Assessing noise-related impacts of acoustic disturbances on marine mammals

We developed the Dynamic Risk Assessment Model for Acoustic Disturbance (DRAMAD), which models the movements of marine mammals before, during and after noise exposure.

Current noise risk assessment models assume that marine mammals are stationary. However, marine mammals move around their environment, which means traditional risk assessments can lead to unrealistic results. As such, Statoil (an oil and gas exploration company) asked us to develop a risk assessment tool that took this into account.

To do this, we developed agent-based modelling to look at sound impacts using the Chukchi Sea as a demonstration area. First, we modelled the hydrodynamics of the Chukchi Sea using our MIKE by DHI software. Next, we extracted environmental variables that could influence the movements of the six species studied:

• bowhead whales
• beluga whales
• bearded seals
• ringed seals
• spotted seals
• walruses

Then, we investigated the relationship between the variables and movement patterns of the whales and seals. By doing this, we could predict areas of high importance within the Chukchi Sea. Finally, we used agent-based modelling to predict the movements of individual marine mammals. We could then model reactions to extracted variables and sound.

DRAMAD gives Statoil more accurate results than current noise risk assessment models on large scale noise-related impacts. It also enables Statoil to convey their environmental awareness to the local communities around the Chukchi Sea. Furthermore, DRAMAD can potentially also be used for large scale risk assessments in new license blocks. A variety of scenarios using a number of sound sources can be modelled. This could help identify risky periods or sensitive areas where impacts could be high. DRAMAD will also greatly increase the amount of information for exploration campaign planning and decision making.