Environmental Risk Assessment Framework for Dredging Sounds

Underwater sounds produced from anthropogenic sources may pose risks to aquatic life, yet there is much uncertainty regarding the prediction of these impacts. A structured risk-based framework for identifying, assessing, and managing risks associated with underwater sounds has been previously proposed; however, real-world applications of the approach are lacking. Therefore, this chapter describes a risk-based framework for evaluating underwater sounds from dredging operations and demonstrates the process using a real-world dredging scenario. The approach described was used to evaluate risks to aquatic biota from a dredging operation in the Port of Alaska, USA. Sound levels were recorded during dredging activities and used to evaluate the relative risk of hearing impairment to the species of concern, including marine mammals and fish. Demonstration of the screening-level approach was beneficial to inform the relative risk of dredging operations, eliminate species of concern from further evaluation, and provide a path forward for future refinements to decrease uncertainties. This approach provides a transparent and repeatable phased methodology to discern ecological risks associated with dredge-induced underwater sounds that is applicable to a wide range of sound sources and site-specific scenarios.