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Revegetation Efforts Build on Discovery of Original Floodplain Surfaces
Restoration - Clark Fork River Restoration
Written by Tom Parker   
willowcDuring spring and early summer 2008, the Clark Fork River scoured away portions of its floodplain upstream from Duck Bridge, leaving acres of exposed gravel and cobble at an elevation that is very close to the final design elevation for floodplain restoration.  This past winter, the State’s restoration design team re-evaluated the floodplain grading and planting plans to see whether we could incorporate this work accomplished by natural river processes.

 

Natural changes allow more wetland features
Comparing the post run-off floodplain surface with the design floodplain surface, we found that many areas will now only require minimal grading and shaping to reach target floodplain elevations.  For the revegetation plan, this means we will be able to leave some exposed depositional surfaces as they are, ready to recruit cottonwood seedlings and other native vegetation that begin their life cycles on gravel bars.  These natural changes also allowed us to design in more wetland features to take advantage of areas that are now low relative to the river’s future stage through this reach.
Old floodplain surface still intact after 100 years
The discovery of the old floodplain surfaces, also near the design surface elevation, provides another opportunity to use soil that is already in place.  While this verifies that the designed floodplain is at the correct elevation, it also reduces our need to import soil for floodplain revegetation.  The old floodplain surface still has intact soil structure, coarse woody debris and roots within the soil profile that have been preserved by one hundred years of constant saturation when the reservoir was in place.  We will watch this area closely this summer to see if any pre-dam era seeds remained viable in the soil.      

Volunteers learn about river processes on weed pulls

cfrweedpull808Last summer, volunteers participated in a weed pull in this same area upstream from Duck Bridge.  Those involved with the weed pull had the opportunity to see the results of the river processes during spring run-off.  Scour and deposition had occurred throughout the floodplain and cottonwood seedlings were already beginning to colonize bare floodplain surfaces.  Another volunteer weed pull is in the works for this summer; stay tuned for more information and another opportunity to see the river at work.  
Other on-going site preparation activities include large scale weed control targeting tansy, leafy spurge, Dalmatian toadflax and other species.  One area that was planted last October will receive periodic maintenance and we will monitor its progress.  We continue to work with native plant nurseries to grow up plants for large scale floodplain revegetation between 2009 and 2012.  This spring, crews are out salvaging and transplanting native willow cuttings and mature willow shrubs ahead of river construction.  Salvaged willows plants and cuttings will be planted in streambanks this fall as river construction proceeds.
We are looking forward to this year as the restoration effort begins in earnest and we combine active revegetation with natural ecological processes to begin re-creating a functioning floodplain ecosystem—hopefully with the help of many community volunteers!