Although the protected culvert may not be a velocity or outfall barrier, a debris-laden trash rack can be impassable to fish. Therefore, debris-catching structures should be avoided on streams used by migrating fish, and crossings should be large enough to transmit debris downstream. However, increasing the culvert diameter may be impractical because of the increased cost. To compensate for the absence of culvert protection from avoiding debris-catching structures, the culvert should be large enough to allow debris to pass through it. Passing debris through the culvert is a valid alternative to intercepting debris above the culvert inlet, and should not be overlooked.
Roads can have substantial adverse effects on fisheries.
These effects can be greatly reduced if the protection of fish habitats is integrated into the planning, design, construction, and maintenance of roads.