May 7, 2013 Field Trip Report
Susitna-Watana Ice Processes Study
Date: May 7, 2013
Crew: Robin Beebee and Nick Schlosstein (HDR Alaska); pilot Alicen Bishop (Jayhawk
Aviation)
Talkeetna Weather: Sunny, clear, temperatures varied from 28 to 48 degrees Fahrenheit (F),
winds W less than 10 mph.
Objectives: Video Susitna River, collect ice progression observations.
Data Collected:
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Photos (JPEG) with GPS points
Georeferenced video
Ice observations with GPS points
Summary: Ice conditions on the Lower River have not drastically changed since May 5, 2013.
The main channel of the Susitna River was largely ice covered above PRM 15.8. Ice cover on
Alexander Slough was largely broken up in the lower 3 miles with long open leads upstream for
5 miles. Anderson Creek was mostly open downstream with lots of overflow on ice further
upstream. There was increasing meltwater on the ice at the Yentna River; Kroto Slough was
partially open and flowing into the main channel of the Yentna River. There was increasing
overflow on the Deshka with some open side channels. Rolly Creek had considerable amounts of
dark brown overflow and was flowing into a long open lead on the mainstem of the Susitna. A
large ice jam had formed at the mouth of the Talkeetna River, but upstream the river appeared
mostly open.
On the Middle River the open leads that were present on May 5, 2013 had continued to widen.
Extensive ice cover on the Middle River began at PRM 166 with overflow and meltwater
replacing periodic open leads.
The Upper River remained mostly ice covered without significant changes from the previous
survey.
Flight Path: From Merrill Field, the team flew to the mouth of the Susitna River and flew
upstream to Kosina Creek.
Lower River Observations
Mouth to Yentna River: Conditions near tide water had changed very little since the previous
flight on May 5, 2013. Within the first mile of the river from the tidal zone there were large open
leads with large amounts of broken ice rafted together and intermittent ice cover; in this section
the east channel was open (Figure 1). Ice bridges terminated at PRM 3.6 on the east and west
channels of the Susitna River. The main channel of the Susitna River became largely ice covered
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by PRM 15.8 with some discontinuous open leads and pockets of standing water on top of the
ice.
Ice in the lower reaches of Alexander Slough was largely broken up; approximately 3 miles up
the slough a large amount of ice appears to have floated and slid downstream forming a small
jam on a bend in the channel (Figure 2). Further upstream, ice cover became more consistent but
with large open leads, becoming mostly covered 8 miles from the main channel. Fish Creek was
mostly frozen at the mouth, but about a mile upstream the ice was partially broken up. At PRM
21.8 an open lead from a partially open tributary entered the main channel along the left bank.
The team landed to check the status of the station at ESS15 and found that the bank had eroded
to within five feet of the station (Figure 3).
The first mile of Anderson Creek was mostly open with some small ice jams and stable ice on
the last bend before entering the Susitna River. Further upstream there was a considerable
amount of overflow. Throughout the day the creek opened up, but the remaining ice did not
appear to be breaking up.
Yentna River: The confluence at the Yentna River was still ice covered with pockets of standing
water on top of the ice; upstream Kroto Slough was partially open and flowing into the Yentna
along the left bank.
Yentna River to Talkeetna: At PRM 44.2, ice on the main channel remained extensive and solid
despite some standing water. Dark, brown water was flowing on top of the ice in Rolly Creek,
leading into a long open lead along the left bank of the Susitna River. The Deshka River
confluence was frozen, but there was some overflow along both banks further upstream as well
as some completely open side channels (Figure 4).
Beginning at approximately PRM 54.6, there were an increasing number of open side channels
and sloughs along the edge of the river, particularly along the east bank. The Kashwitna River
remained frozen at the mouth and well upstream. However, further upstream the lower reaches of
Sheep Creek, Montana Creek, Rabideux Creek, and Sunshine Creek and Slough were largely
open (Figure 5).
Talkeetna and Chulitna Rivers: There was a large ice jam at the mouth of the Talkeetna River
with open leads upstream. Conditions on the Chulitna River appeared unchanged since the last
flight; a few continuous open leads but largely ice covered upstream of the confluence.
Middle River Observations
Talkeetna to Devils Canyon: Upstream of the Talkeetna and Chulitna Rivers confluence, the
Susitna River open leads that were present on May 5, 2013 had continued to open up (Figure 6),
including those near Curry (Figure 7) and at the mouth of the Indian River, though the Indian
River itself remained about 75 percent covered.
Devils Canyon to Dam Site: Large open leads continued into Devil Canyon, occasionally
interrupted by ice jams and bridges with accumulation on the upstream side (Figure 8). More
extensive ice cover began at PRM 166 (Figure 9); leads became thinner and more discontinuous
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with overflow rather than fully open water. Some large open leads were present from Fog Creek
through Tsusena Creek. Many of the smaller tributaries remained frozen.
Upper River Observations
Dam Site to Kosina Creek: Ice cover was extensive on the Upper River with intermittent and
discontinuous leads over the thalweg and along the banks. From PRM 186.8 through 191.7 the
open leads were fairly frequent then became fewer and smaller from PRM 193.8 on, where open
leads gave way to flowing and stationary pools of water on the ice surface.
The team landed at the Kosina Creek confluence where there were remnants of a large, dirty ice
jam. The jam extended upstream of the Kosina Creek. There was evidence of a violent blowout
in the fall with sheared, jumbled ice and logs stripped of bark incorporated into the jam. Kosina
Creek had cut through about 15 feet of the jam and was flowing freely into the main channel
(Figure 10). The main Susitna thalweg was about 20 feet lower than the Kosina mouth, with
some water flowing over the surface of the ice. The snow was rotten.
The team did not fly upstream of Kosina Creek.
Representative Photographs
Figure 1. Facing upstream on the East Channel, PRM 6.
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Figure 2. Open leads on Alexander Creek, 2 miles upstream from Alexander Slough.
Figure 3. Equipment at ESS15, PRM 24.7.
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Figure 4. Overflow along the banks of the Deshka River 6 miles upstream from the confluence.
Figure 5. Main channel near Sunshine Creek and Slough, PRM 89.9.
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Figure 6. Facing north at the confluence of the Talkeetna, Susitna, and Chulitna Rivers, PRM 100.1.
Figure 7. Widening lead at Curry, PRM 122.8.
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Figure 8. Ice jam near downstream end of Devils Canyon, PRM 154.
Figure 9. Increasing ice cover, PRM 169.3.
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Figure 10. Water flowing through large ice jam at the mouth of Kosina Creek, PRM 209
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