Much of the U.S. coastline is rapidly changing--mostly eroding. That fact places increasing pressure on the planners and managers responsible for coastal development and protection, and could have a direct effect on many of the 125 million Americans living within 50 miles of the coast who rely on its resources and beaches for their livelihood or recreation. Although rapid advances have been made in the measurement systems needed to understand and describe the forces and changes at work in the surf-zone environment, their potential for allowing more accurate and reliable planning and engineering responses has not been fully realized. This book assesses coastal data needs, instrumentation, and analyses, and recommends areas in which more information or better instrumentation is needed.