Topographic Differencing Analyses on Glacier Creek, Washington, from 2005 to 2022

Glacier Creek drains a 82 square kilometer watershed that includes multiple glaciers on the north flank of Mount Baker in Whatcom County, Washington. The Washington State Department of Transportation (WSDOT) maintains a bridge along Highway 542 over Glacier Creek near its confluence with the North Fork Nooksack River, where Glacier Creek has formed an alluvial fan. To assist in WSDOT maintenance and planning efforts in this geomorphically-active setting, the U.S. Geological Survey (USGS) conducted topographic differencing analyses along the lower 2.5 kilometers of Glacier Creek using aerial lidar datasets collected between 2005 and 2022. 

Lidar data was available from 2005, 2007, 2013, 2016, 2018, and 2022. Data from 2007 and 2018 was contracted by WSDOT and provided to the USGS directly for this analysis; digital elevation models (DEMs) from those years are provided in this data release. All other lidar data is available from the Washington State Department of Natural Resources lidar portal (https://lidarportal.dnr.wa.gov/). In all cases, analyses started with bare-earth DEMs. After re-projecting all data into a consistent coordinate system (NAD83 UTM 10N; EPSG 26910) with identical grid alignment (1-m resolution), raw DEMs of difference (DoD) were created and visually inspected for horizontal and vertical biases. Horizontal biases were corrected using methods described in Nuth and Kaab (2011); spatially variable vertical biases were corrected using methods described in Anderson and Jaeger (2021). After applying these correlations, final DoDs were then regenerated and areas of geomorphic change along Glacier Creek manually delineated. Those areas were then sub-divided into 100 m swaths as measured along the length of the valley centerline, and the net change estimated within each swath. 

The net changes estimated directly from the DoDs include some amount of change due to different discharges, and so different water storage volumes, between the two differenced surveys. Approximate corrections of those water volume differences were made based on estimated discharge at the time of each survey and discharge-area relations observed from streamflow measurements at USGS streamgage 12205245; details are provided in metadata stored in the 'discharge_corrections' zip file. 

Topographic differencing analyses were performed for the five distinct intervals between sequential lidar datasets. Differencing from 2007 to 2018 and from 2007 to 2022 was also completed to allow comparisons between the sum of sequential differencing results against direct differencing over the same time interval. The 2007 lidar was used as the start point for those assessments because the 2005 lidar only covered the lower-most extents of the study area. 

This data release contains:

The results of each DoD analysis, stored in individual zip files (glacier_dod_xx_yy, where xx and yy are the last two digits of the start and end year, respectively). Each zip file contains the final DoD as a tif file, a geopackage containing supporting vector datasets used in the analysis, a csv summarizing raw change results for that interval, and interval-specific metadata.
The R scripts and data used to estimate the discharge corrections are contained in the 'discharge_corrections' zip folder.
The final corrected estimates of change provided in the 'glacier_creek_compiled_qcor_volumes.csv' file, which aggregates results from all differencing intervals into a single CSV.
Vectors defining the linear referencing scheme used in this analysis are provided in the 'linear_referencing' geopackage.
Lidar DEMs from 2007 and 2018, which are not currently available via the WA DNR lidar portal, are stored in individual zip files as well.


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. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.