Performance Assessment of Secondary-Roadway Infrastructure in Iowa after 2011 Missouri River Flooding

Abstract

The Missouri River flooding in 2011 caused significant damage to secondary roadway infrastructure systems in western Iowa. This paper documents results of an investigation designed to evaluate unpaved roads and bridge approaches in the flood-affected areas. In situ testing was conducted as flood waters receded and several months later to evaluate performance and recovery conditions. In situ tests included falling weight deflectometer, dynamic cone penetrometer, and ground penetrating radar scanning. Field results indicated statistically significant differences over time in roadway support characteristics between flooded and nonflooded areas. Support characteristics in some flooded areas did not recover over the duration of the research reported in this paper (7–8 months after flooding). Multivariate statistical analysis indicated that the dynamic composite stiffness of the flooded unpaved roads was highly dependent on the stiffness of the underlying subgrade layer. Voids were detected in culvert and bridge abutment backfill materials shortly after flooding, and several months after flooding in spite of reconstruction. The results showed that damage from flooding can cause extended problems after the event, and that secondary infrastructure systems are typically not designed to withstand flood events.