FLOOD02685

• County: Larimer
• Basin: South Platte
• Title: Flood Geomorphology of Arthurs Rock Gulch: Paleoflood History
• Date: 1/1/1994
• Prepared For: Larimer County
• Prepared By: Elsevier Science Publishers
• Floodplain - Doc Type: Flood Documentation Report

"

~

18

C.F. Woythomas. R.D. Joma I G.omo'J'hology II (19941 IS-40

105.U'

105",0' 15'

35"

Horsetooth Reservoir
Oow water level)

2101

upper basin

2105

I
I
I

lower basin

middle basin

34'

o
I
J
o

I
0.5

0.5
I

1.0 Miles

I
1.0 Kilometers

SiteS

Fig. 3
lOcale
the Ie:

Contouf interval . 1 SO meters

chan
pres'
exits

EXPLANATION

4. Pa

SURRCIAL DEPOSITS

BEDROcK

~
""""
~
o

Rood deposits

Oebris~f1ow deposits

Colluvial deposits on hnlslopes
manditlg undifterentiated bedrock

CoIIu'Jial deposits on I1iIlslopes
manding sandstone and conglomerate

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~
=
t.:::::::.:J

rmrl

Pegmatite

1m
its. I
"em
of co;
mary
Rock
loose:
durin:
ofba.
1983:
limit,
of the
as a F
the bc
age d.
of the

Sandstone hogbacks

Granodlorite

001!iiI

.5

Site loeation

..
..

Pegmalite blocks displaced by rocklan

x 1BOO

Spot elevation, in meters

Fig. 2. Generalized geologic map of the Anhurs Rock Gulch drainage basin showing the location of study sites and important flood deposilS.

memary rocks of Paleozoic age (Fig. 2). Erosional
(strath) terraces anti prominent Doulder bars and benns
are common along the channel. Near Horsetooth Res-
ervoir the channel lies within a deep V-shaped water

gap cut into north-south trending sandstone hogbacks.
Vegetation in this pan of the basin consists mainly of
prairie grasses. yucca, prickly pear cactus, and low
shrubs. Cottonwood trees are common along the active

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