The NDOT Bridge Hydraulics Section provides statewide support for the hydraulic analysis and design of Nebraska’s highway bridges and related structures, ensuring they are safe and resilient against flood risks and water flow impacts. This section is responsible for developing hydraulic reports, design plans and specifications that adhere to state and federal standards. By assessing floodplain data and waterway dynamics, the Bridge Hydraulics team helps maintain effective drainage and flood management across Nebraska’s bridge network.
Hydraulic Analysis Guidelines
The hydraulic analysis will satisfy requirements of the FEDERAL-AID POLICY GUIDE, 23 CFR 650A (Location and Hydraulic Design of Encroachments on Flood Plains) and Federal Highway Administration Publication No. FHWA-IP-90-017 (Hydraulic Engineering Circular No. 18, Evaluating Scour at Bridges).
The hydraulic engineer is required to define the most practical design for all hydraulic-related issues. The analysis process evaluates, assesses and documents the impacts and consequences an encroachment has on the floodplain environment. The proposed design, countermeasure design and hydraulic-related design parameters are defined by considering hydraulic constraints, cost, risks, regulatory requirements, channel behavior, environmental impacts, engineering requirements and social concerns.
Structure sizing is based on hydraulic requirements for floods up to Q100. High risk sites may require sizing based on Q500 floods. The proposed structure is selected by hydraulically assessing NATURAL, EXISTING and ALTERNATE conditions.
Bridge foundation designs are checked for scour to verify the structure has a reasonable chance of surviving a Q500 flood.
The hydraulic study is based on surveyed cross-sections that define the 100-year floodplain. Normally, a minimum of one upstream cross-section, one downstream cross-section and one encroachment (bridge opening/road grade) cross-section is required. For minor action projects with minimal hydraulic risks, such as culvert extensions, approximate hydraulic calculations based on preliminary road survey data is acceptable. High risk, very complex sites may require the use of additional floodplain cross-sections and/or total station survey data.
For complete procedures and requirements related to bridge hydraulics, please refer to the Hydraulic Analysis Guidelines.
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Bridge Hydraulic Forms
- BR 14: Hydrologic Reference Information PDF | Word Updated 4-15
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BR 359A: Preliminary Data Sheet (Bridge to Bridge) PDF | Word Updated 10-23
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BR 359B: Data Sheet (CBC) (Culvert to Culvert) PDF | Word Updated 11-22
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BR 359C: Data Sheet (CBC) (Bridge to Culvert) PDF | Word Updated 11-22
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BR 366: FEMA Certification and Compliance PDF | Word Updated 4-15
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BR 385C: Bridge Scour Plan of Action PDF | Word Updated 2-19
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BR 385F: Supplemental Hydraulic Findings & Maintenance PDF | Word Updated 4-15