FLOOD08498

• Designation Number: 386
• County: Sedgwick
• Community: Sedgwick
• Basin: South Platte
• Title: Flood Insurance Study - Sedgwick, CO, Sedgwick County
• Date: 8/1/1989
• Designation Date: 11/1/1994
• Floodplain - Doc Type: Floodplain Report/Masterplan

2.0 AREA STUDIED

2.1 Scope of Study

This Flood Insurance Study
Town of Sedgwick, Colorado.
Vicinity Map (Figure 1).

covers the incorporated area of
The area of study is shown on

the
the

The area studied by detailed methods was selected based upon the
extent and validity of available existing hydrologic and
hydraulic data.

Flooding from the South Platte River was studied by detailed
methods within the Town of Sedgwick.

2.2 Community Description

The Town of Sedgwick in west-central Sedgwick County, Colorado,
is located approximately 5 miles south of the Nebraska state
boundary and approximately 24 miles west of the western Nebraska
state boundary. According to 1980 census data, Sedgwick has a
population of 258, an increase of approximately 20 percent from
the 1970 census (Reference 1). The average annual precipitation
is approximately 17 inches. The topography of Sedgwick is
generally a mildly sloping terrain within the town and rolling
hills to the north and south surrounding the town.

2.3 Principal Flood Problems

Flooding along the South Platte River in the Town of Sedgwick
normally occurs from March through September with the most
frequent flooding occurring during June. Annual peak flood
discharges, however, have been recorded throughout the year.
Floods in the Town of Sedgwick normally Occur under non-ice
affected conditions. Ice jams, however, are poss i ble, although
historically their frequency of occurrence is rare.

Floodwaters on the South Platte River in the Town of Sedgwick can
result from intense localized rainfall or general rains, either
of which may be augmented by snowmel t. The intense rainstorm
floods result from intense rainfall over areas of relatively
small areal extent. These storms can produce extremely rapid
concentrations of flood waters and ensuant rapid rises in stream
levels. Because there is little warning time prior to streams
attaining flood stages, this type of storm can produce floods
which are extremely hazardous. This type of flood produces high
peak flood discharge on tributaries in the general vicinity of
the rainstorm. The flood discharge, however, attenuates rapidly
on the South Platte River downstream from the contributing
tributaries due to valley storage of the floodwater.

The general rainstorm floods result from rainfall over areas of
large areal extent. Rainfall from this type of storm can occur
for a period of several days. Because of this time duration, the

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