February 11, 2020
Live Streaming from Bretton Woods
By: Bonnie Dunkel
Last Friday, I stepped away from my desk to spend a few hours out on site with members of Timmons Group’s Stream Restoration team. The project site we visited is a 1,064 foot stretch of stream located entirely within a single HOA-controlled property in the Bretton Woods development in Henrico County, VA. See more from our day in the field in the video below!
The project design for this restoration utilizes a combination of Priority 1 Restoration (raising the streambed to engage the original floodplain during bankfull events) and Priority 2 Restoration (maintaining the existing streambed elevations and creating a new floodplain within the incised valley).
As I learned during my last site visit with the Stream Team, the stream restoration process requires taking a lot of measurements. During this visit, our team was taking measurements to determine bank height, root depth, and bank angle to help establish a Bank Erosion Hazard Index (BEHI). The BEHI helps to determine how susceptible a bank segment is to erosional processes.
The measurements are also used to develop a Near-Bank Stress (NBS) rating for each segment of bank within the study reach. The NBS assessment identifies features such as a tight radius of curvature on a bend, steep channel slope or mid-channel depositional bars to estimate the magnitude of erosive force that a bank segment will likely be exposed to during storm events.
The BEHI and NBS are the two major components of the Bank Assessment for Non-point source Consequences of Sediment (BANCS) model that allow practitioners to estimate the bank erosion rate of a stream in tons/yr/ft.
It has been calculated that this stream restoration will remove 109 lbs. of total phosphorus, 390 lbs. of total nitrogen, and 36,722 lbs. of total suspended sediment per year. The stream restoration and corresponding reduction of these nutrients will prevent future heavy erosion, increase water quality, and create healthy vegetative and aquatic habitats.
To learn more about our Stream Restoration services and to see more projects like this, click here.