Scour Management in Iowa Using Modified HYRISK

Document Type

Conference Presentation

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Floods and resulting scour are responsible for about half of bridge failures in the United States. Catastrophic consequences of bridge failures along with guidelines from the Federal Highway Administration (FHWA) motivated the development of scour assessment tools. HYRISK is one of the available tools for network-level scour analysis and is developed by the FHWA for prioritizing bridges based on their expected scour risk. According to scour management history and experiences in Iowa, this study proposed three major modifications to improve and customize HYRISK estimations for Iowa. Soil erodibility was incorporated into the HYRISK along with a modified failure cost calculation accounting for scour countermeasure installation cost rather than bridge reconstruction that was originally being considered. The modified HYRISK was used to estimate the annual cost of scour risk for Iowa DOT bridge network and also the damage to the affected bridges by the 2008 flood in Upper Mississippi River basin. The results were significantly different from original HYRISK estimations and were in line with the actual annual expenditure on scour maintenance program and also the reported damage from the 2008 flood. Also in order to compare the results from the original and modified versions of HYRISK, a random sample of 30 bridges were selected and ranked based on the estimated risks by the two methodologies. The results showed significant changes in the rankings, and it was also predicted that Iowa DOT would need to install six abutment protections and five pier protections in the next year.


Mechanical and Civil Engineering

Publication Title

97th Transportation Research Board Annual Meeting

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