Powhatan Creek is one of the more significant watersheds in Virginia's Lower Peninsula but this particular stream has suffered from increasing development since the 1930's. JCC Stormwater Director Fran Geissler diagnosed the problem as USS or Urban Stream Syndrome:
- few health benthic communities (things that live in the bottom of a stream)
- too much bacteria
- too much sediment from the eroding stream banks
- wetland starvation - water goes down the steam so fast it doesn't have time to infiltrate to the water table
The Powhatan stream restoration cost about $600,000 and will serve as part of a mitigation bank which will be used to offset future development in the county. This particular project was a bit easier to construct since all the land was owned by a single owner who granted the county and easement on the site. Other restoration projects may be a bit more complicated. The county is in need of $13,000,000 to repair other damaged streams (at about $1,000,000 per mile).
In addition to Ms. Geissler's presentation, we also heard from Senior Watershed Planner Mike Woolson, Stormwater Engineer Wayland Bass and project manager Travis Crayosky of Williamsburg Environmental Group. WEG worked with surveyors Landtech Resources, Inc. and contractors Meadville Land Servcices Inc. to get the project built. After the presentations Mr. Crayosky (below) led the group on a walk of the new stream to see some of the techniques used to restore the stream.
Because of the severe erosion that had occurred in the stream channel, a lot of regrading had to be done. In some places the difference was as much as 8 feet. After regrading, the stream channel has a slope of 1.5- 2%, which may not sound like much, but is pretty steep for a stream in this area, according to Mr. Crayosky. One way to deal with the elevation change was through the construction of several log weirs like the one below.
Another techniques to slow the water was restoring the natural s-shaped curvature to the stream bed, lengthening the distance the water has to travel.
One somewhat controversial issue was the removal of trees. A wide swath of plants, a couple hundred feet wide, had to be removed for regrading of the stream. Although a few 6-8' trees were planted afterward, most of the trees that were planted were very small. However, these young plants should become established fairly quickly. I spoke to our local native plant rescuer Carolyn Will about what was on the site before the reconstruction. She said there weren't any particularly special plants other than some patches of Trillium pusillum (below) and that the county did a good job of protecting them.
To stabilize the newly regraded sides of the stream, they were covered with a biodegradable filter fabric and replanted using several different approaches:
- hydroseed mixes - There were two varieties of seed mix used: wetland and upland. The wetland mix included soft rush, cardinal flower, rice cutgrass and sedges. The upland mix included indian grass, little bluestem, black-eyed Susan and Virginia wild rye.
- 3' live stakes and bundle cuttings of black willow and silky dogwood.
- small trees and shrubs including 1 gallon containers, bare root plants and tubelings. Species included red maple, ironwood, river birch, swamp chestnut oak, tulip poplar, elderberry, clethra, sweetgum and green ash.