Kevin E. White, P.E.

Senior Hydraulic Engineer
Wilbur Smith Associates
Columbus, Ohio

A properly designed highway requires a well-designed drainage system. This requires a determination of the quantity of runoff reaching the drainage structures and an accurate analysis of water flow through the structures in order to properly size them. Also, a working knowledge of structural characteristics of buried pipe systems and effects of environmental factors is necessary to provide for long-term performance. Timely inspection and maintenance of drainage facilities will ensure satisfactory service life. If all of these issues are properly addressed, an efficient drainage system can be developed. Because a large percentage of highway funds is spent on culverts, storm drains, and other drainage facilities, it is incumbent upon the engineer to use funds wisely and create an efficient drainage system. Thus, the roadway and adjacent property will be protected without wasting taxpayers money.

This chapter includes a review of fundamental hydrology considerations and runoff estimation, fundamentals of the hydraulics of open-channel flow, and design considerations and methods for the various components of highway drainage. The design, construction, and service life of both flexible and rigid pipe are addressed, as well as rehabilitation and maintenance. The range of products is broad, extending from small-diameter drainage pipe to long-span structures that may be used for the replacement of short-span bridges. Article 5.6 may be referred to for a general description of the major products available.