Alaska Department of Fish and Game
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Bridge and Culvert - Construction and Maintenance
Bridge or culvert installation and maintenance activities in fish-bearing waterbodies require a Fish Habitat Permit.
The Fish Habitat Permit Application (PDF 69 kB), when completed, will provide the basic information required to evaluate the potential effects to fish and fish habitat for the desired installation. Adequate information regarding the stream discharge past the site at normal and flood flows, and the ability of the proposed structure to carry these flows, is essential to the successful installation and operation of a bridge or culvert.
Bridges that span the floodplain, even with piers within the active channel, offer the best solution for crossing streams. They generally require less instream maintenance over time than do culverts, provide less restriction to flow than do culverts, maintain transport of bedload, and maintain stream structure and flow characteristics better than do culverts. These characteristics also maintain conditions necessary for the passage of fish through the site. Bridges also minimize the disturbance to fish habitat.
Culverts, when properly designed, sized, and installed, provide a cost effective solution for crossing small streams. Factors that must be considered when installing culverts in streams include provisions to maintain transport of stream sediments past the crossing, aufeis formation (glaciation) in winter, flood flow conveyance, and the potential for scouring and scour pool formation at the culvert.
FISHPASS provides the analytical capabilities to identify a culvert or parallel culverts that will pass weak swimming fish safely. The design procedure utilizes hydraulic formulas for profile drag, non-Archimedean buoyant forces, and virtual mass force to quantify the hydraulic conditions within a culvert that weak swimming fish can sustain without exhaustion.