FLOOD01663

• County: Moffat
• Community: Craig, Moffat County
• Stream Name: Yampa River
• Title: Flood Hazard Information
• Date: 9/30/1987
• Prepared For: Craig, Moffat County
• Prepared By: US Army Corps of Engineers
• Floodplain - Doc Type: Floodplain Report/Masterplan

early July, Snowfall in Craig is not extreme];'
heavy with annual totals ranging from 33 t~
77 inches, General rain may occur over the
Yampa River Basin and convective type
cloudburst storms frequently occur in
summer.

Vegetation in the Yampa Riyer Basin
varies according to elevation, l\Iuch of the
valley area is devoted to production of hav,

NATURE OF FLOOD PROBLEMS

As noted, earlier, most of the annual
precipitation in the Yampa River Basin
occurs as snow and a deep snowpack accumu-
lates in high elevation areas. General rain-
storms covering large areas for extended
periods can occur over tributary drainage
areas from late spring through early fall, and
convective type cloudburst storms can be
expected frequently during the summer,

Major flooding in the Craig area has been
the result of rapidJ:,' melting snow, sometimes
augmented by general rain. during the period
from March through June, or pre'cipitated by
ice jams in late winter or early spring.
Snowmelt flooding is characterized by moder-
ate peak flows, large volume of runoff, long
duration, and marked diurnal fluctuation of
flow, Major flooding from general rain alone
is not known to have occurred in the Craig
area. but there is no reason to conclude that
ver;,' large floods resulting from general rain
are not possible in the Yampa River Basin,
Flooding from general rain is characterized
by high peak flows and moderate duration of
floodflows, Flooding from convective type
cloudburst storms is characterized by high
peak flows. short duration of flow, and small

FLOOD HISTORY

Historical references to floods on Fortifica-
tion Creek extend back to 1879, In that year. a
major flood inundated the entire area where
Craig is now located, A minor flood occurred
in 1896 and the first major flood since the
town was established occurred in April 1897.
Agricultural areas now part of the city. and
residential properties east of Fortification
Creek were severely damaged, Floodflows cut

and the nati\'e vegetation has been drastically
modified, In \'alley areas below 8000 feet not
used for a~p'iculture. vegetation is classified as
Northern Desert Shrub: that is, sagebrush,
rabbitbrush. and winterfat with an under-
story of various hardy grasses, Subalpine
Forest (aspen, lodgepole pine, Douglas and
other firs, and Englemen spruce) extends
from about 8000 feet to timberline.

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volume of runoff. Because cloudburst storms
are small in areal extent and short in
duration. they do not constitute a flood threat
on streams as large as the Yampa River,

Ice jams constitute a significant debris
problem, particularly along Fortification
Creek where. historically, ice jams at the
highway and railroad bridges have caused
substantial flood damage. However, channel
improvement work, largely accomplished on
an emergency basis in 1949, and improvement
of the bridges appear to have reduced the
occurrence of ice jams at these locations, Ice in
the Yampa River and the anabranch channel
that carries Fortification Creek flow to the
main stem can also create flood conditions in
Craig, A special significance of ice jams is
that the locations of their occurrence and their
impacts are indeterminate, Not only is it
impossible to predict where an ice jam will
occur, the area that could be affected by
overflow and the resultant depth of flooding
are also elusive. Flow that would otherwise be
non.damaging could, if associated with an ice
jam, flood areas ordinarily considered flood
free,

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new channels through rich agricultural lands
in and around the town, Irrigation ditches and
head gates were washed out, Seven major
flood events (1904. 11, 14, 16. 17.21, and 47)
and five less damaging flood events (1902, 06,
22, 23. and 26) have occurred on Fortification
Creek since the turn of the century, Six flood
events (1914, 17, 20, 21. 57, and 74) occurred
on the Yampa River during that period, Of

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these, the 1914, 1917. 1920. and 1957 floods
were caused by rapidly melting snow, Yampa
River snowmelt flows in 1974 were aug-
mented by rainfall, primarily on snowless
areas between Steamboat Springs and Craig,
The 1921 event was part of widespread rapid
snowmelt and general rains in many localities
of Colorado that year, Flood conditions on
Fortification Creek at that time also resulted
from snowmelt augmented bJ' rain and were
iIltensified by ice jams near the mouth of the
creek. The largest flood flow of record on
Fortification Creek. 841 cubic feet per second.
occurred in March 1947, Studies indicate.
however, that the actual flow may have been
considerably greater due to overbank flows
that were not measured. or to ice conditions
that caused inaccurate gage readings, Also. on
the basis of a high water mark (flood date
unknown), the Colorado Department of High-
ways computed a peak flow of 1,800 cubic feet
per second on Fortification Creek. In March
1971. a snowmelt flood on Cedar Mountain

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Figu re 2

Gulch inundated developing areas near the
Highway 40 culvert crossing. Floodwater
ponded to a depth of more than 6 feet on the
upstream side of the culvert, but did not flow
over the top of the road, On the basis of the
limited information available. it is estimated
that a peak flow between 200 and 300 cubic
feet per second occurred, 1\0 information on
flood events on Brotherton and Pine Ridge
Gulches is available,

Flooding from summer cloudburst type
storms has occurred in and around Craig. but
little definitive data on this type of flood event
are available, A small thunderstorm (.45
inches of rain in Zy, hours) on July 20, 1974
resulted in a measured flow of 102 cubic feet
per second on Cedar Mountain Gulch, More
than Z inches of rain in 1 hour. however, has
been recorded in the Craig area.

The following photographs and newspaper
articles (simulated from the originals) illus-
trate past flood events in and around Craig,

Figure 1

ForUfic-ation Creek floodwater in Craig, February 1904. Durtng the flood, residents had to flee their homes ~n the
middle of the night. The highway bridge was washed out and a locall;r constructed flood C<lntrolle....ee demolished.
(Corps of Engineers file photographs. actual source llnknown.)

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