James S White Karen M Bartelt Brandon T Overstreet 20250710 raster digital data U.S. Geological Survey Data Release doi.org/10.5066/P13SQVZY online U.S. Geological Survey https://doi.org/10.5066/P13SQVZY James S. White Karen M. Bartelt Brandon T. Overstreet Jake R. Kelley 20250701 publication The size and distribution of riverbed grain size plays a foundational role in river morphology and ecology. This study (White and others, 2025) quantifies submerged riverbed grain size at high resolution (1 square meter) across 260 kilometers of geomorphically diverse river corridors in the Santiam River Basin, Oregon, by pairing bathymetric lidar point-clouds collected in 2023 with georeferenced pebble counts. This data release documents the grain size model results of the study, including the median grain size (“D50”) and 84th percentile (“D84”) results for each of the seven study reaches, including the North Santiam River below Big Cliff Dam (“lower North Santiam”), the Little North Santiam River, Breitenbush River, North Santiam River above Detroit Reservoir (“upper North Santiam”), the South Santiam River below Foster Dam (“lower South Santiam”), Quartzville Creek, the Middle Santiam River, and the South Santiam River above Foster Reservoir (“upper South Santiam”). This metadata provides an overview of the data, but users are encouraged to read the associated study for details on model development and limitations (White and others, 2025). Notably, published datasets are limited to areas where bathymetric lidar returns were at least 5 points per square meter, and areas not achieving this point density were removed. Citation and link for associated journal article: White, J. S., Bartelt, K., Overstreet, B. T., & Kelley, J. R. (2025). High resolution mapping of submerged sediment size and suitable salmon spawning habitat using topo‐bathymetric Lidar in the Santiam River basin, Oregon. Water Resources Research, 61, e2024WR039219. https://doi.org/10.1029/2024WR039219 Riverbed grain size maps were developed from bathymetric lidar on seven river reaches in the Santiam River Basin, Oregon. Lidar and georeferenced pebble count data were collected in 2023 and two suites of grain size models were developed: one estimating the median grain size (“D50”), and one estimating the 84th percentile grain size (“D84”) within each square meter of river. The details of grain size model development and limitations can be round in an accompanying publication (White and others, 2025). The purpose of this data release is to publish sediment model results. 20230901 ground condition Complete None planned -123.1487 -121.8828 44.8331 44.3911 ISO 19115 Topic Category geoscientificInformation environment inlandWaters USGS Thesaurus grain-size analysis lidar remote sensing Next Generation Water Observing System NGWOS Integrated Water Science IWS USGS Metadata Identifier USGS:67119696d34e8fed37af0e98 None Oregon Santiam River Basin Willamette River Basin North Santiam River South Santiam River Breitenbush River Quartzville Creek Middle Santiam River None. Please see 'Distribution Info' for details. None. Users are advised to read the dataset's metadata thoroughly to understand appropriate use and data limitations. James S White US Geological Survey Hydrologist mailing and physical

601 SW 2nd Ave Ste 1950

Portland Oregon 97204 5037584623 gs-w-or_sciencebase@usgs.gov These data were collected as part of the U.S. Geological Survey (USGS) Next Generation Water Observing System (NGWOS) Willamette River Basin project to map grain size across large spatial extents. Funding was also provided by the U.S. Army Corps of Engineers, Portland District. James S. White Karen Bartelt Brandon T. Overstreet Jake R. Kelley 20250715 e2024WR039219 publication https://doi.org/10.1029/2024WR039219 Details on the accuracy and precision of the data in this data release can be found in the accompanying journal article (White and others, 2025). Uncertainty of the grain size datasets are documented in the accompanying publication (White and others, 2025). Data were also qualitatively evaluated to ensure reasonableness of results. Data are complete. Details on the horizontal precision of the lidar and pebble count data to develop these models are described in the accompanying journal article. Processing steps are described in detail the associated journal article and users are strongly encouraged to read the complete methodology to understand the assumptions and limitations of the approach. The basic processing steps include collecting georeferenced grain size data and topobathymetric lidar, creating a roughness dataset from the bathymetric point cloud, and then creating regressions of lidar roughness and measured grain size. 20240901 Raster Grid Cell 49700 100156 1 Universal Transverse Mercator 10 0.9996 -123.0 0.0 500000.0 0.0 row and column 1.0 1.0 meters North American Datum of 1983 (NAD 83) WGS_1984 6378137.000000 298.257222 Reachname_Dsediment_size.tif Raster geospatial data file. Producer Defined Value Unique numeric values contained in each raster cell. Producer Defined 2 301 millimeter 1 This data release contains a series of raster files which represent modeled D50 and D84 grain sizes. The naming convention of each file is "Reachname_Dsediment_size.tif". Thus, the D50 model for the Little North Santiam River is "LittleNorthSantiam_D50.tif". White and others, 2025 GS ScienceBase U.S. Geological Survey mailing address

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Denver CO 80225 United States 1-888-275-8747 sciencebase@usgs.gov Unless otherwise stated, all data, metadata and related materials are considered to satisfy the quality standards relative to the purpose for which the data were collected. Although these data and associated metadata have been reviewed for accuracy and completeness and approved for release by the U.S. Geological Survey (USGS), no warranty expressed or implied is made regarding the display or utility of the data for other purposes, nor on all computer systems, nor shall the act of distribution constitute any such warranty. Digital Data https://doi.org/10.5066/P13SQVZY None 20250710 James White US Geological Survey Oregon Water Science Center Hydrologist mailing and physical

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Portland Oregon 97204 5037584623 gs-w-or_sciencebase@usgs.gov FGDC Content Standard for Digital Geospatial Metadata FGDC-STD-001-1998