Unique Sediment-Laden Flows

High sediment-transport rates were generated by lahars, lake "breakouts," and other sudden flows from the eroding debris-avalanche deposit. These flows were considered rare and transient, so they were amply documented to serve unforeseen research needs. Observations and measurements of these unique sediment-laden flows were made whenever possible. Examples of unique sediment-laden flows include:

• Flow release from small lake on debris-avalanche deposit, August 27, 1980;
• Flow from breakout of Jackson Lake during storm flow, February 20, 1982;
• Volcanic lahar in the North Fork Toutle River, March 19-20, 1982;
• Volcanic lahar in the North Fork Toutle River, May 14, 1984;
• Flow release from Spirit Lake tunnel to South Coldwater Creek, April 1985.

Personnel collected sediment data at gaging stations along the route of sediment transport for the period of interest. Basic data were recorded as sediment concentrations and daily sediment-discharge records, and were used in detailed descriptions of some sediment-laden flows (see references in "Chronology of Data Collection and Analysis").