OPR-F330-KR-22 Albemarle Sound Albemarle Sound Geodynamics H13762 5 Alligator River North Carolina United States 5000 2023 Nicholas Damm, CH Navigable Area 2023-02-14 2023-02-24 2023-10-24 Multibeam Echo Sounder Singlebeam Echo Sounder Multibeam Echo Sounder Backscatter Side Scan Sonar meters UTC Atlantic Hydrographic Branch Any revisions to the Descriptive Report (DR) applied during office processing are shown in red italic text. The DR is maintained as a field unit product, therefore all information and recommendations within this report are considered preliminary unless otherwise noted. The final disposition of survey data is represented in the NOAA nautical chart products. All pertinent records for this survey are archived at the National Centers for Environmental Information (NCEI) and can be retrieved via https://www.ncei.noaa.gov/. Products created during office processing were generated in NAD83 UTM 18N, LWD. All references to other horizontal or vertical datums in this report are applicable to the processed hydrographic data provided by the field unit. CC0-1.0 (NOAA Contractors) CC0-1.0 https://creativecommons.org/publicdomain/zero/1.0/ https://creativecommons.org/publicdomain/zero/1.0/legalcode These data were produced under contract with NOAA and any potential copyright was assigned to NOAA. NOAA waives any potential copyright and related rights in these data worldwide through the Creative Commons Zero 1.0 Universal Public Domain Dedication (CC0). Contractor Geodynamics conducted a hydrographic survey in the assigned area of H13762 located in the Alligator River. Within H13762, all survey operations were conducted in accordance with the provided Statement of Work (SOW), Hydrographic Survey Project Instructions (PI), and the March 2022 National Ocean Service (NOS) Hydrographic Survey Specifications and Deliverables (HSSD). Any deviations from the aforementioned guidelines have been approved by the National Oceanographic and Atmospheric Administration (NOAA) Hydrographic Survey Division (HSD) Operations (OPS) branch and are documented in the survey correspondences. 36.029662 76.204558 35.646403 75.920007 Data were acquired to the survey limits in accordance with the requirements listed in the PI and the HSSD. Overview of project survey limits (H13762 shown in blue), overlaid onto Charts 11553, 12205, and 12206 file:///B:/OPR-F330-KR-22/Surveys/H13762/01_HDR/Reports/Descriptive_Report/SupportFiles/H13762_Survey_Limits_Overview.jpg H13762 survey limits overlaid onto Charts 11553 and 12205 file:///B:/OPR-F330-KR-22/Surveys/H13762/01_HDR/Reports/Descriptive_Report/SupportFiles/H13762_Survey_Limits_Sheet.jpg Albemarle Sound in North Carolina is a large, shallow, low-salinity estuary which extends approximately 50 nautical miles inland from the Outer Banks barrier islands. For this project, approximately 522 square nautical miles of modern, high-resolution hydrographic data will be collected in Albemarle Sound and connecting rivers. Commercial and recreational fishing as well as waterfront tourism are important economic drivers for the communities around the sound. Albemarle Sound has been facing recent and drastic decline in water quality and fishing stocks, and since the late 1980s, high levels of contaminants have been documented in the waters and biology of the sound and tributaries. To monitor this situation, the USGS and partners installed a network of monitoring stations as part of a program to study water quality to understand the sources and movement of nutrients and biota. The National Water Center along with the North Carolina Department of Environmental Quality have stated that there is a need for updated bathymetric data in the waterways to inform hydrodynamic models to improve understanding nutrient movement and to predict the effects of future sea-level and coastline change. Data collected by this survey will be used to characterize seabed habitat which will be used to help manage a healthy and sustainable seafood industry and help monitor future changes to the estuary ecology. This hydrographic survey will update NOAA National Ocean Survey (NOS) charts and products to identify hazards and improve navigation safety in a region which includes areas of high need for modern bathymetry based on the age of the prior data (1920) and the Hydrographic Health model. Survey data from this project are intended to supersede all prior survey data in the common area. The entire survey is adequate to supersede previous data. Survey quality in H13762 meets or exceeds requirements set forth in the HSSD. Survey quality was assessed through visual inspection, the analysis of crosslines, and utilizing QC Tools to assess uncertainty and density. Additionally, junction analyses were conducted between overlapping data collected on this project. For more information on methods and results of the survey data quality assessments for this survey, refer to section B.2 of this report. Inshore limit to 3.5 meters (m) 50 m set line spacing Singlebeam Echosounder (SBES). Refer to HSSD Section 5.2.2.4 Set Line Spacing Option C 3.5 m and greater Complete Coverage Side Scan Sonar (SSS) with concurrent SBES (Refer to the Special Data Handling Requirements Section of the PI) The entirety of H13762 was acquired with complete coverage as described in the Special Data Handling Requirements section of the PI and set line spacing in accordance with section 5.2.2.4 Option C of the HSSD (coverage shown in Figure 3). All efforts were made to acquire survey data to the sheet limits or to the Navigable Area Limit Line (NALL), as defined in section 1.3.2 of the HSSD. It should be noted that an exception to the depth that defines NALL, usually 3.5 m, was changed to 2 m at Low Water Datum (LWD) for this project and is stated as such in the PI. Based on field observations, additional guidance from NOAA HSD OPS was given in respect to the SSS coverage requirements that are outlined in the PI. The additional guidance concluded any area deeper than 3.5 m, which is separated from the main central navigation areas by waters shoal of 3.5 m, on the hydrographer's discretion and keeping safety of navigation in mind, may be treated as an area 3.5 m or less, thus not requiring the collection of side scan data. Additionally, to account for the large areas with a flat shallow isobath, it was also agreed upon that in areas with depths that were deeper than 3.5 m but shoaler than 4 m, the collection of side scan data was not required. Maps were provided to NOAA HSD OPS prior to field closure that displayed the side scan coverage obtained in water sheds and tributaries, areas where the developed guidance was most frequently used. The maps were provided to NOAA HSD OPS to assure compliance and welcome feedback to the employed guidance. See DR Appendix II Supplemental Records for related correspondence. Throughout the survey area NALL was often defined by safety limitations before the prescribed depth limit (2 m) was met, particularly along the shoreline or inhibited due to the presence of recreational fishing gear. Adaptive techniques and tools were used in the field to document areas where the 2 m depth contour was not reached due to safety concerns. More detail on these methods can be found in the DAPR. Figure 4 provides an example of the area defined by the 2 m NALL specification. Occasional deviations from the 50 m set line spacing plan were deemed appropriate for vessel safety as shown in Figure 5. Figures 6-8 provide examples of areas where NALL was defined safety limitations. A large portion of shoreline in H13762 contained dangerous trees and submerged stumps within the survey area. Figures 9 and 10 provide examples of these occurrences. H13762 Complete Coverage SSS (greyscale) with bathymetric coverage and assigned sheet limits in black file:///B:/OPR-F330-KR-22/Surveys/H13762/01_HDR/Reports/Descriptive_Report/SupportFiles/H13762_Survey_Coverage.png Area in H13762 where NALL is defined by depth (2m) file:///B:/OPR-F330-KR-22/Surveys/H13762/01_HDR/Reports/Descriptive_Report/SupportFiles/H13762_NALL_Depth.png Several features within SBES set line coverage areas were deemed unsafe to transit directly transit over, and deviations around several charted features were made. file:///B:/OPR-F330-KR-22/Surveys/H13762/01_HDR/Reports/Descriptive_Report/SupportFiles/H13762_SBES_SetLineDeviation.jpg Area in H13762 where safety defined NALL because of fishing gear, resulting in a gap in data file:///B:/OPR-F330-KR-22/Surveys/H13762/01_HDR/Reports/Descriptive_Report/SupportFiles/H13762_FishingGear2.png Area in H13762 where safety defined NALL because of fishing gear, area reported as DTON file:///B:/OPR-F330-KR-22/Surveys/H13762/01_HDR/Reports/Descriptive_Report/SupportFiles/H13762_NALL_Pound_Nets.png Area in H13762 where safety defined NALL because of fishing gear, resulting in a gap in data file:///B:/OPR-F330-KR-22/Surveys/H13762/01_HDR/Reports/Descriptive_Report/SupportFiles/H13762_FishingGear.png Area in H13762 where safety defined NALL due to proximity to trees on the shoreline file:///B:/OPR-F330-KR-22/Surveys/H13762/01_HDR/Reports/Descriptive_Report/SupportFiles/H13762_NALL_Trees.png Area in H13762 where safety defined NALL due to dangerous trees and stumps in area file:///B:/OPR-F330-KR-22/Surveys/H13762/01_HDR/Reports/Descriptive_Report/SupportFiles/H13762_Tree_Nall.png R/V 4Points 319.87 0.0 0.0 54.42 0.0 0.0 0.0 140.97 0.0 R/V Benthos 27.42 10.73 0.0 25.45 0.0 0.0 0.0 0.0 0.0 R/V Chinook 562.5 8.1 0.0 401.45 0.0 0.0 0.0 14.41 0.0 X-15 787.59 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 X-19 992.55 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 2689.96 18.84 0.0 481.32 0.0 0.0 0.0 155.38 0.0 5.74 2 0 0 0 66.2 2023-02-24 2023-02-25 2023-02-26 2023-03-01 2023-03-06 2023-03-11 2023-03-12 2023-03-13 2023-03-14 2023-03-15 2023-03-16 2023-03-17 2023-03-18 2023-03-19 2023-03-20 2023-03-21 2023-03-22 2023-03-23 2023-03-24 2023-03-25 2023-03-26 2023-03-27 2023-03-28 2023-03-29 2023-03-30 2023-03-31 2023-04-02 2023-04-03 2023-04-04 2023-04-05 2023-04-06 2023-04-07 2023-04-08 2023-04-09 2023-04-10 2023-04-11 2023-04-12 2023-04-13 2023-04-14 2023-04-15 2023-04-22 2023-04-23 2023-04-25 2023-04-26 2023-05-02 2023-05-03 2023-05-04 2023-06-09 2023-06-10 2023-06-11 2023-06-12 2023-06-13 2023-06-20 2023-06-21 2023-06-22 2023-06-24 2023-06-25 2023-06-26 2023-07-06 2023-07-07 2023-07-08 2023-07-09 2023-07-10 2023-07-11 2023-07-12 2023-10-07 2023-10-08 2023-10-09 2023-10-10 2023-10-13 2023-10-24 Refer to the OPR-F330-KR-22 Data Acquisition and Processing Report (DAPR) for a complete description of data acquisition and processing systems, survey vessels, quality control procedures and data processing methods. Additional information to supplement sounding and survey data, and any deviations from the DAPR are discussed in the following sections. R/V 4Points 7.62 0.91 R/V Benthos 9.14 0.61 R/V Chinook 9.44 0.61 X-15 4.5 0.65 X-19 4.5 0.65 The following vessels were used for data acquisition during this survey: MBES Kongsberg Maritime EM 2040C SBES Teledyne Odom Hydrographic Echotrac E20 SBES Teledyne Odom Hydrographic Echotrac CV100 SSS EdgeTech 4205 Positioning and Attitude System Applanix POS MV OceanMaster Positioning and Attitude System Applanix POS MV WaveMaster Sound Speed System AML Oceanographic BaseX2 Sound Speed System AML Oceanographic AML-3 LGR Sound Speed System AML Oceanographic MicroX SV Sound Speed System Valeport SWiFT SVP The R/V Benthos and R/V 4-Points were installed with a Teledyne Echotrac E20 while the R/V Chinook was installed with a Teledyne Echotrac CV100. All Geodynamics owned vessels utilized a dual-head Kongsberg EM 2040C multibeam system, a POS M/V OceanMaster positioning and attitude system, an EdgeTech 4205 side scan towfish for side scan operations, and AML Oceanographic surface sound speed units. The X-15 and X-19 utilized a POS M/V WaveMaster for positioning and attitude as well as an Echotrac E20 singlebeam system. For sound speed profiles, the R/V Benthos and R/V Chinook utilized an AML BaseX2 system, the R/V 4-Points utilized an AML-3 LGR, while both X-15 and X-19 utilized a Valport SWiFT SVP. Further details on equipment and software used can be found in the DAPR. Singlebeam crosslines acquired for H13762 totaled 5.74% of mainscheme acquisition. In conjunction with the NOAA HSD PM/COR, it was agreed upon that a crossline percentage of approximately 5% of the mainscheme linear nautical miles was acceptable for mixed coverage sheets. Please see DR Appendix II Supplemental Records for the related correspondence. H13762 crosslines were collected and analyzed in accordance with section 5.2.4.2 of the HSSD. Crosslines were evaluated in CARIS HIPS with a detailed visual inspection followed by a thorough statistical analysis. To conduct the statistical analysis, a 4 m surface was generated with strictly mainscheme data and another, separate 4 m surface was generated with only crossline data. The mainscheme surface was created by mosaicking the mainscheme 4 m SBES CARIS Uncertainty surface (using the shoal layer) with the 1 m MBES CUBE surface (depth layer). A separate 4 m SBES Uncertainty surface containing only crosslines was created and the shoal layer from that surface was used for analysis. It should be noted in mixed coverage sheets crosslines were SBES only. The mainscheme and crossline files were analyzed using the Compare Grids tool in Pydro Explorer, which generated a difference surface and associated statistics. In addition to the direct statistics from the surface differencing, the tool assessed the difference surface statistics and computed the proportion of NOS total allowable vertical uncertainty (TVU) consumed by the mainscheme to crossline differences per surface node. The statistical results of the difference comparison show 95% of nodes falling within +/- 0.09 m, with a mean difference of 0.00 m (Figure 11). Additionally, at least 95% of the difference surface nodes met or exceeded TVU specifications, as described in section 5.1.3 of the HSSD. H13762 crossline to mainscheme difference statistics file:///B:/OPR-F330-KR-22/Surveys/H13762/01_HDR/Reports/Descriptive_Report/SupportFiles/H13762_Crossline_to_Mainscheme_Diff.png ERS via VDATUM 0.0 0.08 R/V 4Points 2.00 N/A N/A 0.05 R/V Benthos 2.00 N/A N/A 0.05 R/V Chinook 2.00 N/A N/A 0.05 X-15 2.00 N/A N/A 0.05 X-19 2.00 N/A N/A 0.05 The finalized CUBE and Uncertainty surfaces were analyzed using the HydrOffice QC Tools Grid QA tool to assure 95% of the surface nodes meet TVU specifications. The results of the Grid QA tool determined that the finalized CUBE and Uncertainty surfaces met or exceeded the TVU specifications, as shown in Figures 12-13. The multibeam surface was finalized with the computed uncertainty, derived from a mix of a priori and real-time uncertainty estimates, assigned as the uncertainty value. The singlebeam surface was finalized with the standard deviation of soundings at 95% confidence interval assigned as the uncertainty value. It should be noted that the uncertainty associated with the SEP model is applied in CARIS as the GPS sounding datum for multibeam data and applied as Tide Zoning for singlebeam data. Additional details related to uncertainty methods may be found in the DAPR. Finalized MBES 1m CUBE surface TVU statistics for H13762 file:///B:/OPR-F330-KR-22/Surveys/H13762/01_HDR/Reports/Descriptive_Report/SupportFiles/H13762_MB_1m_LWD_Final.GQv6.tvu_qc_Final.png Finalized SBES 4m Uncertainty surface TVU statistics for H13762 file:///B:/OPR-F330-KR-22/Surveys/H13762/01_HDR/Reports/Descriptive_Report/SupportFiles/H13762_VB_4m_LWD_Final.GQv6.tvu_qc_Final.png No junctioning surveys were provided for this project (see PI). However, H13762 junctions with H13755, H13758, H13760, H13761, and H13764 (Figure 14). Data overlap between H13762 and the adjacent surveys were attained. To conduct the junction analyses, similar to section B.2.1 of this report, the Pydro Compare Grids tool was utilized. The inputs for this tool were the surfaces for each individual survey. It should be noted for SBES CARIS Uncertainty surfaces the shoal layer was utilized for the analysis. Please reference the Descriptive Reports for H13755, H13758, H13760, and H13761 for junction analyses results to H13762. In addition to the statistical results of the junction analyses, the resultant difference surfaces were visually inspected and CARIS HIPS Subset Editor was used to examine overlapping data for consistency, agreement between surveys, and confirming data met TVU specifications. Overview of H13762 junction surveys file:///B:/OPR-F330-KR-22/Surveys/H13762/01_HDR/Reports/Descriptive_Report/SupportFiles/H13762_Junction_Overview.png H13764 5000 2023 Geodynamics W For H13762 SBES to H13764 SBES, the statistical results of the difference comparison shows 95% of nodes falling within +/- 0.09 m, with a mean difference of 0.03 m (Figure 15). Additionally, at least 95% of surface nodes met or exceed TVU specifications, as described in section 5.1.3 of the HSSD. For H13762 SBES to H13764 MBES, the statistical results of the difference comparison shows 95% of nodes falling within +/- 0.06 m, with a mean difference of 0.05 m (Figure 16). Additionally, at least 95% of surface nodes met or exceed TVU specifications, as described in section 5.1.3 of the HSSD. Junction analysis between H13762 SBES and H13764 SBES file:///B:/OPR-F330-KR-22/Surveys/H13762/01_HDR/Reports/Descriptive_Report/SupportFiles/H13762_VB_4m_LWD_Shoal_Final-H13764_VB_4m_LWD_Shoal_Final_depth_delta.png Junction analysis between H13762 SBES and H13764 MBES file:///B:/OPR-F330-KR-22/Surveys/H13762/01_HDR/Reports/Descriptive_Report/SupportFiles/H13762_VB_4m_LWD_Shoal_Final-H13764_MB_1m_LWD_Final_depth_delta.png Sonar system quality control checks were conducted as detailed in the quality control section of the DAPR. Environmental Influences Affecting Side Scan Imagery Throughout the duration of the survey, side scan acquisition frequently encountered environmental conditions which affected portions of the swath which would hinder the selection of contacts in the affected regions. The persistent challenging environmental influences were communicated with NOAA HSD OPS in the field and was additionally discussed with AHB prior to sheet submission (see project correspondence). These environmental conditions included numerous bait balls (biologic organisms suspended within the water column), vessel prop wash, and effects from water column stratification. The affected portions of side scan imagery which would be considered a holiday due to environmental effects were identified and reacquired with either side scan or multibeam bathymetry to meet the complete coverage requirements. The SSS lines that were reacquired frequently encountered similar environmental influences, and the final mosaic has been layered as best as possible to minimize the portrayal of artifacts. The side scan sonar mosaics are not free from environmental influences, but multiple methods were taken to ensure complete coverage was achieved and side scan sonar imagery was sufficient to identify a 1m x 1m x 1m target. More details on the methods used to ensure complete coverage, assess side scan sonar image quality, and clarifications on the final mosaics can be found in the DAPR and were additionally discussed in the pre-submission meeting with AHB (see project correspondence). Example of environmental influences affecting SSS imagery which were persistent throughout the survey area, present within the final delivered mosaic. file:///B:/OPR-F330-KR-22/Surveys/H13762/01_HDR/Reports/Descriptive_Report/SupportFiles/H13762_SSS_Env_1.jpg Example of the use of MBES recoveries, SBES nadir coverage, and additional overlapping SSS imagery to confirm adequate coverage and identification of any potential seafloor features. file:///B:/OPR-F330-KR-22/Surveys/H13762/01_HDR/Reports/Descriptive_Report/SupportFiles/H13762_SSS_Env_2.jpg Side Scan Towfish Altitude and Coverage Requirement Side scan towfish altitude reports were generated from all side scan navigation data in SonarWiz and examined to ensure compliance with the adjusted altitude specifications as outlined in the PI. Even with the allowable towfish altitude adjusted to 4-20% of the range scale in use (<8m of water depth), occasional deviations were identified. Any side scan lines which did not adhere to the adjusted altitude specifications were identified and the associated .tif images were re-exported from SonarWiz at a range scale which reduced the effective horizontal range to achieve compliance with the towfish altitude requirements. Recoveries were then completed as necessary. Adjusted altitude requirements as well as the approval of the .tif trimming method of addressing deviations from the towfish altitude requirements (as outlined in the PI) can be found in the project correspondence as well as detailed in the DAPR. Hydrographer discretion and best practices were utilized where the depth contour or the NALL defined by safety limitations determined the change in coverage type. Artifacts on the edges of SSS imagery where the coverage type changed were reviewed in detail and reacquired with additional side scan sonar or multibeam bathymetry when safe and practicable. Multibeam Echosounder Ping Drops On very rare occasion, it was observed that the multibeam echosounder would experience a "ping drop" issue that resulted in unexpected missing ping records, which were not observed by the survey vessel at the time of acquisition. An example of this ping drop can be seen in Figure 19. Any holidays in the resultant 1 meter resolution MBES surface were identified and reacquired, and no holidays resulting from these few and intermittent issues remain in the final delivered surfaces. Example of MBES ping drop observed from R/V Benthos on DN 181 file:///B:/OPR-F330-KR-22/Surveys/H13762/01_HDR/Reports/Descriptive_Report/SupportFiles/H13762_MBES_PingDrop.jpg Recreational Fishing Gear Throughout the survey area, crab pots and other types of recreational fishing gear were observed or identified within the data. Particular attention was taken to avoid gear interactions and promote the safety of vessels and equipment, and at times defined the survey limits, as described in section A.4. Crab pots were often identified within the side scan sonar imagery or multibeam data and found to be of dimensions that did not warrant investigation. These objects were rejected from the MBES data if they caused the surface to be pulled past TVU, but were otherwise not rejected. Please see the DAPR and section D.1.4 of this report for more information on fishing stakes. None Exist There were no other factors that affected corrections to soundings. When collecting multibeam data, casts were often taken every two hours, never exceeding the four hour limit, and immediately following transit to a new location. When collecting SBES data, generally two casts per day were conducted. During MBES data collection, surface sound speed was compared in real-time to the sound speed profile. When the comparison differed by more than 2 m/s, a new sound speed profile was acquired. Additionally, Hypack and Kongsberg SIS provided a real-time visual assessment of data quality (bathymetric grids, swath views) aiding the hydrographer in determining when a new cast was required. For more detailed information on sound speed methods, refer to the DAPR. All equipment and survey methods were used as detailed in the DAPR. Density The finalized CUBE and Uncertainty surfaces were analyzed using HydrOffice QC Tools Grid QA tool to assure data met the required density specifications. Density requirements were achieved for the finalized surfaces in H13762 with at least 95% of the MBES CUBE surface nodes (Figure 20) and at least 95% of the SBES Uncertainty surface nodes (Figure 21) containing at least five or more soundings, exceeding the specifications required by section 5.2.2.3 of the HSSD. Finalized MBES 1 m CUBE surface density statistics for H13762 file:///B:/OPR-F330-KR-22/Surveys/H13762/01_HDR/Reports/Descriptive_Report/SupportFiles/H13762_MB_1m_LWD_Final.GQv6.density_Final.png Finalized SBES 4 m Uncertainty surface density statistics for H13762 file:///B:/OPR-F330-KR-22/Surveys/H13762/01_HDR/Reports/Descriptive_Report/SupportFiles/H13762_VB_4m_LWD_Final.GQv6.density_Final.png Flier Finder In addition to a visual inspection, the multibeam CUBE surface was analyzed using HydrOffice QC Tools Flier Finder tool to assure data does not contain fliers (anomalous data as defined by QC Tools flier finding algorithms #2-5). While the Flier Finder tool flags surface fliers meeting a set criteria, it will also flag real surface features that meet the same criteria. Spurious soundings flagged by Flier Finder were cleaned until either no fliers remained or the remaining flagged fliers were deemed valid aspects of the surface. For SBES flier identification, the Uncertainty surface shoal layer was reviewed manually in CARIS. In addition to a thorough visual inspection of the surface, the review involved applying display filters to the surface that flagged potential fliers and helped the hydrographer spot any anomalies. An emphasis was put on manual inspection because the Flier Finder tool in Pydro was found to be unreliable when searching for fliers in the SBES surfaces. See DAPR for more information on SBES quality control measures. Holidays All CUBE surfaces were analyzed using HydrOffice QC Tools Holiday Finder to determine if the surfaces contained holidays, as described in section 5.2.2.3 of the HSSD. The tool scanned the CUBE surfaces, identifying any holidays, and generated an S-57 file to illustrate the locations of holidays. Another method of holiday evaluation was to visually pan the surfaces to identify holidays. The hydrographer would often alter the surface display (color ranges, symbology, shading) to help aid the hydrographer in identifying coverage gaps. The results reflected the same outcome as the tool. These manual evaluation methods were also employed to assess SBES. The main source of data gaps in the MBES surface were the result of dense bait balls which were additionally identified in the side scan imagery. These erroneous soundings were rejected by the hydrographer, were recovered with additional MBES data, and are not reflected in the final surface. The side scan mosaic was extensively reviewed for environmental influences which would prevent the detection of a 1m x 1m x 1m object, and where those were identified, additional SSS or MBES data was acquired to meet complete coverage requirements. Additional information on data quality management can be found in the DAPR. All data reduction procedures conform to those detailed in the DAPR. All sounding systems were calibrated as detailed in the DAPR. Raw backscatter data were collected and stored within the .ALL files. Backscatter data were processed and reviewed for quality assurance in QPS FMGT. In accordance with the HSSD, GSFs and backscatter mosaics were exported from FMGT. Hydrographers in the field monitored backscatter intensities in real-time and made efforts to collect quality backscatter without hindering bathymetric data quality. Refer to the DAPR for more information on backscatter data acquisition and processing procedures. CARIS HIPS and SIPS 11.4.20 CARIS HIPS and SIPS 11.4.22 CARIS HIPS and SIPS 11.4.26 Xylem Hypack 2022.Q3 QPS FMGT 7.10.1 Chesapeake Technologies SonarWiz 7 7.10.02 NOAA Profile Version 2023 It should be noted values for singlebeam surfaces are representative of the shoal layer. The singlebeam grid contains bathymetry data for both set line spacing and for filling the SSS nadir gap in full coverage areas. The multibeam CUBE surface is for fill and investigations. See DAPR for more details on the utilization of each sensor. H13762_MB_1m_LWD_Final CARIS Raster Surface (CUBE) 1 1.11 6.08 NOAA_1m Complete MBES H13762_MB_1m_LWD CARIS Raster Surface (CUBE) 1 2.88 6.08 NOAA_1m Complete MBES H13762_VB_4m_LWD_Final CARIS Raster Surface (Uncertainty) 4 0.38 6.14 NOAA_4m SBES Set Line Spacing H13762_VB_4m_LWD CARIS Raster Surface (Uncertainty) 4 0.38 6.14 NOAA_4m SBES Set Line Spacing H13762_SSSAB_1m_540kHz_1of2 SSS Mosaic 1 NOAA_1m 100% SSS H13762_SSSAB_1m_540kHz_2of2 SSS Mosaic 1 NOAA_1m 200% SSS H13762_MBAB_2m_Benthos_300kHz_1of1 MB Backscatter Mosaic 2 NOAA_2m Complete MBES H13762_MBAB_2m_Chinook_300kHz_1of1 MB Backscatter Mosaic 2 NOAA_2m Complete MBES "H13762_SSSAB_1m_540kHz_1of2" represents the 100% complete coverage of the mainscheme acquisition sheetwide, while "H13762_SSSAB_1m_540kHz_2of2" is the 200% coverage required for feature disproval. It should be noted that SBES data were cleaned with an emphasis to best represent objects extending from the seafloor. The shoal layer within the Uncertainty surface best represents these objects in the grid. These objects were not investigated further because of safety limitations. See Figure 22 for an example of bottom objects within the 4 m Uncertainty surface shoal layer. All surfaces submitted are in compliance with the set line spacing requirement per section 5.2.2.4 Option C of the HSSD and the Complete Coverage SSS with Concurrent SBES Requirements outlined in the PI. In addition to the surfaces listed above, interpolated grids were generated and delivered in accordance with PI and guidance from NOAA HSD OPS. These additional grids are for the National Water Center deliverable and reflect _NAVD88 in their respective filenames. Reference the DAPR section C.1.4 for more information on interpolation and gridding methods, and the project correspondence for more information on National Water Center deliverables. Image with significant bottom objects in SBES surface seen in shoal layer file:///B:/OPR-F330-KR-22/Surveys/H13762/01_HDR/Reports/Descriptive_Report/SupportFiles/H13762_SBES_Shoal_Layer.png Designated Soundings H13762 contains 34 designated soundings in accordance with sections 5.2.1.2.3 and 7.4 of the HSSD. 33 of these designated soundings were created to facilitate feature management and best represent the least depths of features in the Final Feature File (FFF). One designated soundings was utilized for overriding the gridded surface as per HSSD specification 5.2.1.2.3 and is within the boundary of a foul area with the Unique ID of H13762_DTON_08. This feature was investigated before the foul area was fully digitized. Since this designated sounding is within the foul area boundary, the designated sounding is not used as the VALSOU for feature with Unique ID of H13762_DTON_08, as the foul area was not fully ensonified and portions were above water. In the finalized CUBE surfaces, the CARIS HIPS Apply Designated Soundings function ensured designated sounding depths are retained in the finalized surfaces. Additional information discussing the vertical or horizontal control for this survey can be found in the accompanying DAPR. Low Water Datum ERS via VDATUM Albemarle_Sound_NAD83-LWD(LMSLxGeoid20B-0.5ft)_m.csar Albemarle_Sound_ITRF-LWD(LMSLxGeoid20B-0.5ft)_m.csar Real-time positional data were corrected with G2+ and G4+ Global Navigation Satellite System (GNSS) satellite corrections provided by the Fugro Marinestar Satellite-Based Augmentation System (SBAS). To improve the accuracy of the real-time data, real-time position data were post-processed using Applanix POSPac Mobile Mapping Solution (MMS) software. Trimble CenterPoint RTX correction methods were used to create Smoothed Best Estimate of Trajectory (SBET) files, which were applied to the survey data in CARIS HIPS for all multibeam data and in Hypack for all singlebeam data. For further information regarding processing and application of SBET and SEP files, please reference the DAPR. North American Datum 1983 (2011) Projected UTM 18 Real-time positional data were corrected with G2+ and G4+ GNSS satellite corrections provided by the Fugro Marinestar SBAS. A detailed visual comparison was performed in CARIS HIPS between H13762 and the ENCs listed in Table 14 of section D.1.1. Sounding layers were generated from the CUBE and Uncertainty surfaces and overlaid onto the ENCs to visually assess differences between the surveyed and charted depths. In addition to a detailed visual inspection in CARIS HIPS, all soundings from the chart were downloaded as a shapefile from NOAA's ENC Direct to GIS application and differenced with the surveyed depths from the 4 m surface in ESRI ArcPro. A statistical analysis of the difference comparison is shown in Figure 23. The surveyed depths from H13762 generally agree with the charted soundings from the largest scale ENCs within the survey area, with a mean difference of -0.60 m (ENC soundings shoaler on average). Due to the status of the outdated charts and potential risk of excessive bathymetric splits, guidance was provided by NOAA HSD OPS with allowance to omit bathymetric splits when a charted sounding between survey lines was shoal of the surveyed data. Data were reviewed in comparison to the chart but also between surveyed depths, conducting bathymetric splits at hydrographer's discretion. Please see project correspondence and the DAPR for further information on this topic. H13762 statistical analysis of surveyed soundings to charted soundings file:///B:/OPR-F330-KR-22/Surveys/H13762/01_HDR/Reports/Descriptive_Report/SupportFiles/H13762_Chart_Comparison.png US5NC52M 40000 16 2021-10-27 2024-02-05 US4NC53M 80000 38 2023-08-29 2024-03-11 US4NC55M 80000 6 2016-09-26 2018-02-14 No significant shoals were identified to be hazardous in H13762. 13 DTONs were reported and forwarded to MCD and were added to the FFF with Special Feature Type as "DTON". It should be noted that the least depth, position, or feature geometry may change slightly during post-processing for reported DTONs. Refer to the FFF for the remarks and recommendations for each feature. See DR Appendix II Supplemental Records for the Submitted DTON reports and related correspondence with the HSD Project Manager. Disprovals of charted features within areas that were surveyed with SSS coverage requirements were either conducted or attempted. In agreement with the NOAA HSD OPS, all disproval search radii were addressed with consideration of the re-scheme chart scale and were of at least 150 m. When a feature was detected within this radius, completing the disproval was not required and the new feature was addressed as New/Delete. In areas where the coverage requirements changed based on depth, disprovals were conducted at the hydrographers discretion with consideration to navigational significance and safety. Please reference correspondence for more information on disprovals for this project. A side scan sonar contact was detected within the 150 m search radius for the assigned charted features (Unique ID: 5_001_1, 5_100_1 and 5_105_1), therefore, a disproval with 200% SSS was not conducted. The contact was developed with MBES and addressed in the FFF (Unique ID: 5_001_2 and 5_105_2). These features were changed to new obstruction areas after investigations were conducted. Assigned obstruction with Unique ID: 5_027_1, although within the depth range for SSS coverage, was not investigated due to being outside the extents of SSS coverage requirements which are discussed in section A.4 of this report. Additionally, a disproval was not attempted for two assigned features with Unique IDs: 5_075_1 and 5_076_1 due to safety and disproval radius extending into NALL areas. Please see project correspondence for more information on disprovals. Assigned piles with Unique IDs: 5_004_1, 5_005_1, 5_007_1, and 5_009_1 are within a new charted foul area with Unique ID: H13762_DTON_08 and were not disproved because of safety. A disproval was attempted for two assigned charted feature (Unique ID: 5_008_1, 5_083_1), however the radius was not fully ensonified and 200% overlap was not achieved due to safety and proximity to the shoreline. These lines have been included in the respective mosaics and the feature addressed in the FFF with a description of "Retain". In agreement with the NOAA HSD OPS, disprovals were not required for assigned charted features located within the SBES set line spacing coverage areas and these were investigated at the hydrographers discretion with navigational significance and safety in mind, and addressed with a description as "Retain" in FFF (see project correspondence). It should be noted that Chart US5NC52M has an incorrectly charted fairway going through a shoal area. An ASSIST report was not submitted because survey data would benefit the chart update and the currently charted ATONs, Dredged Area, and charted recommended track are accurately charted and positioned. Please see Figure 24 for more details. Side scan contacts were not included for overhead features such as powerlines and bridges as these features are charted and above the surface. These areas were properly assessed to ensure contact shadows are associated with the charted overhead feature and not new, separate features. With respect to the aforementioned deviations, all assigned charted features within H13762 are detailed in the FFF in accordance with section 7.3 of the HSSD. See DR Appendix II Supplemental Records for related correspondence with the NOAA HSD OPS. Image showing where the charted fairway is incorrectly positioned file:///B:/OPR-F330-KR-22/Surveys/H13762/01_HDR/Reports/Descriptive_Report/SupportFiles/H13762_Fairway_Channel.png Throughout the project area, uncharted fishing stakes and pound nets were both observed at the surface and identified in SSS and bathymetric data. In agreement with the NOAA HSD OPS, when identified as contacts or within bathymetric data, these features were developed accordingly with MBES to obtain a least depth when safe and practicable, and have been included in the FFF as new obstructions. SSS contacts with Unique IDs: CH_H13762_83_3, CH_H13762_83_4, CH_H13762_83_5, CH_H13762_83_6, CH_H13762_83_7, CH_H13762_83_8, CH_H13762_83_9, CH_H13762_83_10, CH_H13762_83_22, 4P_H13762_160_13, 4P_H13762_160_14, 4P_H13762_160_15, CH_H13762_192_1, CH_H13762_192_2, CH_H13762_192_3 were deemed unsafe to develop with MBES. These contacts are located in the FFF with the Unique IDs: H13762_DTON_09 and H13762_DTON_10. The originally submitted DTON area features were extended to include these submerged contacts, as they seem of the same origin of the fishing stakes that were visually observed above the water's surface (used to digitize the area for original DTON submission) and were unsafe to further develop with MBES. SSS contacts with Unique IDs: CH_H13762_083_1, CH_H13762_083_2, and CH_H13762_083_21 located within the area feature with Unique ID: 5_143_1 were not developed because the contact shadows extended past the edge of the SSS imagery, relatively shallow MBES depths, and the presence of dangerous fishing stakes directly south. This feature was attributed with TECSOU "found by side scan sonar", WATLEV "unknown", QUASOU "depth unknown" due to the inability to further develop the SSS contacts with MBES. SSS Contact (Unique ID: CH_H13762_115_6), was identified beyond the 3.5m depth boundary where SSS acquisition was not required. This contact was deemed unsafe to develop further with MBES, and is located outside the assigned sheet limits. Six new features (Unique IDs: 5_137_1, 5_118_1, 5_121_1, 5_134_1, 5_128_1, and 5_117_1) were identified within the Intracoastal Waterway (ICW) channel that did not meet the specifications to warrant consideration as features (i.e. less than 1 m vertical), but were included in the FFF as new features due to the navigational significance of being located close to or within the channel. Please see section D.1.5 of this report for more information on channel analysis. In agreement with the NOAA HSD OPS, heights were not calculated for above water features, and the TECSOU and WATLEV for these features were attributed as "Unknown" and QUASOU as "Depth Unknown" in the FFF. A comparison of the surveyed depths to the depth range value 1 attribute listed in the most up to date ENCs was conducted for all charted channels within the Alligator River in H13762. The portion of the Intracoastal Waterway (ICW) contained within H13762 extends between Alligator River Light 10, and Alligator River Light 49. Surveyed depths within the channel were generally shoaler then the charted DRVAL1 from current ENCs, with the most significant shoaling between Alligator River Light 31 and Alligator River Light 49. Ten uncharted features were identified within or very close to the ICW, and are detailed in the FFF. Several features were found within the boundaries of the ICW which do not meet typical feature height requirements, however these are included in the FFF and the USACE Channel Analysis report as their least depth values exceeded the charted DRVAL1 value. Two DTONs identified which were within or near the ICW (Unique IDs: H13762_DTON_03, H13762_DTON_12). An unnamed channel is present in H13762 and extends south from the ICW near Alligator River Light 39. Details on the depth comparison of this channel can be found in the Channel Analysis report. A detailed analysis of the surveyed depths in the channels was provided to NOAA HSD OPS in accordance with section 1.6.2.1 of the HSSD. It was concluded that a separation model from LWD to MLLW was not provided and would be required for a more detailed comparison to USACE MLLW controlling depth values. Please see DR Appendix II Supplemental Records for related correspondence with NOAA HSD OPS. Three ATONs within the survey area were not observed during survey operations and considered missing/off-station while one ATON, associated with Alligator River Light “26”, was observed to be a red lighted buoy and therefore was mischarted on ENC US5NC52M as a BCNLAT with DAYMAR. A Local Notice to Mariners was sent out and listed the mischarted feature as either Daymark Missing or STRUCT DEST/TRLB. An ASSIST report was submitted for all four of these ATONs. Alligator River Daybeacon 35 was not observed during survey operations. This ATON was determined to be Type 1 and a Discrepancy Report was filled out and submitted to the USCG. Please see DR Appendix II Supplemental Records for related correspondence. No Maritime Boundary Points were assigned for this survey. Two bottom samples were acquired in accordance with section 7.2.3 of the HSSD and are described completely in the FFF. Several features were assigned which are associated with the bridge crossing for U.S. Hwy 64 in the northern section of H13762 and are detailed in the FFF. The assigned feature with Unique ID 5_101_1 was not observed but unable to be disproved because of the presence of shoreline construction surrounding the charted LNDARE. In agreement with the NOAA HSD OPS, heights were not calculated for above water features. Figure 25 shows the charted LNDARE slightly off from the data and aerial imagery. Aerial imagery along with SSS imagery and SBES bathymetry should be used to more accurately chart the location and extent of these assigned features. Bridge crossing of U.S. Highway 64, in the northern section of the Alligator River. Image shows bathymetric data (rainbow) and SSS data (greyscale) file:///B:/OPR-F330-KR-22/Surveys/H13762/01_HDR/Reports/Descriptive_Report/SupportFiles/H13762_BridgeCrossing.jpg No submarine features exist for this survey. No platforms exist for this survey. No ferry routes or terminals exist for this survey. No abnormal seafloor or environmental conditions exist for this survey. No present or planned construction or dredging exist within the survey limits. No new surveys or further investigations are recommended for this area. No new ENC scales are recommended for this area. As Chief of Party, field operations for this hydrographic survey were conducted under my direct supervision, with frequent personal checks of progress and adequacy. I have reviewed the attached survey data and reports. All field sheets, this Descriptive Report, and all accompanying records and data are approved. All records are forwarded for final review and processing to the Processing Branch. The survey data meets or exceeds requirements as set forth in the NOS Hydrographic Surveys Specifications and Deliverables, Field Procedures Manual, Letter Instructions, and all HSD Technical Directives. These data are adequate to supersede charted data in their common areas. This survey is complete and no additional work is required with the exception of deficiencies noted in the Descriptive Report. Nicholas Damm Chief of Party 2024-04-27 Data Acquisition and Processing Report 2024-03-17 Coast Pilot Report 2024-03-08