What does a BDA have to do with Spa Creek?
Stage 1 of phragmites removal behind Bates and the Chesapeake Children's Museum is complete and restoration work has moved to the opposite side of Spa Road.
Beaver Dam Analog (BDA) devices have been installed in the wetland area below the salt dome adjacent to Spa Road. The BDAs will eventually trap sediment washed into the stream bed from stormwater, as well as stabilize the stream near Chinquapin where a huge pipe drains water from several acres of pavement. Currently this contaminated stormwater rushes directly into the headwaters of Spa Creek with no filtration whatsoever.
BDAs are made of live willow stakes that will root over time. Live siltation (sometimes known as Vertical Brush Layering) is a revegetation technique used to secure the toe of a streambank, trap sediments, and create fish rearing habitat. The system can be constructed as a living or a non-living brushy system at the water’s edge or in flood plains. We will be using the technique in several places, particularly the area where the rock gabions are being removed. This will be using the brush layering "bank" installation to naturalize the banks.
Specific tree and shrub species that root well from cuttings in water or moist soil conditions are available as live stakes, fascines, or brush layers. They are used as part of a strategy to stabilize streambanks and create natural shorelines.
Live stakes are dormant woody cuttings with the branches removed. They can be used alone or to secure other bioengineering materials such as erosion control blankets or root carpets. Live stakes are easier to install than bare-root trees and shrubs, because they require a 2-inch pilot hole, compared to an 18-inch hole for a tree or shrub.
Fascines (also called wattles) are living branches bundled together to trap sediment and protect against erosion. They are laid horizontally along streambank contours to impede water flow before it reaches the new streambank. Fascines can also be used above the water line to slow down water flow and help prevent erosion.
Brush layers are living branches placed on a terrace along streambank contours, between layers of soil. They are typically used in conjunction with encapsulated soil lifts, which are layers of soil wrapped in erosion control blankets, to completely rebuild a streambank or slope.
There is a large wooded swamp in the area bordered by Spa Road, Forest Drive, Chinquapin Round Road and West Street. The water draining into this area goes into Spa Creek. As the BDAs take hold stormwater will filter through the ground taking out suspended solids and unwanted chemicals. Fish and other critters will return to this natural habitat and the water flowing into Spa Creek will be much cleaner than it currently is.