R10 SUPPLEMENT 7709.56b-91-1
EFFECTIVE 5/6/91
6.05-6.24
Page 1 of 2
6.05 - Definitions.
9. Fish Passage Discharge. The average discharge of a stream during the
time that fish migration occurs. Different flow rates may be appropriate at
different times of the year for various fish species.
6.08 - References. Use FSH 2609.24, R10 Aquatic Habitat Management Handbook.
An exhaustive list of additional references on this topic is impractical. Use any
appropriate text or reference available. The following references limited to the
hydrology and hydraulics of streams in Alaska may be helpful:
1. Channels.
j. "Hydraulics Manual," State of Alaska, Department of Highways and
Public Facilities.
k. "Design Guide for Determination of Design Flow Hydraulics in SE
Alaska," USDA, Forest Service, Region 10
l. "Flood Frequency in Alaska," USGS Open File Report, 1970.
m. "A Proposed Streamflow Data Program in Alaska," USGS Open File
Report, 1970.
n. "Small Stream Flood Investigations in Alaska," USGS Basic Data
Report, 1973.
2. Culverts.
l. "Fish Versus Culverts, Some Considerations for Resource Managers,"
USDA, Forest Service, Region 4, Engineering Technical Report ETR 7700-5.
6.1 - HYDRAULIC DESIGN OF CHANNELS.
1. Fish Passage. Structures that retain a natural streambed (bridges, fiords,
and open bottom arches) normally do not create barriers to fish migration. Analyze
the waterway at fish passage discharge to ensure that water depth and flow velocity
will allow fish movement. Refer to section 6.26 for fish passage through culverts.
Except for temporary disturbance during periods of construction, bridge abutments,
intermediate piers, and other substructure elements, do not create barriers to fish
migration.
Where preservation or minimum disturbance of fish spawning or rearing habitat is
a critical factor in determining the length of a structure, analyze the waterway and
streambed associated with the fish passage discharge, not the maximum design
flood discharge.
R10 SUPPLEMENT 7709.56b-91-1
EFFECTIVE 5/6/91
6.05-6.24
Page 2 of 2
6.2 - HYDRAULIC DESIGN OF CULVERTS.
6.21 - Location and Installation.
12. Where it is necessary to place culverts on weak, compressible subgrades
(muskeg, peat), make appropriate settlement and bearing capacity analyses to
assure an acceptable final grade. Where excessive settlement is anticipated,
consider initial cambering of the culvert, or preloading of the road fill, prior to
installation of the pipe.