High-resolution Thermal Infrared and True-color Imagery Mosaics, Longitudinal Stream Temperature Profiles, and Thermal Points of Interest from Airborne Surveys of the Quillayute and Bogachiel Rivers, Washington, August 15, 2023

This U.S. Geological Survey (USGS) data release provides high-resolution thermal infrared (TIR) and true-color red, green, blue (RGB) imagery mosaics, longitudinal stream-temperature profiles (LTPs), thermal points of interest (POIs), and river centerlines from airborne surveys of 47 river kilometers (29 river miles) of the Quillayute and Bogachiel Rivers, Washington. The TIR and RGB imagery mosaics and river centerlines were processed and digitized by NV5 Geospatial (NV5), whereas the LTPs and thermal POIs were produced by the USGS.

TIR and RGB images were acquired by NV5 on August 15, 2023, using a FLIR SC6000 long-wave infrared sensor (LWIR) and a Sony Alpha 7R III camera mounted in a fiberglass enclosure to a Bell 206 Long Range helicopter. Imagery was acquired during afternoon hours. At a flying altitude of 350-450 meters (1,148-1,476 feet) above ground level, the FLIR SC6000 and Sony Alpha 7R III achieved ground sampling distances of less than 50 centimeters (20 inches) and 10 centimeters (4 inches), respectively.

NV5 produced TIR imagery mosaics for individual surveys in GeoTIFF format (.tif), a true-color RGB mosaic for the study area in MrSID format (.sid), and river centerlines in shapefile format (.shp). Points were then generated by USGS every 50 meters (164 feet) along the centerlines to quantify the LTPs (.shp). LTPs assist in identifying longitudinal spatial patterns in measured water temperature along the river corridor.

Summary statistics, in degrees Celsius (C), were computed by USGS for each point in the LTP profile by sampling pixel values of water temperature along the centerline in the corresponding TIR mosaic within a 2-meter (6.56 feet) radius buffer around each point. This statistical information was used by USGS to identify sampling points that fall on non-water features such as boulders or bridges and then filter these points from the final dataset.

Thermal points of interest (POIs; .shp) were manually identified by USGS across the channel, riparian zone, and floodplain. Such features include locations exhibiting temperature differences relative to surrounding areas. POIs were classified as one of four types: (1) tributary; (2) lateral groundwater, side channel, or small tributary; (3) hyporheic or diffuse groundwater; or (4) point-source effluent. Summary statistics were computed by USGS for each POI using a sample of water temperature values from pixels in the corresponding TIR mosaic within a 0.6-meter (1.97 feet) radius buffer around each point. The automated sampling of the POIs included pixels that are not purely water but instead mixed with other in-stream and riparian features, such as boulders, wood debris, and tree canopy. Therefore, the water temperatures reported for POIs where the 0.6-meter radius sampling area contains mixed pixels may be biased.

All spatial data are projected in Universal Transverse Mercator Zone 10 North and referenced to the North American Datum of 1983 (2011).

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.

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