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More on Swales and Berms

April 24, 2018

Recent research in Spokane, Washington, as well as Florida has documented the stormwater quality benefits from swales and low-lying areas by reducing the flow and allowing slower infiltration into the groundwater system.

This is a finding which past generations were aware of. In our hurry to pave the world wit concrete, we threw our knowledge of swales and berms out with the storm water (how’s that for a mixed metaphor?).

It is best when designing the home landscape to preserve low-lying areas such as wetlands and swales. These low-lying areas retain storm water, provide water quality filtration and may allow for some infiltration to replenish groundwater supplies.

Swales can either be grassed, gravel or rocked. All designed to slow and retain the flow of runoff. They can also be used instead of costly curbs and gutters found in most neighborhoods and communities today.

As an example, a 678-acre residential development 40 miles northwest of Chicago in Grayslake, Ill. adopted conservation designs to reduce runoff rates and volumes and to reduce pollutant loads.

Storm water is routed into swales, rather than storm sewers. The swales provide initial storm water treatment, primarily infiltration and control sedimentation. The prairies diffuse the water and soils retain contaminants, slowing storm water velocity.

The development expects about 60 percent of the land to be devoted to open spaces. Residents also employ rain gardens and expect to retain 65 percent of its storm water onsite and reduce nutrient loads and reduce heavy metal pollutants by 85 to 100 percent.

Maintenance costs for storm water controls are expected to drop, downstream conditions have improved and there’s less flooding. A sign of success has been thriving populations of native fish in the 22-acre lake.

Key elements to consider when building a swale include:

Swales are not intended to move water but to hold water for soil absorption.

The width of the swale should be covered by the crown of the mature surrounding trees.

Soil in the swale should not be compacted or sealed but should be loose to encourage absorption.

Surprisingly one tree can reduce stormwater runoff by 4,000 gallons a year thus greatly reducing the need to build costly water treatment plants. So, swales lined with native trees are an extremely-cost effective, and often overlooked low-tech, water conservation technique.

Swales with the proper plants and trees help manage runoff and make water healthy for people, nature and fish.

Swales we believe to be a better solution for catching rain than a tank or barrel.

Catching rainwater in tanks or barrels takes a certain amount of engineering skill.

You have to: Buy a bunch of parts. Connect the downspout to the tank. Link more than one tank together.

Route the overflow either back to the sewer or run the overflow into the landscape.

Add mosquito dunks regularly and clean out the barrel at least yearly. You also need a spigot for filling up a watering can or connecting a hose.

Plus, all of these parts will eventually degrade with sun and weather and need fixing or replacing.

And finally, there is very little water pressure from rain barrels, so using the water is quite frankly a pain in the ass. Believe me, watering by hand takes a long time without water pressure. The solar pump I tried didn’t work very well. I think the inventors know that because it isn’t on the market anymore.

Good soil is thirsty. Organic matter acts like a sponge, easily holding several times its weight in water. Experts tells us that three quarts of dry soil can easily hold one quart of water. When we translate that to the soil in our yard, if our yards were covered in one foot deep of rich, moist soil, it would hold as much water as a 3-inch-deep lake the size of the yard.

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