FLOOD04566

• County: Boulder
• Community: Boulder
• Stream Name: Gregory, Bear Can, Bluebell Can Creeks, Viele Chan
• Basin: South Platte
• Title: Major Drainageway Planning Volume 1, Part C
• Date: 9/1/1970
• Prepared For: Boulder County
• Prepared By: CWCB
• Floodplain - Doc Type: Floodplain Report/Masterplan

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b. On steep s lopes, velocity may be controlled by artiffcfally
created head losses due to manholes and/or bends.

c. When it is desirable to achieve a velocity abov.e 25 fps, the
lower portion of the conduit shall be armored with steel sheet,
rai Is, etc.

d. The hydraulic grade line shall be, maintained below the ground
surface.

7. Irriqatlon Ditches. All irrigation ditches and laterals will be
provided for, though laterals will not be shown on master plans.
Use on-grade flumes where feasible to reduce silt and maintenance
problems. Capacity of crossings will be limited to cause storm
runoff in ditches to enter waterways. Irrigation ditch crossings
wi 11 be designed to obviate picking up of overflow from waterways.

8. Underdrains. The use of underdrains will be limited to those reaches
where trickle channels would conflict with sanitary sewers. Sedi-
mentation problems will be considered on all underdrains to reduce
future maintenance problems. Perforated underdrains will be utilized
to control groundwater as needed.

9. Drops and Checks. Channel drops will be used as needed to control
the hydraulic grade line and velocity to within reasonable slopes
and limIts. Drops will be of concrete, riprap, or riprap in gabions,
be of pleasing appearance, have gravel filter blankets under the rock
to control undercutting, and be properly notched for the trickle channel.
Design must account for potential vandalism. Checks wIll be end pro-
tected to eliminate side cutting.

10. Enerqy Dissipators. These will usually consist of natural rock Impact
blocks with suitable riprap or gabion protected bottom and side slopes.
Design will account for potential vandalism.

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11. Flood Plain Definition. Natural waterways having adequate capacity
for the design runoff will be flood plain zoned to protect their
capacity from encroachment.

12. Detention Storaqe. Storage will be utilized wherever practical to
reduce peak flow rates.

13. Boulder Creek and South Boulder Creek. Design backwater computations
from Boulder Creek assuming the 25-year flood in Boulder Creek of 3300
cfs and In South Boulder Creek of 2200 cfs.

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14. Sedimentation. Collect debris and sediment in suitable basins in all
creeks except David's Draw. The design criteria anticipate the regular
removal of sediment and debris from the basins for use as construction
materials and for solid waste disposal cover material.