WSP02645

• File Number: 5700
• Description: Flood Protection Section - Flood Control Projects
• State: CO
• Basin: Statewide
• Date: 7/1/1985
• Author: BRW Inc - WRC Engine
• Title: Feasibility Study for the Cherry Creek Basin Drainageway - for Cherry Creek Basin TAC and Parker-Jordan Metropolitan District
• Water Supply Pro - Doc Type: Report/Study

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001017

"A" - Meander Belt (Figure-7): This alternative is the "status quo" or
"do nothing" alternative. The channel is allowed to move within its historic
meander belt as defined by the aerial photographs, soils information, and field
observations (see Figure-3). This alternative is the least costly but would
require adjustment to the floodway area, since the channel could move outside
the floodway in certain areas. which essentially relocates the floodway.

"B" - Stabilize Existing Alignment (Figure-8): This alternative uses
revetment (i .e.. riprap) to protect and stabilize the critical or outside banks
of the channel. Since the channel is unstable in certain areas, a substantial
or heavy revetment would be required to maintain the existing alignment. This
alternative allows full use of the 1/2-foot floodway.

"C" Construct Stable Alignment (Figure 9): This alternative
reconstructs a channel with more stable geometry (i .e., degree of curvature,
radius, and distance between curves). The advantage of this approach is that a
lesser degree of protection (revetment) is required for the outside bends and
the channel would have better flood conveyance. The cost of the excavation
work would determine if this alternative would be less costly then alternative
"B" . A di sadvantage of thi s a I ternat i ve is the steeper bed profi I e, whi ch
would have some offsite effects of sediment deposition and onsite erosion.

2. Increased Land Utilization

The alternatives developed to increase the land utilization are as
follows:

"0" - Flood Fringe Filling (I/2-foot floodway): This alternative uses the
typical floodplain management approach of leaving a f100dway (the channel and
the floodplain area required for the safe passage of the IOO-year flood) and
reclaiming the fringe of the floodplain by filling with earth. The Arapahoe
county floodplain regulations require that the filling of the floodplain
fringe does not increase the IOO-year water surface by more than 1/2-foot.
This alternative has relatively low cost, but does not reclaim a substantial
amount of property, relative to other alternatives. The area reclaimed with
this approach is presented in Table-I.

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