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additional reading of the icane Camille event: Photo: Tom Gathright

For additional reading of the Hurricane Camille event: Photo: Tom Gathright

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For additional reading of theHurricane Camille event:

Photo: Tom Gathright

THE ROLE OF DEBRIS FLOWS IN LONG TERM DENUDATION AND LANDSCAPE EVOLUTION

OF THE CENTRAL APPALACHIANS

L. Scott Eaton, Ph.D.L. Scott Eaton, Ph.D.Department of Geology and Environmental Department of Geology and Environmental

ScienceScienceJames Madison UniversityJames Madison University

Death Valley, CA

La Conchita, CA

Landslide: the downslope movement of rock, soil, or artificial fill under the influence of gravity.

Venezuela, 1999

Photos: Matt Larsen, USGS

Blue Ridge Mountains, central Virginia

~ 150 fatalities

Photo: Tom Gathright, 1969

C C

Madison County, Virginia

Rapidan Storm,June, 1995

775 mm,ppt

Research Question:Research Question:

In the Appalachians, are debris flows a In the Appalachians, are debris flows a

significant process in the significant process in the transportation of transportation of

sediment from sediment from mountainous terrain to mountainous terrain to thethe

lowland floodplains?lowland floodplains?

What is the frequency of debris flows in the What is the frequency of debris flows in the Appalachians?Appalachians?

How much sediment is transported during an event?How much sediment is transported during an event?

What are the long term erosion (denudation) rates in What are the long term erosion (denudation) rates in the central Appalachians?the central Appalachians?

What are the dominant geomorphic processesWhat are the dominant geomorphic processesoperating within the basin?operating within the basin?

Frequency of debris flowsFrequency of debris flows

DEBRIS FLOW FREQUENCY IN THE UPPER RAPIDAN BASIN

from Eaton and others, 2003

Nelson County

Sediment Transport and Denudation(from Springer, Shroyer, and Eaton, 1997)

0.398 km2

Before After

? ?

?

13, 364 m3

0.398 km2

Volume = 13, 364 m3

Area 0.398 km2 or 398,000 m2 = 0.034 m

= 3.4 cm

Summary of Basin Denudation of Blue Ridge Systems

Event 

BasinBasin Area (km2)

Volume ofSediment Eroded

(m3)

Mean Basin

Denuda-tion (cm)

HurricaneCamilleNelson Co.

Willis Cove

4.08 173,488 4.3

HurricaneCamille,Nelson Co.

Ginseng Hollow

1.75 88,727 5.1

HurricaneCamille,Nelson Co.

Polly Wright Cove

2.47 87,707 3.6

Rapidan Flood,Madison Co.

Jenkins Hollow

0.398 13,364 3.4

Rapidan Flood

Teal Hollow 0.123 2,492 2.0

Long Term and Episodic Denudation

0

1

2

3

4

5

6

7

8

9

10

Nelson County Madison County

Den

ud

atio

n (

cm) Long Term

Episodic

3,500 Years 1 Day

2,500Years 1 Day

HurricaneCamille

RapidanStorm

Dominant geomorphic processes….Dominant geomorphic processes….

~ 2 m

From Ballantyne and Harris,1994

Solifluction Deposits and Landforms

From Ballantyne and Harris,1994

One model of Appalachian landscape evolution and sediment transport…..

BEFORE…..

BEFORE…..

AFTER…..

High MagnitudeLow Frequency

Low MagnitudeHigh Frequency

Other considerations……• regional frequency (~15 yrs)• multi-basin impacts