FLOOD06449

• County: Delta
• County: Montrose
• Community: Collbran, Cedaredge, Paonia
• Stream Name: Buzzard, Plateau, Grove Creeks
• Basin: Gunnison
• Title: Hydrology Report Unincorporated Areas of Delta and Montrose Counties
• Date: 4/1/1979
• Prepared For: FIA
• Prepared By: Meuer Serafini & Meuer, Inc.
• Floodplain - Doc Type: Floodplain Report/Masterplan

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HYDROLOGY:
Montrose, Delta and Mesa Counties, Colorado

Gunnison River (See Figure 1). The streams on both sides of the
divide were grouped together for the regional hydrologic analysis
because the range of precipitation and elevation is similar on both
sides of the divide.

The topography and precipitation are similar through the region,
although the vegetation is sparser in the Plateau Creek Basin. The
elevation ranges from approximately 11,200 feet above mean sea
level on the Grand Mesa to approximately 5,000 feet around Orchard
City at the southwest corner of Region 1. Most of the area is
mountainous and steep, except in the southern part around Cedaredge
and Orchard City which consists of a more gently sloping plateau.

Region II consists of the wat'ershed for the San Miguel River in
southwestern Colorado. Region II also contains part of the
Gunnison River which has a similar topography and climate. The
highest elevation is about 14,000 feet above mean sea level on the
Continental Divide, and the lowest is about 5,000 feet at Uravan,
Colorado. The topography is characterized by mountainous terrain
and steeply sloped valleys. The vegetation at the lower elevations
is very sparse and scrubby, consisting mainly of sagebrush and
pinon. Aspen and pine forests are common at the higher elevations.

3. Climate and Flood Characteristics - The climate in each of the
regions is arid to semi-arid at the lower elevations. The precipi-
tation is higher at the higher elevations and consists mainly of
snowfall. Thunder showers develop during the time from May to
early October and are usually of high intensity and short duration.

In Region I major flows are produced from early May to late June
from snowmelt runoff. They feature moderate peaks, large volumes
and long flow durations. Although precipitation may raise the peak
flows somewhat, the effect is usually not large.

During the summer the rainstorms are usually of short duration but
may cause very high peaks above the decreased snowmelt base;
however, these peaks are often still lower than the snowmelt peaks.
Major floods caused by thunderstorms are usually in watersheds
where most of the area is below 8,000 feet.

Heavy flows were experienced in mid-May of 1941 and in early June
1957 throughout Region I. Surface Creek at Cedar edge sustained a
flow of approximately 1200 cfs on May 13, 1941, which ranks
statistically between the 100- and 500-year frequency flows.
Across the Grand Mesa divide heavy flows also occurred in 1941. The
highest recorded flow for Plateau Creek near Collbran occurred on
May 27, 1922. This flow was 3,080 cfs, which (for that station
alone) has a return frequency of approximately 95 years. No
historic outliers were recorded for the streams used.

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