The Constructal Law provides a basis for analyzing public policy with respect to natural and social flow systems, including catastrophic events. Whether or not social actors are individual or collective, there are four basic types of behavioral response to flow systems: obstruction, avoidance, facilitation, and inaction. Responses can be directed either at the flow system or to competing flow systems. The success of different responses is determined by four dimensions of flow systems: scale, velocity, pressure, and time.