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1. High-resolution Thermal Infrared and True-color Imagery Mosaics, Longitudinal Stream Temperature Profiles, and Thermal Points of Interest from Airborne Surveys of the Quillayute River Basin, August 2022

This dataset presents high-resolution thermal infrared (TIR) and true-color RGB (red, green, blue) imagery mosaics, longitudinal stream temperature profiles, thermal points of interest, and river centerlines from airborne surveys of the Quillayute, Dickey, Sol Duc, Calawah, South Fork Calawah, Sitkum, and Bogachiel Rivers (203 river kilometers; 126 river miles total). All datasets were produced and initially processed by NV5 Geospatial (NV5). The U.S. Geological Survey (USGS) performed additional processing of the longitudinal stream temperature profiles and thermal points of interest, as described below. TIR and RGB images were acquired by NV5 on August 29-31, 2022, using a FLIR SC6000 LWIR sensor and a Sony Alpha 7R III camera mounted in a fiberglass enclosure to a Bell 206 Long Range helicopter. Images were acquired during afternoon hours to maximize the thermal contrast between the river water and the banks. At a flying altitude of 350-450 m (1,148-1,476 ft) above ground level, the FLIR SC6000 and Sony Alpha 7R III achieved ground sampling distances of less than 50 cm (20 in.) and 10 cm (4 in.), respectively. TIR imagery mosaics (.tif) for individual surveys and a single RGB imagery mosaic (.sid) for the entire study area were developed by NV5, and river centerlines (.shp) were manually digitized by NV5 using the imagery mosaics as guides. Points were then generated by NV5 every 50 m (164 ft) along the centerlines to quantify the longitudinal stream temperature profiles (LTPs; .shp). Summary statistics, in degrees Celsius, were computed by NV5 for each point in the profile by sampling pixel values of water temperature along the centerline in the corresponding TIR mosaic within a 2-m (6.56 ft) radius buffer around each point. The 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. LTPs assist in identifying the water temperature gradient in the river and changes in the gradient due to the potential influence of thermal exchange processes, such as water inflows (tributaries, lateral groundwater flow, hyporheic flow, etc.) or increased heating from a low percentage of effective riparian shading. These profiles are also an important component of models that estimate water temperature based on climate and land use scenarios. Thermal points of interest (POIs; .shp) were manually identified by NV5 and USGS across the channel, riparian zone, and floodplain. Such features include cold-water anomalies that may represent thermal refuges and serve as salmonid habitat. POIs were classified by USGS as one of four types: (1) tributary; (2) lateral groundwater / side channel / small tributary; (3) hyporheic / 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-m (1.97 ft) 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, woody debris, and tree canopy. Therefore, the water temperatures reported for POIs where the 0.6-m radius sampling area contains mixed pixels are often skewed. The POI temperatures should thus serve as indicators where thermal heterogeneity requires additional investigation and potentially more precise quantification. All data is projected in UTM 10N and the horizontal datum is NAD83(2011).

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