Understanding how alluvial fans form in periglacial environments

Regions: Gwich'in Settlement Area

Tags: physical sciences, water quantity, sediment transport, ground ice, LiDAR survey

Principal Investigator: Palucis, Marisa C. (1)
Licence Number: 16522
Organization: Dartmouth College
Licenced Year(s): 2019
Issued: Mar 28, 2019
Project Team: Justin V. Strauss (Co-Investigator, Dartmouth College), Frances Rivera-Hernandez (Postdoctoral Researcher, Dartmouth College)

Objective(s): To conduct a detailed characterization of one alluvial fan located near Aklavik, to assess how the alluvial fan is developing, to determine the role of melted ground ice and snow in transporting sediment from the Aklavik Range to the alluvial fan, and to sort out whether these alluvial fans have characteristics that can be identified on Mars.

Project Description: The research team are proposing to conduct a detailed characterization of one alluvial fan located near Aklavik. The team want to assess how the alluvial fan is developing, determine the role of melted ground ice and snow in transporting sediment from the Aklavik Range to the alluvial fan, and sort out whether these alluvial fans have characteristics that can be identified on Mars.

Once on the alluvial fan, the team will walk up and down the alluvial fan to make general observations about sediment grain sizes, where the team will observe channels. If there are sediment deposits in those channels, the team will determine how large the channels are, and where vegetation can be seen.

As the alluvial fan is canvassed, the research team will look for three to five sites at the top of the fan, mid-fan, and downstream of the fan to make detailed measurements. The team will dig very shallow pits (<1 meter deep) at these locations to document the presence of ice in the ground, as well as measure the size of ~100 sediment clasts per site (using a ruler). In the case that digging pits is too invasive, the team are exploring non-invasive techniques (such as using ground penetrating radar, where pulses of low-energy light image the subsurface).

The research team will take photo-documentation on the alluvial fan, both with handheld cameras and cameras mounted on a pole or a small unmanned aerial vehicle (UAV) or drone. The team will use a terrestrial LiDAR scanner to make detailed topographic maps of portions of the fan. These scanners use light to re-create 3D models of the ground surface, which will later be used for modeling hypothetical snowmelt or runoff events on the fan. Much of the region has been imaged with LiDAR from aircraft, but ground-based LiDAR can provide the opportunity to see smaller scale features (and mimics what a rover can see on Mars).

A key goal of this research is to determine the role of water/ice in building the fan, and so the research team will estimate how much water is stored in the sediment on the fan as unfrozen water and ice. To do this, the plan is to sample the sediment, weigh it in the field, and then use a battery- or solar-powered field oven to remove the water (i.e., bake it) before weighing it again. This allows the team to get at unfrozen water content without taking any soil samples back to Dartmouth College. The team might also employ soil moisture probes or temperature probes while there, but these are non-invasive and can easily be removed when leaving the area.

While it is unlikely the research team will be there during snowmelt, in the case where there is flowing water on the fans, the team will bring two stream gages (to measure water volume per time), a velocimeter (to measure stream flow velocity), and sediment traps (bags where we collect, weigh sediment and then release it).

The research team is interested in connecting with local scientists (and citizen scientists) to help document how the field site changes over time (by making observations, measurements, or helping to maintain a camera/stream gage to monitor the fan over the course of a year). The team is arranging a presentation for the local communities during or after the fieldwork to talk about what is being done and the implications it has for understanding Mars. The team also plan to design materials for classroom activities about alluvial fans and Mars that can be distributed to local schools (if they are interested).

The research team will hold public talks / Q and A’s, followed up with outreach to local schools through Skype, and also summarize results in a plain language report.

The fieldwork for this study will be conducted from August 1, 2019 to August 31, 2019.