Title

Characteristics of underwater explosions conducted at Triangular Island in the Shoalwater Bay Defence Training Area

Objective

To determine the spatial extent and intensity of the acoustic impact of detonations conducted in the intertidal zone by the Department of Defence during Clearance Diver training exercises at Triangular Island.

Relevance

This project forms part of the dugong research program being funded by Defence to assess the effects of underwater explosions which are conducted at two intertidal sites at Triangular Island during occasional Clearance Diver training courses.

Feasibility

Modern underwater piezoelectric sensors can be deployed at various distances and depths from an underwater detonation so as to record the amplitude, frequency and shallow water propagation behaviour of the pressure wave and associated noise.

Methodology

Arrays of sensors are planned to be deployed at different distances from Triangular Island by underwater sound specialists from the Defence Science and Technology Organisation (DSTO). This equipment and associated recording gear will be used to monitor detonations during two Clearance Diver training courses between September and November 1999. On-site real-time analysis of each detonation will enable the sensor positions to be optimised during the first course, so that the propagation and decay characteristics of the pressure wave emanating from each of the two intertidal training sites can be determined as accurately as possible. The results will subsequently be used to model an acoustic ‘contour map’ of the region. The map will then be compared with a ‘dugong use’ map produced from recent dugong satellite tracking in Shoalwater Bay and the planned aerial monitoring project (refer Project 19).

Approximate cost

Approximately $45 000 (comprising $20 000 (DSTO) for deployment of DSTO personnel, sensors and monitoring equipment, $10 000 (DEO) to enable purchase of the sensor array cabling; and

$12 000 (DEO) for the acoustic modelling analyses and mapping).

Time required

July 1999 to April 2000