Estimated Median Riverbed Grain Size (D50) throughout the Willamette River Basin, Oregon

Riverbed grain-size is an important indicator of geomorphic and ecological processes and conditions, as it provides a key building block for channel form and benthic aquatic habitats. Understanding the distribution of riverbed sediment throughout a basin can help inform a variety of river and ecosystem management questions. This dataset provides estimates of median riverbed grain-sizes (D50) throughout the Willamette River Basin for each segment of the medium resolution (1:100,000 scale) National Hydrography Dataset (NHD). These estimates were developed by applying the critical Shields equation using an approach similar to that described in Snyder and others (2013). This equation was parameterized at each NHD segment with two outputs from USGS StreamStats: a) the 0.5 annual exceedance probability streamflow (often referred to as the 2-year recurrence interval flow) and b) associated wetted width at that streamflow (herein bankfull width). Users are encouraged to carefully read the documentation to understand the assumptions and limitations of this dataset.

Snyder, N.P., Nesheim, A.O., Wilkins, B.C., and Edmonds, D.A., 2013, Predicting grain-size in gravel-bedded rivers using digital elevation models: Application to three Maine watersheds: GSA Bulletin, v. 125, no. 1–2, p. 148–163, at https://doi.org/10.1130/B30694.1.