Assessing the vulnerability of Delaware's coastal bridges to hurricane forces

There exists a need for new guidelines to address the threat of hurricane forces to coastal bridges. Researchers at the University of Florida, Ocean Engineering Associates, Inc., Modjeski and Masters, Inc., Moffatt & Nichol, and the Federal Highway Administration have developed a three-level assessment to determine the vulnerability of coastal bridges to hurricane forces. The original research was performed in the State of Florida and is being tested in the Gulf and Atlantic Coasts. The purpose of this study is to analyze a sample of Delaware's coastal bridges to determine the applicability of the specifications to the Middle Atlantic coast and to determine any risk to Delaware's bridge inventory. Feedback will also be provided to DelDOT on the specifications and the safety of their bridges.;Three bridges in Delaware were chosen to analyze using the specifications. They are the Indian River Inlet Bridge (Bridge 3-156), the Fenwick Island Bridge (Bridge 3-437), and the Old Mill Bridge (Bridge 3-460). They were chosen because of their proximity to the coast, low elevations, and criticality in evacuation or rescue operations during a hurricane.;The results for the study were that the 100-year wave crest elevation, in addition to the design storm water elevation, was not high enough to impact any of the three bridge superstructures. In each case, the minimum 1 ft of required clearance was maintained. The risk to Delaware's coastal bridge inventory from hurricane forces is very low and it was determined that the specifications used are acceptably applicable to Delaware. Additionally, the recommendations to DelDOT are to become familiar with the specifications to use for future bridge design and to also become familiar with recovery techniques if a disaster does occur to a coastal bridge.