upper Osage River umbrella mitigation Bank Site 1 -

Pottawatomie Creek

Miami County, Kansas

Situated at the confluence of Pottawatomie Creek and Cockers Branch, the 278-acre Pottawatomie Creek mitigation site is the first location developed as part of the Upper Osage River Wetland and Stream Umbrella Mitigation Bank, a regional mitigation program that operates across much of east-central Kansas.

In its pre-mitigation state as an agricultural property, this site consisted of large expanses of artificially drained flat farm fields with some hillsides in its northern and southwestern portions.  There are more than 18,750 feet of perennial, intermittent, and ephemeral streams on the property but almost all of that linear footage was significantly degraded.  For instance, several small oil wells were operating in close proximity to one intermittent stream and two ephemeral channels and presented a risk of chemical contamination.  Most notably though, almost all stream channels were highly incised, mostly severing the connections between all streams other than Pottawatomie Creek and their respective floodplains.  The stream base incision was also causing bank erosion and endangering many surrounding mature trees by exposing their root systems.  In addition to these impairments, two ephemeral streams had been partially channelized and riparian buffers were relatively thin.

Swallowtail addressed these impairments through the following activities:

  • Restored or enhanced 101 acres of riparian buffers

  • Established 67 acres of forested wetlands and almost 10 acres of emergent wetlands

  • Restored or enhanced an additional 4.5 acres of wetlands

  • Established or preserved almost 94 acres of wetland buffers and adjacent uplands

  • Reduced bank erosion along Pottawatomie Creek by constructing longitudinal peaked stone toe protection

  • Constructed 21 rock grade control structures and 26 log grade control structures in seven streams to address stream incision

  • Restored normal sinuosity and channel dimensions to the two channelized ephemeral streams

  • Ceased oil extraction on the site

In addition, severe incision within one intermittent stream was addressed through the use of the relatively new method of regenerative stream restoration where the incised channel was partially filled to re-establish a stable and healthy new channel to improve floodplain connectivity.  Rock riffles were then constructed to maintain that stability.  Floodplain connectivity was also greatly increased along the highly incised Cockers Branch as a result of a floodplain connectivity weir that diverts some stormwater flows onto tens of acres of new wetlands while still allowing low flows and some storm flows to pass through the structure.

Swallowtail environmental