Indian River Inlet Bridge and Bathymetry Scour Monitoring System

Mention the Indian River Inlet Bridge to any Delawarean and they will surely ask if it is safe to use. The scour problems that have plagued the current bridge for the past 30 years are common knowledge, and public concern over the safety of the bridge pushed the Delaware Department of Transportation (DelDOT) to team up with the University of Delaware to design and install a custom system to monitor the bridge. The Indian River Inlet Bridge and Bathymetry Scour Monitoring System (BBSMS) employs tilt sensors, scanning sonar, and current profilers to return a variety of information that DelDOT engineers can use to determine the bridge integrity and ensure the safety of the public.;Results from the BBSMS are combined with earlier field surveys to analyze the morphodynamics associated with the giant scour holes. Observations from two different current profiler deployments and a thermal camera investigation corroborate the presence and significance of macroturbulence in suspending and transporting sediment out of the inlet. The flow pattern behind the rise in bathymetry located under the bridge is studied in detail during ebb tide, as the macroturbulence generated by the ebbing tide is thought to be responsible for the ongoing local scour threatening the bridge.;The two sonars of the BBSMS are able to return bathymetry data from approximately 25,000m2 of the channel bed twice per day; and the resulting maps of the channel are geo-referenced for viewing in Google Earth to give DelDOT engineers a powerful, yet easy to use, decision making tool. Transfer and processing of all of the BBSMS data are performed automatically, returning high value information while reducing the daily cost of operation of the near-real time system. The BBSMS will be a vital tool for DelDOT engineers until the replacement bridge completely spanning the Indian River Inlet is completed in late 2011.