How to Size Culverts

Culverts are specially designed conduits used in the construction of roads to help manage and control water drainage. They're used as part of a drainage system to help control excessive runoff and reduce or prevent flood damage to roadways. Using a properly sized culvert is key to its success, and sizing a culvert depends on three major factors: Soil type, the slope of the land and the size of the area the culvert is associated with all impact the sizing.

Instructions

• 1

  Measure the size of the drainage area the culvert will account for. The number of acres that will drain into the culvert system will help to determine the maximum capacity needed.

• 2

  Determine the slope of the ground of the drainage area. You can determine the slope of the area by using a topographic map. Find the vertical distance of the area and divide it by the horizonal area then multiply the result by 100.

• 3

  Take account of the soil and vegetation in the drainage area. Dense, hard-packed soil with very little vegetation cover will result in more water flow than light soil with heavy vegetation.

• 4

  Use Talbot's Table to determine the required culvert size. Match your calculated drainage area, slope rating and soil condition with the ratings on the chart.