Research in the area of culvert hydraulics has centered on concrete box culverts and circular corrugated metal pipe culverts. The hydraulic analyses of these culvert types have been well defined for conventional installations, but not for environmentally sensitive and nontraditional culverts. It is desirable to design and construct some culvert crossings to minimize their impact on the natural environment. Culverts are now being designed to maintain natural velocities and minimize turbulence to allow migratory species to pass through the culvert barrel. Such designs may add baffles on the invert, bury the culvert invert, or use bottomless culverts to provide for a natural stream invert. Other designs use larger and wider culverts to reduce the amount of contraction and acceleration.