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ID: 2402

Boyce, J. and D. H Goodman. 2018. Large wood placement at channel rehabilitation sites by the Trinity River Restoration Program, 2005-2016. Report TR 2018-57 for the Trinity River Restoration Program (TRRP). Arcata, California. Available: http://www.trrp.net/library/document?id=2402.

Abstract.? The Trinity River Restoration Program implements large wood augmentation as part of a broader restoration strategy to restore ecological processes and increase the production of naturally-spawned anadromous fishes. Restoration efforts are implemented under an adaptive management framework whereby monitoring data are used to test restoration hypotheses to help inform subsequent restoration implementation decisions. Here, we summarize large wood placement at 27 rehabilitation sites immediately after construction from 2005-2016 to assist with the development of a large wood management strategy for the program and provide feedback for the adaptive management process. A total of 7,591 large wood pieces and 1,919 large wood structures have been placed in the restoration reach since 2006. Fifty-nine percent of those LW pieces were incorporated into weirs, deflectors and constructed wood jams. We found that the number of large wood pieces and thenumber of constructed wood jams per river kilometer placed during construction of rehabilitation sites have increased over our monitoring period. However, the level of complexity of constructed wood jams, as estimated by the number of LW pieces per structure, was variable. We also found that over 80% of the large wood pieces and structures are placed in off-channel areas such as high and low flow side channels and 60% are located within the bankfull channel and are inundated at streamflows at or below 14.2 cms (500 cfs). At eight of 27 sites, rehabilitation site design reports include specific LW placement objectives that were met over 75% of the time during construction. However, we could not identify specific LW design objectives for the other 19 sites. The increased use of large wood in channel rehabilitation likely reflects the growing awareness and demonstrated utility of large wood augmentation and off-channel habitat creation as means to improve restoration of riverine ecosystems and fish production immediately after construction. The database we accessed to summarize large wood placement at rehabilitation sites contains data from multiple re-visit surveys, which will be leveraged in future efforts to assess inter-annual large wood dynamics, longevity of wood installations and provide additional information to facilitate improvements in future restoration efforts.

First Posted: 2018-08-24 00:47:51

Post Updated: 2018-08-24 00:48:12