FLOOD04278

• County: Jefferson
• Community: Morrison and Evergreen
• Stream Name: Bear Creek
• Basin: South Platte
• Title: Coarse-sediment Distribution as Evidence of an Elevation Limit for Flash Flooding
• Date: 12/8/1995
• Prepared For: CWCB
• Prepared By: Elsevier Science Publishers
• Floodplain - Doc Type: Flood Documentation Report

M. Grimm et aL / Geomorphology 00 (1995) 000-00O

Table ..
Results of radiocarbon and dendrochronologic analyses in Bear Creek Basin

9

Sample site

Radiocarbon ages

Dendrochronologic age (yr)

Reported age'

Calibrated ageb

22

Lower Bear Creek

8575" 190
(GX-18271)
2556,,53
(GX-18272-AMS)
6355" 110
(GX-18273)
365 J:l1O
(GX-18275)

Turkey Creek

Cub Creek

Upper Bear Creek

7546 B.C.
(7890-7436)
782 B.C.
(799-564)
5277 B.C.
(5428-5221)
1490 A.D.
1605 A.D. (1437-1655)
1613 A.D.

70

aAge in radiocarbon years before present. with lab number in parentheses. GX indicates Geochron Laboratoty. AMS indicates accelerator mass
spectrometer date.
~adiocmbon age calibrated in calendric year B.C. or A.D.. with age range in parentheses (SIuiverand Reimer. 1993).

our estimated elevation limit of 2100 m and Jarrett's
(1993) limit of 2,300 m may be insignificant in view
of the precision and scarcity of available data. Jarrett's
selection of 2300 m was based on stream flow gaging
station data covering the late 1880s through 1988 from
935 gages in Colorado. Prior to the work described
here, no systematic field studies assessed the variability
of the elevation-limit among individual basins and
independent of gage locations. The discrepancy could

100

also be caused by basin characteristics such as aspect,
which would affect the response of flood-producing
storms and introduce minor variations in the elevation
limit along the Colorado Front Range.
Drainage basin area is an important factor in deter-
mining the amount of runoff that is generated, all other
factors being equaL Corral Creek has the largest drain.
age area of the six tributary basins (Table 1) and,
therefore, the largest runoff per unit area potential. Cor-

90

+

+

80
70
E
.2- 60 +
~
N
Cii 50
~
"0
t: 40
~
Q.
30
.
20 .
10

+

+

+
+

.

.
. .

o
1750 1860 1950 2050

. D..

+ D_

:;
+ +
+ ++ + +
+ +
+
. .. . .
. . .
2150 2250 2350 2450 2550 2650 2750
E1evatior] (m)

Fig. 2. Particle-size characteristics in relation to elevation. D~ indicates intermediate diameter of median clast size measured at each site; Dmu.
indicates intermediate diameter of largest clast judged to be ftuvially transported on the basis of proximity to the active channel. and clast
rounding and imbrication.

Journal: GEOMOR Article: 368