Statewide Flood Resiliency Analysis - Map

The statewide flood resiliency analysis focused on screening the Primary Highway System to identify locations vulnerable to a 100-year flood event. The analysis was comprised of three broad components under which seven individual factors were considered, with the goal of developing a composite metric to assess Iowa’s vulnerability to flooding. Robustness component: analyzes the vulnerability of the highway network to a 100-year flood event based on the 100-year floodplain boundary, whether past flooding events have occurred, and roadway shoulder data to estimate how sensitive a specific location may be to flooding. Including: 100-year flood exposure and bridge scour (45 percent), Evaluation of past flood events (15 percent) , Roadway resistance (10 percent) Redundancy component: reviews the extent of alternative routes that can be employed in the event that elements of the system lose function. Including: System availability (20 percent). Criticality component: identifies the most operationally important assets within the system. Including: Federal functional classification (4 percent), Annual average daily truck traffic (4 percent), Social vulnerability index (2 percent). The data for each attribute were normalized on a 1 (worst) to 10 (best) scale, then combined based on the weighting identified above. This weighting was determined by the Iowa DOT’s Resiliency Working Group. The maximum composite score is 100; higher scores indicate greater resiliency towards a 100-year flood event, whereas lower scores indicate greater vulnerability to those events. The analysis helps identify corridors where there is a greater risk of flood events and where strategies related to preparedness for possible flooding events and infrastructure improvements to enhance the resiliency of the system may be most beneficial. The overall distribution of corridor-level composite ratings ranged from 36.6 to 93.4, with a corridor-level average of 82.4. To identify corridors of most concern from a long-range planning standpoint, corridors that had a composite score that was one or more standard deviation below the statewide average were identified. There are 72 such corridors which have a composite score of 75.1 or less and are highlighted on Figures 5.24 and 5.25.