Umatilla River Floodplain Assessment and Action Plan

The Umatilla River is 89 miles long and drains a watershed area of about 880 square miles. Some of the most prevalent human influences in the subbasin are associated with agriculture, exotic weed introduction, forest practices, livestock grazing, transportation, urbanization, and water development. The result of these activities have led to negative physical impacts, which include stream channelization, reduced instream water volume, high water temperatures, riparian vegetation loss, increased erosion and sedimentation into streams, and land conversion and degradation. The ecological effect of these negative impacts include increased flood frequency, reduced water quality, separation of stream channels from floodplains, loss of exchanges between the hyporheic zone and river flow, and loss and degradation of habitat for aquatic and terrestrial wildlife species.



This project will develop a floodplain-scale, geomorphic-based assessment of current habitat conditions, identify necessary data gaps, and develop an action plan for the Upper Umatilla River Subbasin (Figure 1, attached proposal file). Given the dramatic differences in management in the sections of river, the additional municipalities included, and the previously identified boundaries that have been established by a variety of projects, it was decided to include that portion of the Umatilla River Watershed from the city of Nolin to the headwaters of the North and South Fork of the Umatilla River. This assessment and Action Plan will be floodplain centric and include the mainstem of the Umatilla River and the connectivity to the mainstem of the confluences of the upper tributary streams.



This project is expected to take 2-3 years to complete. This first year will be mostly focused on public outreach, compiling and beginning the data analysis, and drafting documents for circulation. It is anticipated that a subcontractor will be necessary to aid in defining the actual documents and direction taken, as well as with all of the items mentioned for Year 1. Primary use of PCSRF funds would be to support these project activities.



Project Objectives: The goal of this project is to create an assessment and action plan that clearly identifies the limiting factors and treatments by prioritized reaches and species. The specific project objectives include:

• Develop a floodplain assessment for the Umatilla River, with an emphasis on stakeholder support and a technical team approach.

• Utilize the assessment as the foundation and technical support to produce an Action Plan that prioritizes restoration priorities, both geographically and by type of action.

• Utilize modelled expected climate impacts and use that information to prioritize restoration areas and species, as well as predicted future fish distributions.

• Develop and implement an effective public relations/outreach plan for this project.



We have developed a framework for our approach to completing this project on those previous assessments. This framework utilizes a watershed and reach-scale geomorphic analyses to support assessment and prioritization of river, floodplain, and fish habitat restoration alternatives in the basin. The analyses are intended to facilitate the understanding of expected riverine and floodplain processes and identify restoration projects that are consistent and compatible with natural reach scale hydraulic and sediment transport processes. This scope is intended to support the vision and strategy of the CTUIR Umatilla River Vision (Quaempts et al. 2018; Jones et al. 2011) and the general natural resource goals of partner agencies and stakeholders that will result in restored riverine function and salmonid habitat, while considering necessary constraints and protections for infrastructure.

The assessment will serve to explain stream conditions as related to fish habitat needs, water quality, hydrology, and land uses, and it includes compiling and reviewing summaries of existing data and conducting technical analyses to provide a summary of the geomorphic setting including historic and current conditions. The action plan element of the work will involve effective stakeholder communication of assessment outputs, systematically compile potential projects supported by assessment outputs, create potential new solutions, evaluate restoration alternatives, and document the preferred path to monitor physical and ecological function from implemented habitat and stream improvements. A primary goal of the planning effort is to attenuate the limiting factors/ecological concerns/nonfunctional River Vision Touchstones related to habitat. The assessment will also serve to characterize the non-point sources of pollution (NPS) issues identified in the Umatilla River Basin Total Maximum Daily Load (TMDL), and the restoration projects identified in the action plan will include how each project addresses NPS issues, in order to help support implementation of Section 319 of the Clean Water Act. It is hoped that through these actions, additional local concerns about flooding and management of the floodplain/stream channel can be addressed and resolved. Additionally, the Action Plan will identify long term management objectives for the floodplain.



The riparian quality varies from moderately or largely intact in the headwaters, to moderate or highly disturbed in the lowlands. The lower sections are dominated by agriculture and rangeland. Relative to historical conditions, the lower portion of the study area in the Umatilla River Subbasin is highly simplified, straightened, restricted from floodplains, reduced riparian zone, and impacted by irrigation withdrawals. There are a variety of passage barriers in the upper headwaters that currently limit anadromy that will be identified and evaluated for relative population level impacts.