FLOOD09665

• Designation Number: 564
• County: Summit
• Community: Breckenridge
• Basin: Colorado Mainstem
• Title: FIS - Breckenridge
• Date: 6/20/2001
• Prepared For: Breckenridge
• Prepared By: FEMA
• Floodplain - Doc Type: Current FEMA Regulatory Floodplain Information

The stream distances along Blue River are measured from Cemete~y Road.
rhe str8am distances along any tributary of the Blue River are measured
f-.Eem----t-fie--c-B-fl-f----l-u-e-n-c--e-- -w-:i-th--t-fle- -B-lue- -Riv--e-r--,-

Channel roughness factors (Manning's "nl') used in the hydraullc
computations were chosen by engineering judgment and based on field
observations of the main channel and flood plain areas. Roughness
values for the main channel of t~e Blue River ranged from 0.035 to
0.050, and overbank roughness values ranged from 0.035 to 0.050 for all
floods. The roughness value for the main channels of Lehman Gulch,
Illinois Gulch, and Sawmill Gulch was 0.040, and overbank roughness
values from 0.040 to 0.100 for all floods.

The starting water-surface elevations for the Blue River were
calculated using the slope-area method. Starting water-surface
elevations for Lehman Gulch, Illinois Gulch, and Sawmill Gulch were
obtained from normal depth calculations.

Flood profiles were drawn showing computed water-surface elevations to
an accuracy of 0.5 foot for floods of the selected recurrence intervals
(Exhibit Ii.

The depths for the areas of shallow sheet flow were determined using
normal depth calculations.

The elevation for the shallow ponding area near Lehman Gulch '-'las
determined using culvert computations to estimate the inflo~l from the
Blue River.

The hydraulic analyses for this study were based on unobstructed flow.
The flood elevations shown on the profiles are, thus, considered valld
only if hydraulic structures remain unobstructed, operate prop~rly, and
do not fail.

All elevations are referenced to.the National Geodetic Vertical Datum
of 1929 (NGVD). Elevation reference marks used in the study are shown
on the maps. ERMs shown on the FIRM represent those used d1Jring the
preparation of this and previous Flood Insurance Studies. Th~
elevations associated with each ERM were obtained and/or de~Jeloped
during FIS production to establish vertical control for determination
of flood elevations and floodplain boundaries shown on the FI?M. Users
should be aware that these ERM elevations may have changed sifise ,:he
publication of this FIS. To obtain up-tO-date elevation information on
National Geodetic Survey (NGS) ERMs shown on this map, please contact
the Information Services Branch of the NGS at [phone], or visit
their website at www.nqs.noaa.'jsv. Map users should seek verifisaticn
of non-NGS ERM monument elevations when using these elevations for
construction or floodplain management purposes.

4.0 FLOOD PLAIN MANAGEMENT APPLICATIONS

A prime purp0se of the National Flood Insurance Program is to encG~ra?e S~a~e
and local governments to adopt sound flood plain management prsgra~s. Lac~
Flood Insurance Study, therefore, includes a flood boundary ma~ Qesi~r.eQ ~G
assist communities in developing sound flood plain management ~eas~~es.

The NFIP encourages State and lccal governments to adopt sound ~~GG~~:a~~
management programs. To assist in this endeavor, each FIS pro/iass :~G-year
floodplain data, which may include a combination of the follo~lng: ~v-, SO-,
100-, and SOO-year flood elevations; delineations of the lOO-yea~ ~~d :0C-
year floodplains; and lOa-year floodway. This information is pressn~ed ~..
the FIRM and in many components of the FIS, including Flood Profi:es,
Floodway Data tables and Summary of Stillwater Elevation tables. Users
should reference the data presented in the FIS as well as additional

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