Maxwel F. Schwid Mackenzie K. Keith Brandon T. Overstreet 20250826 tabular digital data https://doi.org/10.5066/P135FWPP In cooperation with the U.S. Army Corps of Engineers (USACE), the U.S. Geological Survey (USGS) surveyed ground control points and coordinated aerial photograph acquisition of Hills Creek Lake, a multi-purpose reservoir in western Oregon impounded by the 92-meter ([m]; 302-foot [ft]) tall Hills Creek Dam. Aerial photographs were acquired by the Civil Air Patrol (CAP) on December 20, 2023 and December 28, 2023 when water levels were at 443 and 441 m (1453 ft and 1448 ft; National Geodetic Vertical Datum of 1929 [NGVD 29]) elevation, respectively, about 10 m above typical annual “low pool” or minimum pool for flood risk management operations. Photographs were acquired at about the same altitude with a WaldoAir XCAM Ultra 50 camera mounted on a Cessna aircraft and captured the entire reservoir area as defined by full pool (or maximum conservation pool elevation), including major tributaries entering the reservoir such as the Middle Fork Willamette River and Hills Creek, upstream of Hills Creek Dam. Dam operations at the 1,107-hectare (2735-acre) Hills Creek Lake, located about 19 kilometers upstream of the confluence of the Middle Fork Willamette River and the head of Lookout Point Lake, along with other hydrogeomorphic conditions, result in a diverse array of geomorphic processes and landforms within the reservoir. To document reservoir floor geomorphology, the USGS applied structure-from-motion (SfM) techniques to these aerial photographs, following the workflow outlined in Over and others (2021), and generated three-dimensional xyz point clouds, digital surface models (DSMs), and orthomosaics of Hills Creek Lake. This data release includes ground control points, dataset footprints, original aerial photographs, point clouds, DSMs, and orthomosaics of Hills Creek Lake with varying aerial extents and resolutions that were developed from imagery acquired December of 2023: (1) the December 20 model (HillsCreekLake_20231220) covered the entire reservoir area with an average point density of 27.6 points per square meter, DSM resolution of 19 centimeters per pixel, and orthomosaic ground resolution of 9.52 centimeters per pixel; (2) the December 28 model (HillsCreekLake_20231228) covered the entire reservoir area, excluding a portion of the Larison Creek arm, with an average point density of 29.8 points per square meter, DSM resolution of 18.3 centimeters per pixel, and orthomosaic ground resolution of 9.15 centimeters per pixel. All DSMs and orthomosaics are formatted as Cloud Optimized GeoTIFFs (COGs) for enhanced web visualization (GDAL, 2024). This documentation describes a CSV file containing ground control point locations collected on December 17, 2024, that were used to spatially register SfM datasets of Hills Creek Lake, Oregon. References: Agisoft, 2025, Agisoft Metashape User Manual - Professional Edition Version 2.2: Agisoft LLC, 115 p., accessed August 11, 2025, at https://www.agisoft.com/pdf/metashape_2_2_en.pdf. American Society for Photogrammetry and Remote Sensing [ASPRS], 2008, LAS Specification Version 1.2: ASPRS, approved September 2, 2008, 13 p., accessed August 11, 2025, at https://www.asprs.org/wp-content/uploads/2010/12/asprs_las_format_v12.pdf. Geospatial Data Abstraction Library [GDAL], 2024, COG -- Cloud Optimized GeoTIFF generator: GDAL, webpage, accessed August 11, 2025, at https://gdal.org/drivers/raster/cog.html#raster-cog. Over, J.R., Ritchie, A.C., Kranenburg, C.J., Brown, J.A., Buscombe, D., Noble, T., Sherwood, C.R., Warrick, J.A., and Wernette, P.A., 2021, Processing coastal imagery with Agisoft Metashape Professional Edition, version 1.6—Structure from motion workflow documentation: U.S. Geological Survey Open-File Report 2021–1039, 46 p., https://doi.org/10.3133/ofr20211039. Schwid, M.F., Keith, M.K., and Overstreet, B.T., 2025, High-resolution orthoimagery and digital surface models of Fern Ridge Lake, Oregon, during annual low pool, January and February, 2023: U.S. Geological Survey data release, https://doi.org/10.5066/P1Q5K657. The original aerial photographs acquired by CAP, along with the point clouds, DSMs, and orthomosaics covering Hills Creek Lake were created to provide high-resolution datasets depicting the reservoir floor that are exposed during low pool (443 and 441 m/1453 ft and 1448 ft NGVD 29) conditions. These datasets are useful for evaluating geomorphic characteristics of the reservoir floor and assessing other landscape conditions; when compared with future datasets, these datasets will also be useful for tracking changes in reservoir floor conditions. 20241217 ground condition Complete None planned -122.44756 -122.37958 43.72305 43.61244 ISO 19115 Topic Categories biota elevation environment inlandWaters geoscientificInformation imageryBaseMapsEarthCover USGS Thesaurus structure from motion geospatial analysis aerial photography remote sensing geomorphology geospatial datasets digital elevation models image collections GPS measurement None fluvial geomorphology SfM photogrammetry orthoimagery orthophotograph orthomosaic GeoTIFF Cloud Optimized GeoTIFF dam reservoir drawdown river processes Civil Air Patrol Cessna Waldo USGS Metadata Identifier USGS:68193529d4be0208bc3e03c6 Geographic Names Information System (GNIS) Hills Creek Hills Creek Lake Lane County Larison Cove Larison Creek Middle Fork Willamette River Packard Creek State of Oregon None Willamette Valley none These data are in the public domain in accordance with Creative Commons Zero v1.0 Universal Public Domain Dedication (CC0-1.0) and have no use constraints. Users are advised to read the dataset's metadata thoroughly to understand appropriate use and data limitations. The U.S. Geological Survey shall not be held liable for improper or incorrect use of the data retrieved from the system. Public domain data from the U.S. Government are freely redistributable with proper metadata and source attribution. The U.S. Geological Survey should be acknowledged as the data source in products derived from these data. Schwid, Maxwel F. U.S. Geological Survey Hydrologist Mailing and Physical

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Portland OR 97204 United States 503-758-5589 gs-w-or_sciencebase@usgs.gov Funding for this study was provided by the U.S. Army Corps of Engineers. None Unclassified None Agisoft Metashape Professional Version 2.2.0; Esri ArcGIS Pro Version 3.2.49743; GDAL Version 3.6.2. An R12i Trimble global navigation satellite system (GNSS) receiver with Trimble’s real-time precise point positioning technology, Real Time eXtended (RTX), was used to collect the ground control points. All data were acquired and handled in a consistent manner. Two crewed flights were contracted through the USACE to the Civil Air Patrol, Eugene, Oregon on December 20 and December 28, 2023. A total of 1,427 aerial photographs were captured at an average flight altitude about 1,700 meters above ground level, collectively covering about 43 square kilometers. Photographs were acquired as three-band (RGB) images in JPEG format using a WaldoAir XCAM Ultra 50 camera, consisting of two oblique-mounted Canon EOS 5DS R cameras that were triggered simultaneously, mounted to a Cessna 182 aircraft. A NovAtel OEMStar GPS recorded camera positions in the image file EXIF data in UTC time zone. All aerial photographs were contemporaneously aligned in Agisoft Metashape software. Agisoft software determined which aerial photographs were used in SfM product (point clouds, DSMs, and orthomosaics) generation based on photograph alignment and the validity of identified tie points, which represent common pixels in photographs as determined by the software. To provide check points for model accuracies, a portion of the ground control points were excluded from SfM product generation and used for model validation. Specifically, 15 checkpoints out of the 56 survey points were excluded for the December 20, 2023, datasets and 12 out of 57 were excluded for the December 28, 2023, datasets. The tie points were visually inspected and filtered to exclude obvious anomalous points from the derivative products (dense point clouds, DSMs, and orthomosaics). Aligned, referenced aerial photographs and their corresponding filtered tie points were separated into the two domains (20231220 and 20231228) for dense point cloud and derivative product generation. The orthomosaics contain compression-derived artifacts occurring as erroneous pixel values that border the outer extent of each rasters’ multiple overviews; these artifacts do not occur in, nor affect the underlying full-resolution images. Photographs from the two flights were processed separately after alignment due to differences in ground conditions during collection, including reservoir pool elevations and sun angle/shadowing. The dataset is considered complete and consists of ground control points, coverage footprints, raw aerial photographs, dense point clouds, DSMs, and orthomosaics for the two separate acquisition efforts. All 64 surveyed ground control points are listed in the CSV text file and all 1,427 aerial photographs are included in each associated zipped flight file. All aerial photographs were used to create SfM products (point clouds, DSMs and orthomosaics). Dense point clouds were generated for each domain from tie points identified in the Agisoft Metashape software after a standardized filtering process that excludes low-certainty or anomalous points. Filtered dense point clouds were used to create DSMs and orthomosaics. The dense point clouds and DSMs generated may contain false topography and high error propagated from the software’s identification of false tie points below the translucent, shallow water surface of the pool or in areas influenced by lake waves (Over and others, 2021). The DSMs and orthomosaics were clipped during export from Agisoft software to exclude areas of high uncertainty or distortion, particularly in densely vegetated or forested areas or near edges where minimal photograph overlap inhibited photogrammetric processing. Differences in spatial extent of the datasets resulted from variations in photograph coverage between the two flights. No formal horizontal accuracy tests were performed. Sources of potential error that affect the horizontal accuracy include ground control point accuracy and error incurred during alignment, optimization, and ground control processing procedures within the Agisoft Metashape software. Although the aerial photograph locations (recorded by a NovAtel OEMStar GPS located on the aircraft) are used by the photogrammetric software during initial alignment, these location data are not included in the generation of any derivative products and therefore the positional accuracy and potential errors do not contribute to the overall horizontal accuracy of the products (point clouds, DSMs, and orthomosaics). Horizontal accuracy likely decreases with distance from ground control. Ground control points surveyed with an RTX-enabled GNSS receiver had a reported horizontal precision ranging from 0.01 to 0.30 meters. Though not an assessment of horizontal or vertical accuracy, horizontal positions of ground control points were used to calculate a root mean square (RMS) estimate of positional error at discrete locations by the photogrammetric software and are described here. Additionally, residuals between withheld ground control points (check points) and the model can serve as an indication of accuracy. Ground control and check point error is reported by the software with precision that is higher than provided by model inputs (RTX-GNSS precision) and thus has been rounded. For the December 20 model, 41 ground control points were used to construct SfM datasets, and the model had a horizontal error of 21 centimeters, vertical error of 10 centimeters, and overall error of 24 centimeters. The 15 ground control points withheld as check points were compared to the model and had a horizontal error of 44 centimeters, vertical error of 23 centimeters, and overall error of 49 centimeters. For the December 28 model, 45 ground control points were used to construct SfM datasets, and the model had a horizontal error of 14 centimeters, vertical error of 5 centimeters, and total error of 15 centimeters. The 12 ground control points withheld as check points were compared to the model and had a horizontal error of 30 centimeters, vertical error of 32 centimeters, and overall error of 44 centimeters. Visual comparison of generated orthomosaics to publicly available aerial imagery indicated horizontal displacement was minimal for all datasets, although some obvious distortion (for example, holes, blurry areas, and discontinuity or irregularity of linear features) is noticeable where vegetation is present or there was very little photograph overlap. Increasing noise at surface water locations occurs within each model; these areas were not edited. No formal vertical accuracy tests were performed. However, vertical accuracy likely decreases with distance from ground control. Ground control points surveyed with an RTX-enabled GNSS receiver had a reported vertical precision ranging from 0.03 to 0.93 meters. Though not an assessment of horizontal or vertical accuracy, horizontal positions of ground control points were used to calculate an RMS estimate of positional error at discrete locations by the photogrammetric software and are described here. Additionally, residuals between withheld ground control points and the model can serve as an indication of accuracy. Ground control and check point error is reported by the software with precision that is higher than provided by model inputs (RTX-GNSS precision) and thus has been rounded. For the December 20 model, 41 ground control points were used to construct SfM datasets, and the model had a horizontal error of 21 centimeters, vertical error of 10 centimeters, and overall error of 24 centimeters. The 15 ground control points withheld as check points were compared to the model and had a horizontal error of 44 centimeters, vertical error of 23 centimeters, and overall error of 49 centimeters. For the December 28 model, 45 ground control points were used to construct SfM datasets, and the model had a horizontal error of 14 centimeters, vertical error of 5 centimeters, and total error of 15 centimeters. The 12 ground control points withheld as check points were compared to the model and had a horizontal error of 30 centimeters, vertical error of 32 centimeters, and overall error of 44 centimeters. Digital surface models, particularly in edge areas where photograph overlap was limited, may contain false topography as a result of the photogrammetric reconstruction process and/or model interpolation within sparse dense point cloud areas. American Society for Photogrammetry and Remote Sensing 20080902 publication online American Society for Photogrammetry and Remote Sensing https://www.asprs.org/wp-content/uploads/2010/12/asprs_las_format_v12.pdf Digital and/or Hardcopy 20080902 publication date ASPRS (2008) Laser file format specifications for point clouds. Jin-Si R. Over Andrew C. Ritchie Christine J. Kranenburg Jenna A. Brown Daniel D. Buscombe Tom Noble Christopher R. Sherwood Jonathan A. Warrick Phillipe A. Wernette 2021 publication online U.S. Geological Survey https://doi.org/10.3133/ofr20211039 Digital and/or Hardcopy 20210614 publication date Over and others (2021) Software settings and processing procedures. Maxwel F. Schwid Mackenzie Keith Brandon T. Overstreet 2025 dataset https://www.sciencebase.gov U.S. Geological Survey https://doi.org/10.5066/p1q5k657 Digital and/or Hardcopy 20250311 publication date Schwid and others (2025) Software settings and processing procedures. Agisoft 2025 publication online Agisoft https://www.agisoft.com/pdf/metashape_2_2_en.pdf Digital and/or Hardcopy 20250211 publication date Agisoft (2025) Software settings and processing procedures. Geospatial Data Abstraction Library (GDAL) 2024 3.6.2 application/service online Geospatial Data Abstraction Library (GDAL) https://gdal.org/drivers/raster/cog.html#raster-cog https://gdal.org/api/python_bindings.html Digital and/or Hardcopy 20240218 publication date GDAL (2024) Raster conversion program for Cloud Optimized GeoTIFF creation. Aerial photographs were acquired by the Civil Air Patrol on December 20, 2023, between 14:04 to 14:47 Pacific Standard Time (PST) covering approximately 43 square kilometers of the reservoir area. Photographs were acquired as high-resolution JPG images using a WaldoAir XCAM Ultra 50 camera, consisting of two oblique-mounted Canon EOS 5DS R cameras that are triggered simultaneously, mounted to a Cessna 182 aircraft. A NovAtel OEMStar GPS recorded camera positions in the image file EXIF data in UTC time zone. The pilot flew in longitudinal passes at about 1,700 meters above ground level over Hills Creek Lake. A total of 918 photos were taken from takeoff to landing of flight. 20231220 Aerial photographs were acquired by the Civil Air Patrol on December 28, 2023, between 13:49 to 14:12 Pacific Standard Time (PST) covering approximately 40 square kilometers of the reservoir area. Photographs were acquired as high-resolution JPG images using a WaldoAir XCAM Ultra 50 camera, consisting of two oblique-mounted Canon EOS 5DS R cameras that are triggered simultaneously, mounted to a Cessna 182 aircraft. A NovAtel OEMStar GPS recorded camera positions in the image file EXIF data in UTC time zone. The pilot flew in longitudinal passes at about 1,700 meters above ground level over Hills Creek Lake. A total of 509 photos were taken from takeoff to landing of flight. 20231228 The USGS surveyed 64 control point features throughout Hills Creek Lake on December 17, 2024, using an RTX-enabled GNSS receiver. The control points consisted of static infrastructure features (for example, parking lot pavement arrows, retaining-wall corners, stumps) that were visible in the photographs. 20241217 NAD 1983 UTM Zone 10N 0.9996 -123.0 0.0 500000.0 0.0 coordinate pair 0.000000002220024164500956 0.000000002220024164500956 meter D North American 1983 GRS 1980 6378137.0 298.257222101 North American Vertical Datum of 1988 (NAVD88) 0.001 meters Explicit elevation coordinate included with horizontal coordinates HillsCreekLake_20241217_groundcontrolpoints.csv A control point file (.csv) with # Name (name of the control point), ym (y coordinate in meters), xm (x coordinate in meters), zm (z coordinate in meters), HorzPrec and VertPrec (horizontal and vertical precision, respectively, in meters), PDOP, HDOP, and VDOP (position, horizontal, and vertical accuracy, respectively, in meters), and 1220 and 1228 (indicator of use as control point, check point, or neither by dataset). USGS # Name Name of the control point USGS Label to identify points. ym y coordinate of point USGS 4829015.555 4841262.693 Meters xm x coordinate of point USGS 544578.400 549972.902 Meters zm z coordinate of point USGS 373.964 478.532 Meters HorzPrec Horizontal precision from network-based RTK-GNSS USGS 0.014 0.298 Meters VertPrec Vertical precision from network-based RTK-GNSS USGS 0.030 0.929 Meters PDOP Position Dilution of Precision. PDOP indicates the three-dimensional geometry of the satellites. When satellites are widely spaced relative to each other, the DOP value is lower, and position accuracy is greater. When satellites are close together in the sky, the DOP is higher and GPS positions may contain a greater level of error. PDOP is related to HDOP and VDOP as follows: PDOP² = HDOP² + VDOP². RTK-GPS output 0.979 1.735 Unitless HDOP Horizontal Dilution of Precision. HDOP indicates the accuracy of horizontal measurements. When satellites are widely spaced relative to each other, the DOP value is lower, and position accuracy is greater. When satellites are close together in the sky, the DOP is higher and GPS positions may contain a greater level of error. RTK-GPS ouptut 0.472 0.918 Unitless VDOP Vertical Dilution of Precision. VDOP indicates the accuracy of vertical measurements. When satellites are widely spaced relative to each other, the DOP value is lower, and position accuracy is greater. When satellites are close together in the sky, the DOP is higher and GPS positions may contain a greater level of error. RTK-GPS output 0.833 1.472 Unitless 1220 Indicates control point or check point for December 20 dataset. USGS Control Control point Producer defined Check Check point Producer defined 1228 Indicates control point or check point for December 28 dataset. USGS Control Control point Producer defined Check Check point Producer defined NA No Data Producer defined U.S. Geological Survey - ScienceBase Mailing and Physical

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Denver CO 80225 United States 1-888-275-8747 sciencebase@usgs.gov Although these data have been used by the U.S. Geological Survey, U.S. Department of the Interior, no warranty expressed or implied is made by the U.S. Geological Survey as to the accuracy of the data. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the U.S. Geological Survey in the use of these data, software, or related materials. The use of firm, trade, or brand names in this report is for identification purposes only and does not constitute endorsement by the U.S. Geological Survey. The names mentioned in this document may be trademarks or registered trademarks of their respective trademark owners. ASCII 0.00569 https://doi.org/10.5066/P135FWPP None. This dataset is provided by USGS as a public service. 20260424 Schwid, Maxwel. F U.S. Geological Survey Hydrologist Mailing and Physical

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Portland Oregon 97204 United States 503-758-5589 gs-w-or_sciencebase@usgs.gov FGDC Content Standard for Digital Geospatial Metadata FGDC-STD-001-1998 local time