FLOOD05425

• County: Delta
• Community: Delta
• Stream Name: Gunnison, Uncompahgre River
• Basin: Gunnison
• Title: City of Delta Confluence Park Project
• Date: 10/1/1989
• Prepared For: Delta
• Prepared By: US Army Corps of Engineers
• Floodplain - Doc Type: Floodplain Report/Masterplan

This launc..1 facility would require excavation of the
riverbank from about elevation 4,928 to about elevation
4,923, two feet below the 10-year flood elevation. The
bottom of the river channel would not be disturbed. The
length of the launch would be determined during final
design. Assumiag about: a 10 percent grade, the length for
approach and egress would be about 100 feet: total. The
width of the egress and launch area should allow for
comfortable pas,sage of two motorized vehicles.
Stabilization of the riverbank at each end of the launch
facility as well as along cut slopes should be considered.
Bank stabilization techniques are covered in section 12 of
this study. Th~ surface of the travel way E:hould also be
stabilized. As,suming about a 100-foot-Iong launch and
another 100 feet for ingress and egress, it is estimated
that about 1,500 to 2,000 cubic yards of bank excavation may
be required, an.j about 600 cubic yards of riprap
stabilization may be required. Al1:ernative stabilization
methods may als'J be considered. Due to the erosive nature
of the soil, ri.;Jrap stabilization would also require a
filter layer uniierneath it. Stabilizing mat:erial assumes a
2-foot layer of riprap on a 1 vertical to 2 horizontal slope
for a 300-foot length; it may be modified or eliminated to a
large extent if greater maintenance and risk is acceptable.
Typical details of other launch facilit:y features that may
be desirable to incorporate are shown on a set of blueprints
provided to the City of Delta, titled Elkhorn Hegional Park,
Yolo County, California, by the Sacramento District, Corps
of Engineers.

Lagoon Type Lau:1ch:

The lagoon -type launch facility would be si 1:ed at the
confluence of t:.1e drain and the river, near station 36700.
The access to t:.1e river would be provided by launching the
craft in a stil.L lagoon, isolated from .the river, then
navigating the Graft through an opening to the river. The
approach to the launch for upstream craft would be limited
due to the need to limit the lagoon opening for hydraulic
considerations. In addition, the river hydraulics would
need to be modi "ied to provide a deeper pool of water at the
lagoon entrance: currently, during lower flows a riffle
exists at the location of the proposed lagoon entrance. The
river hydraulic:; could be altered with either a small drop
structure downs1:ream of the lagoon entrance or by
channelization. Both methods carry risk of failure and need
for continual modification. The lagoon dep.th would need to
include a reservoir for sedimentation in addition to
matching the ri'rer channel depth at the lagoon opening.
Although this s:"te is located closer to the parking area
than the previollsly discussed site, access and egress by
motorized vehic:,es may be more problematic due to the
configuration 0:: this type of launch and due to the presence
of the existinCf drain which must be incorporated into the
access design.

21