Demonstration Weir

The Demonstration Weir is a prototype structure and was originally constructed in October 1999. It is located 1.7 miles downstream from the Historic Lateral Weir.

It is a rock riprap structure consisting of approximately 47,000 tons of rock, and recycled concrete. It runs from north to south across the Wash and is approximately 350 feet long and 125 feet wide.

Activities at the Demonstration Weir include a pilot project to determine the strategy for construction and revegetation methods for future erosion control projects. The picture below (taken in 1998) shows how the Demonstration Weir site looked during the planning stages, prior to any construction activity.

It was decided that the crook of the bend would make an excellent spot for a grade control weir to be built. This spot was chosen because the natural bedrock at the site allowed for easy foundation construction, and the location was readily accessible through existing roads. In addition, there is a large area of sediment in front of the bend providing a great location for wetland development.

All of this material was carefully piled into the stream channel to form a weir that would resemble a small natural waterfall type structure that could help control the flow of water while also helping to build up wetland area as it pooled water.

It is estimated that this small structure helped create over 2 acres of wetland habitat that now provides homes for an abundance of birds like these two small coots enjoying a mid summer day in their new home.

This structure is currently in re-design after geotechnical surveys uncovered fault lines that may interfere with the stability of the weir in its current location.