Malibu Paleochannel Survey

In 2012, Sea Surveyor, Inc. conducted a seismic reflection (subbottom profiling) survey of a 1.5 square mile area along famous Malibu Beach, California. The survey’s purpose, to map the paleochannel and determine the elevation of buried bedrock, is in support of a proposed City plan to inject treated wastewater into the buried paleochannel for transport to sea. The bathymetric chart and buried bedrock elevation map (left) prepared by Sea Surveyor was used to calibrate the hydrologic model used to assess the engineering feasibility of the concept.

Sea Surveyor conducted the seismic reflection survey using two (2) sizes of CHIRP subbottom profilers towed behind our 72’ research vessel LIGHTNING. The 500-lb SB-0512 towfish penetrated 40’-50’ into the subbottom, while the 200-lb SB-216 towfish provided high-resolution acoustic images of the stratigraphy in the upper 30’.

The bathymetric contour map is referenced to NAVD-88 elevation, accomplished by correcting water depth measurements collected during the survey for tide fluctuations measured by NOAA at Santa Monica Pier. To determine bedrock elevations, the thickness of overlying sediment observed in the seismic reflection records is added to the NAVD-88 elevation of the seafloor.