Nehalem Bay Sediment Study

Science Center Objects

Assessment of Sedimentation Changes in the Nehelam Bay, Oregon

nehalem map

Aerial view of Nehalem Bay.

(Public domain.)

This study will provide the Port of Nehalem with an assessment of the magnitude, spatial patterns, and volumetric rates of sedimentation in the Nehalem Bay from 1891 to 2012 through comparison of U.S. Coast and Geodetic Survey (USCGS). Systematically identifying locations of sedimentation and quantifying the rate of change over time will provide a baseline for understanding the extent and rate of sedimentation. Motivation for this study stems from observations of aggradation by the Port of Nehalem in recent decades. These observations are consistent with a qualitative review of the nautical charts from the USCGS from 1891 and 2012, which indicates decreases in water depth from Wheeler to Fishery Point in the Nehalem Bay, and a recent USGS study1 that documented increases in gravel bar area and decreases in channel width in the Nehalem Bay between 1939 and 2009. Bay aggradation may result in potential impacts to river navigation, reductions in estuarine habitats for juvenile salmonids, and flood risks for infrastructure near the City of Wheeler, including private docks, marinas, motels, and storm water outlets. Results from this study will be helpful to the Port of Nehalem as it seeks to communicate sedimentation observations to federal and state agencies.