Hydraulic Design

General
Hydraulic structures must be designed to provide proper drainage for highways and roads. Guidelines for the design of hydraulic structures are contained in the TxDOT
Hydraulic Design Manual
.
Federal Requirements
  1. 23 CFR Part 650, Subpart A
    – Describes procedures for the location and hydraulic design of highway encroachments on flood plains.
    1. Minimum standards for hydraulic studies are listed.
    2. 23 CFR §650.115(a)(2)
      requires the design flood for encroachments by through lanes of interstate highways to not be less than the flood with a 2 percent chance of being exceeded in any given year (50-year design frequency).
    3. FHWA Additional Guidance on 23 CFR 650A, Attachment 2
      (formerly the Federal-Aid Policy Guide Non-regulatory Supplement, Attachment 2) – Lists the procedures for coordinating highway encroachments on floodplains with the Federal Emergency Management Agency (FEMA).
State Requirements
  1. 43 TAC §§5.59
    ,
    15.56
    ,
    26.33
    and
    27.56
    – Requires projects to be designed in accordance with TxDOT manuals, procedures, standards and guidelines. For regional mobility authority (RMA), toll and pass-through financed projects, preliminary design information must be sent to TxDOT for review and approval when the design is approximately 30 percent complete.
Required Practices
In general, the LG is responsible for selection of a design frequency for the drainage design of the roadway and is also responsible for coordinating floodplain management issues with FEMA and the local floodplain administrator. The
LGPM Guide
describes the required practices for hydraulic design.