• 2-D bed sediment transport modeling of a reach on the Sagavanirktok River, Alaska

      Ladines, Isaac A.; Toniolo, Horacio; Barnes, David; Schnabel, Bill (2019-05)
      Conducting a 2-D sediment transport modeling study on the Sagavanirktok River has offered great insight to bed sediment movement. During the summer of 2017, sediment excavation of two parallel trenches began in the Sagavanirktok River, in an effort to raise the road elevation of the Dalton Highway to remediate against future floods. To predict the time in which the trenches refill with upstream sediment a 2-D numerical model was used. Three scenarios: (1) a normal cumulative volumetric flow, (2) a max discharge event, and (3) a max cumulative volumetric flow, were coupled with three sediment transport equations: Parker, Wilcock-Crowe and Meyer Peter and Müller for a total of 9 simulations. Results indicated that scenario (1) predicted the longest time to fill, ranging from 1-6 years followed by scenario (2), an even shorter time, and scenario (3) showing sustained high flows have the capability to nearly refill the trenches in one year. Because the nature of this research is predictive, limitations exist as a function of assumptions made and the numerical model. Therefore, caution should be taken in analyzing the results. However, it is important to note that this is the first time estimates have been calculated for an extraction site to be refilled on the Sagavanirktok River. Such a model could be transformed into a tool to project filling of future material sites. Ultimately, this could expedite the permitting process, eliminating the need to move to a new site by returning to a site that has been refilled from upstream sediment.
    • Analysis of the 2015 Sagavanirktok River flood: associated permafrost degradation using InSAR and change detection techniques

      McClernan, Mark Timothy; Meyer, Franz; Zwieback, Simon; Minter, Clifton (2020-08)
      In 2015, the Sagavanirktok River experienced a sequence of high, early-winter temperatures that lead to a buildup of aufeis. The buildup displaced the spring runoff causing widespread flooding. Flood waters inundated the surrounding tundra introducing heat into ground ice-baring soils. The Sagavanirktok River flood was caused by an extensive ice dam that developed the previous winter. The first flooding pulse started in April 2015, when an aufeis obstruction diverted river water to the surface. The obstruction caused flooding along 24 km of the Dalton Highway and its surroundings, necessitating a prolonged highway closure and emergency repairs. A second flooding pulse was caused by annual spring runoff in May 2015, which was driven by rapid snowmelt due to warm seasonal temperatures. The washed-out highway had to be closed again. Field investigations showed that thermal erosion of ice wedges in the tundra adjacent to the Dalton Highway caused local subsidence by several meters. However, the full environmental impact of the flood has not yet been quantified regionally or temporally. Thermokarst formation, can cause rapid ecological and environmental changes. Thawing of permafrost can lead to terrain instability as the melting of ground ice induces subsidence and loss of soil strength. The processes involved in permafrost degradation are complex, as is predicting terrain stability and the associated impacts to permafrost surrounding infrastructure. The immediate impact of the 2015 Sagavanirktok River flood is evident, which caused rapid terrain collapse in the vicinity of the Dalton Highway and the Trans-Alaska Pipeline near Deadhorse, North Slope Borough, Alaska. Thermal degradation of permafrost can be expressed as the change in the surfacemicrotopography over several years following a flood. Change detection, digital elevation model differencing, and InSAR were employed within the area of interest to understand the extent of the flood and deformation within inundated areas. To determine the likely impacted areas within the area of interest and expanse of the flood, an unsupervised change detection technique of high resolution TerraSAR-X and Sentinel-1 amplitude images was utilized. The topographic deformation analysis to determine the motion on the ground surface used a short baseline subset InSAR analysis of Sentinel-1 data during the summer season following the Sagavanirktok River flooding events. Additional deformation analysis was conducted with ALOS-2 data for annual comparison of the 2015 to 2019 summers. TanDEM-X digital elevation model differencing compared surface models generated from before and after the Sagavanirktok River flood. Elevation model differencing would identify the absolute change between the acquisition time of the surface models. A joint data analysis between deformation and differenced elevation models analyzed the contrast within inundated and flood-unaffected areas; thus, the changes and impact to the permafrost following the 2015 Sagavanirktok River flood. The Sagavanirktok River flood highlights the vulnerability of ice-rich permafrost to flooding. A change in the vicinity of the Sagavanirktok River Delta to the hydrological cycle led to widespread increases in terrain instability. Analysis of summer season deformation data suggested inundated permafrost areas showed lower seasonal deformation in years following the flood. Analysis of annual deformation shows permafrost subsidence intensified in inundated areas in the years following the flood. Digital elevation model differencing produced a statistically ambiguous result. This research illustrates the value of combining TerraSAR-X, TanDEM-X, Sentinel 1, and ALOS-2 microwave remote sensing missions for evaluating widespread surface changes in arctic environments. However, annual deformation data proved the most usable tool in observing the changing permafrost ecosystems around the Sagavanirktok River.
    • Bibliography of Published Reports and Articles Related to Hydrological Research on the Sagavanirktok River

      Youcha, Emily; Toniolo, Horacio (2017-08)
      Researchers from the Water and Environmental Research Center (WERC), University of Alaska Fairbanks (UAF), are conducting a study of sediment transport conditions along the Sagavanirktok River. This document, as part of the study, provides a compilation of published literature related to the Sagavanirktok River (or adjacent watersheds with similar characteristics) including previous or ongoing hydrological and sedimentological research in the Sagavanirktok River basin. The literature referenced includes research on climate change, hydrology, sedimentology, permafrost and soils, meteorology, field data, satellite or aerial imagery, geophysics, modeling, water quality, and geochemistry in the Sagavanirktok River basin.