Upper Walla Walla River Assessment and Action Plan
Click here to read full assessment and action plan.
Over-widened channel with plane-bed morphology in the lower Walla Walla mainstem river, Washington.
This project was completed for the Confederated Tribes of the Umatilla Indian Reservation (CTUIR) in collaboration with state resource managers in Washington and Oregon, federal and local agencies, and other stakeholders. Rio ASE led a team to complete a watershed- and reach-scale geomorphic, hydraulic, and biological assessment of historical, current, and desired conditions throughout 71 miles in the upper Walla Walla River. The assessment was based on a data-driven analysis of landscape pattern, geomorphology, hydrology, hydraulics, riparian vegetation, fish status, habitat capacity, habitat suitability, and stream temperature.
A flood of record occurred immediately prior to project initiation in 2020. As a result, Rio ASE worked with the CTUIR to leverage this dynamic event by capturing new LiDAR and habitat data to compare pre- and post-flood conditions. Using LiDAR acquired by others, Rio ASE prepared 2D hydraulic models from both the pre- and post-flood LiDAR data-sets spanning 71 miles each. Pre- and post-flood hydraulic results comparisons enabled an accurate comparison of physical habitat and evaluation of channel evolution and trajectory.
The results of the analysis were compiled into a functional assessment quantifying impacts and limiting factors at a reach scale. Additionally, the team developed restoration targets and appropriate actions to achieve those targets that were prioritized by reach to facilitate project development aimed at restoring functional streams, floodplains, and uplands to sustain healthy fish populations.
An existing restoration site, featuring multiple flow paths over a broad floodplain.
LiDAR imagery from the Assessment showing North Fork Walla Walla channel deposition (blue) and erosion (red), comparing 2019 and 2020 data.
Example of a riparian shade analysis that Ecosystem Sciences completed for the Assessment and Action Plan report. This image is based on LiDAR-derived vegetation height and a solar routing model to calculate solar radiation and shade output.