A screening method for bridge scour estimation and flood adaptation planning utilizing HAZUS-MH 2.1 and HEC-18

The American Society of Civil Engineers’ 2013 Report Card for the Nation’s Infrastructure indicated that over 10 % of the roughly 670,000 bridges in the USA are structurally deficient with a $120 billion investment over the next 15 years required for mitigation. In addition, the Intergovernmental Panel on Climate Change indicates that the frequency of severe precipitation events is increasing as well as associated flooding. These factors coupled with scour as a leading cause of bridge degradation demonstrate a need to develop screening methods for assessing and prioritizing bridges most deserving of adaptation measures. This paper proposes a method for utilizing FEMA’s HAZUS-MH software along with the United States Department of Transportation’s Hydraulic Engineering Circular 18 scour equations to predict the relative scour impact for a bridge to assist in adaptation prioritization. The estimation method develops a scour factor for a bridge using contraction, pier and abutment scour estimates for a base-year and future-year flood event. The scour factor is then used in conjunction with estimated bridge replacement cost to predict monetary damages for a future flood event. The method was validated using repair cost data for eight bridges located in Davidson County (Nashville), Tennessee, from a severe flooding event in May 2010. An extended case study application was also conducted by applying the methodology to a set of flood-prone bridges in the Little Rock, Arkansas area. The results of this research suggest that the proposed methodology may offer municipalities a useful screening tool for prioritizing bridges for adaptation planning.