3.4.5 Landform Inventories

This insight into past processes also contributes to anticipating future trajectories of change. Landform inventories can contribute to better understanding ground ice distribution, testing and validating remote sensing tools and predictive models, as well as facilitating the assessment of landscape change.

Landform inventories exist for different areas of the Canadian Arctic (Lewkowicz and Way, 2019; Segal et al., 2016 a,b,c; Sladen et al., 2020; Sladen et al., 2021; Rudy et al., 2020), however, these have not been systematically collected and are often tied to specific research questions. As a result, there is no standardization between inventories that rely on different data models (legends) and mapping protocols. Inventories are also collected through an array of methods i.e. on the ground mapping, air photo interpretation, semi and automatic detection using remote sensing, and may be represented as points (spatial coordinates), lines, or polygons. There is a need to define landforms objectively and reproducibly. However, nomenclature in regards to different landforms may vary across disciplines (experts), certain landforms are easier to identify than others, and certain landscapes allow for feature identification more readily (Evans, 2012).

3.4.5.1 Data sources

Geomorphologic feature mapping methodology developed for the Dempster Highway and Inuvik to Tuktoyaktuk Highway corridors: The terrain mapping utilized recent high-resolution imagery: Worldview (2012-15), orthophotos (2004, 2011), SPOT (2016), and LiDAR (2011) data to identify geomorphological features and landscape types within the 10-km-wide and 875-km-long corridor. Methodologies include rendering Worldview imagery in three dimensions with Summit 3D software, and digitizing features directly into ArcGIS using DAT/EM's Capture Interface LiDAR data, where available, is used in combination with associated orthophotos and features are digitized directly into ArcGIS (https://doi.org/10.4095/328181).

NWT Thermokarst Collective: The objective of the NWT Thermokarst Mapping Collective is to establish a collaborative approach to develop and implement a mapping methodology to generate NWT-wide thermokarst and permafrost feature inventory maps. Three landform themes are the focus: periglacial, hydrological and mass wasting features. Outputs will provide information relevant to all NWT regions, inform and validate modelling efforts, and support community climate change adaptation. (Contact: Steve Kokelj, steve_kokelj@gov.nt.ca)

Broad-scale mapping of terrain impacted by retrogressive thaw slumping in Northwestern Canada: Mappable cells were created using a 15 km by 15 km grid covering a land area of more than 1.2 million km2. Trained technicians assessed several disturbance and landscape attributes for each grid cell by viewing the georeferenced SPOT 5 and SPOT 4 orthomosaics from 2005-2010 (NWT Centre for Geomatics, 2013; Latitude Geographics Group Ltd., 2014). (Contact: NTGS@gov.nt.ca )

Inventory of active retrogressive thaw slumps on eastern Banks Island, Northwest Territories: All active retrogressive thaw slumps in the eastern Banks Island study region were digitized on-screen using georeferenced imagery in Google Earth, ESRI ArcMap (versions 10.0 and 10.1), and the NWT Spatial Data Warehouse Geospatial Portal (NWT Centre for Geomatics 2013; Latitude Geographics Group Ltd.). Slumps were identified based on the presence of exposed sediments, poorly developed vegetation, and a well-defined headwall. (Contact: NTGS@gov.nt.ca)

Inventory of active retrogressive thaw slumps in the Peel Plateau, Northwest Territories: All active retrogressive thaw slumps in the Peel Plateau study region were digitized on-screen using georeferenced imagery in Google Earth, ESRI ArcMap (versions 10.0 and 10.1), and the NWT Spatial Data Warehouse Geospatial Portal (NWT Centre for Geomatics 2013; Latitude Geographics Group Ltd.). Slumps were identified based on the presence of exposed sediments, poorly developed vegetation, and a well-defined headwall (Contact: NTGS@gov.nt.ca)

Inventory of retrogressive thaw slumps in the Willow River watershed, mapped using 1986, 2002, and 2018 Landsat imagery: Retrogressive thaw slumps were digitized using Landsat images (30 m resolution) from 1986, 2002, and 2018. Thaw slumps were identified as slope disturbances characterized by a well-defined headwall, exposed sediments or poorly-developed vegetation. The extent of each feature was digitized in ArcMap. Mapper interpretations were verified by field reconnaissance during the summer of 2019. (Contact: NTGS@gov.nt.ca)

Inventory of retrogressive thaw slumps on the Peel Plateau and on southeastern Banks Island, Northwest Territories using 2017 Sentinel imagery: Retrogressive thaw slumps were digitized using 2018 Sentinel (10 m resolution) imagery. Thaw slumps were identified as slope disturbances characterized by a well-defined headwall, exposed sediments and poorly-developed vegetation. The extent of each feature was digitized in ArcMap. (Contact: NTGS@gov.nt.ca)

An inventory of rock glaciers in the central British Columbia Coast Mountains, Canada, from high resolution Google Earth imagery: The rock glacier inventory was completed using high-resolution Google Earth satellite imagery (2004/2005). Google Earth uses SPOT or products from DigitalGlobe (e.g., IKONOS or Quickbird). Only snow-free and cloud-free imagery was used in the survey, and identification was supplemented with field validation where access permitted. (Data in Charbonneau & Smith, 2018: 10.1080/15230430.2018.1489026)

Extremes of summer climate trigger thousands of thermokarst landslides in a High Arctic environment: Google Earth Engine Timelapse data, covering the period 1984–2016 was accessed through a web-based interface to generate novel information regarding RTS activity. Documented here are the year of feature initiation, the longevity of RTS, the location of initiation in the landscape (Fig. 1b), and the relation of RTS activity to other landscape change over an area of 70,000 km2 . (Data in Lewkowicz & Way, 2019: https://doi.org/10.1038/s41467-019-09314-7)

3.4.5.2 Strengths and Limitations of Datasets

Manual delineation/identification: Expert knowledge (i.e., ability to identify an array of permafrost landforms) is used to identify, classify, and delineate the extent of permafrost landforms or add a point on the feature of interest. This process is time-consuming and its accuracy is limited by the expertise of the mapper, image resolution, and the ability to include quality control (independent mappers, e.g., Schmid et al., 2015) in the data generation process. Datasets are valuable when used as inputs to train and validate models and remote sensing tools.

Gridded mapping: Mapping is done using grids, with spatial resolution often differing between studies. Landforms are identified by presence/absence and in some cases, an approximate extent or count is attributed to a grid cell. Datasets are empirically based and highlight landscape forms and their patterns at a regional and broad scale.

References – Landform Inventories

Charbonneau, A.A., and D.J. Smith, 2018: An Inventory of Rock Glaciers in the Central British Columbia Coast Mountains, Canada, from High Resolution Google Earth Imagery, Arctic, Antarctic, and Alpine Research, 50(1), doi.org/10.1080/15230430.2018.1489026.

Evans, I.S., 2010: Geomorphometry and Landform Mapping: What is a Landform? Geomorphology 137(1), 94-106, doi.org/10.1016/j.geomorph.2010.09.029.

Lewkowicz, A.G., and R.G. Way, 2019: Extremes of Summer Climate Trigger Thousands of Thermokarst Landslides in a High Arctic Environment. Nature Communications, 10(1), 1329-11, doi.org/10.1038/s41467-019-09314-7.

Rudy, A.C.A., and S.V. Kokelj, 2020: Inventory of Retrogressive Thaw Slumps in the Willow River Watershed, Mapped Using 1986, 2002, and 2018 Landsat Imagery. Northwest Territories Geological Survey, 4, doi.org/10.46887/2020-011.

Rudy, A.C.A., S.V. Kokelj, and J. Kokozska, 2020: Inventory of Retrogressive Thaw Slumps on the Peel Plateau and on Southeastern Banks Island, Northwest Territories Using 2017 Sentinel Imagery. Northwest Territories Geological Survey, 5, doi.org/10.46887/2020-012.

Segal, R.A., S.V. Kokelj, T.C. Lantz, K. Durkee, S. Gervais, E. Mahon, M. Snijders, J. Buysse, and S. Schwarz, 2016: Broad-Scale Mapping of Terrain Impacted by Retrogressive Thaw Slumping in Northwestern Canada. Northwest Territories Geological Survey, 17, doi.org/10.46887/2016-008.

Segal, R.A., T.C. Lantz, and S.V. Kokelj, 2016a: Acceleration of Thaw Slump Activity in Glaciated Landscapes of the Western Canadian Arctic. Environmental Research Letters, 11(3), 34025, doi.org/10.1088/1748-9326/11/3/034025.

Segal, R.A., T.C. Lantz, and S.V. Kokelj, 2016b: Inventory of Active Retrogressive Thaw Slumps on Eastern Banks Island, Northwest Territories. Northwest Territories Geological Survey, 8, doi.org/10.46887/2015-021.

Segal, R.A., T.C. Lantz, and S.V. Kokelj, 2016c: Inventory of Active Retrogressive Thaw Slumps in the Peel Plateau, Northwest Territories. Northwest Territories Geological Survey, 8, doi.org/10.46887/2015-021.

Schmid, M.O., P. Baral, S. Gruber, S. Shahi, T. Shrestha, D. Stumm, and P. Wester, 2015: Assessment of Permafrost Distribution Maps in the Hindu Kush Himalayan Region Using Rock Glaciers Mapped in Google Earth. The Cryosphere, 9(6), 2089-2099, doi.org/10.5194/tc-9-2089-2015.

Sladen, W.E., S.A. Wolfe, P.D. Morse, 2020: Evaluation of threshold freezing conditions for winter road construction over discontinuous permafrost peatlands, subarctic Canada, Cold Regions Science and Technology, Volume 170, 102930, ISSN 0165-232X, https://doi.org/10.1016/j.coldregions.2019.102930.

Sladen, W.E., R.J.H. Parker, S.V. Kokelj, P.D. Morse, 2021: Geomorphologic feature mapping methodology developed for the Dempster Highway and Inuvik to Tuktoyaktuk Highway corridors, Natural Resources Canada,
Geological Survey of Canada, Open File 8751, 2021, 56 pages, https://doi.org/10.4095/328181