Draft in progress

Rain Gardens:

Why?

Reasons we can all relate to:

1) Street flooding. (Image ) Rain gardens can help diminish street flooding by slowing the rate at which water flows into city’s drainage system.

2) Diminish subsidence. (Image) Subsidence occurs with water removal because    a) organic matter in New Orleans’ spongy soils oxidize and shrink when the water is removed, and

               b) the particles of that soil collapse onto one another  when water is removed. (cite: http://www.guttertogulf.com/Why-is-New-Orleans-sinking/)Rain gardens can help reverse subsidence by perking water back into the soil, one garden at a time.

               - An article in Nature cited on NASA’s Earth Observatory website used satellite imagery to determine that, in the three years before Katrina, most parts of the city sank 8 mm. per year while some parts – those that received the worst flooding – sank at annual rate of 28.8 mm per year. (http://earthobservatory.nasa.gov/IOTD/view.php?id=6623)

               - Not only do the buildings sink; the pipes sink and crack. This in turn creates more drainage problems and more flooding.

3) Overburdened drainage systems : cities with older drainage systems are in danger of violating the clean water act because they have combined sewer systems, which overflow in heavy rains and can send raw sewage into nearby bodies of water. The EPA is encouraging older cities like New Orleans to develop multifaceted approaches for slowing the rate at which rainwater is dumped into their drainage infrastructure to keep us in compliance with the clean water act. Rain gardens are part of this overall strategy to “think outside the pipe”. Important in New Orleans – we average 64 inches of rain a year.

Other reasons:

4) They’re nice. (Image of Magellan Street Garden)

5) Make use of a resource (rainwater) that is otherwise wasted.

6) Chance to explore native plants that tolerate flooding AND drought.

6) One part of the garden you won’t have to pay a utility company to water.

What Is a Rain Garden?

Dr. Bill Schuster, EPA: “Basically a shallow bowl …. (that) accumulates stormwater runoff” and acts as a sort of sponge.

-        Can be elaborate: e.g LSU Hammond’s rain garden (photo), which drains a paved surface by means of an underground pipe and collects water in a subsurface tank.

-        Can be raised, e.g. Tulane University’s Rain Garden exhibit in New Orleans Botanical Garden (2 images). This has a solar-powered pump that drives rainwater from a retention pond to planters y means of a system of tubing.

-        Can also be very simple: (Image-Groundwork NOLA’s vacant lot garden at N. Prieur and Caffin) A low-lying area excavated so that it will capture significant rainwater, then planted appropriately.

Impervious paved surfaces and creating too much combined sewer system overflows. CSO’s combine stormwater and sewage into same pipe. In heavy rains,. Sewage can overflow untreated into nearby water bodies.

Older cities have these systems. Cities are being driven by threat of running afoul of the U.S. Clean Water Act because they have too much volume

Dr. Bill Schuster – any tool or technology we can use to keep water out of the combined sewer system

Rain gardens one of those technologies

“rain gardens are a very simple and effective way of infiltrating stormwater runoff … potentially soak up a lot of water and function as a sort of sponge

Basically consists of a shallow bowl or patch within a vacant lot … bowl accumulates stormwater runoff

What puts the garden in “rain garden” is that the community plants species that are drought tolerant as well as can tolerate periods of saturation