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

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foot. Ten other cross sections spread about the monitored South Platte experienced
degradation since 1986, the most being 2.7 feet.

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Aggradation has appeared over a period of nine years at four cross sections, the most
being two feet. Three of these are between 104th Avenue and Interstate 270, a reach
affected by in-river construction during the 1995 spring flood season. A significant
amount of erosion occurred upstream from 88th Avenue because the construction project
was flooded for a period exceeding three months.

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The Engineered reach of river has functioned well, experiencing no apparent damage
from the prolonged spring runoff in 1995. Vegetation is appearing in the riprapped
banks and on portions of the bed.

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In 1996, there are only nine eroding banks in a total of 106 banks being monitored at the
53 cross sections. Six of these are in the north Rural reach between 104th Avenue and
Brighton and three in the north Suburban reach between Interstate 270 and 104th
Avenue.

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The most serious bank erosion is in between monitored cross sections in the north Rural
reach and can be seen on aerial photographs taken in the winter of 1995-96.

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Some of the areas of the northern Rural river which were bars with a few seedlings of
cottonwoods and willows in 1986 are now densely vegetated with groves of young
riparian forest.

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During the winter months ofthe last year, a large portion of the gravel and cobble bed
of low-flow channel of the South Platte River in the Denver metropolitan area was
covered with a growth of algae and sometimes a deposit of organic solids. Spring runoff
can remove most of this Urban Veneer.

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The Metro Wastewater Reclamation District is undertaking improvements to the South
Platte River between 88th and 74th Avenues. The purpose is to aerate the river water
which has passed through its wastewater treatment plant upstream.

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In general, the river corridor is much more pleasant now than nine years ago, and much
more accessible. With the exception of a small segment between 50th Avenue and
Franklin Street, there is a bike path running continuously from a mile north of 88th
Avenue to Highway C-470 near the Chatfield Dam. In places, the path is on both sides
of the river. Parks, rest areas, and planted trees are more numerous.

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A review ofthe 1985 Major Drainageway Planning, South Platte River Report ( Master
Plan) is in order and changes should be made to accommodate the existing infrastructure
as well as the needs of the river. The findings on river morphology changes presented
in this report provide part of the much needed data for the review. The ideals set forth
for river morphology in 1983 are still considered valid, but changes may be in order to
create a river with different environmental qualities. Also, the review should reevaluate
the effect that grade-control structures have had on the river's vertical and horizontal

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