FLOOD08630

• Designation Number: 82
• County: Weld
• Community: Unincorporated Weld County
• Stream Name: South Platte River
• Basin: South Platte
• Title: Special Flood Hazard Information Report - South Platte River, Volume III, Logan County - Sedgwick County, CO
• Date: 6/1/1977
• Designation Date: 11/1/1977
• Floodplain - Doc Type: Floodplain Report/Masterplan

dlschargeswereexperlencedalongportlonsofthemalnstetnOfthe
South Platte River for most of the month of May and on into June.
Hlghwater mark data f~ thIs flood In Logan and Sedgwick COunties
Is contained In table 4. The Flooded Areas, Plates .3 through 28,
show the area flooded by this flood.

Table 4
High Water Mark Data from the
South Piette RIver Flood of 1973 In
Logan and Sedgwick Counties, Colorado

PlateNa.

High Water
Mark No.

ElevatIon

Fut-ureFloods
Floods of the same or lerger magnitude as those that have occurred
could occur In the future. To determine the flood hazard posed by
the South Platte River In Logan and Sedgwick COunties, the IO-year,
50-year,IOO-year,and500-yearfloodswereanalyzed. Therroagnltudes
of these future floods are presented In thIs report In table 5 and In
the form of water surface profiles, stege-discharge curves, flood
width delineations, end the relationship of these future flOOds to
the flood of May-June 1973.

,
I

28
"
"
"
25
"
"
25
"
"
22
22
"
20
20
11
11
11
"
"
"
"
"
l3
"
9
8
8
8
,
,
'"
8
,,,
5
,
.
.
.
3
3

,
2
3
.
,
6
,
8
9
10
"
12
l3
"
"
"
11
18
19
20
2l
22
23
"
"
26
27
28
28
30
"
32
33
"
33
36
37
'"
39
"
"

3435.3
3456.9
3457.2
3464.6
3510.0
3521.2
3521.3
3521.4
3533.1
3550.5
3564.9
3594.8
3611.2
3657.0
3675.6
3690,7
3710.0
3719.2
3741.2
3755.3
3774.4
3793.6
31115.1
3649.6
3865.0
3910.4
3928.8
3930.6
3942.3
3946.8
3957.4
3969,0
3962.7
3990.2
4001.1
4007.0
4016.5
4034.6
4938.9
4052.6
4053.6

Frequency
The 500-year flood Is not the largest flood that can occur but
the probability of larger floods Is remote. As can be see... from
the g8gl"'9 records for the South Platte River, discharges smaller
tha~ either the loo-yoer or '.l00-year floods are much more common.
Large floods, however, can happen; thIs was clearly demonstrated
by the Denver area floods of 1965, the BlaCk HIlls, South Dakota
areaflQOdsofJune 1972,andtheJuly 1976 floods In the Big
Thomp~ CanVO'" near Loveland, Colorado.

Hazards of LarQe Floods
The extent of damaQe caused bv any flood deoends on the tooogra~hy
of the area flooded, depth and duration of flooding, velocity of flow,
rate of rise, developments on the flood plain, amount of debris in
thefloodwater,and lcecondltlons, if Ice Isaprobletn In that
p~rtlcular area. A 100-year flood or a 500-year flood on the South

"

12