FLOOD10331

• County: Weld
• Community: Wattenberg
• Stream Name: South Platte River
• Title: Flood Hazard Mitigation Plan, Wattenberg, Weld County, Colorado
• Date: 8/1/1996
• Prepared For: Wattenberg
• Prepared By: Kistner and Associates
• Floodplain - Doc Type: Flood Mitigation/Flood Warning/Watershed Restoration

W A lTENBERG, COLORADO FLOOD HAZARD MmGA nON PLAN

AUGUST 1996

Damage Assessment

As statewide flood damage cost exceeded
$38 million, Governor Romer allocated $2.9
million to public -works projects throughout
Colorado. In late August, following the
damage survey, state officials allocated
$100,000 to Weld County Commissioners
for road and bridge repairs. With a total
repair bill of more than $1,000,000, the state
funds only minimally funded the projects.

Following the Flooding of 1995 the
Community of Wattenberg conducted
meetings to determine a mitigation program
for their area to alleviate potential future
flooding. Although, no significant damage
was reported in Wattenberg in the Flood of
1995, the community feels that next time it
could be their turn.

RIVER AND
CHARACTERISTICS

FLOOD

South Platte Basin and Stream
Characteristics

Wattenberg is directly affected by the South
Platte River just east of the community. The
South Platte River flows in a general
northernly direction from the Adams-Weld
County line to apporximately Miliken,
Colorado where it turns and flows in a
northeasternly direction. Throughout the
reach in Wattenberg and Weld County area
the South Platte Rover flows in a relatively
well defined channel. This channel is
typically braided and is situated in a broad
shallow valley ranging in width from about
3,000 feet to about 9,000 feet and is flanked
by rolling plains. The streambed slope of
the South Platte River in Weld County is

relatively uniform, slowly transitioning from
about 9 feet per mile in the upstream reaches
to about 6 feet per mile downstream.

The drainage area of the South Platte varies
considerably from the Adams-Weld-Morgan
County line due mainly to the number of
relatively large tributaries draining the
eastern slope of the Rocky Mountains (See
Figure 4). At Ft. Lupton, the nearest gauge
location to Wattenberg, the drainage area is
5,010 square miles.

Flooding along the South Platte River in
Wattenberg and surrounding areas normally
occurs from May through August, with the
most frequent flooding occurring during
June. Serious floods however, have
occurred from February through December.
Though the South Platte River flooding is
the focal point concerning potential flood
damage, flood damage has occurred due to
small culvert sizing, and the silting up of
local drainage channels.

What is a 100 year Flood Event?

The science of predicting the effect of floods
on lives and property falls largely to
hydrologists. They estimate future floods by
studying the past behavior of a stream.
Floods are categorized according to their
return interval-IO-, 50-, 100-, and 500 year
floods. Each flood interval is related to
percent chance that a flood may actually
occur within a given year (See Figure 5).

This has caused considerable confusion at
times: a 100-year flood does not happen
with absolute regularity every 100 years.
Rather, a 100-year flood may occur at any
time within a given year. Colorado State
law, however, requires that the 100-year
floodplain be used for land use regulations

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