Designing For Resiliency - A Passive-Aggressive Approach To Large-Scale Restoration of A River-Wetland Corridor In The Upper Grande Ronde River, Oregon

The U.S. Bureau of Reclamation’s Columbia-Pacific Northwest Region River Systems Restoration Group (USBR) planned, designed, and performed engineering during construction of two large-scale river wetland corridor restoration projects in proximity to each other on the Upper Grande Ronde River in northeast Oregon from 2015 to 2021. These two projects, Bird Track Springs (BTS) and Longley Meadows (LM), are in a continuous unconfined floodplain 4 miles in length previously identified in an assessment from USBR as a prioritized reach for improving habitat for endangered salmonids. Both projects have mixed landownership, public and private, with most of the acreage on the Wallowa Whitman National Forest. BTS and LM are separated by private property. Constraints with private property, robust cultural resources, and infrastructure including State Highway 244 required designs that maximized habitat uplift and considered potential impacts to property, infrastructure, and resources. USBR utilized a passive-aggressive approach to design these projects to be resilient in a changing climate by restoring the river plan form from a single thread degraded river to a functioning river-wetland corridor consisting of complex multi-threaded channel networks (aggressive) and connecting existing relic features on the landscape (passive). Significant data collection including RTK survey, LIDAR, discharge measurement, and geomorphic assessment was performed to support design. A systematic approach of creating proposed 3-D surfaces, followed by iterative 2-D hydraulic modeling, and field verification was utilized leading to final designs that were implemented using GPS controlled machines. The design process was a team effort with collaboration from engineers, geomorphologists, archeologists, and fish biologists. Natural channel design is an artform that was honed over the course of four years of designing these significant projects. Design consists of iterating horizontal and vertical alignments, while accounting for flow partitioning throughout a complex multi-threaded channel network. Channel material design consisted of developing native material gradations and placement locations to function as natural elements in the stream corridor while balancing excavation cut-fill on-site. Construction implementation while working in ESA-listed streams requires significant planning. Care of water including by-pass channels, temporary bridges, fish removal, and turbidity management were carefully sequenced to minimize impacts to species of concern and wetlands. Several lessons were learned during the design and implementation of these large-scale restoration projects. Examples include: 3-D design surfaces tend to over-estimate fill volumes, timing and placement of plants and live-stakes greatly contributes to survival and succession, utilizing large wood structures and bank-treatments that are modular/adaptable can help account for variances of bank height and source wood size, large cobbles required for riffle design can be difficult to source on-site, and planning for unknowns like fire restrictions and global pandemics is strongly recommended to be successful.