FLOOD08996

• County: Weld
• Community: Weld County
• Stream Name: South Platte River
• Basin: South Platte
• Title: Special Flood Hazard Info Report Volume 1
• Date: 4/1/1977
• Prepared For: Weld County
• Prepared By: US Army Corps of Engineers
• Floodplain - Doc Type: Floodplain Report/Masterplan

ho~ever, attenuates rapidly on the South Platte River downstream
from the contributing trIbutaries due to valley storage of the
floodwater,
Thegenerlll ralnstormfloodsresultfromralnfalloverllreas
at large areal extent. Rainfall from this type of storm may occur
over several days, Because of this time duration, the affected
streams rise relatively slow; sometimes over a period of several
days. The duration of the flood period also Is sometImes of con-
siderable length. Because of the large areal extent of rainfall,
more tributaries contribute to the peak discharge on the South
Platte River. This results In IncreasIng discharge progressively
downstream over a consIderable length of the South Platte River.
However, downstream from the contrIbutIng tributaries, the effects
of valley storage cause flood discharge attenuation.
Erosive effects can be considerable in the event of any flood
regardless of Its origin. Floods resulting from Intense rainstorms
typically create severe erosion damages in 1l Short periOd of time
due to tho relatively large peak dIscharge and high velocity of
the floodwater. ErOSion damages from snowmelt or general rainstorm
floods usually result from prolonged exposure of the floodwater
because of the long duration typical of these floods.
Intense rainstorm floods as well as general raInstorm floods
have occurred on the South Platte River. Examples of the Intense
storms are the 1965 events on Plum Creek and BljouCreekand the
1976 ~ent on the Rig Thomrson River. Ex~rnples of the I~rg"r more
gonorallzed storms aro the 1969 ~nd 1973 events producing flooding
on the South Platte River.

Past Flood~
Several floodS have occurred along the South Platte River in
Morgan and Washington Counties. Tables 2 through 4 IndIcate ye~rly
p9~k discharges experienCed ~t the three stre~m gaging stations oper-
~ted in th" past by th" \), S. Goological Survey In Morgan County.

,

South

Table 2
Annual Peak Discharge for the l/2/
Platte River near Woldona, Colorado-

"", Olschar!1e
<C.f.s.)
" ,,' 1957 14,200
" .., 1958 8,840
6 JyO 1961 7,740
19 JyO 1955 18,800
" JyO 1969 17,000
14 JyO 1970 14,000
" 'pc 1971 7,400
e 'OV 1973 26,800

11

From U.S.G.S. Gaging Station located 400 feet downstream from
Colorado State Highway 144 ~nd 2.8 miles southeast of Weldona.

y

Only those years having a peak discharge of 5,000 c.l.s, or
greater are indicated.

For period of gaging record, see table I.

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