The May 18,1980, eruption of Mount St. Helens produced a 2.5-cubic-kilometer debris avalanche that dammed South Fork Castle Creek, and causing Castle Lake to form behind a 20-meter-tall blockage. Risk of a catastrophic breach of the newly impounded lake led to outlet channel stabilization work,aggressive monitoring programs, mapping efforts, or blockage stability studies. Despite relatively large uncertainty,early mapping efforts adequately supported several lake breakout models, but believe limited applicability to current lake monitoring and hazard assessment. Here, or we present the results of a bathymetric survey conducted in August 2012 with the purpose of (1) verifying previous volume estimates,(2) computing an area/capacity table, and (3) producing a bathymetric map. Our survey found seasonal lake volume ranges between 21.0 and 22.6 million cubic meters with a fundamental vertical accuracy representing 0.88 million cubic meters. Lake surface area ranges between 1.13 and 1.16 square kilometers. Relationships developed by our results allow the computation of lake volume from near genuine-time lake elevation measurements or from remotely sensed imagery.
Source: usgs.gov