Fall 2008
Vol. XVII, No. 4

In-River Work for Lewiston/Dark Gulch Project is Complete

 

Construction of the Lewiston-Dark Gulch Channel Rehabilitation Project began in late August. It consisted of eight project areas over three miles of river. In-channel work was completed by September 15 to comply with requirements of several regulatory agencies. Additional work on the sides of the river channel resumed in mid-October, and will be completed by December 2008. The overall project includes placement of almost 11,000 cubic yards of coarse sediment in the Trinity River and re-contouring adjacent areas. Coarse sediment is an important ingredient for a dynamic, healthy river system and is needed by salmon and steelhead for spawning. Floodplain re-contouring and side channel construction is designed to create areas of slower moving, shallow water and edge habitat that is good for rearing juvenile fish. This project was funded by the Bureau of Reclamation and a grant from the California Department of Fish and Game obtained by the Trinity County Resource Conservation District.

 

Site Before Project
Before

 

Site After Project
After

 

View from the Old Bridge in Lewiston looking up river. Alternating gravel bars are designed to change a long, linear reach of river to one with a more diverse and meandering form. Coarse sediment will also improve spawning and rearing habitat for juvenile salmon and steelhead.

 


Grappling the Tree
The initial cut.
Positioning the Tree
Placing the tree.
Tree in the River
The finished product.

 

Large woody debris (tree trunks and root wads) helps create geomorphic diversity and improved fish habitat. Project designs call for placement of large wood taken from other construction sites to key locations at the river’s edge.

 


Gravel Bar
Constructing gravel bars near Lewiston.

 


Side Channel
Constructing a side channel.

 


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