Scott Beason, Mount Rainier park geologist, provided information on recent glacial outburst floods and debris flows at the September NRC meeting.

1. National Park Service
U.S. Department of the Interior
Mount Rainier National Park
Friday, September 18, 2015Longmire, WA September Nisqually River Council Meeting
Photo: NPS/Scott Beason

2. National Park Service
U.S. Department of the Interior
Mount Rainier National Park
Friday, September 18, 2015Longmire, WA September Nisqually River Council Meeting
TAHOMA
GLACIER
SOUTH
TAHOMA
GLACIER
Point Success
(14,158 ft)
Saint Andrews Rock
(10,992 ft)
Sunset Amphitheater
Emerald Ridge (RER)
Seismograph
Source:GoogleEarth
Glacier
Island
Pyramid Peak
(6,937 ft)
1.Setting2.History3.August134.Findings5.Future6.Conclusions

3. National Park Service
U.S. Department of the Interior
Mount Rainier National Park
Friday, September 18, 2015Longmire, WA September Nisqually River Council Meeting
Attribute Value
Type Mid-elevation cirque glacier
Aspect Southwest
Source 10,500 ft (3,200 m)
Terminus 6,800 ft (2,072 m)
Length 2 mi (3.2 km)
Area 550 ac (2.2 km2)
Estimated Volume 79,200 acre-feet
Water Storage 23 billion gallons
Source:NPS/MORAGIS
1.Setting2.History3.August134.Findings5.Future6.Conclusions

4. National Park Service
U.S. Department of the Interior
Mount Rainier National Park
Friday, September 18, 2015Longmire, WA September Nisqually River Council Meeting
Referencees:Walder&Driedger,1994;NPS/MORAArchives
• 37 debris flows between 1967-2006
• High intensity between 1967-1971
and 1986-1992
• No debris flows between 2007-2014
• Nearly all began as “hydrologic
anomalies”
• Stagnating ice is a major factor
1.Setting2.History3.August134.Findings5.Future6.Conclusions

5. National Park Service
U.S. Department of the Interior
Mount Rainier National Park
Friday, September 18, 2015Longmire, WA September Nisqually River Council Meeting
Photos:NPS/MORAArchives;NationalAgriculturalImageryProgram(NAIP)
1.Setting2.History3.August134.Findings5.Future6.Conclusions

6. National Park Service
U.S. Department of the Interior
Mount Rainier National Park
Friday, September 18, 2015Longmire, WA September Nisqually River Council Meeting
Sources:PacificNorthwestSeismicNetwork(PNSN);USGS/CVO;MountRainierNPDispatchRecords
Time Event
09:49 – 10:01 First debris flow on RER seismograph
10:16 – 11:02 Second debris flow on RER seismograph
11:21 – 11:43 Third debris flow on RER seismograph
11:58 Visitor Zach Jones videos debris flow on West Side Road (next slide…)
12:02 VIP Yogev radios dispatch about outburst flood
12:26 – 12:34 Final debris flow on RER seismograph
13:01 Surge #5 seen from Wonderland trail suspension bridge
13:28 Surge #6
14:13 Surge #7
14:52 Surge #8
15:27 Surge #9
15:35 Surge #10
16:58 Surge #11
18:22 Surge #12
1.Setting2.History3.August134.Findings5.Future6.Conclusions

7. National Park Service
U.S. Department of the Interior
Mount Rainier National Park
Friday, September 18, 2015Longmire, WA September Nisqually River Council Meeting
Video:ZacharyJones,UsedwithPermission
1.Setting2.History3.August134.Findings5.Future6.Conclusions
11:58 AM, DF Surge #3

8. National Park Service
U.S. Department of the Interior
Mount Rainier National Park
Friday, September 18, 2015Longmire, WA September Nisqually River Council Meeting
Photo:NPS/ScottBeason
Significant loss of debris-
covered stagnant ice
(calving?) at terminus
1.Setting2.History3.August134.Findings5.Future6.Conclusions

9. National Park Service
U.S. Department of the Interior
Mount Rainier National Park
Friday, September 18, 2015Longmire, WA September Nisqually River Council Meeting
As many as four discrete
debris flow signatures on the
Emerald Ridge seismograph
Source:PacificNorthwestSeismicNetwork(PNSN);SethMoran,USGS/CVO
DF #1: 09:49 – 10:01
DF #2: 10:16 – 11:02
DF #3: 11:21 – 11:43 (most energetic)
DF #4: 12:26 – 12:34
1.Setting2.History3.August134.Findings5.Future6.Conclusions

10. National Park Service
U.S. Department of the Interior
Mount Rainier National Park
Friday, September 18, 2015Longmire, WA September Nisqually River Council Meeting
Photo:NPS/ScottBeason
Significant discharge (2-3x)
observed from South Tahoma
Glacier for at least 2 days
1.Setting2.History3.August134.Findings5.Future6.Conclusions

11. National Park Service
U.S. Department of the Interior
Mount Rainier National Park
Friday, September 18, 2015Longmire, WA September Nisqually River Council Meeting
Source:Worldview2Satellite;NPSMORAGIS
Main channel
shifted to the
east just
downstream of
the terminus
1.Setting2.History3.August134.Findings5.Future6.Conclusions

12. National Park Service
U.S. Department of the Interior
Mount Rainier National Park
Friday, September 18, 2015Longmire, WA September Nisqually River Council Meeting
Significant incision into
“Little Ice Age” moraine
lead to “bulking up” of
sediment and instability
of upper basin
Photo:NPS/ScottBeason
1.Setting2.History3.August134.Findings5.Future6.Conclusions

13. National Park Service
U.S. Department of the Interior
Mount Rainier National Park
Friday, September 18, 2015Longmire, WA September Nisqually River Council Meeting
Photo:NPS/HeatherSharp
As many as 12 discrete high flow or
hyper-concentrated flows observed
by park staff and visitors
1.Setting2.History3.August134.Findings5.Future6.Conclusions

14. National Park Service
U.S. Department of the Interior
Mount Rainier National Park
Friday, September 18, 2015Longmire, WA September Nisqually River Council Meeting
Debris flows ended in the vicinity
of the Tahoma Creek Trail
1.Setting2.History3.August134.Findings5.Future6.Conclusions
Photo:NPS/MitchHaynes

15. National Park Service
U.S. Department of the Interior
Mount Rainier National Park
Friday, September 18, 2015Longmire, WA September Nisqually River Council Meeting
Area loss: 5.85 acres
Average Thickness: 16.7 ft
Volume: 4.2 million ft3
Source:Worldview2Satellite;DavidShean,UniversityofWashington
1.Setting2.History3.August134.Findings5.Future6.Conclusions

16. National Park Service
U.S. Department of the Interior
Mount Rainier National Park
Friday, September 18, 2015Longmire, WA September Nisqually River Council Meeting
Photo:USGS/CarolynDriedger
Given its step-like morphology and what appears to be a large area
of stagnant ice, we are potentially entering a period of increased
glacial outburst floods & debris flows from the South Tahoma Glacier
1.Setting2.History3.August134.Findings5.Future6.Conclusions
Glacial Ice
Terminus
Debris-covered
Stagnant Ice
8/13
Source
Terminus
Pro-glacial Debris

17. National Park Service
U.S. Department of the Interior
Mount Rainier National Park
Friday, September 18, 2015Longmire, WA September Nisqually River Council Meeting
Photo:NPS/ScottBeason
1.Setting2.History3.August134.Findings5.Future6.Conclusions

18. National Park Service
U.S. Department of the Interior
Mount Rainier National Park
Friday, September 18, 2015Longmire, WA September Nisqually River Council Meeting
• South Tahoma Glacier and Tahoma Creek have a
rich history of outburst floods and debris flows
1.Setting2.History3.August134.Findings5.Future6.Conclusions

19. National Park Service
U.S. Department of the Interior
Mount Rainier National Park
Friday, September 18, 2015Longmire, WA September Nisqually River Council Meeting
• South Tahoma Glacier and Tahoma Creek have a
rich history of outburst floods and debris flows
• The 8/13/15 event was likely caused by an
outburst flood and calving event that “bulked up”
in pro-glacial lateral moraine debris
1.Setting2.History3.August134.Findings5.Future6.Conclusions

20. National Park Service
U.S. Department of the Interior
Mount Rainier National Park
Friday, September 18, 2015Longmire, WA September Nisqually River Council Meeting
• South Tahoma Glacier and Tahoma Creek have a
rich history of outburst floods and debris flows
• The 8/13/15 event was likely caused by an outburst
flood and calving event that “bulked up” in pro-glacial
lateral moraine debris
• Four debris flows and 12 high flow surges were
seen
1.Setting2.History3.August134.Findings5.Future6.Conclusions

21. National Park Service
U.S. Department of the Interior
Mount Rainier National Park
Friday, September 18, 2015Longmire, WA September Nisqually River Council Meeting
• South Tahoma Glacier and Tahoma Creek have a
rich history of outburst floods and debris flows
• The 8/13/15 event was likely caused by an outburst
flood and calving event that “bulked up” in pro-glacial
lateral moraine debris
• Four debris flows and 12 high flow surges were seen
• The event was exceedingly well documented
1.Setting2.History3.August134.Findings5.Future6.Conclusions

22. National Park Service
U.S. Department of the Interior
Mount Rainier National Park
Friday, September 18, 2015Longmire, WA September Nisqually River Council Meeting
• South Tahoma Glacier and Tahoma Creek have a
rich history of outburst floods and debris flows
• The 8/13/15 event was likely caused by an outburst
flood and calving event that “bulked up” in pro-glacial
lateral moraine debris
• Four debris flows and 12 high flow surges were seen
• The event was exceedingly well documented
• New technology is allowing us to better
understand outburst floods and debris flows
1.Setting2.History3.August134.Findings5.Future6.Conclusions

23. National Park Service
U.S. Department of the Interior
Mount Rainier National Park
Friday, September 18, 2015Longmire, WA September Nisqually River Council Meeting
1.Setting2.History3.August134.Findings5.Future6.Conclusions
A new debris flow
occurred Saturday,
September 12,
2015, between
17:24 – 17:50
Accompanied by
increased stream
flow for 24-48
hours
MUCH larger
event!

24. National Park Service
U.S. Department of the Interior
Mount Rainier National Park
Friday, September 18, 2015Longmire, WA September Nisqually River Council Meeting
Scott Beason
Park Geologist
Mount Rainier National Park
Scott_Beason@nps.gov
(360) 569-6781
Photo: NPS/Scott Beason