Relocation and permanent evacuation of activities at flood hazard locations are nonstructural flood damage mitigation measures. These plans modify the susceptability to flood damage of flood plain activities by permanently removing them to flood free locations. The benefits from evaluation plans arise from the willingness-to-pay on the part of the removed activities and other affected parties rather than do without the plan. The purpose of this paper is to present the conceptual basis for the existence and measurement of National Economic Development (NED) benefits from permanent evacuation and relocation of flood prone activities. In addition, the paper is intended to clarify the appropriate methodology for measuring these benefits, based on established economic principles. The discussion below presents the theory of the identification of relocation benefits as a part of a broadly applicable theory of flood damage mitigation benefits. The theory indicates the sources of benefits from relocation and the relationship between NED benefits and Federally subsidized flood damage relief programs, particularly flood insurance. Subsequent sections present the past and current Corps of Engineers guidelines for the evaluation of benefits and the current practice employed in specific Corps relocation project reports.