(Conservation Currents,
Northern Virginia Soil and Water Conservation District, May-June
2003)
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The Northern
Virginia Soil and Water Conservation District’s urban
conservation engineer Asad Rouhi works with Arlington County’s
Environmental Services and Parks departments to stabilize
120 feet of Four Mile Run in Benjamin Banneker Park.
Rouhi designed the restoration plan for the highly eroded
stream segment under a contract with Arlington County. Here
he directs the backhoe operator to regrade the highly
eroded stream bank. On the opposite bank, not visible
in the photo, is an active floodplain. During a storm, when
the channel receives a large volume of fast flowing water,
the water can spread out over the floodplain to lessen the
erosive energy of the flow. |
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A double
row of biologs will protect the toe of the newly graded
bank from the erosiveness of the stream flow. These tightly
bound cylinders of coconut (coir) fiber are held together
with coir fiber netting. The material is tough, flexible,
and absorbent. Once installed, the biolog becomes saturated
with water, and vegetation can be planted directly in it.
By the time the log degrades in seven or eight years, a
root network of plants will have been established through
and behind it. Biodegradable matting on the sloped bank
will hold the soil and grass seed in place. The grass will
grow through the mat and prevent erosion of the soil. |
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With the biodegradable
logs and matting in place, Arlington County staff planted
about 60 riparian species including willows, dogwoods,
and alders. In time, the banks will provide a lush wildlife
habitat and shade for the stream critters. |
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