Happy Hour is here again! - Long Draught Branch Dam Removal and Stream Restoration

ABSTRACT ONLY - This presentation is a case study focused on the Long Draught Branch (LDB) dam removal and stream restoration project, highlighting best practices and the success story of the project. Long Draught Branch is a perennial flowing river in a highly urbanized area of Gaithersburg, MD just outside of the Washington DC beltway. LDB is a as recreational trout waters and feeds into Clopper Lake in Seneca Creek State Park, a known fishery. However, the upper reach of LDB was bisected by an earthen embankment dam, original constructed in the early 1970s to provide flood control. The crossing of LDB by the dam created a fish blockage, inhibiting the passage of any species from Lake Clopper into the upper reaches of the stream. The dam was initially damaged by Hurricane Agnes in 1972 and by the 2000s the dam needed significant maintenance upgrades and had outlived its functional use. The Maryland State Highway Administration (SHA) developed an ambitious plan to remove the dams and restore the in-stream aquatic habitat for of 3,500 linear feet of the stream. This plan was targeted at eliminating SHA's maintenance responsibilities for the dams, providing an improved natural resource for the surrounding community, and restoring aquatic habitat opportunity and water quality within the upper reaches of Long Draught Branch.
Design of the project commenced in 2014. The stream design utilized natural channel design principles and focused on the recreation of a sustainable channel geometry that balanced sediment transport needs with in-channel hydraulic forces. Reconstruction of the new channel through the dams and legacy impoundments was done using a riffle-pool channel morphology that was reliant on bioengineering plantings for long-term stabilization of the new channel banks and in-set floodplain benches graded through the legacy sediments. Construction of the project was completed in early 2019, starting a new success story on using natural channel design with green channel design principles in the removal of legacy dam.
Today, the Long Draught Branch restoration is functioning as a vibrant ecosystem. Within the first growing season after construction, the return of aquatic organisms to the upper reach of LDB exceeded the expectations of everyone involved in the project. Substantial populations of fish and macroinvertebrates can be seen in the stream during the spring. Three years post construction, the bioengineering / green channel design is exhibiting stability throughout the project reach, setting up a healthy future for the system.