FLOOD05175

• County: Summit
• Community: Breckenridge
• Stream Name: Blue River
• Basin: Colorado Mainstem
• Title: Technical Addendum Floodplain Information Blue River
• Date: 12/1/1974
• Prepared For: Summit County
• Prepared By: Leonard Rice Consulting Water Engineers, Inc.
• Floodplain - Doc Type: Floodplain Report/Masterplan

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APPENDIX II

AVERAGE STom; APPROACH

This approach attempted to describe the complexity of the
storm causing the 100 yr. event. Average updraft crossectional
area was deterimed from Auer & }IDrwitz IS data for eight HE
Colorado thunderstorms. This average area as well as the max-
innun area reported were used to define the eff'ective area. over
which precipitation would f'all f'or four dif'f'erent cell config-
urations. The average updraf't area was 32.8 Ini~ (85 kIn.1-). The
maxinnun area reported was 66.4 mi: (172 kIn.1-).
Average case
System IAI is a seven cell configuration. There are four cells
per complex with one common cell. The cells are arranged symetrically.
Only two of' the cells are precipitating at anyone time.per complex.
I' Cell radius 6.18 Ini.(9.95 kIn.)
'\ i -\ (: ~ ( . Four cell complex area 119.83~
, I Ini. (310.76 km.... )
y'('1 "--' C.., y. . Approximate system areal cov-
~! S:=/ erage,204.2 mi; (530 lon.~ )

System 'B' is a four cell configuration. It has two cells per
complex. The cells are arranged so the complex straddles the
Continental Divide. Only one cell is precipitating at anyone time.
per complex. Cell radius 3.2 mi. (5.2 kIn.)
Tl~o cell complex area 80.59
mi.~ (208.74 kIn.... )
Approximate system areal cov-
erage, 161.18 Ini.1- (417.48
kIn.1..)
Cell center to center distance
within complex 7.4 Ini.(11.9
kIn. )

(

/

'..... I .~.'

/

_./'

~
.".J.

/'

~,

cell is a diff'erent complex.
elevated areas. Only one cell
Cell radius 3.2mi. (5.2 km.)
Approximate systom areal cov-
erage 80.59Ini:- (208.74 km:- )
Center to center distance of'
cells 7.4 Ini.(1l.9 kIn.)

System 'c' is a t\ro cell system. Each
The cells are located directly over the
is precipitating at any time.

\...

/
/~

System 'D' is an overlapping two cell system. They are also located
over the elevated areas. Only one cell is precipitating at any time.
, Cell radius 3.2 mi.{5.2 kIn.)
. Approximate system areal cov-
erage 65.64 mi~,(170.0 kIn..... )

,r--.
(

,
,
.,

,

l'Jaxinnun case
System '3'

System 'c'

System IDI

radius 4.6 Ini.(7.4 kIn.) areal coverage 136.3mi:{353.0
kIn.... )
radius L~.6 Ini. {7.4 lon. ) areal coverage 132.8 mi; (341+.0km.~)

radius same asIC' areal coverage 265.6 Ini~ (688.0 kIn;)

System 'A' cell radius saIne as 'C' areal coverage 509.7 mi~ ( ...
1320.17 kIn.)