According to a public notice posted on the Schoharie County website, the Federal Emergency Management Agency is planning a grand flood-mitigation project in the town of Blenheim, where the Schoharie Creek runs fast and wide right alongside Route 30.
According to the announcement, which is dated April 7 and is available for public comment until April 21, FEMA and the New York State Department of Transportation want to dredge gravel 4,300 cubic yards of gravel and install four rock "cross vanes" to keep the stream from threatening the road:
The proposed project calls for a series of rock structures called cross vanes to be installed within the main channel opposite the secondary channel. The purpose of these structures is to concentrate the stream’s velocity into the center of the channel and away from the banks. The structures would improve the stream’s ability to transport bed load, which would reduce the formation of gravel deposits within the channel. By concentrating the stream’s energy into the center, bank erosion would be reduced.
A minimum of four cross vanes would be placed over an approximately 462 foot long area where sediment built-up has been occurring. The specific locations and spacing of the cross vanes would be determined during the engineering design. The cross vanes would help the stream maintain its cross- sectional area and plan form geometry while conveying flood flows more effectively through the main channel. This would reduce hydraulic pressure on the secondary channel and would aid in protecting the banks on both sides of the stream.
The project would require coffer dams and water pumps to divert the flow to the secondary channel during construction. Excavation of approximately 4,300 cubic yards of gravel would be required to increase the channel’s cross-sectional area and reduce the current width/depth ratio.
