OPR-J325-KR-23 Mobile Bay, AL Mobile Bay, AL David Evans and Associates H13840 7 Darling Landing to Fairhope Alabama United States 5000 2023 Jonathan L. Dasler, PE, PLS, CH Navigable Area 2023-07-26 2023-10-25 2024-02-11 Multibeam Echo Sounder Side Scan Sonar Multibeam Echo Sounder Backscatter 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 16N, MLLW. 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 David Evans and Associates, Inc. (DEA) conducted a hydrographic survey of the assigned area in the vicinity of Mobile Bay, AL. Survey H13840 was conducted in accordance with the Statement of Work and Hydrographic Survey Project Instructions dated July 26, 2023. The Hydrographic Survey Project Instructions reference the National Ocean Service (NOS) Hydrographic Survey Specifications and Deliverables Manual (HSSD) (March 2022) as the technical requirements for this project. 30.525365 88.002019 30.440624 87.91791500000001 Survey limits were surveyed in accordance with the requirements in the Project Instructions and the HSSD. The assigned survey areas are outlined in Figure 1. OPR-J325-KR-23 Assigned Survey Areas file:///B:/OPR-J325-KR-23/Surveys/H13840/01_HDR/Reports/Descriptive_Report/SupportFiles/OPR-J325-KR-23_Survey_Area.png The purpose of this survey, defined in the Project Instructions, is as follows: "This project will provide modern bathymetric data for Mobile Bay and the Tensaw River. The project area was identified as a high priority area for NOAA's National Water Center, and is a statistically significant hot spot within the 2018 hydrographic health model, a risk model that Coast Survey uses for evaluating priorities based upon navigational risks and the necessary quality of data to support modern traffic. Prior surveys in the area are from 2007, and there have been significant changes to the bay and its water circulation with the last several years of storm events. In addition, the Port of Mobile handles in excess of 55 million tons of international and domestic cargo delivering $85 billion in economic value to the state of Alabama each year (1). Conducting a modern bathymetric survey in this area will identify hazards and changes to the seafloor, update NOAA National Ocean Survey (NOS) charts and products, and provide forecasters at NOAA's National Water Center with bathymetric data for critical hydrodynamic modeling necessary to understand the timing and impact of rapid river stage increases and decreases, the duration of high water, inundation or drought. Survey data from this project is intended to supersede all prior survey data in the common area." (1) https://www.alports.com/economic-impact/ The entire survey is adequate to supersede previous data. All waters in survey area less than 8 meters water depth Side Scan Sonar Data may be acquired at an altitude of 4-20% of the range scale. Sheets 3 - 7 Complete Coverage (Refer to HSSD Section 5.2.2.3 Option B). Complete Coverage using 100% side scan sonar (SSS) coverage was collected concurrently with multibeam echosounder (MBES) data over the entire survey area. Backscatter was logged during all multibeam acquisition. This coverage type follows Option B of the Complete Coverage requirement specified in Section 5.2.2.3 of the 2022 HSSD. The inshore limit of hydrography was the Navigable Area Limit Line (NALL) as defined in Section 1.3.2 of the HSSD with the exception that the Project Instructions defined the use of the surveyed 2-meter depth contour instead of the surveyed 3.5-meter contour as listed in the HSSD. Survey coverage for feature disprovals followed disproval radii size determination based on the largest scale charts published at the time of the disproval evaluation. Several new gridded ENCs were issued during the survey to replace older legacy ENCs as part of the NOAA rescheming process. According to Office of Coast Survey (OCS) guidance, features outside the 2-meter NALL were investigated and ensonified as much as was safe to do so. For features in which the disproval radius was seaward and shoreward of the NALL, the radius became the sheet boundary and limit of safe navigation. Additional details can be found in Appendix II - Supplemental Survey Records & Correspondence. H13840 Survey Outline file:///B:/OPR-J325-KR-23/Surveys/H13840/01_HDR/Reports/Descriptive_Report/SupportFiles/H13840_Outline.png Richard T Brennan 0.0 3.1 0.0 0.0 0.0 869.82 0.0 37.26 0.0 0.0 3.1 0.0 0.0 0.0 869.82 0.0 37.26 0.0 4.27 0 0 0 0 17.32 2023-10-25 2023-11-10 2023-11-11 2023-11-12 2023-11-13 2023-11-17 2023-11-29 2023-11-30 2023-12-01 2023-12-02 2023-12-03 2023-12-04 2023-12-05 2023-12-07 2023-12-08 2023-12-09 2023-12-12 2024-01-11 2024-01-13 2024-01-14 2024-01-15 2024-01-17 2024-01-18 2024-01-31 2024-02-01 2024-02-02 2024-02-09 2024-02-10 2024-02-11 Refer to the 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. Richard T Brennan 34.0 2.0 Richard T Brennan file:///B:/OPR-J325-KR-23/Surveys/H13840/01_HDR/Reports/Descriptive_Report/SupportFiles/Richard%20T%20Brennan.jpg MBES Teledyne RESON SeaBat T50-R SSS EdgeTech 4200 SSS EdgeTech 4205 Positioning and Attitude System Applanix POS MV 320 v5 Sound Speed System AML Oceanographic Micro SV-Xchange Conductivity, Temperature, and Depth Sensor AML Oceanographic SmartX Multibeam crosslines were run across 4.27% of the entire survey area to provide a varied spatial and temporal distribution for analysis of internal consistency within the survey data. Crossline analysis was performed using the CARIS Hydrographic Information Processing System (HIPS) Quality Control (QC) Report tool, which compares crossline data to a gridded surface and reports results by beam number. Crosslines were compared to a 1-meter Combined Uncertainty and Bathymetry Estimator (CUBE) surface encompassing mainscheme, fill, and investigation data for the entire survey area. DEA performed an additional crossline analysis using the NOAA Pydro Compare Grids tool to analyze the differences between gridded mainscheme depths and gridded crossline depths. Input grids were 1-meter resolution CUBE surfaces of mainscheme and crossline depths. Results from the crossline-to-mainscheme difference analysis are depicted in Figure 4, with units represented in meters. H13840 Crossline Difference file:///B:/OPR-J325-KR-23/Surveys/H13840/01_HDR/Reports/Descriptive_Report/SupportFiles/H13840_MB_1m_MLLW_XL-H13840_MB_1m_MLLW_MS_depth_delta.png ERS via VDATUM 0.05 0.1 Brennan 1.0 n/a n/a 0.5 Additional discussion of these parameters is included in the DAPR. During surface finalization in HIPS, the "Uncertainty" option was selected, where uncertainty values from the source surface are applied to the finalized surface uncertainty. This method, which incorporates grid uncertainties computed during the TPU process, was deemed to better reflect actual grid uncertainty when compared to the option to use standard deviation values scaled to 95% confidence interval. To determine if the surface grid nodes met the International Hydrographic Organization (IHO) Order 1a specification, a ratio of the final node uncertainty to the allowable uncertainty at that depth was established. As a percentage, this value represents the amount of error budget utilized by the Total Vertical Uncertainty (TVU) at each node. Values greater than 100% indicate nodes exceeding the allowable IHO uncertainty. The resulting calculated TVU values of all nodes in the submitted finalized surface are shown in Figure 5. Node TVU Statistics - 1 meter, Finalized file:///B:/OPR-J325-KR-23/Surveys/H13840/01_HDR/Reports/Descriptive_Report/SupportFiles/H13840_MB_1m_MLLW_Final.GQv6.tvu_qc.png Survey H13840 has junctions with current survey H13837 and prior survey H11624. Figure 6 depicts H13840 and the junctioning surveys. Survey Junctions with Registry Number H13840 file:///B:/OPR-J325-KR-23/Surveys/H13840/01_HDR/Reports/Descriptive_Report/SupportFiles/H13840_Junctions.png H13837 5000 2023 David Evans and Associates, Inc. N The mean difference between H13840 and H13837 is 1 centimeter (H13840 shoaler than H13837), shown in Figure 7. Distribution summary plot of survey H13840 1-meter vs H13837 1-meter file:///B:/OPR-J325-KR-23/Surveys/H13840/01_HDR/Reports/Descriptive_Report/SupportFiles/H13840_MB_1m_MLLW_Final-H13837_MB_1m_MLLW_Final_depth_delta.png H11624 10000 2007 David Evans and Associates, Inc. S The mean difference between H13840 and H11624 is 6 centimeters (H13840 shoaler than H11624), shown in Figure 8. Distribution summary plot of survey H13840 1-meter vs H11624 2-meter file:///B:/OPR-J325-KR-23/Surveys/H13840/01_HDR/Reports/Descriptive_Report/SupportFiles/H13840_MB_1m_MLLW_Final-H11264_MB_2m_combine_depth_delta.png Multibeam data were reviewed at multiple levels of data processing, including CARIS HIPS conversion, subset editing, and analysis of anomalies revealed in CUBE surfaces. Side scan data were reviewed at multiple levels of data processing, including during the initial SonarWiz import and preliminary stages of bottom-tracking, navigation review, and contact identification. Data were also reviewed during the final stages of mosaic generation, data coverage and quality assessment, and contact correlation and attribution. Split Line The Hypack SSS data file 2023RI3141902A.HSX does not have a corresponding 2023RI3141902A.RAW file because the file 2023RI3141902.RAW contains data for both lines 2023RI3141902 and 2023RI3141902A. Survey line 2023RI3141902 was rejected and not processed. Teledyne RESON T50 Receive Array Reson T50 multibeam data quality at nadir and in the outer beams started to degrade, with a more notable difference in the generally shallower water and soft mud in H13840, over days DN014, DN015, DN017, DN018, and DN031 (5 survey days total). Diagnostic testing identified some faulty elements in the receive array. The T50 receiver was replaced at the end of DN031. Affected tracklines for days surveyed between DN014-DN031 were heavily filtered to remove outer swath noise, resulting in a narrower swath width in comparison to the rest of the survey. No data were acquired on DN016, and DN019 through DN030. None Exist There were no other factors that affected corrections to soundings. 30-minute intervals For H13840 survey operations, casts were distributed both temporally and spatially based on observed changes in sound speed profiles. Sound speed readings were applied in CARIS HIPS using the "nearest in distance within time" option with a two-hour interval. All sound speed profiles were acquired within 500 meters of the survey limits. Survey speeds were maintained to meet or exceed along-track sounding density requirements and side scan sonar ensonification requirements. Multibeam data and side scan mosaics were thoroughly reviewed for holidays and areas of poor-quality coverage due to biomass, vessel wakes, or other factors. Significant side scan sonar contacts were developed with multibeam sonar to obtain a least depth, meeting the survey’s coverage requirements where it was safe for the vessel to operate. Survey coverage for feature disprovals was acquired inside disproval radii to meet the coverage requirement for the area. Disproval radii were covered with 200% SSS. Additional discussion of coverage methods can be found in the DAPR. There is a known holiday in the H13840 survey area near the Grand Hotel. It was not possible for survey crew to safely navigate close enough to fill this holiday. Density The sounding density requirement of 95% of all nodes, populated with at least five soundings per node, was verified by analyzing the density layer of the finalized surface. Surface results are stated in Figure 9. Node Density Statistics - 1 meter, Finalized file:///B:/OPR-J325-KR-23/Surveys/H13840/01_HDR/Reports/Descriptive_Report/SupportFiles/H13840_MB_1m_MLLW_Final.GQv6.density.png Data reduction procedures for survey H13840 are detailed in the DAPR. All sounding systems were calibrated as detailed in the DAPR. Multibeam time series backscatter data (RESON 7058 normalized backscatter datagram) were logged in HYPACK 7K format and are included with the H13840 raw digital deliverables. Backscatter data were referenced to processed multibeam bathymetric data and processed in QPS FMGT. A 2-meter backscatter mosaic is included with the H13840 processed deliverables. A GSF export containing the final bathymetry and backscatter with edits retains the original file names of the raw data files but with the postfix "_merged." Although two different RESON T50 receivers were used on the Brennan during acquisition of H13840, only one mosaic was generated due to normalized backscatter 7058 datagrams being logged throughout the entirety of the sheet. See the OPR-J325-KR-23 DAPR for more details. CARIS HIPS and SIPS 11.4.14 CARIS HIPS and SIPS 11.4.29 (Only for surface finalization) QPS FMGT 7.11.1 Chesapeake Technology, Inc. SonarWiz 7.11.02 (64-bit) NOAA Profile Version 2023 A detailed listing of all data processing software is included in the OPR-J325-KR-23 DAPR. H13840_MB_1m_MLLW.csar CARIS Raster Surface (CUBE) 1 1.155 5.096 NOAA_1m Complete MBES H13840_MB_1m_MLLW_Final.csar Finalized CARIS Raster Surface (CUBE) 1 1.155 5.096 NOAA_1m Complete MBES H13840_MB_2m_NAVD88.tiff CARIS Raster Surface (CUBE) 2 1.339 5.229 NOAA_2m Complete MBES H13840_MB_2m_NAVD88_Interpolated.tiff CARIS Raster Surface (CUBE) 2 1.339 5.229 NOAA_2m Complete MBES H13840_MBAB_2m_RI_400kHz_1of1.tif MB Backscatter Mosaic 2 0.0 0.0 N/A Complete MBES H13840_SSSAB_1m_540kHz_1of2.tif SSS Mosaic 1 0.0 0.0 N/A 100% SSS H13840_SSSAB_1m_540kHz_2of2.tif SSS Mosaic 1 0.0 0.0 N/A 200% SSS Bathymetric grids were created relative to Mean Lower Low Water (MLLW) in CUBE format using Complete Coverage resolution requirements as specified in the HSSD. Grid resolution for the backscatter mosaic was determined by the HSSD frequency-dependent resolution requirement. In addition to the standard gridded data products prescribed in the HSSD, the survey deliverables also include grids and interpolated grids in geotiff format relative to NAVD88 for NOAA's National Water Center as required by the OPR-J325-KR-23 Project Instructions. To create the 2-meter NAVD88 grid, CARIS HIPS was used to initially create a 2-meter CUBE surface relative to MLLW (using the NOAA_2m CUBE grid parameters file). After creation, the grid was then transformed from MLLW to NAVD88 using CARIS Base Editor. The transformation utilized a shift file containing elevations corresponding to the difference between MLLW to NAVD88 as determined from the MLLW and NAVD88 separation models provided with the OPR-J325-KR-23 project files. After the NAVD88 transformation, an interpolated version of the grid was created where gaps in the data coverage were filled to create a seamless digital elevation model (DEM) of the survey area. The interpolated 2-meter grid was generated from a triangulated irregular network (TIN) using the natural neighbor method in CARIS BASE Editor. The TIN was constrained to prevent interpolation shoreward of survey coverage using long edge controls and by applying a polygon mask. A summary of the horizontal and vertical control for this survey follows. Mean Lower Low Water ERS via VDATUM OPR-J325-KR-23_MobileBay-TensawRiver_2023-06-26_NAD83-MLLW_PtCloud_1sigma10cm.csar OPR-J325-KR-23_NAD83(2011)-NAVD88(GEOID18)_1sigma7cm.csar OPR-J325-KR-23_MobileBay-TensawRiver_2023-06-26_NAD83-MHW_PtCloud_1sigma10cm.csar In addition to the standard gridded data products relative to MLLW prescribed in the HSSD, the survey deliverables also include grids and interpolated grids in geotiff format relative to NAVD88 for NOAA's National Water Center as required by the OPR-J325-KR-23 Project Instructions. The NAD83(2011) to NAVD88(GEOID18) separation file listed in Table 13 was used to generate the Water Center grids. The mean high water (MHW) separation model listed in Table 13 was used to determine the appropriate water level effect (WATLEV) attribution for features included in the FFF and when applicable was used to determine height attribution for any features that are always dry. North American Datum 1983 (2011) Projected UTM 16 The NAD83 to MLLW separation model listed in Table 13 was provided with the Project Instructions and used for sounding correction within the assigned survey area. Real-time navigation for all MBES survey lines were overwritten with post-processed navigation solutions in SBET format. Additional discussion on post-processing methods and survey control is included in the DAPR. The chart comparison was performed by comparing H13840 survey depths to a digital surface generated from Band 4 and Band 5 electronic navigational charts (ENCs) covering the survey area. A 5-meter product surface was generated from a triangular irregular network (TIN) created from the ENC's soundings, depth contours, and depth features. Any part of the TIN Model that extended into a charted un-surveyed area was removed from the interpolated product surface. An additional 5-meter HIPS product surface was generated from the 1-meter CUBE surface. The chart comparison was conducted by creating and reviewing a difference surface using the ENC surface and survey surface as inputs. The chart comparison also included a review of all assigned charted features within the survey area. The results of the comparison are detailed below. The relevant chart used during the comparison was reviewed to check that all United States Coast Guard (USCG) Local Notice to Mariners issued during survey acquisition, and impacting survey area, were applied and addressed by this survey. The ENCs used in the chart comparison are listed in Table 14. Figures 10 and 11 show the magnitude of differences along the comparison area. Depth Difference Between H13840 and Band 4 ENC file:///B:/OPR-J325-KR-23/Surveys/H13840/01_HDR/Reports/Descriptive_Report/SupportFiles/H13840_US4_CC.png Depth Difference Between H13840 and Band 5 ENC file:///B:/OPR-J325-KR-23/Surveys/H13840/01_HDR/Reports/Descriptive_Report/SupportFiles/H13840_US5_CC.png US4AL1CB 40000 2 2024-03-05 2024-05-31 US5MOBFF 10000 1 2024-05-08 2024-05-31 US5MOBEF 10000 2 2024-05-08 2024-05-08 US5MOBGF 10000 3 2024-05-08 2024-05-14 Three Danger to Navigation (DtoN) reports were submitted for this survey. -H13840 DtoN 01, submitted December 11, 2023, reported an uncharted obstruction in the survey area. -H13840 DtoN 02, submitted January 16, 2024, reported an uncharted obstruction in the survey area. -H13840 DtoN 03, submitted May 24, 2024, reported three uncharted obstructions in the survey area. The hydrographer recommends updating the charts to depict the DtoNs as portrayed in the Final Feature File (FFF). All assigned features included in the project Composite Source File (CSF) are included in the FFF with remarks and recommendations. Some assigned features located inshore of the NALL, or that could not be fully disproved because of their proximity to the NALL, were not addressed by the survey. All disproved features have been included in the FFF with a description of "Delete." All new features have been included in the FFF with the surveyed feature depicted and a description of "New." Contact heights included in the side scan contact .000 file have been sourced from the shadow height measurement obtained from SonarWiz. Due to the limitations in computing accurate heights from side scan shadow lengths, contact heights may not match heights from correlating contacts or feature heights measured from multibeam data included in the FFF. The height field for contacts created on baring features observed in side scan data have been intentionally left blank. The FFF contains charting recommendations for several charted and uncharted fish havens located within or in the vicinity of the H13840 survey area. Recommendations were made with consultation from staff from the Alabama Department of Conservation and Natural Renounces (ADCNR) who maintains these reefs. Associated correspondence and ADCNR contact information is included in Appendix II. All uncharted features are portrayed in the FFF as surveyed and attributed with the description of "New." Refer to the FFF for additional information. No channels exist within the survey limits. A charted BCNSPP (General warning mark) was not observed during survey operations and disproved using 200% SSS. In addition, a charted BCNSPP (private USACE scientific monitoring pile) that was not published in the USCG Light List was found to be charted out of position. These discrepancies were reported to the Marine Chart Division (MCD) via the ASSIST customer service chart reporting system. Correspondence related to this issue is included in Appendix II. Other ATON discrepancies were reported to USCG via the Navigation Center Online Discrepancy Report Form. The Grand Hotel Yacht Basin Daybeacon 1 was surveyed in a location different from the USCG Light List and also missing its dayboards. The USCG Light List only includes a general position for a single daybeacon marking the Klondike Fishing Reef, but eight uncharted daybeacons were located by the survey in a position not matching the Light List. Copies of the discrepancy reports and associated correspondence are included in Appendix II. All other AtoNs charted within the survey area were found to be on-station and serving their intended purpose. No maritime boundary points were assigned for this survey. No bottom samples were required for this survey. No overhead features exist for this survey. 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. New gridded ENC cells were released for Mobile Bay over the course of hydrographic project OPR-J325-KR-23. The cells included both Band 4 and Band 5 ENCs, however, Band 5 cells were not published for the eastern side of Mobile Bay which excluded large scale chart coverage for much of the shoreline including the City of Fair Hope, the City of Daphne, Point Clear, and several marinas frequented by recreational boaters. The hydrographer is not certain if this was intentional or an oversight and recommends considering publishing Band 5 ENCs in these areas. 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. Jonathan L. Dasler, PE, PLS, CH NSPS-THSOA Certified Hydrographer, Chief of Party 2024-07-22 Jason Creech, CH NSPS-THSOA Certified Hydrographer, Charting Manager / Project Manager 2024-07-22 James Guilford, CH(A) NSPS-THSOA Certified Hydrographer, Lead Hydrographer 2024-07-22 Jason Dorfman, CH NSPS-THSOA Certified Hydrographer, Lead Hydrographer 2024-07-22 Sam Werner Data Processing Manager 2024-07-22 Data Acquisition and Processing Report 2024-05-01