Scale Matters - Lessons Learned From Large-Scale Floodplain Restoration In The Upper Grande Ronde River, Oregon

The Upper Grande Ronde River (UGR) in NE Oregon (HUC 17060104) is a historically important river for salmon production. The UGR has been impacted by human activities since European settlers arrived to trap beaver in the early 1800’s. Historic impacts included logging with splash dams, railroad construction, road construction, grazing livestock, and trapping beaver. Historic impacts have resulted in degraded river and wetland conditions which have contributed to a multitude of environmental effects including degraded fish habitat, reduced floodplain connectivity, increased stream temperatures, and reduced base flows. In 2014, the U.S. Bureau of Reclamation Columbia-Pacific Northwest Region (USBR) completed a tributary assessment of the UGR to prioritize reaches for restoration to improve fish habitat conditions. The assessment resulted in prioritizing four unconfined reaches within the UGR for restoration activities. In 2015, Reclamation partnered with the Confederated Tribes of the Umatilla Indian Reservation (C.T.U.I.R.) and the U.S. Forest Service (USFS) to restore the river-wetland corridor on the Bird Track Springs-Longley Meadows reach (BTS-LM). The BTS-LM is an unconfined 4-mile reach of the UGR with an 800-acre floodplain. The reach has mixed ownership to include USFS lands, two private ranches and a private gun club. Reclamation provided planning and design services to the C.T.U.I.R. for two large-scale floodplain restoration projects. The Bird Track Springs project (BTS) addressed 1.9-miles of the UGR with 265-acres of historic floodplain. BTS was designed from 2016 through 2018 and was implemented in two phases during 2018 and 2019. BTS consisted of 5,000-feet of main channel construction, 9,500-feet of side channel construction, 85,000-cubic yards (CY) of excavation and the placement of approximately 4,500 trees as large wood structures. The Longley Meadows project (LM) addressed 1.9-miles of the UGR with 210-acres of historic floodplain. LM was planned from 2018 through 2020 and was implemented in two phases during 2020 and 2021. LM consisted of 2,850 feet of main channel construction, 7,250-feet of side channel construction, 42,000 CY of excavation and the placement of approximately 4,500 trees as large wood structures. During the late 1990’s the BTS-LM reach of the Grande Ronde River was “restored”. Previous attempts at restoring this reach consisted of the placement of instream structures including rock weirs, rock barbs, and large wood buried in banks, but those attempts were largely unsuccessful. This is likely due in part to the scale of previous attempts considering environmental conditions and historic impacts. Restoration of active river-wetland corridors requires taking a different view of the riverscape than the dominant view of a single-thread channel meandering through the landscape. Active river-wetland corridors are often messy and consist of multi-threaded channels and active processes that are dynamic. Restoring conditions that allow for dynamic sediment and wood-loading processes to occur often requires bold plans that can match the scale of historic disturbances. The BTS and LM projects have been tested by several floods since implementation and have shown resilience provided by natural processes.