Troy Brandt, Principal Biologist

Willamette River BasinInundation Mapping

December 11, 2012Courtesy Eagle Digital Imaging, Inc.

Acknowledgements

• What is inundation mapping?

• Who will use the information?

• How will the information be used?

A cost-effective analysis for predicting floodplain inundation associated with a given flood event.

Fish and wildlife agencies, conservation/restoration organizations, planners, emergency responders(?).

To assess how regulated flows influence the floodplain• Ecological• Social• Economic

Study Areas• Willamette River –

Eugene to Oregon City

• Middle Fork and Coast Fork Willamette River

• McKenzie River

Map Development• Use available gage data• Determine 2-year

discharge and stage• Create 2-year discharge

profile and layer

• Overlay on topographic surface model

• “Bathtub” model – based on elevations, not a hydraulic model

Method Limitations• Based on elevation differences• Does not account for obstructions (e.g. roads)• Mainstem depth relates to elevation above water

surface at time of LiDAR acquisition• Not for regulatory use

Willamette River Profile

Calapooia River Confluence

Grand Island

Harkens Lake

Map Use• USACE revetment analysis• Floodplain habitat fish use• Conservation easement prioritization• Historical wetlands analysis• Emergency responder access

USACE Revetment Analysis

Progress, challenges, and the future• Maps and GIS data offer a tool for restoration

planning and other efforts

• Products are useful for assessing historical conditions and predicting possible ecological outcomes associated with river management

• Help direct restoration prioritization and spending

Data• Currently available

- Mainstem Willamette River Regulated 2-year water surface GIS layer Regulated 2-year inundation maps in pdf format 2012 Flood air photos 2012 Flood air photo maps in pdf format

• To come- MF-CF Willamette River GIS, maps and documentation- McKenzie River maps GIS, maps and documentation

www.riverdesigngroup.com info@riverdesigngroup.com