Shifting Sediment Dynamics in the Coos Bay Estuary in Response to 150 Years of Modification

Journal Article Resource
February 2021

The diverse users of Oregon’s Coos estuary share a need to better understand water circulation and sediment transport in the estuary under present and future conditions. A collaborative research project led by the University of Oregon and South Slough National Estuarine Research Reserve filled data gaps and modeled how estuarine circulation and sediment respond to perturbations due to both natural and human-induced causes—such as dredging or inundation caused by sea level rise.


Estuaries worldwide are commonly dredged to accommodate development. Related modifications, including dumping of dredge spoils, construction of jetties, waterfront reclamation, and so on all serve to change the geometry of estuaries. These modifications can result in changes to how water and sediment flow through the estuary. We used a high‐resolution model of water and sediment dynamics in the Coos Bay estuary in Oregon, together with modern and historic bathymetric (depth) data from the estuary, to assess how 150 years of modification (dredging and other projects) have altered the storage and transport. Overall, the model results suggest that the estuary now retains more sediment, owing largely to sediment trapping in the deepened navigation channel. This is an effect of changes in how water flows through the system and the additional space created to hold sediment (accommodation space). More nuanced changes have occurred on shallow intertidal flats and in subembayments, which have also led to increased sediment retention

About this article

This article, published in JGR Oceans in 2020, describes the use of a high-resolution model of water and sediment dynamics used in the Coos Bay estuary in Oregon to assess how 150 years of modification have altered sediment storage and transport.


Eidam, E.F., Sutherland, D.A., Ralston, D.K., Conroy, T., Dye, B., 2021. Shifting Sediment Dynamics in the Coos Bay Estuary in Response to 150 Years of Modification. Journal of Geophysical Research: Oceans 126, e2020JC016771.

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