Twenty-nine months of geomorphic change in upper Monterey Canyon (2002–2005)

Abstract

Time serial multibeam bathymetry is used to evaluate geomorphic trends and submarine processes in the upper 4 km of Monterey Canyon, California. Seven high-resolution bathymetric surveys conducted between September 2002 to February 2005 show that the upper canyon axis and head grew in volume 1 000 000 m 3 ± 700 000 m 3, at an average annual rate of 400 000 m 3/a ± 300 000 m 3/a through lateral erosion and vertical incision. This net loss of substrate during the 29-month period is parsed between local erosion of 1 400 000 m 3 and local deposition of 350 000 m 3. A submarine landslide with a scar void volume of 70 000 m 3 and debris pile of 52 000 m 3 occurred between March 2003 and September 2004. During the subsequent months until February 2005, the slide scar grew 40% in volume while the debris pile shrank by 80%. The canyon-head rim adjacent to Moss Landing Harbor prograded seaward and retreated shoreward significantly (up to 50 m) during the study suggesting frequent episodes of sediment build up and subsequent down-canyon failure. A large field of sand waves located in the channel axis was completely reworked in each time series except for a 24 h period where no wave crest movement was noted, and a 32 day period where up-canyon migration of approximately 7 m was recorded in the northern tributary.