Version 2025.0.00

9.0 Physical Seabed Samples

For NOAA ISD surveys, if Field Units have been tasked with collecting physical seabed samples, the character of the bottom must be determined, particularly in harbors, designated anchorages, and other areas where vessels may anchor. 

 

In general, sampling the surface sediment layer is usually adequate to define the bottom characteristics for charting. Clamshell bottom snappers or similar physical seabed samplers should be used to obtain as large a sample as possible. For NOAA ISD surveys, if a more detailed study of the ocean floor is required, the Hydrographic Survey Project Instructions will specify the type of sampler to use.

 

For NOAA ISD surveys, if a Field Unit is assigned to conduct seabed samples, the Field Unit must review their Project Instructions for the total number of required samples and determine a sampling plan based on:

  • Data acquired during survey operations that differentiates varying seafloor characteristics (e.g. multibeam echo sounding backscatter data).
  • Areas of potential vessel anchoring, i.e. samples must not be taken in depths greater than 80 meters or within dredged channels (DRGARE), pipeline and cable areas (PIPSOL, CBLARE), or fairways and approaches to a channel (FAIRWY).

 

For NOAA ISD surveys, in areas where seabed samples are not required but where the general trend of the newly surveyed depths significantly differs from charted depths, the Field Unit must contact their OCS Project Manager as appropriate to determine if seabed samples are necessary and to define the sample density.

 

The hydrographer must record the position of each sample obtained. In addition, each sample must be described and attributed in the Feature File. Refer to the Feature Attribute Encoding Guide for more details on physical seabed sample encoding.