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Program Downloads: Hydraulic and Hydrologic

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Program Downloads

Culvert Corrosion

This program calculates the design life of a metal culvert using CalTrans methodology based on corrosion from the surrounding soil and the flow of the culvert. Typically, WSDOT does not use this approach, but the underlying theory is valid.


This Microsoft Excel spreadsheet calculates peak flows for small drainage areas that can be either natural or developed. It uses the rational method as described in the WSDOT Hydraulics Manual.

Pipe Angle Calculation Worksheet

Before finalizing the storm drain layout, designers should verify the layout is constructible with respect to the angle between pipes entering or exiting a junction. That is, in order to maintain the structure integrity of a junction there are minimum clearance requirements that must be met depending on the pipe diameter. Designers can verify the minimum pipe angle with the Pipe Angle Calculation Worksheet at the following link.

Storm Drain Design

This Microsoft Excel spreadsheet accomplishes a storm sewer design using the rational method, as described in the WSDOT Hydraulics Manual.

USGS Regression Spreadsheet

This is a Microsoft Excel spreadsheet that calculates runoff using the 2001 version of the USGS regression equations for Washington State. The user should have a 2004 copy of the WSDOT Hydraulics Manual or USGS Fact Sheet 016-01 to determine the input parameters. We are currently working with MIS to deploy the National Flood-Frequency (NFF) program statewide. Until then, the spreadsheets can be used.

If using the routing table, use this link for the Pond Hydraulics Excel spreadsheet.

An optimization routine is available, but it is not included in WHAM, the public domain version of the program. The optimization routine is available through MGS Software.

Water Quality Wet Pond Calculator

Inlet Analysis Spreadsheets

Inlet Spacing with Side Flow 

This Microsoft Excel spreadsheet combines the procedures described in the WSDOT Hydraulics Manual to calculate roadway runoff and inlet interception for a roadway. For roadways on a longitudinal slope greater than 2% and with velocities between 3-5 ft/s the spreadsheet uses the methods described in the Hydraulics Manual section 5-5.1 Capacity of Inlets on a Continuous Grade. For velocities less than 3ft/s and have longitundal slopes less than 2%, this spreadsheet will also consider the side flow interception as described in the Hydraulics Manual section 5-5.2 Side Flow Interception.

Sag Worksheet

This is a Microsoft Excel spreadsheet that uses the procedure described in the WSDOT Hydraulics Manual to locate inlets in a sag condition.

Short Duration Rainfall Depth Converter

This spreadsheet converts the 2 year, 2 hour storm to the 3 hour storm for any of the four Eastern Washington Climatic Regions. For further explanation of how to calculate the 3 hour storm, see Appendix 4D of the Highway Runoff Manual.