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Lester A. Tinkham; P.E., PS

Course Outline

As development of land continues, more and more natural conditions of a watershed are being replaced with hard surfaces, e.g. roofs and pavements, creating a situation where rainfall which once soaked into the ground now runs off and must be somehow controlled, managed and properly transported to an adequate point of re-use or disposal. This 2-hour course provides a review of the need for an easy to use tool for making hydraulic analysis as well as the complete evaluation technique and methodology for calculating storm water runoff discharges using the Rational Formula and their use in developing a system and designing its features to handle and control those discharges. It includes procedures for the development of design parameters and peak discharges along with the formulae necessary to design infrastructure components of a Storm Water Management Facilities.

This course includes a multiple-choice quiz at the end, which is designed to enhance the understanding of the course materials.

Learning Objective

At the conclusion of this course, the student will be able:

Intended Audience

This course is intended for Hydrologist, Design Engineers, Public Works officials and Regulatory Agency Staff and also to Professional Surveyors in states now requiring hydraulic calculations.

Benefit to Attendees

Attendee will be able to easily perform necessary calculations to determine storm water runoff calculations and peak discharges on small watersheds and to apply those calculations in the design of storm water management conveyance, re-use, and/or disposal systems

Course Introduction

The Rational Formula was developed around 1889. It relies on the determination of only 3 parameters to calculate the peak storm water runoff from small watershed areas, and provides a simple, easy to use formula for performing the necessary calculations, appropriate values of the calculation parameters are provided. The course describes how the results of those calculations can be applied to basic standard design formulae for determining and selecting appropriate storm water system components. 

Course Content

In this lesson, you are required to download and study the following document:


Please click on the above underlined hypertext to view, download or print the document for your study. Because of the large file size, we recommend that you first save the file to your computer by right-clicking the mouse and choosing "Save Target As ...", and then open the file in Adobe Acrobat Reader from your computer.

Course Summary

Hydraulic calculations are necessary to comply with Federal and State regulations and to determine design of infrastructure components of a Storm Water Management System. The Rational Formula has long been a staple for calculating the peak storm water rainfall runoff from small drainage areas. This course provides the essential components for these calculations and for design of needed drainage facilities.


Once you finish studying the above course content, you need to take a quiz to obtain the PDH credits.

DISCLAIMER: The materials contained in the online course are not intended as a representation or warranty on the part of PDH Center or any other person/organization named herein. The materials are for general information only. They are not a substitute for competent professional advice. Application of this information to a specific project should be reviewed by a registered architect and/or professional engineer/surveyor. Anyone making use of the information set forth herein does so at their own risk and assumes any and all resulting liability arising therefrom.