Flash Flooding in the Colorado

National Monument: Geomorphic Process and Neighborhood

Nuisance

Gigi A. Richard

Associate Professor of Geology

Colorado Mesa University

Grand Junction, CO

Prepared in cooperation with the

Colorado National Monument

US National Park Service

And with the assistance of the

Association of Women Geoscientists’

Geologist in the Park Program

Image from http://earthobservatory.nasa.gov,

Posted March 6, 2011. Acquired April 2, 2002

“The forces of water and wind,

freezing and thawing, acting over vast

spans of time, built the spires, domes,

and sheer canyon walls of Colorado

National Monument.”

Prof. Bill Hood, http://www.nps.gov/colm/naturescience/erosion

.htm

“Colorado National

Monument was

established to

preserve, study, and

enjoy the geological

resources and

processes…”http://www.nps.gov/colm/naturescience/envi

ronmentalfactors.htm

Photo: G. Richard

Drainages of

the Colorado

National

Monument

Redlands Area

City of Grand

Junction

No Thoroughfare Canyon along Monument Road

Sept 7, 1978

No Thoroughfare Wash at Monument Rd September 7, 1978

No Thoroughfare Wash - September 7, 1978

No Thoroughfare Wash at Monument Rd, Sept. 1978

No

Thoroughfare

Wash

Sept. 7, 1978

Flood

Sediment

deposition

Red Canyon at S. Camp Rd.

Sept. 7, 1978

Flash Flood

Potential Steep canyons

Bare rock

Low permeability

Intense rainfall

Sparse vegetation

Flood Producing Rainfall

Date

CNM Daily

Rainfall *

(inches)

Grand

Junction

Walker Field

Daily

Rainfall *

(inches)

GJDS Daily

Rainfall

(inches) Storm Rainfall (inches)

CNM

Monthly

Rainfall *

(inches)

August 24, 1921 1.43 3.65 in at Walker Field (GJDS)

August 8, 1948 0.13 0.89 0.89 in (0.42in/15min) (CNM) 2.34

July 3, 1949 0.16 0.85

July 7, 1949 0.02 1.02

July 28, 1950 0.14 0.12 1.70

August 6, 1957 2.55 0.56 0.21 1.87 in/2hrs (CNM) 6.66

August 8, 1968 1.93 4.24

September 7, 1978 0.66 0.43 0.64 3 in between GJ & Clifton (GJDS) 0.75

September 2, 1990 0.26 0.53 0.75 in/45 min (GJDS) 1.74

July 11, 1992 0.02 0.44 0.74

July 24, 1998 0.09 2 in/40 min (GJDS) 0.89

July 10, 2001 1.61 0.3 0.9 in total, 0.75in/1hr (GJDS - in Glade Park) 2.33

CNM = Colorado National Monument Gage and Records*

GJDS = Grand Junction's The Daily Sentinel

*All gage records were obtained from the Western Regional Climate Center, http://www.wrcc.dri.edu/

Recurrence

Interval

CNM

Headquarters

Rainfall (inches)

24-hr 24-hr 6-hr

100-yr 2.6 2.6 1.8

50-yr 2.3 2.3 1.6

25-yr ----- 2.1 1.5

10-yr 1.5 1.7 1.2

5-yr 1.0 1.4 1.0

2-yr 0.7 1.0 0.8

NOAA Atlas 2

Rainfall (inches)

Rainfall Frequency

Flash Flood

History

Flash Flood

History

Fruita Canyon

1968

August 8, 1968

August 8, 1968

Results of Historic Study

Flash floods

Result from intense and localized rainstorms over the CNM

Have occurred repeatedly in recent, historic and

geologic time

Nothing new…

What HAS changed

Increased suburban development in potentially flood prone areas

• Not mapped by FEMA

Led to more questions…

2007 Study of

Channel

Morphology of

No

Thoroughfare

Wash

Channel-forming

discharge?

Incision rates?

Upper Canyon Reach – Incision rates

Alluvial Reach

Future Possibilities

Better understanding of magnitude and frequency of rainfall that causes flash floods More rain gages?

Use of RADAR data?

Streamflow data Needed for calibration of models

Study of morphology and channel-forming discharge in other drainages Greg Indivero’s study

Acknowledgements

Dave Price, National Park Service

AWG, Geologist in the Park Program

2007 NSF-REU students - Aaron Becker, Lauren

DiPerna, Kathryn Ladig, John Wellik

Prof. Jim Johnson, photos

Bill Hood, Paul VonGeurard and Megan McGuire

And in honor of Peter LarsonA pdf of the report is available at home.mesastate.edu/~grichard