Identifying Characteristics of Bridges Vulnerable to Hydraulic Hazards Using Bridge Failure Data

Hydraulic failure, which encompasses scour, flooding, and overtopping, accounts for most bridge failures in the United States. The research reported herein aimed to evaluate the current practice of bridge hydraulic vulnerability assessment, and to identify characteristics of bridges most prone to hydraulic failure using a historical bridge failure database. Using an inductive, data-driven approach, a bridge failure population was created by synthesizing the National Bridge Inventory (NBI), United States Geological Survey (USGS) station streamflow, and available bridge failure data. Many failures that occurred before mid-2000 had incomplete assessments; this reflected the low share of structures with completed assessments in NBI. In subsequent years, state bridge inventories had completed assessments and hydraulic failures had significantly lower scour critical ratings, which indicated an improvement in identifying structures most vulnerable to failure. The most common bridge types within the overall inventory were generally overrepresented within the bridge failure population (especially those used before the Interstate Era). Differences in structure age, geometry, and condition ratings were most noticeable between failures and the overall waterway bridge inventory. Bridge deck width was narrower for failures and might explain a mechanistic cause of hydraulic failure. Waterway bridges built prior to the Interstate Era resemble those that have historically failed in that era. However, failures of bridges constructed within the Interstate Era did not resemble current waterway structures built in the same time period.