About Culverts

Culverts are enclosed drains used to channel a stream, creek, sewer or other form of running water. They are traditionally built into bridges or other road structures so vehicles can pass over without disrupting the flow of the water. They are also used to divert rainwater away from roadways.

Significance

Though the main purpose of culverts is to keep roadways dry, they also serve a secondary function. This function is to keep water from collecting on the sides of roads, where it can eventually erode away the soil underneath the road. Without such culverts, significant reconstruction would be required overtime.

Size

The shape and size of a culvert is largely dictated by the size, depth and speed of the water it is transporting. Engineers use these measurements to determine whether a round, square, elliptical or pear-shaped culvert is ideal. Diameter of culverts also varies dramatically, typically ranging between a few feet to several yards.

Types

Culverts are built from a number of building materials. Historically, they were built from stone. However, sturdier, more reliable components have since made stone culverts largely obsolete. Presently, steel is the most popular material for building culverts, followed by concrete and polymer plastic.

Warning

Special care must be taken by the engineer to ensure that a culvert design is both safe and effective. For example, if improper calculations result in inadequate drainage during periods of high rain, then flooding may overtake the culvert and roadway. Improper galvanization may also lead to structural instability that could result in the collapse of the culvert.

Expert Insight

In recent history, some people have expanded the definition of the culvert to include any ditch or conduit built for the purpose of water drainage. As such, ditches, concrete channels and other unenclosed structures are also sometimes referred to as culverts. However, the classical definition requires the culvert to be enclosed.