Hydraulic Engineering Circular No. 22, Third Edition

URBAN DRAINAGE DESIGN MANUAL
This circular provides a comprehensive and practical guide for the design of storm drainage
systems associated with transportation facilities. Design guidance is provided for the design
of storm drainage systems which collect, convey, and discharge stormwater flowing within and
along the highway right-of-way. As such, this circular covers the design of most types of
highway drainage. Two exceptions to this are the design of cross-drainage facilities such as
culverts and bridges, and subsurface drainage design. Guidance for the design of crossdrainage
facilities is provided in HDS-1, Hydraulics of Bridge Waterways,(1) HDS-5, Hydraulic
Design of Highway Culverts,(2) as well as the AASHTO Highway Drainage Guidelines Volume
IV,(3) and Volume VII.(4) Subsurface drainage design is covered in detail in Highway
Subdrainage Design.(5)
Methods and procedures are given for the hydraulic design of storm drainage systems.
Design methods are presented for evaluating rainfall and runoff magnitude, pavement
drainage, gutter flow, inlet design, median and roadside ditch flow, structure design, and storm
drain piping. Procedures for the design of detention facilities and the review of storm water
pump stations are also presented, along with a review of urban water quality practices.
The reader is assumed to have an understanding of basic hydrologic and hydraulic principles.
Detailed coverage of these subjects is available in HDS-2, Hydrology,(6) HDS-4, Introduction
to Highway Hydraulics,(7) Design and Construction of Urban Stormwater Management
Systems,(8) as well as basic hydrology and hydraulic text books.
This document consists of nine additional chapters and four appendices. The nine chapters
cover System Planning, Urban Hydrologic Procedures, Pavement Drainage, Roadside and
Median Channels, Structures, Storm Drains, Stormwater Quantity Control Facilities, Pump
Stations, and Urban Water Quality Practices. Appendixes include: Appendix A, Design
Charts; Appendix B, Gutter Flow Relationship Development; Appendix C, Literature
Reference, and Appendix D, Blank Forms.
Several illustrative design examples are developed throughout the document. By following the
design examples, the reader is led through the design of a complete stormwater management
system. In the main body of the manual, all procedures are presented using hand
computations in both SI and English units.
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