthy.

Installing a green roof on your commercial or residential building is just one small contribution you can make int he Urban Core to help protect water supplies.

Manatees Gather at Blue Springs, Green Roofs Can Help Keep Florida's Springs Clean

Spring Run - Blue Springs to St Johns River

Today's fun topic is about the West Indian Manatee (Trichechus manatus).

What do Manatees have to do with Green Roofs?  Read on and you will find out.

While it has been an unusually cold winter with lower than normal air temperatures, Florida's springs usually stay approximately 67F (20C).

With the colder temperatures, the rivers cool too.

Because the West Indian Manatee (Trichechus manatus) is a mammal, they are warm blooded and need warmer waters to survive.

So in the winter when the river temperatures plunge, the manatees seek out the constant temperatures of the springs.

Now 67F (20C) is not warm - on a hot 100F (38C) summer day there is nothing better than a jump into the 67F cool waters of a Florida Spring.

West Indian Manatee (Sea Cow or Mermaid)

Florida has a wealth of springs.  Because most of the underlying rock is limestone and much as been eroded into underground caves and tunnels where cold, clear water flows.

Some of these underground tunnels filled with cold, clear water discharge at the surface, creating a 'spring'.  The water flows from the cave, out of the spring and down to a river or lake.

The water is clear, but note the yellowish tint

Florida has over 700 large freshwater springs.  For more information on springs from the FDEP website click here.

Limestone is eroded by water acidified through CO2 in the air.

Green roofs help to preserve Florida's springs and winter habitat for the West Indian Manatee by providing two benefits, including;

Momma and Calf

1. Green Roofs remove CO2 from the air, sequester carbon and produce oxygen, keeping the limestone intact and preventing erosion of the springheads.

2.  Green Roofs remove nitrogen and other contaminants from rainfall.  Without green roofs, nitrogen, phosphorous and other contaminants found in smog and air pollution enter Florida's waterways.  Green roof plants adsorb the nutrients from the rainwater, filtering the runoff and keeping the ground water from building high levels of nitrogen and other contaminants.

Look closely, hundreds of manatees line the far shoreline

Florida's springs have always had clear water.  That is until ten years or so ago.  Now we are seeing more and more springs exhibit the greenish and yellowish tint symptomatic of algae blooms feeding on increased dissolved nitrogen levels.

Green roofs can help stop the nutrient problem and clean groundwater, lakes, springs and rivers.

Green roofs can provide a safe and clean refugee for the West Indian Manatees.


As always, email your questions or comments.

Happy Green Roofing!

Kevin

Green Roofs Help Clean and Attenuate Stormwater Runoff

Roof Drains, Jacksonville, Florida

The photos here are of a commercial facility adjacent to a hospital on Beach Blvd. in Jacksonville, Florida. 

The commercial facility has a large flat roof with stormwater runoff collected in the gutters and directed towards a ditch running through the hospital then down a larger creek/ditch directly into the St. Johns River and out into the Atlantic Ocean.

Roof Drains send water into the St. Johns River

The technology shown is no different that the gutters and ditches we see in excavations in old cities of the Roman Empire.

We've had well over 2,000 years as a civilization to think about our water resources and the way we treat stormwater.

The bad news is our rivers, lakes, streams and oceans have become more and more polluted.  Here in Jacksonville the St. Johns River becomes filled with green algae every summer due to the high nutrient loading in stormwater runoff.

The nutrients are primarily from residential and commercial lawn care and application.  Smog and air pollution is another source of nitrogen, one I refer to as another form of 'slow release fertilizer' becuase the smog deposits on roofs and is washed into adjacent waterbodies during a rainfall event.

The photo depicted here is of the Caloosahatchee River in Florida. 

Though the Caloosahatchee is not representative of all the rivers in Florida, it is however representative of a serious problem we have in Florida - that of nutrient runoff into our waterways.

The good news is Green Roofs can help to reverse the nutrient runoff problem by filtering atmospheric nitrogen and other nutrients from stormwater runoff, sequestering carbon and removing particulate matter that phosphorous may bind with.

Green roofs must take the lead and add zero additional fertilization to our ecosystems.

Green roofs must be designed to survive on atmospheric nutrients, leaf litter and detritus from the green roof plants and adjacent sources, bird feces and other natural sources of fertilization.

To be sustainable, green roofs must not use broadcast type fertilizer applications, fast or slow release.

Green roofs are about being eco-friendly.

The good news, again is green roofs can provide a solution.  Green roofs can:

• Filter and clean stormwater
• Provide much needed habitat for wildlife
• Provide habitat for rare and endangered plants
• Sequester Carbon, Nitrogen, Phosphorous and othe pollutants
• Provide Oxygen and clean SMOG
• Provide beauty to the asphalt jungle

Green roofs are one of the 'Green' answers to the global water quality crisis.

As always email your questions or comments here.

Happy green roofing!  Kevin

Stormwater Modeling for Volume Storage of Green Roofs in Europe

Great Blog article from Piped Up! about volume storage for stormwater and green roofs.

You can view the Piped Up blog here.

The Stormwater Modeling PDF file they refer to can be downloaded here.

It is exciting that green roofs are becoming accepted in the engineering community as a legitimate way to work with site design runoff and stormwater.

Happy Green Roofing!

Kevin