Mechanical Channel Rehabilitation
| Bank Rehabilitation | |
| Future Projects and Schedule | |
| Active and Existing Projects | |
| Bank Rehabilitation | |
| Side Channel Rehabilitation | |
| Valdor Gulch Photos | |
| Conner Creek photos | |
The TRRP currently has an aggressive schedule to construct 47 channel rehabilitation sites in the floodplain of the Trinity River along the forty miles between Lewiston Dam and the North Fork of the Trinity River. These sites are at locations identified in the EIS/EIR and rehabilitation will involve removal of fossilized riparian berms along the banks of the river that prevent access by the river to the historic floodplain. The rehabilitation projects are designed to encourage river meandering and to maximize habitat creation (flooding) at high flows. Recent planning efforts have focused on completing the first 24 sites (Phase 1) by 2008. The first site is called Hocker Flat and involves about one mile of privately owned river floodplain. Construction contract award is scheduled for July 2005. Full implementation of the ROD releases and construction of the channel rehabilitation sites are dependant upon identifying and implementing an appropriate realty strategy for private landowners along the river.
Restoring the Trinity River to a healthy alluvial river to benefit salmon and steelhead populations requires converting the present riparian berm-dominated channel back to the pre-TRD channel form, but at a smaller scale. Studies conducted in 1995 and 1998 found that flood flows greatly exceeding 24,000 cfs would be needed to “naturally” remove the berm. However, since Trinity Dam is only capable of a maximum controlled release of 13,750 cfs, a one-time mechanical removal (using heavy equipment) of selected berms between Lewiston Dam and the North Fork Trinity River is needed to “unshackle” the river and restore the channel, if scouring flows of at least 6,000 cfs are released at least every two years.
Flow and sediment management will be used after the one-time mechanical removal of the berms to create and maintain high-quality aquatic and riparian habitat. Observations at rehabilitation sites constructed between 1991 and 1993 have shown that once the riparian berm is removed and new bars have formed, flow and coarse sediment management directed by the Record of Decision is capable of maintaining the desirable channel morphology.
Future Projects and Schedule
The following chart illustrates the current time schedule for channel rehabilitation sites.
Map - Upper River Site 2007
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| click to enlarge |
Map - all Phase 1 and Phase 2 sites
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| click to enlarge [PDF] |
Active and Existing Projects
The graphic below illustrates the active and existing mechanical channel rehabilitation projects. Click on the name of a project to get more information.
Bank Rehabilitation
Riparian berms that confine the river will be removed, and sand contained in the berm relocated outside of the floodway. Floodplains will be constructed to be periodically inundated by flows 6,000 cfs and larger. At sites closer to Lewiston Dam with limited gravel supply, coarse sediment will be introduced as gravel/cobble point bars to increase gravel storage, improve channel dynamics, and increase salmon spawning and rearing habitat.
Riparian vegetation will be planted on restored floodplains, and high flow releases have been developed to encourage natural riparian growth on floodplains while discouraging riparian encroachment on newly formed gravel bars. A strategy using a combination of native riparian planting and natural regeneration can quickly re-vegetate a floodplain rehabilitation project (see photo below).
Sheridan Creek Bank rehabilitation site with newly formed gravel bars.
Natural regeneration (foreground) and riparian planting (background) one year after floodplain construction on Clear Creek, showing expected conditions on Trinity River rehabilitation sites shortly after construction.
Side Channel Rehabilitation
Side channels will also be constructed at selected sites close to Lewiston Dam that have a high likelihood of maintaining themselves. Side channels provide additional salmon and steelhead spawning and rearing habitat to make up for that lost above the dams.
Side channel rehabilitation site
| Construction Completed at the Canyon Creek Suite of Channel Rehabilitation Sites Valdor Gulch and Conner Creek site photos are shown below mouse over for photos |
 Valdor Gulch pre-construction, April 4, 2005 |
Valdor Gulch during construction, October 11, 2006 |
Valdor Gulch after construction, December 8, 2006 |
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| Map of Valdor Gulch project [PDF - 500kb] | ||
| Conner Creek pre-construction, July 6, 2006 |
Conner Creek during construction, November 9, 2006 |
Conner Creek after construction, December 7, 2006 |
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| Map of Conner Creek project [PDF - 1mb] | ||
| All four Canyon Creek site maps are available on the Canyon Creek project page. | ||