FLOOD05049

• County: Larimer
• Community: Larimer County
• Stream Name: Cooper Slough
• Basin: South Platte
• Title: Cooper Slough within Larimer County
• Date: 11/1/1993
• Prepared For: Larimer County
• Prepared By: Love & Associates, Inc.
• Floodplain - Doc Type: Floodplain Report/Masterplan

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· Just south of the railroad on the right overbank, there ~lre two 1 OO-YE~ar floodplain
lines presented, A check needs to be done by Love & Associates and only one
line shown,

· Sase flood elevations need to be carried out throu';jh &Ie zone of shallow
flooding.

· Final report needs to have an hydrologic table and/or schematic that: explains,
preferably section by section, the discharges, addition IJr loss of discharge and
where these discharges come from or go.

· A recent aerial ph<Jto was obtained of the Clverflow areal and additional buildings
from this mapping were blocked out in the model. The,se buildings will be put on
the final mapping and the aerial photo refemnced in the! report.

· The Overflow model has a section that comes before S~ictjOn A that lies
completely in the 130xelder Creek floodplain and thl3refore has a known water
surface elevation. Section A through F have a split flow line that runs along the
eastern edge of L~Lke Canal. Spills over this split flow line travel down the low
ground between Lake and the Cache La Poudre Cunals eventually joining with
our first section at the Soxelder Creek floodplain. Most of the flow ends up in the
basin between the two canals. No losses were modeled leaving over the top of
Cache La Poudre Canal. This analysis is similar to the analysis performed by
Simons and Li for the Soxelder Creek Study.

· In all cases, Lake Canal and Cache La Poudre Canal am assumed to be flowing
full so that top of bank to top of bank is the channel invl9rt.

· The area marked as "shallow flooding" between Lake Calnal and the Cache La
Poudre Canals is tiJ be changed to read "approximate 1 DO-year floodplain".

· Field inspection indicates that Lake Canal/Cooper Slough will overtop the canal
bridge at Sherry Dlive, Thus, the bridge will act as a wek Sherry Drive receives
only a small amount of flow down the road. The remainder of the flow continues
along a similar flow path to Lake Canal.

.. The Overflow and ~;herry Drive floodplains do not <Xlineide.

.. A table will be provided to cross reference section IEltters with section numbers.

o A letter will be sent to the City and County offices dE~taiJing the debris blockage
assumptions at each crossing and requesting acceptance of these assumptions.

.. At Vine Drive the ct. !vert was rated and water surfa~! elevations balanced on
either side of the road.