FLOOD04125

• County: Statewide
• Basin: Statewide
• Title: Interim Procedures for Evaluating Scour at Bridges
• Date: 9/1/1988
• Prepared By: Federal Highway Administration
• Floodplain - Doc Type: Educational/Technical/Reference Information

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CHAPTER 7
PLAN OF ACTION FOR INSTALLING SCOUR COUNTERMEASURES

A. INTRODUCTION

Scour Countermeasures are those features incorporated in the original bridge
design or at a later date to make a bridge less vulnerable or invulnerable to
damage or failure from scour.

For new bridges, recommended scour countermeasures have been addressed in
Chapters 3 and 4. In summary, the best solutions for minimizing scour damage
include:

o locating the bridge to avoid adverse floodflow patterns;

o streamlining bridge elements to minimize obstructions to the flow; or

o deepening the foundations to accommodate scour.

For existing bridges, the approaches available for protecting the bridge from
scour are .listed below in a rough order of cost:

o providing riprap at piers and abutments;

o constructing guide banks (spur dikes);

o constructing channel improvements;

o strengthening the 'bridge foundations;

o constructing sills or drop structures; and

o constructing relief bridges or lengthening existing bridges.

In developing a plan of action for protecting an existing scour critical bridge,
the three aspects that need to be considered are:

o ,the selection and design of the scour countermeasures;

o the scheduling of work to construct the scour countermeasures;

o the monitoring, inspecting and closing of the bridge until the
countermeasures are installed;

These considerations are discussed in the following sections.

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