Analysis of Acoustic Effects on Marine Mammals for the Proposed Undersea Warfare Training Range

摘要

The U.S. Navy is preparing a Draft Environmental Impact Statement/Overseas Environmental Impact Statement (DEIS/OEIS) for the proposed Undersea Warfare Training Range (USWTR). The DEIS includes an assessment of the effects of Navy sonars on marine mammals during exercises to occur on the range as required by the Marine Mammal Protection Act (MMPA). The Naval Undersea Warfare Center (NUWC) Division, Newport, RI, has completed this assessment for three sites: the preferred site of Onslow Bay, NC, and the alternate sites of Wallops Island, VA, and Jacksonville, FL. This document describes the modeling approach, input data, and analysis method employed to estimate the number of marine mammals that could be affected by operation of Navy tactical sonar systems at the USWTR. The input data that are key to this methodology fall into five categories: (1) Marine mammal density estimates for the proposed range locations, (2) Definitions for Level A and Level B harassment thresholds for Navy sonar systems, (3) Geophysical data for the sites, (4) Characterization of Navy training scenarios and the military sonars to be used, and (5) Operational characteristics for the sonar systems to be used (many of these parameters are classified). The Marine Mammal Effects Model calculates an area for which each source produces a total energy flux (also referred to as total acoustic energy or total energy flux density) above the defined Level A and Level B harassment thresholds. This is calculated for each combination of training scenario, source, and season. This area is multiplied by the mammal population density for each species and the number of scenario occurrences per year to determine the estimated number of takes that will occur annually. Data are summarized by harassment thresholds for the respective sonar system, scenario, and species. A summary of the input data for the methodology is provided in figure 1-1, and a flow chart for the modeling is shown in figure 1-2.