Development of Environmental Mitigation Measures for the Sound Sources of Autonomous Underwater Vehicles (AUVs)

Abstract

Autonomous Underwater Vehicles (AUVs) will be vital to support future Marine Research and enhance Defence capabilities. As these new technologies emerge it is important to ensure all possible environmental impacts have been assessed and appropriately mitigated. Unmanned Underwater Vehicles (UUVs) and Autonomous Underwater Vehicles can comprise of a wide variety of acoustic sensors as can the accompanying survey ship. National and European legislation is in place to protect habitats and species from harm which includes the disturbance to marine mammals (The Conservation of Offshore Marine Habitats and Species Regulations, 2017; The Habitats Directive, 1992). Emission of impulsive sound from acoustic sensors have the potential to adversely impact marine mammals (Finneran, 2015;Harris, et al., 2016). These impacts can range from general disturbance to hearing damage when certain thresholds of the received sounds are breached. In the most severe cases, permanent shifts to hearing thresholds can occur (Southall, et al., 2019). Understanding the environmental impact and developing appropriate mitigation measures for UUVs and AUVs will therefore ensure these new Defence capabilities are minimising the impact to marine mammals whilst ensuring Defence operations are not at risk. A first screening and scoping study determined the environmental aspects and impacts related to the sensors onboard AUVs procured in Defence. Further analysis is being conducted to inform the extent of the impact and to determine if any existing mitigation strategies could be adopted and integrated into the Standard Operating Procedures for planned AUV use and exercises e.g. running bespoke Sonar Risk Assessments ahead of deployments together with temporal (seasonal) and/or spatial planning of operations. This paper explores the environmental management techniques adopted to understand the environmental impact and introduce mitigation measures for future challenges related to the deployment of AUVs such as the cumulative effects of multiple AUVs functioning together and the deconfliction of other anthropogenic sound sources.