FLOOD03064

• County: Statewide
• Basin: Statewide
• Title: Evaluating Scour at Bridges
• Date: 11/1/1990
• Prepared By: Federal Highway Administration
• Floodplain - Doc Type: Floodplain Report/Masterplan

B. THE EVALUATION PROCESS

The following approach is recommended regarding the development
and implementation of a program to assess the vulnerability of
existing bridges to scour:
STEP 1 Compile a list of those bridges with actual or
potential problems due to'scour. Structures that are
candidates for this scour susceptible category include:

(a) Bridges currently experiencing scour or that have
a history of scour problems during past floods as
identif~ed from maintenance records and
experience, bridge inspection records, lane, etc.

(b) Bridges over erodible bed streams with design
features that make them vulnerable to scour,
including:

(1) piers and abutments designed with spread
footings or short pile foundations;

(2) superstructures with simple spans or non-
redundant support systems that render them
vu:nerable to collapse in the event of
foundation movement; and

(3) br~dges with inadequate waterway openings or
with designs that collect ice and debris,
Particular attention should be given to
structures where there are no rel:.ef bridges
or embankments for overtopping, and where all
water must pass through or over the
structure,

(c) Bridges on aggressive streams and waterways,
including those with:

(1) active degradation or aggregation of the
stl:eam bed;

(2) significant lateral movement or erosion of
st::earn banks;

(3) steep slopes or high velocities;

(4) in-stream materials mining operations in the
vicinity of the bridge; and

(5) histories of flood damaged highways and
bridges,

76