Quantifying Pavement Damage from Transient Flooding Using Subsurface Moisture Profile and Empirical Analysis

Flooding can reduce pavement capacity not only during the inundation, but also after standing water has receded, when the subgrade remains weakened due to infiltrated water. This study develops an integrated framework to quantify flood-induced pavement deterioration by linking transient subsurface moisture response, postflood recovery behavior, and pavement’s present serviceability index (PSI) based pavement life prediction. Finite-element seepage modeling was first used to simulate transient moisture redistribution beneath flexible pavement systems during flooding and drainage. The postflood recovery period was then identified as the time interval after surface water dissipation during which the subgrade moisture state remained above the preflood design condition. A reduced average equivalent resilient modulus was used to represent the weakened structural condition during this recovery stage. This flood-affected modulus was incorporated into the AASHTO 1993 pavement performance equation to generate life curves under different flood exposure scenarios. Results show that recovery behavior is strongly influenced by soil type and groundwater depth. In the representative thin pavement case with a 30 in. groundwater table, recovery duration ranged from several hours for coarser soils to nearly 1 day for fine-grained subgrades. The average equivalent resilient modulus during recovery decreased by approximately 15% to 25% relative to optimum conditions, with larger reductions observed for A-6 and A-7-5 soils. PSI calculations further demonstrated that increasing flood frequency can shorten pavement service life, with the fine-grained A-6 case showing life reductions of 4 to 29 months relative to the no-flood scenario. These findings demonstrate that postflood recovery should be explicitly considered in pavement design and management for flood-prone regions.