AUV Survey in the Loukkos River near Larache, Morocco
In October 2009, a survey was conducted in the Loukkos River starting at the river mouth near the present day seaport of Larache, Morocco and proceeding up-river past two possible locations for the ancient Port of Lixus. The survey was conducted using both an AUV (Ocean Server IVER2) and a small manned surface craft (local fishing boat). The survey results were expected to serve two purposes: (1) Archeological search for a physical port at Lixus and (2) Studies of coastal change in the Loukkos River. The survey techniques included: GPS navigating (AUV and support boat), single-beam echo sounding (AUV), sub-bottom profiling (support boat) and side scan imaging (AUV). In planning and running the survey, it was important to be mindful that the Loukkos is a narrow meandering river. For that reason the survey began by “running the river” to confirm (even though we had Google Earth imagery) exactly where the river was in WGS-84. The plan included indirect mapping of water depths at the point bars on the inside of the river bends using the AUV’s side scan sonar, rather than direct mapping of water depths using its single beam echo sounder. The plan allowed for building confidence in running the IVER2. Consequently the IVER2 was run tightly coupled to the survey boat, loosely coupled with the survey boat and totally free of the survey boat. The October 2009 survey results include: (1) water depths in the Loukkos River, which varied from 0.5 to 20 meters at high water; (2) delineation of different bedforms, which varied from virtually non-existent through ripples to dunes: (3) interesting sub-bottom features which may be indications of ancient Lixus maritime infracture; and (4) a better understanding of the pros and cons of conducting riverine surveys with an AUV. The seminar is based on a presentation given at the Hydro2010 Conference Rostock Germany November 2010.
Lloyd Huff has over 37 years in private industry and the federal government, working with acoustic instrumentation and oceanographic equipment. He received his Doctorate in Ocean Engineering in 1976 from the University of Rhode Island and is one of the lead professionals in the Office of Coast Survey (OCS) working to bring multibeam side scan sonars and multibeam bathymetric sonars into standard practice for shallow water hydrography. He was Chief of the OCS Hydrographic Technology Programs from 1988-1999.
Dr. Huff is working on new approaches for a range of hydrographic activities including the application of RTK techniques.