Alaska Highway Study: Groundwater Flow, Permafrost Degradation, and Transportation Infrastructure Stability
The Alaska University Transportation Center (AUTC) of the University of Alaska, Fairbanks, supported a research project to study the effects of groundwater flow on permafrost degradation and resulting road instability. The stability of permafrost below roadways and embankments is increasingly affected by warming surface temperatures caused by climate change, but may also be affected by heat transfer from groundwater flow. Studies have shown that groundwater flow can accelerate permafrost degradation by several orders of magnitude compared to thaw caused by heat transfer from the atmosphere alone.
With US DOT support, AUTC researched the effect of advective heat transfer (i.e., the effect of horizontal flow of heat) from groundwater on permafrost. Previous research has primarily considered only the effects of conductive, or vertical, heat flow from soil and groundwater. The research and modeling of advective heat transfer effects is described in the report Impact of Groundwater Flow on Permafrost Degradation & Transportation Infrastructure Stability. The overall goal of the research was to develop a better understanding of the complex interaction between groundwater flow, permafrost degradation, and embankment stability.
In this collaborative study, field work was conducted at an Alaska Highway test section location near Beaver Creek, YT, Canada. The study included laboratory measurements of hydraulic conductivity (the ease with which water can move through spaces in the soil and rock) and unfrozen water content, and modeling of the interaction among these complex phenomena.
The model produced included both conductive and advective heat flow rates that simulated groundwater flow measured in the field. Results from the fully-coupled conductive and advective heat transfer model indicate that the thermal effects from groundwater flow are significant, producing even warmer temperatures than those from the conduction-only model. Groundwater flowing through the porous gravel embankment in the summer causes thaw into underlying, ice-rich foundation soils. This results in thermal degradation, which is manifested as longitudinal and transverse cracks and an irregular driving surface.
Based on these research results, the report provides the following recommendations:
- Employ terrain analysis as an early step in the route selection of infrastructure. This will allow the planners to identify and avoid thaw-sensitive permafrost. Where re-routing of existing is proposed but is not possible, “eco-geomorphologic terrain unit maps” can aid in the identification of areas where near-surface groundwater flow will require additional mitigation techniques (such as intercepting ditches, culverts, drainage ditches, retention basins, impervious membranes, and porous embankments).
- Incorporate groundwater flow in thermal modeling for areas where it is recognized as an issue.
This Adaptation Clearinghouse entry was prepared with support from the Federal Highway Administration. This entry was last updated on February 2, 2015.
Publication Date: 2013
- University of Alaska Fairbanks
- Academic research paper
- Permafrost melt