Since 2010, RDG has worked with Willamette Basin stakeholders to better understand river-floodplain interaction under river regulation. As part of a small team lead by Meyer Memorial Trust and the Oregon Watershed Enhancement Board, RDG collaborated with academics, watershed councils, and conservation organizations to map the 2-year floodplain using a LiDAR surface model, gage hydrology, and observed high flows information. While the original goal of this effort was to develop a tool that restoration practitioners could use to help better understand floodplain connectivity, the maps have been an educational tool used by the broader conservation community to inform understanding of river processes, vegetation patterns, and revetment effects. An unforeseen map use included a request from Benton County Emergency Service to use the maps to help predict flood-related road closures and resulting emergency vehicle access issues. With the success of the initial mapping, RDG completed similar analyses on the Coast Fork and Middle Fork Willamette River and the lower McKenzie River for The Nature Conservancy in 2012, and the Santiam River system in 2016.

The inundation mapping effort has expanded RDG’s professional network and increased our collaboration with Willamette Valley watershed councils, professors and graduate students at OSU and UO, The Nature Conservancy, and others. The maps have enhanced stakeholder understanding of the river while also creating a commonality that diverse stakeholders can relate to.

Troy Brandt, MS

Oregon Watershed Enhancement Board
The Nature Conservancy
Meyer Memorial Trust

Willamette Valley, Oregon

ArcGIS remote sensing
Aerial imagery acquisition
Hydrologic modeling
Inundation map creation and verification