Stabilization of a Severely Eroding Streambank on Lake Waramaug Brook

A case study of designing and permitting a slope stabilization project on Lake Waramaug Brook in Warren, CT. The case study will also present the construction of the streambank stabilization project.

Full Abstract: Lake Waramaug Brook is the primary sources of water to Lake Waramaug in northwest Connecticut. Much of the watershed of Lake Waramaug Brook consists of agricultural land with no stormwater management systems. Lake Waramaug Brook has a meandering flow path through a field prior to entering a wooded area which is approximately 1 mile above Lake Waramaug. The brook makes a 90 degree to the right and then another 90 degree turn back to the left. The slope at the second turn is heavily armored with large stones which has prevented erosion of the channel bank.
The first corner is not armored and has experienced a significant amount of erosion. Due to the continuous erosion, the slope is now close to a 1:1 which makes it more susceptible to further erosion. This erosion has undermined the root systems of several trees which have fallen in the brook. Additionally, the eroded material has been deposited on the channel bottom covering the gravel substrate.
This project regrades the eroded slope to a maximum of 2:1 and involves the placement of three rows Koirlogs at the bottom of the slope with live staking. The regraded slope will be seeded with a Native Conservation seed mixture and then be covered with Koirblankets to stabilize the slope while the seed mixture germinates.
The inside corner of this turn will also be improved to provide a smoother hydraulic flow path. The corner of the bank is being cut back and made less sharp and will also be protected by three layers of Koirlogs. This project has received all necessary approvals from the Town of Warren.
This case study will go through the design aspects of the stabilization as well as the actual construction work to demonstrate how this type of eroded condition can be stabilized without the use of structural methods such as riprap.