FLOOD09450

• County: Logan
• Community: Sterling
• Stream Name: Sand Creek, Pawnee Creek overflow
• Basin: South Platte
• Title: Summary Report Floodplain Information
• Date: 1/1/1987
• Prepared For: Sterling
• Prepared By: Charles F. Leaf, PE
• Floodplain - Doc Type: Floodplain Report/Masterplan

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Tneresults in the comprehen,ive report reflect infOrIfUltion fro mall
the above sources. However, for purposes of floodp 1 ai n manage~lent, the
detailed results herein will supersede information previously developed by
Mr. Bennett and Corps of Engineers for Pawnee Creek only. Corpsinformatlon
on the South Platte River remains unchdnged. The flood plain information
developed in the comprehensive report and sUr.J11arized here for 5 and Creek
is new work.

Mapping and Surveying
Topographic mapping of the stu~ area w~s pre~ared using photogrammetric
methods by Blevins Mapping Co., Denver. Colorado. 1975 and landmark Mapping.
lakewood, Colorado, 1981. Map scale is 1" = 200' with two~foot contour
intervals.
Field surveys were completed with assistance from the City Engineer to
supp1e~~nt the topographic mapping as required. Spot elevations were taken
at locations where elevations were critical to the hydraulic computations.
In general, field information was consistent with the topographic mapping.
Field surveys provided additional physical details necessary for computer
modeling. These included hydraulic roughness coefficients, channel dimensions.
ill,dan "ccountinq of rlrainage structures and their state of repai r.
Major drainage basins were determined from U.S. Geological Survey 1:24,000
scalellldps. Subcatchmentswithinthelorgerdraindgeareaswerealso
delineated based on these maps.
Permanent reference monuments were established in the field based on
U.S. Coast and GeOdetic Survey mean sea level datum to aid in transferring
data in this report to actual qround conditions. A su~ry of these monuments
is contained in Table 8. Elevations of vertical control points for the
aerial photography and mapping are on file with the Director of Public Works.

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II. FlOODIlISTORY

Pawnee and Sand Creek have caused serious flooding in the Sterling
area several times in the past 65 years. Major floods occurred in 1921,
1935.l965,and1963. Each of these floods resulted from intense
rainfall. The 1921. 1935. and 1965eventswereproducedby1arge*sca1e
general storms; whereas the 1968 event on Sand Creek occurred as the
result of more local intense rainfall west of the city. Iladian (1982)
has presented a comprehensive history of flooding in the Ster1in9 area.
The followin9 flood accounts abstracted from the U.S. Army (1978)
flood information report highlight major flood events which have occurred
along theSoutl1 Platte River in and adjacent to the Sterling area. They
are presented here to give some insight as to the source and magnit ude
of flood waters from ~wnee Creek. Sand Creek, and the South Platte River
affecting the Sterling Area.
1844 ~~ Flood waters purportedly covered the bottomlands in the
Denver vicinity from bluff to bluff.
M~.z_:_J)lne 1864 -- Three separate floods caused by he.lvy rains
over snow occurred during May and June on the ~outh Platte
River. Flooding occurred in late May and again in early
tomid-Junc. The South Platte River flood was augmented
downstream from Denver by tributary inflow from both the
mountain and plains tributaries.
~876 -- The flood of late May 1876 resulted from rainfall on
snowpacL It was reputed to have been the highest flood
since 1864 in at least the Denver area.
June 1894 -- Heavy rainfall over the Front Range of the Rocky
Mountains caused flooding on the South Platte River in
late May ancl early June. Floodwaterspurported1ycove"ed
hundreds of acres in the Brush vicinity. Old timers said
the South Platte River was "fullytwomi1eswide". The
FortMorganTimcsofJunc8,1894statedtnat"for24hours
on 2 June. the flood tOUChed the caps on the tops of the

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