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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The existing topography in this area also creates
problems. A flow split will occur at Riverdale Road,
in which some flow will travel over the Brighton Ditch
embankment di rect1y into the South Pl atte Ri ver, and
the remainder will travel northward along the west side
of Riverdale Road. This confluence area has been
analyzed two ways. The first method assumes all Todd
Creek flow is conveyed di rect 1y into the South Pl atte
River. The second method identifies that portion of
the flow split traveling north along the west side of
Riverda1e Road. Floodplain limits for both methods
are shown to the extent of the mappi ng 1 imi ts. Refer
to Sheets 13 and 25.

1. A flow split may occur at the upper study limit. Field
investigations of the area past the mapping limits
indicate that floodwaters reaching the northwest corner
of the East 160th Avenue and Yosemite Street
intersection will likely split. A portion of the flow
would travel over the intersection and head
southeastward in the hi stori c drai nage pattern. The
remainder of the flow would travel east along the north
si de of East 160th Avenue about 900 feet to the low
point in the road. At this point, floodwaters would
cross the road through a culvert and by overtopping and
travel southward in a distinct swa1e. The flows would
combine in an irrigation reservoir about 1500 feet
downstream of the original flow split. Refer to Sheet
14.

Tributary 1: The study reach for Tributary 1 begins at its confluence
with the main stem (Cross Section No. 1.10) and ends just below the
intersection of East 160th Avenue and Yosemite Street (Cross Section
No. 1.25). Floodplain limits and the water surface profile for this
reach are shown on Sheets 9 and 14.

2. The small online irrigation reservoir may be subject to
severe spillway erosion. The embankment does not
overtop, and because all flow is confined to the narrow
spillway, the water surface rises about three feet
above that level shown on the date of survey. No
residential flooding occurs as a result of this rise,
however. Refer to Sheet 14.

The single stream crossing in this reach consists of a dirt access
road near the upstream study limit. The narrow floodplain is
generally well confined within the existing channel. The stream slope
is generally steep (about 2%) and will result in high velocities and
erosion during flood flows. Development along Tributary 1 is almost
completely agricultural. A few oil and gas well installations are
present, but located out of the fl oodp 1 ai n. A small rural farmi ng
cluster is located near the upper study limit.

Tributary 2: The study reach for Tributary 2 begins at it confluence
with the main stem (Cross Section No. 2.10) and ends immediately
upstream of Monaco Street (Cross Section No. 2.24). Floodplain limits
and the water surface profile for this reach are shown on Sheets 6,
15, and 16.

Two specific problem areas along Tributary 1 are discussed following:

Stream crossings in this reach include Monaco Street and Quebec
Street. The floodplain for this reach is generally well confined to
the channel when not i nfl uenced by small reservoi rs or streets. The

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