FLOOD08913

• Designation Number: 203
• County: Larimer
• Community: Fort Collins
• Stream Name: Dry Creek
• Basin: South Platte
• Title: Major Drainageway Planning - Dry Creek, Fort Collins, Larimer County, Colorado
• Date: 4/1/1980
• Designation Date: 1/1/1983
• Floodplain - Doc Type: Floodplain Report/Masterplan

w
~
m
>!
" ~
> w
w
<
, u
w
~ Z
> ~
<
0 ~
~

" ..- 0 . ..- .
. .
.- ........,.. . .- 0
., uu . - -
8" :il515151 .
ww
w,
.. ,
~! . .. . , " . .
. NO . . . 0
. N - N - -
"
.~ N N - N 0 - -No
,- . , . .;~ui
., 0 0 0 - - - ,
.. ~ - - - - --
~~ .. .. :il5151:il
.' . . - . . 0
, 0 . .
". , "':"':"':':;i";":.-;":
, ~$$~:il$iii~5!
8'
,
;~ . " - '0 . . N
. . .c . N .
. . .0 0
>< 0 U 0 ~~ - -
> . . ...
"d
>~ . > - - NO . > 0
., . ' , -
'. . 8 ...<Q...... 0
. > ~ 0 ~~U ~ ~
0' . .
-0
,
.. . . . . .. . . .
w_ . . , . .
~~ . . . 00 g
. . . . .. ~ .
/, . .. . .. . .
,
~~ . .. . .. . . .
0 , . , . ~. . ,
. . .
~~ , O' . .0 . N .
.0 . ON 0 . .
N N N N N N N
i
~ > . :1t>~~51 - N
> > . .
~

DAMAGE ASSESSIIENT

The study area was divided into three reaches according to cO~IDunity
boundaries. The upstream reach, Reach A, c);tends fr= the upstream
~tudy limit to the Larimer-Weld Canal (Eaton Ditch) and is in
unincorporated Larimer County. The middle reach, Reach B. begins
at the Lurimer-Weld Canal and proceeds downstream to Le~ay Avenue.
This reach is qenerally within Fort Collins. Reach C, the downstream
reach, extends fron Lel1ay Avenue to the Poudre River confluence with
Dry Creek, and is again within Larimer County. The study area was
divided in this manner so that flood damages and improvement costs
could be attributed to the City and County separately.

The object of this evaluation is to identify the average annual flood
damage potential within each study reach. Through the construction
of channel improvements, those damages can be eliminated or greatly
reducea and are the major benefit resulting from the drainageway
irr.provement.

A det<liled bydraulic analysis was conducted, resulting in determination
of the velocity, width and depth of flooding far the 2-yeilr, lO-year,
50-year, lOO-year and SOO-year flood events. Potential flood damages
for structures within the study reach were estimated using damage curves
developed by the Federal Insurance Administration (FIA) (Reference 9) and
curves developed at Colorado State University (Reference IO). These
curves tabulate damage as a percent of total st~ucture value based
upon flood depth above the structure's ground floo<1 levsl.

Fro~l field investigations, first floor elevations of structures within
the flood plain were estimated to be one foot above the adjacent ground
and ap~roximately one-half of the residential structures have basements.
In addition, from these field visits, mobile homes were estimated to be
two-feet above adjacent ground as an ~vera~e.

Indirect danagcs are those dd-mages that include' the loss of business "n<l
services, the cost of alleviating hardship, safeguarding health, rerouting
traffic, delays, etc. these damages were assessed by taking a percentage
of the direct damages that would occur. For commercial and industrial
- 22-