Sonar surveys play key role in South Australia port development

Paul Boughton
Tom Hiller reports on how wide swath bathymetric sonars are being used for regular hydrographic port surveys.

Two GeoSwath wide swath bathymetric sonars are being used for regular hydrographic port surveys around the South Australian coast, providing bathymetry and side scan data for use in the development and maintenance of this important national infrastructure.

Recent projects include the pre-, progress-, and post-dredge monitoring of the major shipping channels to Port Adelaide and Port Giles which were deepened to accommodate panamax vessels.

HydroSurvey Australia is the hydrographic survey business arm of Flinders Ports, with the core task of performing recurrent surveys of navigational channels and berths for design and maintenance purposes. As well as using the GeoSwath data for planning future port developments this survey programme is an integral part of Flinders Ports' risk mitigation strategy. HydroSurvey now carries out regular navigational hydrographic work at all the main shipping ports and minor boat havens in South Australia, over 100km of channels and 50 berths.

As a core part of their expanding range of survey equipment HydroSurvey has taken delivery of a second GeoSwath interferometric sonar from GeoAcoustics Ltd (Great Yarmouth, UK), a Kongsberg Maritime Company. The wide swath width demonstrated by their first GeoSwath (delivered in 2000 and upgraded in 2004) allowed unprecedented rapid survey coverage in shallow waters, resulting in significant productivity gains and achieving total insonification over large areas, with sounding data exceeding IHO S44 special order survey standard for depth accuracy.

The two GeoSwath systems are mounted on HydroSurvey's NoosaCat twin-hulled survey launches. The 'Pathfinder' is an 11 metre NoosaCat 3900-Series with a 250kHz GeoSwath head deployed on a central 'periscope'-mount between the hulls. The Felix is a trailerable 5 metre NoosaCat 1800-Series with a mounting plate for a customised 250kHz GeoSwath transducer arm fixed to the port side gunwale.

In addition to their core survey functions, HydroSurvey Australia undertakes contract hydrographic and bathymetric surveys for various projects including: design and construction of commercial ports and marinas; locating shoals and reefs; and to measure coastal sand migration. The GeoSawth Sonar's shallow water capabilities also make it ideal for river and lake surveys; in 2001 HydroSurvey were commissioned to survey Lake Burragorang (behind Warragamba Dam), 60km west of Sydney.

With a storage volume of 2 million megalitres this is one of the largest domestic water supply dams in the world, supplying approximately 80 per cent of the water delivered to Sydney. Sydney Catchment Authority required a bathymetric survey to measure the volume of sedimentation post-construction and to form a baseline for future surveys. The 'Felix' performed the GeoSwath survey in a single field operation providing total bottom coverage of the lakebed to the existing water level.

The GeoSwath Plus sonar allows wide swath bathymetry and side scan data to be collected from small vessels of opportunity in water depths up to 200m beneath the transducers. The system was designed to meet the need for a wide swath system capable of high productivity surveys in very shallow waters, and can achieve swath widths over 12 times water depth. The GeoSwath provides high accuracy, high resolution bathymetry (depth measurement accuracy exceeding the latest IHO specifications), and co-registered side-scan data. GeoSwath versions are now also available for mounting on small ROVs and AUVs.

Tom Hiller is with Advanced Products Manager, GeoAcoustics Ltd, Great Yarmouth, UK. and Ltd. (Great Yarmouth, UK) has been manufacturing marine survey equipment for more than 25 years, and is a world-leading manufacturer of sonar survey equipment for engineering geophysics and Naval survey applications. Principle product lines are swath bathymetry systems for shallow waters, side scan sonars and sub-bottom profilers. Kongsberg Maritime acquired GeoAcoustics Ltd in September 2008.

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