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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

~ 140 fatalities

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Blue Ridge Mountains, VA

Rapidan Storm,June 1995

775 mm

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

floodplains?floodplains?

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

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

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

frequency of debris flowsfrequency of debris flows

DEBRIS FLOW FREQUENCY IN THE RAPIDAN BASIN

from Eaton and others, 2003

Sediment Transport and Denudation

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)

HurricaneCamille

Willis Cove

4.08 173,488 4.25

HurricaneCamille

Ginseng Hollow

1.75 88,727 5.07

HurricaneCamille

Polly Wright Cove

2.47 87,707 3.55

Rapidan Flood

Jenkins Hollow

0.398 13,364 3.36

Rapidan Flood

Teal Hollow 0.123 2,492 2.03

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

A Model of A Model of AppalachianAppalachian

Landscape EvolutionLandscape Evolution

BEFORE…..

AFTER…..

HIGH “M”LOW (f)

LOW “M”HIGH (f)