In 2012, more than nine inches of rain caused significant flooding and infrastructure damage in Duluth. Barr provided evaluation and design services for a damaged reach on Coffee Creek, a popular trout stream that runs through Enger Park Golf Course. We worked with the city to obtain funding to stabilize and restore the most severely damaged section through a former irrigation pond. Using natural channel design principles, Barr designed restoration of the stream’s pattern, profile, and dimension to emulate a stable reference condition, protect infrastructure, stabilize streambanks, and improve trout habitat. We also conducted hydraulic modeling to confirm that channel dimensions and materials would resist bankfull flow velocities and to support FEMA permitting for changes to the floodplain.
Design, permitting, and construction for restoration of 1,200 feet of channel were completed in 2015. Barr observed construction, which entailed daylighting 250 feet of stream previously confined to an undersized culvert and realigning the channel within the bed of a former irrigation pond. At the former pond outlet, we designed a permanent stream crossing that allows for fish passage at bankfull flows. The bankfull-width box culvert contains a natural-material streambed and was evaluated using FishXing and HEC-RAS. Barr prepared a FEMA letter of map revision, which became effective in March 2017 and reflects a modified (mostly lowered) floodplain elevation.