Synthesis: Techniques for Freeboard and Other Simplified Approaches to Account for Uncertainty
Freeboard is widely considered as the vertical clearance above a design water-surface elevation to reduce bridge and culvert vulnerability to flood-related hazards; however, current guidance across agencies on freeboard is inconsistent and often lacks transparent treatment of hydrologic, hydraulic, and debris-related uncertainty. Texas Department of Transportation (TxDOT) Hydraulic Design Manual does not specify a recommended freeboard value, which creates challenges for consistent and defensible design decisions. The research team will conduct a structured synthesis of national- and state-level guidance, tools, and research related to freeboard determination for bridges and culverts and other simplified approaches for addressing uncertainty. Where directly relevant and readily comparable, selected international guidance will be included as supplemental examples to provide additional context. Researchers will systematically review authoritative design manuals, federal guidance, DOT practices in different states, and prior research to document how freeboard is defined, justified, and applied, including consideration of design events, structure types, technical rationale, uncertainty treatment, and any exception procedures. The research team will develop traceable synthesis products, including annotated catalogs, evidence matrices, and cross-agency comparison tables, to clearly summarize current practice and identify areas of inconsistency or ambiguity. The primary outcome will be a set of synthesis materials organized for direct use by TxDOT to support consistent, transparent, and risk-aware freeboard determination and to inform future updates to TxDOT’s hydraulic guidance.
Language
- English
Project
- Status: Active
- Funding: $64,994.87
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Sponsor Organizations:
Texas Department of Transportation
125 E. 11th Street
Austin, TX United States 78701-2483 -
Managing Organizations:
Texas Department of Transportation
125 E. 11th Street
Austin, TX United States 78701-2483 -
Project Managers:
Smith, Anne
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Performing Organizations:
Center for Transportation Research
3925 W. Braker Lane
Austin, TX United States 78759 -
Principal Investigators:
Lee, Jun-Whan (Michael)
- Start Date: 20260901
- Expected Completion Date: 20270831
- Actual Completion Date: 0
Subject/Index Terms
- TRT Terms: Bridge design; Culverts; Floods; Hydraulics; Literature reviews; Overtopping; Risk management; Uncertainty
- Identifier Terms: Texas Department of Transportation
- Subject Areas: Bridges and other structures; Design; Highways; Hydraulics and Hydrology;
Filing Info
- Accession Number: 02001117
- Record Type: Research project
- Source Agency: Texas Department of Transportation
- Files: RIP, STATEDOT
- Created Date: Aug 28 2026 10:01AM