Portland NWAEP Lunch & Learn - Modeling Historic Flood Impacts to the Columbia River

Modeling Historic Flood Impacts to the Columbia River

Presented by Lumas Helaire; Graduate Student - Civil Engineering; Portland State University

The Lower Columbia River Estuary (LCRE) has undergone extensive modifications since the 19^th century. Construction of dams, installation of jetties and dikes, dredging of the navigation channel and filling-in of tidal wetlands have all contributed significantly to alterations in tidal dynamics and the flow regime, with consequences for habitat inundation and salinity intrusion.   In this talk we discuss the development and implementation of a 19^th century flow model for the LCRE, using a digital elevation model based on historic bathymetry.   The model has been calibrated with recently re-discovered and digitized tide data from the 19^th century.    With the model, we focus on the following questions:

1) For the same flow, how have wetland inundation patterns changed since the 1890’s?

2) How has salinity intrusion changed in the estuary?

3) What particular anthropogenic changes have had the most effect on river physics (dams, channel dredging, jetty construction, filling of tidal wetlands)?

Initial results suggest that salinity intrusion patterns have shifted and that wetland inundation patterns have been impacted by the up-to 10% increase in estuary tidal range since the 19^th century. 

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Lumas Helaire is a Master’s of Science candidate in Environmental Engineering at Portland State University.  Lumas works in the Hydrodynamic Processes and Ecosystems Group within the Civil and Environmental Engineering Department. His present research is focused on the development of a historic hydrodynamic model of the Lower Columbia River Basin.  The model is representative of the bathymetry of the late 19^th century, i.e. before large-scale dredging of the main channel, filling of tidal flats and the construction of any of the major dams on the on the Lower Columbia River.  Lumas would like to utilize the Historic Columbia River Model to study the water level and inundation profile of the 1876 Columbia River flood and study how anthropogenic changes to the river system affect river hydrology.