Proper assessment of flooded pavement is very critical for reducing the risk and ensuring the safety of construction crews, department of transportation personnel and the public. The objective of this paper is to present a rational procedure for the assessment of vulnerability of asphalt pavements to flood-induced damage. A system dynamics-based methodology was developed to determine the critical time (Tcritical) for full saturation of the unbound base and for failure of the bound surface layer. The methodology and the web-based simulation tool presented here will help the users to identify potentially vulnerable stretches of highway prior to flooding and either take action to improve them or monitor them closely to obtain preflood conditions which can be compared against post-flood conditions to detect deterioration; it will help them decide whether emergency and non-emergency vehicles can be allowed during and immediately after flooding, and in planning post-flooding investigative actions. © 2014 The Chartered Institution of Water and Environmental Management (CIWEM) and John Wiley & Sons Ltd