Bottomless (or three-sided) culverts use the natural channel bed and are environmentally attractive alternatives to traditional closed culverts. They are often promoted as alternatives for replacing short bridges. This report describes a two-phase study conducted at the FHWA Hydraulic Laboratory: Phase I: a preliminary investigation focused on measuring maximum scour depths at the culvert entrance and developing equations for estimating inlet scour. Phase II: a follow-up investigation to include scour measurements at the outlet, submerged entrance scour measurements, detailed velocity and depth measurements with a prescour fixed bed to refine the equations, and evaluation of various potential scour countermeasures to reduce scour at the culvert inlet and outlet.

Topics: Introduction to Bottomless Culverts Test Facilities and Instrumentation Model Bottomless Culvert Shapes Experimental Parameters Scour protection: Riprap Analysis Theoretical Background Clear Water Scour Experiments Riprap Stability Design Coefficients Use of Cross Vanes for Inlet Scour Control Scour Calculation Examples.

Intended Audience: This course is intended for Hydraulic, Civil, Transportation, Water Resources, and other engineers whose job description may require a general knowledge of the scouring effects of streams and rivers on culvert and bridge structures.

Publication Source: US DOT (Federal Highway Administration)