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.ABSTRACT ..................................................................................................................................... i
LIST OF FIGURES ......................................................................................................................... i
LIST OF TABLES ....................................................................................................................... xiv
ACKNOWLEDGMENTS AND DISCLAIMER ........................................................................ xvi
CONVERSION FACTORS, UNITS, WATER QUALITY UNITS, VERTICAL AND
HORIZONTAL DATUM, ABBREVIATIONS, AND SYMBOLS .......................................... xvii
ABBREVIATIONS, ACRONYMS, AND SYMBOLS .............................................................. xix
1 INTRODUCTION ................................................................................................................... 1
2 STUDY AREA ........................................................................................................................ 2
2.1 Sagavanirktok River near MP318 Site 066 (DSS4) ......................................................... 7
2.2 Sagavanirktok River at Happy Valley Site 005 (DSS3) .................................................. 7
2.3 Sagavanirktok River below the Confluence with the Ivishak River (DSS2) ................... 9
2.4 Sagavanirktok River near MP405 Site 042 (DSS1) ....................................................... 10
3 METHODOLOGY AND EQUIPMENT .............................................................................. 13
3.1 Pits .................................................................................................................................. 13
3.1.1 Excavation............................................................................................................... 13
3.1.2 Surveying ................................................................................................................ 14
3.2 Surface Meteorology ...................................................................................................... 15
3.3 Aufeis Extent .................................................................................................................. 17
3.3.1 Field Methods ......................................................................................................... 18
3.3.2 Imagery ................................................................................................................... 18
3.4 Water Level Measurements ............................................................................................ 19
3.5 Runoff............................................................................................................................. 20
3.6 Suspended Sediment ...................................................................................................... 21
3.7 Turbidity ......................................................................................................................... 22
3.8 Stable Isotopes................................................................................................................ 22
4 RESULTS .............................................................................................................................. 23
4.1 Meteorology ................................................................................................................... 23
4.1.1 Air Temperature ...................................................................................................... 23
4.1.2 Precipitation ............................................................................................................ 31
4.1.2.1 Cold Season Precipitation ................................................................................ 31
4.1.2.2 Warm Season Precipitation ............................................................................. 36
4.1.3 Wind Speed and Direction ...................................................................................... 39
iv
4.2 Aufeis Extent .................................................................................................................. 40
4.2.1 Historical Aufeis at Franklin Bluffs ........................................................................ 41
4.2.2 Delineating Ice Surface Elevation with GPS and Aerial Imagery .......................... 45
4.3 Surface Water Hydrology ............................................................................................... 52
4.3.1 Sagavanirktok River at MP318 (DSS4) .................................................................. 58
4.3.2 Sagavanirktok River at Happy Valley (DSS3) ....................................................... 61
4.3.3 Sagavanirktok River near MP347 (ASS1) .............................................................. 65
4.3.4 Sagavanirktok River below the Ivishak River (DSS2) ........................................... 66
4.3.5 Sagavanirktok River at East Bank (DSS5) near Franklin Bluffs ............................ 70
4.3.6 Sagavanirktok River at MP405 (DSS1) West Channel .......................................... 78
4.3.7 Additional Field Observations ................................................................................ 82
4.3.8 Preliminary Rating Curves and Estimated Discharge ............................................. 85
4.4 Stable Isotopes................................................................................................................ 86
4.5 Sediment Grain Size Distribution .................................................................................. 90
4.5.1 Streambed Sediment Grain Size Distribution ......................................................... 90
4.5.2 Suspended Sediment Grain Size Distribution ......................................................... 94
4.6 Suspended Sediment Concentration ............................................................................... 95
4.6.1 Sagavanirktok River near MP318 (DSS4) .............................................................. 95
4.6.2 Sagavanirktok River at Happy Valley (DSS3) ..................................................... 100
4.6.3 Sagavanirktok River below the Ivishak River (DSS2) ......................................... 105
4.6.4 Sagavanirktok River near MP405 (DSS1) ............................................................ 111
4.6.5 Discussion ............................................................................................................. 114
4.7 Turbidity ....................................................................................................................... 116
4.7.1 Sagavanirktok River near MP318 (DSS4) ............................................................ 116
4.7.2 Sagavanirktok River at Happy Valley (DSS3) ..................................................... 119
4.7.3 Sagavanirktok River below the Ivishak (DSS2) ................................................... 124
4.7.4 Sagavanirktok River near MP405 (DSS1) ............................................................ 126
4.7.5 Discussion ............................................................................................................. 130
4.8 Analysis of Pits............................................................................................................. 130
4.8.1 Photographs of Pits ............................................................................................... 130
4.8.2 GIS Analysis of Pit Bathymetry ........................................................................... 141
4.8.3 Pit Sedimentation .................................................................................................. 142
4.8.4 Erosion Surveys .................................................................................................... 149
4.8.5 Patterns of Sediment Transport Along the River .................................................. 156
v
4.9 Hydraulic Modeling ..................................................................................................... 158
4.9.1 Model Development .............................................................................................. 160
4.9.2 Results of Simulation ............................................................................................ 165
5 CONCLUSIONS ................................................................................................................. 171
6 REFERENCES .................................................................................................................... 174
7 APPENDICES ..................................................................................................................... 18
