Buncombe County Government, NC Cooperative Extension, 9 Feb 2012

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From YouTube: Installing a Rain Garden

Description

Rain Gardens are a great way to prevent soil erosion and increase the amount of water that goes back into our groundwater supply. Combine a Rain Garden with a Cistern and you have a great way to retain rain water for personal use, while also preventing erosion. Join Watershed Coordinator Diane Silver and Extension Watershed/Water Quality Agent Mitch Woodward as they show you how to install these great additions to any property.

GrowBC2012 is a Buncombe County Government Campaign that promotes creating healthier, kinder, greener, safer, and smarter habits to improve not only how the county works to better itself for its citizens, but also for a great way for everyone to better themselves.

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Here we are at the Swannanoa 4-h center, where experts from the Cooperative Extension Service are installing to stormwater management practices at one of the new buildings, a rain garden and a cistern. We're going to show you how these practices are installed. Here's.

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Our building and and take a look at the downspouts, a real opportunity here, was to capture water from this downspout and also from its mirror image spout on the other side of the of the building. So when we took that measurement and we looked at an opportunity- we said this- this is great.

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It's not right by the front door, it's off to the side and we definitely have flow coming not only down this hill, but also out of these two downspouts we're going to capture runoff from this downspout and we're going to send it into this into this rain barrel. So for every one square, foot on the roof, we have one gallon of storage into this rain barrel. Will capture about one and a half one inch? Storm events? That's that's a good! That's a good way to go. All this is is a large rain barrel.

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What you'll see is you'll see people with a 55-gallon rain barrel at the bottom of a downspout that services maybe 600 to 800 square feet of roof top area. So if I had again 1200 square feet of roof top area, how big should my tank be 1,200 square feet, which is what we have here: 600 on the front 600 on the back 1,200 square feet, 1,200 gallons, that's about what we have here, 1,100 gallons, when it rains more than an inch well in this case, is more than an inch and a half or two inches.

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That tank is going to be completely full, and at that point we are going to construct an overflow outlet. That's going to drain into our ring guard. You need to have an outlet absolutely because otherwise you're going to backwater up into your system and possibly could cause damage to the house.

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It's gonna be up like this, so.

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Here's our completed rain garden, here's how it works previously when it rained water, came down the downspout and when it went all the way down to the ground and the water shot out of the end of the downspout and float across the ground into the creek, and it was a roading away. The ground as it went now, with our two practices in place. Rain comes down the downspout and it goes into the pipe that takes it into the cistern. It collects in the cistern until it gets to the top level where the overflow pipe is.

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If the cistern isn't big enough and there's even more rain water, then it flows out the overflow pipe and it comes down onto the splash guard and flows into the rain garden and now the rain garden is all this much storage for additional rain water that gives the water a chance to soak down into the ground and replenish groundwater rather than flowing off to the creek.

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It doesn't flow off to the creek until it fills all the way up to the top level of the rain garden and it flows over the berm, and only then does it flow across the land and off to the creek. And if that happens, the speed is much slower than when the volume of runoff is coming down off the roof during the rain event, while it's raining, and so even if we have some runoff to the creek, it doesn't have the erosive power that it did previously. So the rain garden is doing three things.

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One is it's collecting the water and slowing it down, so it's not as fast and powerful. That's taking away the erosive power and it's reducing erosion. The second is it's giving that water a chance to soak down into groundwater and replenish our local groundwater sources rather than being lost to the ocean by flowing downstream. The third is it's filtering out pollutants that might be contained in the water before it gets to the stream or gets down into groundwater by having that water filter, filter, filter down through the soil and through the substrate.

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