The United States Department of Agriculture is cooperating in an interagency study to plan for the future development and control of the water resources of the Potomac River Basin.' One assignment undertaken by the Farm Economics Research Division, Agricultural Research Service, is that of appraising both the agricultural damages from floods, and the benefits from alternative combinations of control structures on the main stem and the major tributaries of the Potomac River. Techniques were developed for using sample cross-sectional data and airphoto interpretation, rather than the conventional detailed field surveys, to help us measure agricultural damage from floods. This paper discusses the development of these techniques and indicates how they may be applied to flood-damage studies in other areas.