The Alaska Department of Transportation and Public Facilities (ADOT&PF) is examining the concept of building a roadway from the Dalton Highway in the vicinity of Coldfoot, past Bettles, to near the area around the village of Kobuk along the south side of the Brooks Range. This is an area of Alaska almost completely void of both environmental data (meteorological, hydrological, biological, etc.) and research studies. It is an area of discontinuous permafrost, mostly forested (except in the high alpine areas), mostly rolling foothills bordered by low lying areas that are poorly drained with lots of lakes, ponds and wetlands to the south and the Brooks Range to the north.
The region has a continental climate (warm summers and cold winters) dominated by snow, ice and permafrost. Several very large lakes on the southern edge of the Brooks Range dot the landscape. For this region of the state, the main engineering challenges when building a highway are stability of permafrost and well-engineered stream crossings. There is some experience in building the Dalton Highway to the North Slope of Alaska across similar terrain. While on the North Slope the rivers drain from south to north, here they drain from north to south until rivers like the Koyukuk and Kobuk start collecting other streams and start trending to the west. While the Dalton Highway is basically a north-south roadway that does not cross many major rivers (of course it crosses the Yukon River), the road proposed here is primarily an east-west road that would cross several medium sized streams.
Two villages are in close proximity of the northern route of the roadway; Bettles near the eastern end and Kobuk near the western end. During the total duration of this project we will probably at best collect environmental data for three or four years along and upstream of the Ambler northern route corridor. The US Geological Survey has gauged several rivers in this area in the recent past (Koyukuk River, Dahl Creek, etc.). In addition, the US Fish and Wildlife Service (USFWS) is presently gauging several streams in the vicinity of Kanuti Flats National Wildlife Refuge. While most of the USFWS streams drain lower gradient watersheds south of the area of interest, they are gauging the Koyukuk River near Bettles. Also, on the western end of the study area, GW Scientific is measuring the Kogoluktuk River near Kobuk for the Alaska Village Electric Cooperative (AVEC). The long-term funding by USFWS and AVEC of these stream gauging sites is uncertain. Seldom will we get an idea or likelihood of the magnitude of extreme events over such a short study period; to get a confident estimate of events with low probability or high return period it is necessary to collect data for 25 or so years. Only one stream in the region (Dahl Creek at Kobuk) has been gauged for 25 years, the others range from 7 to 22 years (the average is 13 years). We can use these stations as indices to develop a better understanding of the runoff response of rivers in the region; however, this area is really lacking in complementary meteorological data such as regional air temperatures, spatial precipitation (both rainfall and snow water equivalent) and wind velocities.
In the summer of 2012, we installed eight new meteorological observation stations with four of them on and near the proposed route. Four of these stations are collocated with new hydrological stations that measure continuous water levels where stream gauging is carried out by UAF. The remaining four meteorological stations are located in the headwaters of the south flowing rivers. At each meteorological station, we measure summer rainfall, continuous winter snow depth, air temperature, relative humidity, wind speed and direction, net radiation (mostly during warm season as ice and snow on the sensor during the winter compromise the data), and soil moisture and soil temperature. A camera is also present at each station to observe weather and river conditions.
We began measuring continuous water levels, along with individual measurements of discharge, in the summer of 2012 and plan to measure discharge frequently during spring breakup in 2013 and continue into the summer months. Stations are located at the Koyokuk River near Bettles (in partnership with USFWS), Reed River, Alatna River, and South Fork Bedrock Creek (a tributary of the Alatna River). As stated earlier, a meteorological station will be collocated with each gauging station. Meteorological station are installed in the headwaters of each of these gauged streams at a higher elevation to provide us with complementary data to examine precipitation/runoff responses.However, stations could not be installed at the uppermost parts of the watersheds due to Gates of the Arctic Wilderness area.
In addition to continuous water levels, we take suspended and bedload sediment measurements during each visit and also collect suspended sediment data each day with an Isco sampler. We are also monitoring turbidity continuously with a sensor placed in the river. Both the Isco sampler and turbidity sensor are placed in the river after break-up when the rivers are free of ice. During site visits, suspended sediment profile measurements are made so they can be correlated with the suspended sediment concentrations obtained by the Isco samplers. We will also attempt to make some bedload measurements when in the field.
Beginning in spring 2013 we will conduct end-of-winter snow surveys to ascertain both snow depth and snow water equivalent (SWE) over the area of interest. Snow surveys will be done at each of the stations and points in between. Altogether we will probably establish about 60 new snow survey sites where we take 50 depth measurements (in a L-shaped pattern 25 m by 25 m) and five randomly located snow density measurements. At each of the instrumented sites we continuously (hourly) monitor the snow depth on the ground. At sites that we visit frequently during break-up (like the river gauging locations), we will also do daily snow surveys (same methodology as described above) to document ablation. We anticipate more variation of snow on the ground on the south side of the Brooks Range than we find on the north side. On the north side there is fairly even winter precipitation over the coastal plain, foothills and mountains; on the south side we expect that there will be greater winter precipitation with elevation.