Longmont Supply Passage and Stream Restoration Longmont, Colorado
As part the 2013 flood recovery efforts within the St. Vrain Creek watershed, the multi-phase restoration project re-establishes floodplain connectivity, enhances the health of local ecology, and adds resilience to the area’s communities from future flooding. With funding from a disaster relief planning grant, those efforts include the reconfiguration of a reach where creative solutions were necessary to meet numerous objectives and stakeholder needs.
“Threading the Needle” through Constrains to Reconfigure a Reach that Provides A Reliable, Local Water Source and Protects Habitat
Understanding that this would be a complex field-fitting project, the assembled project team was specifically built with an emphasis on flexibility, willingness to compromise, and an ability to brainstorm solutions. An alternatives analysis evaluating various bypass structure design and channel alignments was developed to address a variety of project constraints, including the minimization of water surface rises to avoid a conditional letter of map revision (CLOMR), protecting the existing Preble’s Meadow Jumping Mouse habitat, and avoiding disturbance to ditches’ ability to divert legally decreed water rights. The final design increases floodplain connectivity while adding low-profile features that complement the natural function and variability of the river, restoring native riparian and aquatic habitat in the process. The resulting passage of native fish and sediment, reduction of flood energy, and improved water quality benefit local communities and ecology alike. Otak coordinated closely with Boulder County Parks & Open Space, along with other stakeholders including ditch representatives, Colorado Parks and Wildlife, US Fish and Wildlife, and Department of Water Resources in establishing the final design and overseeing construction activities. The partnership with Boulder County continues with monitoring and adaptive management support.
The new stream design removed a small four-foot dam allowing fish passage through the reach, as well as reduced high-energy flows directed at the railroad ballast and ditch head gates. Adjustability from stop logs allow for more flow to move down the fish passage channel in the off-irrigation season. The project reach is being monitored for ecologic and geomorphic function with the intent to improve project benefit and success through adaptive management. This continued partnership informs future planning to remove fish barriers and make other connectivity improvements throughout other Colorado Front Range creeks and rivers.
