FLOOD09310

• County: Adams
• Community: Adams County
• Stream Name: Todd Creek
• Basin: South Platte
• Title: Flood Hazard Area Delineation
• Date: 12/1/1985
• Prepared For: Adams County
• Prepared By: UDFCD
• Contract/PO #: &&
• Floodplain - Doc Type: Floodplain Report/Masterplan

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- FLOOD HISTORY -

there are few residents along Todd Creek, and essentially all are well
out of the 100-year floodplain. Past events likely occurred which
simply were not observed or recorded. Finally, numerous small
reservoi rs and stock ponds exi st along Todd Creek. Many of these
probab 1y have suffi ci ent storage avail abl e to attenuate the runoff
peaks.

Records of flooding along Todd Creek are lacking. Several sources of
information were contacted for flood history data, including the Adams
County Historical Society, the Division of Water Resources of the
State Engineer's Office and the Brighton Blade newspaper. The first
two sources have no records of Todd Creek floods. The newspaper
indicated some accounts may exist, but that specific dates are
required to locate these.

- HYDROLOGY AND HYDRAULIC DETERMINATIONS -

Four long time residents along Todd Creek were contacted for possible
eyewitness accounts or knowledge of flooding. One resident has lived
in the area since 1930. None of these residents ever witnessed a
major flood on Todd Creek. It was noted that several cloudbursts in
the past have generated one or two feet of depth at the lower end of
Todd Creek, but no roads or culverts were washed out. No specific
dates were recalled on these events.

Hydrologic Analysis

The best account of a major flood on Todd Creek was passed on to one
resident by his father. The breached dam embankment just upstream of
the Riverda1e Road crossing was known as D.J. Fort Reservoir back in
the 1920's. A flood occurred on Todd Creek in the late 1920's which
overtopped the dam and eventually washed out the embankment near the
right abutment. This was the second time this dam had been breached,
although the cause and date of the first breach were not known. The
owner elected not to repair this second breach.

Hydrologic analysis of the Todd Creek drainage basin was performed to
est imate peak di scharges and flood hydrographs at selected poi nts
along the study reaches. Flood di scharges were determi ned for the
10-, 50- and 100-year rainfall events assuming future developed basin
conditions. Table I shows the peak flow rates estimated for hydraulic
mOdeling.

There are several reasons that notable flooding events have not been
recorded on Todd Creek. The entire drainage basin is largely
undeveloped. Only one small subdivision is present in the basin, with
the remainder of land being agricultural. Cultivated fields with very
little impervious area generate far less runoff than typical urban
development. Another reason for the lack of flood records is that

The hydrologic analysis for the Todd Creek drainage basin involved
dividing the basin into fourteen sub-basins and utilizing the Colorado
Urban Hydrograph Procedure (CUHP) to determine runoff hydrographs from
each sub-basi n. The hydrographs were combi ned and routed through
downstream channels using the EPA Storm Water Management Model (SWMM),
as modified by the Missouri River Division of the U.S. Army Corps of
Engi neers and adapted for use on personal computers by the UDFCD.
Several i rri gation and stock pond reservoi rs currently exist within
the basi n. Past experi ence of the UDFCD has shown these reservoi rs
cannot be relied upon to remain in place to provide attenuation of the
flood peaks. Therefore, at the request of the UDFCD, the effects of
the existing reservoirs were not incorporated into the hydrology
modeling. The resulting flood hydrographs were used to select the

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