FCD is pleased to announce the completion of project work on a 4,000-foot stretch of Trumbull Creek southwest of Columbia Falls. The project will alleviate flooding on adjacent private property by removing debris, re-establishing channel depth, and restoring the integrity of existing levees.
Trumbull Creek is a highly modified stream system located between Kalispell and Columbia Falls in northwest Montana. It was channelized for agricultural purposes in the 19th century. Since then, other factors, including livestock grazing and encroachment of golden willows, have contributed to a loss of channel function and increased flooding. A landowner in the Upper Reach (bounded to the north by US Hwy 2 east and to the south by US Hwy 2 north) had experienced flooding since the 1980s, which was thought to be at least partially due to an inadequate levee downstream. The flooding was especially severe in 2006 and 2010 because above average spring precipitation resulted in several rain-on-snowmelt events, and the landowner filed a 310-complaint in 2011. FCD retained a consultant to conduct an initial assessment, which identified bank restoration alternatives and recommended livestock grazing management to alleviate flooding. Concurrently, FCD also received a 310-complaint in regard to flooding associated with a culvert crossing on the Lower Reach (south of Hwy 2 north) of Trumbull Creek. The landowner contended that flooding on his property was exacerbated by an inadequate culvert system located downstream.
The persistent flooding on both reaches of Trumbull Creek was damaging private property. Willow encroachment and minimal grazing management were contributing to bank instability, which was intensifying the flooding. These were natural resource concerns for FCD because of detrimental impacts on water quality (from erosion and sedimentation) and riparian areas (from livestock).
FCD procured funding from the Montana Department of Natural Resources and Conservation – Conservation Districts Grant Program (HB223) to address the landowner issues in both the Upper and Lower Reaches of Trumbull Creek. Specifically, the District sought to design and implement work on the Upper Reach to mitigate flooding by increasing bank heights, restoring the existing levees, and managing livestock grazing with fencing and a water gap. The grant also funded a technical assessment on the Lower Reach to conduct a hydraulic analysis of a problematic culvert system in a creek crossing.
This project accomplished significant remediation on the Upper Reach of Trumbull Creek, which directly affected nine landowners. Approximately 3,200 feet of creek was excavated to return the channel to its original shape and depth and to promote the natural water flow. Excavated material was placed on the east embankment to restore the integrity of the existing levee and mitigate runoff on that side of the creek. Encroaching woody vegetation was removed because it was creating bank instability. Over 700 feet of fencing was installed to prevent livestock from trampling the streambank, and a hardened water gap was built for livestock water access. These activities have already improved the downstream flow of the creek, and FCD is hopeful that it will also minimize future flooding on adjacent land.
In addition to the project implementation on the Upper Reach, a hydraulic analysis for a culvert crossing on the Lower Reach of Trumbull Creek was conducted. The analysis concluded that the culvert system was undersized and exacerbating the flood hazard on the upstream property. This information will guide future projects and priority development on the Lower Reach.