View
531
Download
0
Tags:
Embed Size (px)
DESCRIPTION
From Atmospheric Rivers to Rivers Of Debris: Coupling Extreme Precipitation Events, Glacial Retreat, Debris Flows, And Channel Changes On Mount Rainier, Washington. Presented by Gordon Grant at the "Perth II: Global Change and the World's Mountains" conference in Perth, Scotland in September 2010.
Citation preview
From atmospheric rivers… to rivers of debris.
Gordon Grant PNW Research Station
USDA Forest Service
Anne Nolin, Lauren Parker, Beth Copeland
Stephen Lancaster, Jonathan Ellinger
Oregon State University
Paul Kennard, Erin Tainer Ian Delaney
Mt Rainier National Park Whitman College
Coupling extreme precipitation events, glacial retreat, debris flows and channel changes on Mount Rainier, Washington
November 6, 2006
November 7, 2006
was a dark, stormy,
and very wet night...
Pineapple Express /
Atmospheric River
NASA Earth Observatory
Oct 31-Nov 7, 2006
Mount Rainier
> 100yr Flood
Tahoma Creek, Washington
Hwy 35
Mount Hood Debris Flows
Eliot Creek
West Fork Middle Fork Hood
0
1
2
3
4
5
6
7
8
1947 1952 1957 1962 1967 1972 1977 1982 1987 1992 1997 2002 2007
# o
f d
eb
ris
flo
ws
0
1
2
3
4
5
6
7
8
1947 1952 1957 1962 1967 1972 1977 1982 1987 1992 1997 2002 2007
# o
f d
eb
ris
flo
ws
Debris flow data from Driedger, Walder, Kennard
Mount Hood
Mount Rainier
Cascadian Periglacial Debris Flow Project
1) Atmospheric
rivers 2) Initiation
of debris
flows
3) Downstream
consequences Climate
Change?
Are debris flows correlated with Pineapple Express and
Atmospheric River (PE/AR) events?
PE/AR = Lots of rain
Pineapple Express event of November 5 and 6, 2006
+ High Freezing levels
Rainier
Hood
Mountain peak elevations
Mount Rainier Freezing Altitudes Mt Rainier
peak elevation
Associated with strong southwest flow
Dettinger, 2004
A debris flow was considered PE/AR related if a PE/AR event occurred
on the same day as a debris flow, or on the day prior.
PE/AR event non PE/AR event
Pineapple Express (PE) events (Dettinger, 2004) and Atmospheric Rivers (AR) (Neiman et al., 2008); Debris flow data from Driedger, Walder, Kennard
Mount Hood
Mount Rainier
Classification of storms proceeding debris flows
Classification of storms proceeding debris flows
0
10
20
30
40
50
60
70
80
90
100
10/26/86
10/15/8811/8/89
10/2/9011/4/91
9/7/929/19/92
10/19/039/28/05
11/5/06
One Day Prior to Debris Flow Event Date
SW
E (
mm
)
Mount Rainier
Antecedent SWE
…and 3) Little snow cover
Iverson, pers comm.
RAIN
SNOW DEPTH
Geomorphic factors associated with debris flow
initiation All recent initiation sites are:
• In areas exposed by recent (5-10 year) glacier retreat
• Near glacier termini or debris-mantled stagnant ice
• At heads of steep-walled gullies flanked by steep debris-mantled slopes
2001-2006
debris flow
initiation sites
1913
Glacier Extent
2008
Ellinger, 2010
• water concentrated in sub- or supra-glacial channels.
• flow directed toward unstable, sediment mantled slopes below/adjacent to glaciers.
Fire Hose Effect?
Photo: NPS
Source areas • Moraines • Ice-cored debris • Debris mantled
slopes
Runout Zone
Deposition in larger channels
Downstream channel response?
0.1
1.0
10.0
100.0
1000.0
0.1 1.0 10.0 100.0 1000.0
Re
cen
t A
ggra
dat
aio
n R
ate
s (c
m/y
r)
Long term (1910-2006) Aggradation Rates (cm/yr)
1997-2006 2006
Aggradation rates within Mount Rainier National Park
Lower Van
Trump
Longmire
Sunshine
Point
White
River
1) Evidence for
widespread
aggradation
(not incision)
2) Higher than
long-term
average in last
decade
1951
1989
1960
1978
Tahoma Creek
post 2006 storm
Christopher Magirl, USGS
Aggradation rates downstream of Mount Rainier National Park
Effects of climate change?
• Change in
intensity/frequency of
PE/AR events
• Continued
glacial
retreat / fragmentation
• Increased
length of
snow free
period
• Downstream
signal?
No smoking gun yet… • Atmospheric events producing
debris flows come in different flavors
• Apparent recent increase in debris flows, but record is incomplete and potentially biased
• Consistent pattern of aggradation within Mt Rainier National park itself
• No consistent aggradation in larger rivers