FLOOD09594

• Designation Number: 63
• County: Adams
• County: Arapahoe
• County: Douglas
• Community: Denver Metro Region
• Stream Name: SJCD Basins 6200 North and South, 6100.5
• Basin: South Platte
• Title: Major Drainageway Planning - Volume I
• Date: 7/1/1976
• Designation Date: 11/17/1976
• Floodplain - Doc Type: Floodplain Report/Masterplan

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Chapter 5
FLOODING PROBLEMS AND SOLUTIONS

On the basis of the hydrology-hydraulics work discussed in
Chapter 4, flooding problems in the basins were defined for
the 2-year, 10-year and 100-year floods under existing channel
conditions. Flood problem areas were also identified from
local resident experiences.

Flood water level, flow velocity, depth of inundation and area
of flooding during a selected flood event were considered in
each reach of channel within each drainage basin. The flood
water levels along the channeLs from the hydrology-hydraulics
study were plotted on a topographic map with 2-foot contour
intervals and a scale of 1 inch = 100 feet to determine the
horizontal limits of flooding or flooding areas. This mapping
is shown on the plan-profile sheets in Volume II. The high
flood flow velocities in the main channel and flood plain, as
determined from the hydraulics analysis, were important indica-
tions of the erosion potential along the channel. Finally,
the inundation depth and flooding area were used to evaluate
the degree of damage in the flood benefit-cost anaLysis discussed
below.

Alternative solutions to possible future flooding problems
were investigated reach-by-reach for each basin, as discussed
at the end of this chapter. The types of solutions considered
included channel shaping with grass lining, instalLation of
drop structures and underground conduits, storage detention,
replacement of waterway crossings, and regulatory actions.

A benefit cost analysis was made of the alternative solutions
for each basin reach. The method and results of this analysis
are documented in the Phase A report. The solutions suggested
by CH2M HILL were reviewed and commented on by the Urban
Drainage and Flood Control District, Arapahoe County, and
Jefferson County. The final solutions presented in Chapter 2
were developed through the joint work of all these entities.

FLOODING PROBLEMS

The flooding problems associated with the 100-year design
flood are discussed below for Basin 6100 and the North Tributary
to Basin 6200 under existing channel conditions. The 2- and
10-year frequency flood drainage problems are described in
Chapter 5 of the Phase A report. The Kiewit Area and Direct
Flow Basin 6100.5 drainage problems are identified in Chapters 7
and 8.

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