• Hydro-sedimentological Monitoring and Analysis for Material Sites on the Sagavanirktok River

      Toniolo, H.; Tschetter, T.; Tape, K.D.; Cristobal, J.; Youcha, E.K.; Schnabel, William; Vas, D.; Keech, J. (2016-04)
      Researchers from the Water and Environmental Research Center at the Institute of Northern Engineering, University of Alaska Fairbanks, are conducting a research project related to sediment transport conditions along the Sagavanirktok River. This report presents tasks conducted from summer 2015 to early winter 2016. Four hydrometeorological stations were installed in early July 2015 on the west bank of the river. The stations are spread out over a reach of approximately 90 miles along the Dalton Highway (from MP 405, the northernmost location, to MP 318, the southernmost location). These stations are equipped with pressure transducers and with air temperature, relative humidity, wind speed, wind direction, barometric pressure, and turbidity sensors. Cameras were installed at each station, and automatic water samplers were deployed during the open-water season. The stations have a telemetry system that allows for transmitting data in near-real time. Discharge measurements were performed three times: twice in July (early and late in the month), and once in mid-September. Measured discharges were in the order of 100 m3/s, indicating that measurements were performed during low flows. Suspended sediment concentrations ranged from 2 mg/l (nearly clear water) to 625 mg/l. The average grain size for suspended sediment from selected samples was 47.8 μm, which corresponds to silt. Vegetation was characterized at 27 plots near the stations. Measurements of basic water quality parameters, performed during winter, indicated no potential issues at the sampled locations. Dry and wet pits were excavated in the vicinity of each station. These trenches will be used to estimate average bedload sediment transport during spring breakup 2016. A change detection analysis of the period 1985–2007 along the area of interest revealed that during the present study period, the river was relatively stable.
    • Hydrological, Sedimentological, and Meteorological Observations and Analysis on the Sagavanirktok River

      Toniolo, H.; Youcha, E.K.; Tape, K.D.; Paturi, R.; Homan, J.; Bondurant, A.; Ladines, I.; Laurio, J.; Vas, D.; Keech, J.; et al. (2017-12)
      The Dalton Highway near Deadhorse was closed twice during late March and early April 2015 because of extensive overflow from the Sagavanirktok River that flowed over the highway. That spring, researchers from the Water and Environmental Research Center at the University of Alaska Fairbanks (UAF) monitored the river conditions during breakup, which was characterized by unprecedented flooding that overtopped and consequently destroyed several sections of the Dalton Highway near Deadhorse. The UAF research team has monitored breakup conditions at the Sagavanirktok River since that time. Given the magnitude of the 2015 flooding, the Alyeska Pipeline Service Company started a long-term monitoring program within the river basin. In addition, the Alaska Department of Transportation and Public Facilities (ADOT&PF) funded a multiyear project related to sediment transport conditions along the Sagavanirktok River. The general objectives of these projects include determining ice elevations, identifying possible water sources, establishing surface hydro-meteorological conditions prior to breakup, measuring hydro-sedimentological conditions during breakup and summer, and reviewing historical imagery of the aufeis extent. In the present report, we focus on new data and analyze it in the context of previous data. We calculated and compared ice thickness near Franklin Bluffs for 2015, 2016, and 2017, and found that, in general, ice thickness during both 2015 and 2016 was greater than in 2017 across most of the study area. Results from a stable isotope analysis indicate that winter overflow, which forms the aufeis in the river area near Franklin Bluffs, has similar isotopic characteristics to water flowing from mountain springs. End-of-winter snow surveys (in 2016/2017) within the watershed indicate that the average snow water equivalent was similar to what we observed in winter 2015/2016. Air temperatures in May 2017 were low on the Alaska North Slope, which caused a long and gradual breakup, with peak flows occurring in early June, compared with mid-May in both 2015 and 2016. Maximum discharge measured at the East Bank station, near Franklin Bluffs was 750 m3/s (26,485 ft3/s) on May 30, 2017, while the maximum measured flow was 1560 m3/s (55,090 ft3/s) at the same station on May 20, 2015. Available cumulative rainfall data indicate that 2016 was wetter than 2017. ii In September 2015, seven dry and wet pits were dug near the hydro-sedimentological monitoring stations along the Sagavanirktok River study reach. The average grain-size of the sediment of exposed gravel bars at sites located upstream of the Ivishak-Sagavanirktok confluence show relatively constant values. Grain size becomes finer downstream of the confluence. We conducted monthly topo-bathymetric surveys during the summer months of 2016 and 2017 in each pit. Sediment deposition and erosion was observed in each of the pits. Calculated sedimentation volumes in each pit show the influence of the Ivishak River in the bed sedimenttransport capacity of the Sagavanirktok River. In addition, comparison between dry and wet pit sedimentation volumes in some of the stations proves the complexity of a braided river, which is characterized by frequent channel shifting A two-dimensional hydraulic model is being implemented for a material site. The model will be used to estimate the required sediment refill time based on different river conditions.
    • Sagavanirktok River Spring Breakup Observations 2016

      Toniolo, H.; Tape, K.D.; Tschetter, T.; Homan, J.W.; Youcha, E.K.; Vas, D.; Gieck, R.E.; Keech, J.; Upton, G. (2016-12)
      In 2015, spring breakup on the Sagavanirktok River near Deadhorse was characterized by high flows that destroyed extensive sections of the Dalton Highway, closing the road for nearly 3 weeks. This unprecedented flood also damaged infrastructure that supports the trans-Alaska pipeline, though the pipeline itself was not damaged. The Alaska Department of Transportation and Public Facilities (ADOT&PF) and the Alyeska Pipeline Service Company made emergency repairs to their respective infrastructure. In December 2015, aufeis accumulation was observed by ADOT&PF personnel. In January 2016, a research team with the University of Alaska Fairbanks began monitoring and researching the aufeis and local hydroclimatology. Project objectives included determining ice elevations, identifying possible water sources, establishing surface meteorological conditions prior to breakup, measuring hydrosedimentological conditions (discharge, water level, and suspended sediment concentration) during breakup, and reviewing historical imagery of the aufeis feature. Ice surface elevations were surveyed with Global Positioning System (GPS) techniques in late February and again in mid-April, and measureable volume changes were calculated. However, river ice thickness obtained from boreholes near Milepost 394 (MP394) in late February and mid-April revealed no significant changes. It appears that flood mitigation efforts by ADOT&PF in the area contributed to limited vertical growth in ice at the boreholes. End-of-winter snow surveys throughout the watershed indicate normal or below normal snow water equivalents (SWE 10 cm). An imagery analysis of the lower Sagavanirktok aufeis from late winter for the past 17 years shows the presence of ice historically at the MP393–MP396 area. Water levels and discharge were relatively low in 2016 compared with 2015. The mild breakup in 2016 seems to have been due to temperatures dropping below freezing after the flow began. Spring 2015 was characterized by warm temperatures throughout the basin during breakup, which produced the high flows that destroyed sections of the Dalton Highway. A comparison of water levels at the East Bank Station during 2015 and 2016 indicates that the 2015 maximum water level was approximately 1 m above the 2016 maximum water level. ii Maximum measured discharge in 2016 was approximately half of that measured in 2015 in the lower Sagavanirktok River. Representative suspended sediment sizes (D50) ranged from 20 to 50 microns (medium to coarse silt). An objective of this study was to determine the composition and possible sources of water in the aufeis at the lower Sagavanirktok River. During the winter months and prior to breakup in 2016, overflow water was collected, primarily near the location of the aufeis, but also at upriver locations. Simultaneously possible contributing water sources were sampled between January and July 2016, including snow, glacial meltwater, and river water. Geochemical analyses were performed on all samples. It was found that the overflow water which forms the lower Sagavanirktok aufeis is most similar (R2 = 0.997) to the water that forms the aufeis at the Sagavanirktok River headwaters (Ivishak River), thought to be fed by relatively consistent groundwater sources.