The work upon which this report is based was supported in part by funds provided by the United States Department of the Interior, Office of Water Research and Technology, as authorized under the Water Research and Development Act of 1978. The Office of Water Research and Technology has since been terminated effective August 25, 1982, by Secretarial Order 3084 and its programs transferred to other bureaus and offices in the Department of the Interior. The Mount St. Helens Research and Development Program was among those transferred to the Bureau of Reclamation. The research projects were coordinated through the Water Research Centers and Institutes of the states of Idaho, Montana, Oregon, and Washington. Preparation of this report was carried out through the State of Washington Water Research Center.