FLOOD02337

• County: Statewide
• Community: State
• Stream Name: South Platte River
• Basin: South Platte
• Title: Geomorphic Assessment at Surveyed Cross-sections South Platte River
• Date: 6/1/1996
• Prepared For: UDFCD
• Prepared By: Michael Stevens
• Floodplain - Doc Type: Floodplain Report/Masterplan

Cross Section 7

Station 259+60 At 136th Ave. (Extended)

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East Bank: Slight erosion oflO ft in 10 years. Bank is gravel with a 2-ft topping of fine fill.
At the base, there are some dumped stones for protection. There is a sprig of
grass on the bank; the floodplain is prairie.

West Bank: Stable, far from the main current. Materials are sandy silt, vertical for the top
2 ft, then sloping to gravel with weeds at the base. Immediately downstream,
dumped concrete rubble protects the bank.

River Bed: Main channel is stable, braided, and on the east side. The bed is gravel with
some Urban Veneer. The wide bed ofsand, gravel, and small cobbles between
the main channel and the overflow channel at the west bank was weeds with.a
few cottonwood seedlings in 1986 (Spot Photo 11). There were some
cottonwood snags lying about Now, one cannot seen through the cottonwoods,
willows, and grasses from the channel to the west bank (Spot Photo 12). The
river is building up this area.

Cross Section 8

Station 280+00 S. of 136th Ave. (Extended)

East Bank: Stable at this time, with new deposits at its base, but had eroded 20 ft between
1986 and 1988. Materials are overburden, gravel, and concrete rubble. Lower
level has grasses and willow seedlings; upper level is grass.

West Bank: Stable with grass, weeds, and bare spots. This section of bank is protected by
a groin of large stones built out normal to the bank upstream from the cross
section. The bank is mostly clay with a few stones at the bottom.

River Bed: Possibly about one foot of degradation in the last 10 years. On the west side,
the low-flow channel is gravel. The bars are sand and gravel. The only
vegetation on the bed is a cottonwood with a skirt of willows and weeds in the
center of the river, possibly a remnant of the old floodplain now destroyed. The
reach is straight Now, there is a grade-control structure downstream.

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