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Posts published in “Hydraulics”

Various types of drainage facilities are required to protect the highway against surface and subsurface water. Drainage facilities must be designed to convey the water across, along, or away from the highway in the most economical, efficient, and safe manner without damaging the highway or adjacent property. The purpose of this manual is to provide detailed information on the subjects of hydrologic and hydraulic analysis related to highway design. This manual should be used in conjunction with the Washington State Department of Transportation (WSDOT) Highway Runoff Manual and the WSDOT Design Manual, specifically Section 1210.

Mean Annual Runoff

Sometimes it is necessary to determine the mean annual flow or runoff for a given stream. When published flow records are available they are the…

Flood Reports

Flood reports have been developed for many rivers in Washington State. Most of these reports, and the ones that are most readily accessible, have been…

USGS Regression Equations

While measured flows provide the best data for design purposes, it is not practical to gage all rivers and streams in the state. A set…

Published Flow Records

When available, published flow records provide the most accurate data for designing culverts and bridge openings. This is because the values are based on actual…

Santa Barbara Urban Hydrograph Method

When designing flood control structures and some stormwater treatment facilities, the designer must know more than just the peak flow that will occur. Along with…

The Rational Method

General The rational method is used to predict peak flows for small drainage areas which can be either natural or developed. The rational method can…

Drainage Basin

The size of the drainage basin is one of the most important parameters regardless of which method of hydrologic analysis is used. To determine the…

Selecting hydrology analysis method

Each of the first five methods listed above are appropriate to use for different design conditions and none of the methods will cover all situations.…

General Hydrology

The Washington State Department of Transportation (WSDOT) Olympia Service Center (OSC) Hydraulics Branch uses several methods of determining runoff rates and/or volumes. Experience has shown…