OPR-R340-KR-23 Bristol Bay, AK Bristol Bay Terrasond H13714 1 na Kvichak Bay Alaska United States 40000 2023 Andrew Orthmann Navigable Area 2023-01-30 2023-06-07 2023-09-09 Multibeam Echo Sounder Multibeam Echo Sounder Backscatter meters UTC Pacific 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 04N, 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 The survey area is located in Bristol Bay, Alaska. Bristol Bay is located in southwestern Alaska. The area is ecologically rich and renowned for its wildlife and salmon fisheries. It is bound by the volcanic mountains of the Alaska Peninsula to the south, and tundra-covered landscapes to the north. The area is remote and disconnected from the road system, with area communities small and accessible only by air or water. The largest nearby community (and hub for the region) is Dillingham (population 2,203 in 2021). An intricate network of rivers feed the bay, especially the Kvichak, Nushagak, Naknek, and Igushik. The rivers transport and deposit large amounts of sediment into the bay, resulting in seafloor variability with shifting sandbars and constantly changing depths. River current combined with the large daily tide range of the area (4-5 meters) causes very strong currents, especially at the approaches to the area rivers. The area is unnavigable for much of the year due to sea and river ice. During the ice free period, approximately June through October, weather is frequently inclement, with sudden storms and dense fog common occurrences. The unpredictable weather pattern, coupled with the changeable seafloor and outdated charts of the area, pose significant navigational challenges for vessels. Vessel traffic in the region is largely from fishing vessels (mostly smaller vessels of approximately 32' length) with a mix of larger fish tender vessels. Tug-and-tow barges also frequent the area, bringing fuel and supplies to the communities that border the bay, as well as communities further up the various rivers. Field work for hydrographic data collection was carried out from June through September of 2023 under project OPR-R340-KR-23, with final processing and reporting occurring from October, 2023 through January, 2024. This area was surveyed concurrently with fourteen other areas in the Bristol Bay project in accordance with the Hydrographic Survey Project Instructions (dated January 30th, 2023), accompanying Scope of Work, and the NOAA Hydrographic Surveys Specifications and Deliverables (HSSD, 2022 edition). 58.88717972222222 157.9507258333333 58.45065027777778 156.93565027777777 Overview of the survey extents. SupportFiles\H13714_Survey_Extents.png Tug-and-tow barge traffic in upper Kvichak Bay. SupportFiles\H13714_TugNTow.png The survey extents were achieved. Note that the original planned extents of the survey as provided in the PRF were modified during operations as follows: After completing a recon of upper Kvichak Bay, and subsequent discussions on the survey recommendations, it was agreed that the survey limits should be extended NE to where two channels merged near Koggiung / Graveyard Point. This would ensure continuous data upriver at least to this point. This extended the survey area about 5 NM further upriver than originally planned. The area is shown in the image below. The applicable correspondence is included with the survey deliverables. Original PRF survey boundary shown in red, with final coverage overlaid. The survey was extended NE to Graveyard Point aboout 5 NM to ensure continuous coverage up to the point the two channels merged. SupportFiles\H13714_ExtendedNE.png The purpose of this survey is described as follows in the Project Instructions: Bristol Bay is important to the US economy as the largest sockeye salmon fishery in the world, and second ranked fishing port in the United States. Known as “America’s Fish Basket”, the combined economic value of the commercial fishery, processing, visitor industry, and tourism is $1.1 Billion. It is home to 25 Alaska Native villages and communities who rely on the Alaska maritime infrastructure for goods and fuel. The Bristol Bay project will provide contemporary surveys to update National Ocean Service (NOS) nautical charting products and services. Seventy percent of the project was last surveyed between 1945 and 1960, the rest has never been surveyed. Updated bathymetry and feature data will be used to create larger scale charts in the area, reducing the risk to navigation, and serve as the foundational dataset to support modeling, industry, and science. The project will directly support the maritime services available to the remote coastal communities by providing the base data to update nautical products for nearby waters, including targeting navigational channels near the Port of Naknek, Ekuk, and Port Heiden. These products can improve the safety of subsistence fishing, marine transportation, and shipment of goods. It is noteworthy that Port Heiden has moved inland because of erosion. The priority areas focus on collecting data for vessel lightering areas identified by the Western Alaska Tanker Lightering Best Practices Committee, as part of the Alaska Maritime Prevention & Response Network. These areas are used for Ship-to-Ship transfers of oil products, including fuel which is of key importance to local residents. The lightering areas, together with the Automatic Identification Systems (AIS) traffic patterns, regional requests, and hydrographic health modeling were used to identify 2300 square nautical miles of priority project area. Data from this project will supersede all prior survey data providing modern hydrographic survey data for this area and updating the local charting products. The entire survey is adequate to supersede previous data. All waters in survey area (Any lines of data provided including opportunity data) Complete a minimum of 15,606 LNM. Unlogged transit mileage, system calibration mileage and data which do not meet HSSD specifications shall not count towards the completion of the LNM requirement. Notify the COR/Project Manager upon nearing completion of LNM requirement. The final survey area shall be squared off and ensure the full investigation of any features within the surveyed extent. Set Line Spacing system of MBES (HSSD Section 5.2.2.4 Option A). Sheet H13714 Sounding lines shall be acquired with spacing adequate to collect data at an interval of at least 240 meters. PRF Designated Investigation $AREAS for Naknek Run preliminary investigation lines. Provide a recommendation and reasoning of what line spacing or coverage would be suitable for delineating the navigationally significant area, taking into account the surveyed depths, features, local traffic and mariner’s needs. Upon agreement of the target area with the COR and CO, acquire sounding lines with spacing adequate to collect data at an interval of at least 120 meters. This would support a sounding selection grid spaced at 120 meters. The inshore depth contour definition of the depth NALL is modified to the agreed area. The LNM budget for Naknek is 500 LNM. All Shoreline Sheets SDB Checklines Within each shoreline sheet, acquire four geographically dispersed sounding lines that extend to the inshore limit of safe navigation. The field unit will chose the location for the safe and efficient acquisition of shoal depths. Coverage requirements were met. Additional clarification on specific requirements are provided below. LNM Requirements: A minimum of 15,606 LNM of MBES data was required project-wide. 15,997 was actually acquired. The excess of 391 was collected to compensate for inefficiencies incidental to data collection such as crossline mileage that exceeded requirements, data acquired on run-ins or run-outs (including in shallow water in order to scout between lines), and excess overlap (if any). LNM quantities do not include transit or calibration data, or data that does not meet HSSD requirements. Splits: After acquiring a number of splits on charted soundings during this survey, it was observed that there was a project-wide trend of nearly all charted soundings being shoaler than survey data, and excessive effort and LNM would be required to continue performing splits on the charted soundings. This was brought to the attention of the NOAA COR and an exception was approved to de-prioritize bathymetric splits over shoal charted soundings and use hydrographer's discretion when choosing these splits. Splits were still acquired where necessary to develop shoals. Correspondence is included with the survey deliverables. NALL: The inshore depth contour definition of the NALL was specified to be 4.5 m for this survey. 4.5 m (or shoaler) was successfully achieved fully along the coast. A shoaler NALL of 2 m (or shoaler) was successfully achieved (where applicable) in the upper Kvichak ($AREAS polygon in the PRF), discussed further below. Note that 2 m could not be acquired due to the presence of seawalls or docks on some lines in the vicinity of the community of Naknek. Shoreline Traces: In some areas there are gaps between mainscheme lines and shoreline traces. Shoreline traces, which roughly parallel bathymetric contours nearshore, were run early in the project to scout the general location of the depth NALL (normally 4.5 m). When mainscheme was later collected they were normally terminated when the depth NALL was reached. However, in some areas, the shoreline traces are well inshore of 4.5 m, leaving a gap between the data sets. The gaps were not filled due to being inshore of the NALL. Note that the shoreline traces are still included as they add value to the overall survey results. SDB Checklines: SDB (Satellite Derived Bathymetry) checklines, to be used for SDB calibrations, were acquired at geographically dispersed locations chosen by the field crew. These were also run co-incident with NASA ICESat-2 data provided by NOAA when practical per NOAA's request for overlap (see included correspondence), but personnel and vessel safety took precedence in location decisions. For the checklines, the ASV-CW5 vessel collected data as shallow as possible, until it was deemed unsafe to continue closer to shore. These checklines were normally acquired at mid- to high- tide in order to achieve as shoal of a tide-corrected depth as possible. All checkline data is incorporated in the final surface submitted with the survey deliverables. Six checklines were acquired for this sheet; their location relative to the survey area is shown below. In addition, much of the work done within the $AREAS polygon in upper Kvichak Bay including the area around Naknek returned very shallow depths that will be useful for SDB checks. Note that negative depths were actually achieved on some lines (especially in the $AREAS polygon), but data shoaler than 0 m depth was excluded from the final surface during the finalization process per HSSD requirements for the depth ranges of submitted grids. However, the negative depths are available in the unfinalized version of the depth grid. Recon and $AREAS Polygon: Per the Work Instructions, prior to mainscheme data collection, a recon was carried out in upper Kvichak Bay, with bounds defined by the $AREAS polygon in the PRF. The recon results and recommendations were forwarded to NOAA in a Recon Report "H13714 Recon Results and Recommendations" on June 14th, 2023. Following the report and subsequent discussions, the area was divided into four areas. The areas were successfully surveyed to the agreed-upon requirements, itemized below. The image below shows the areas. Note that the recon lines are included in the final surface as they add value to the dataset. 1. Area 6, the lower portion of the bay, was surveyed at 240 m in to 4.5 m or the survey boundary, whichever came first. 2. Areas 2 and 3, which were found to be the best channels heading upriver, were surveyed with a 480 m zig-zag pattern, resulting in approximately 240 m spacing at the center of the pattern, in to 2 m or the survey boundary, whichever came first. 3. Area 5, which is the area in and around the community of Naknek, was surveyed with a 240 m zig-zag pattern, resulting in approximately 120 m spacing at the center of the pattern, in to 2 m or the survey boundary, whichever came first. All applicable correspondence is included with the survey deliverables. Overview of the relative location of SDB checklines and the least depths achieved. SupportFiles\H13714_SDB_Sds.png Overview of the upper Kvichak survey area, which was divided into four areas to be surveyed. SupportFiles\H13714_ReconRecommendations.png Overview of the survey coverage. SupportFiles\H13714_Survey_Coverage.png Arctic Seal 0.0 1070.6 0.0 0.0 0.0 0.0 0.0 103.5 0.0 ASV-CW5 0.0 1199.8 0.0 0.0 0.0 0.0 0.0 80.0 0.0 LC25 0.0 324.1 0.0 0.0 0.0 0.0 0.0 46.1 0.0 0.0 2594.5 0.0 0.0 0.0 0.0 0.0 229.6 0.0 8.8 15 0 20 0 266.3 2023-06-07 2023-06-08 2023-06-09 2023-06-10 2023-06-11 2023-06-12 2023-06-13 2023-07-22 2023-07-23 2023-07-24 2023-07-25 2023-08-01 2023-08-02 2023-08-03 2023-08-04 2023-08-05 2023-08-18 2023-08-19 2023-08-20 2023-08-21 2023-08-22 2023-08-23 2023-08-24 2023-08-26 2023-09-08 2023-09-09 This area has an extremely active salmon fisheries that begins in mid-June and is largely over by late July, with hundreds of boats participating. The upper part of Kvichak Bay is where most of the fishing activity occurs, though the rest of the bay experiences substantial traffic during this period as well. Therefore the area was avoided during the bulk of the fishing season; recon and shoreline traces were completed in June before the fishing season, with the majority of the mainscheme data collected after fishing activity had largely ceased. 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. Arctic Seal 39.6 2.0 ASV-CW5 5.5 0.6 LC25 7.9 1.0 The Arctic Seal in the Bristol Bay survey area. SupportFiles\Arctic_Seal.png The ASV-CW5 in the Bristol Bay survey area. SupportFiles\ASV-CW5.png The LC25 on the Arctic Seal deck. SupportFiles\LC25.png The Arctic Seal is a 40 m steel-hull, landing-craft style vessel owned and operated by Support Vessels of Alaska. The Arctic Seal acquired multibeam data and provided housing and facilities for on-site data processing. The vessel was also used to collect bottom samples, conduct sound speed casts, and deploy/recover the ASV-CW5 (uncrewed) launch and LC25 (crewed) launch. The ASV-CW5 (ASV) is a 5.5 m aluminum-hull Autonomous Surface Vessel (ASV), C-Worker 5 model, owned and operated by L3-Harris ASV. The ASV was operated in an uncrewed but monitored mode, collecting multibeam data in close proximity to the Arctic Seal, as well as in areas too shallow for the larger vessel. The LC25 is a 8 m aluminum landing-craft style launch, owned and operated by Support Vessels of Alaska. It was deployed via crane as needed from the Arctic Seal. It was used to survey particularly shallow and challenging areas that were not possible to reach or survey with the other vessels. MBES Teledyne RESON SeaBat T50-R MBES Backscatter Teledyne RESON SeaBat T50-R MBES Teledyne RESON SeaBat T20-P MBES Backscatter Teledyne RESON SeaBat T20-P Positioning and Attitude System Applanix POS MV 320 v5 Sound Speed System Valeport SWiFT SVP Sound Speed System AML Oceanographic MicroX SV The survey vessels were configured for MBES data collection with nearly identical survey equipment and software. The Arctic Seal and ASV-CW5 utilized Reson Seabat T50-R MBES systems, with surface sound speed measurements provided by AML Oceanographic Micro-X sensors. Both vessels used Applanix POSMVs (integrated into the T50-R MBES systems) with submersible IP-68 rated IMUs for attitude and position measurements. Sound speed profiles were collected using a Valeport SWiFT sensor, deployed while underway using a C-MAX Vigo winch, on the Arctic Seal. QPS QINSy software, running on Microsoft Windows 10-based PCs, was used for multibeam data logging and vessel navigation. The LC25 was similarly equipped, except with a Reson Seabat T20-P MBES system, and a non-integrated Applanix POSMV Wavemaster II for attitude and position measurements. LC25 crew took sound speed casts by hand with a Valeport SWiFT sensor. The percentage of crossline to mainscheme miles is 8.8%. Effort was made to ensure crosslines (XLs) had good temporal and geographic distribution, were angled to enable nadir-to-nadir comparisons, and that the required minimum percent of mainscheme LNM was achieved. Crosslines were conducted with all vessels to ensure there was ample overlap for inter-vessel comparisons, with each vessel crossing the other's mainscheme lines. Since the Arctic Seal and ASV-CW5 vessels worked in close proximity and normally ran parallel lines, crosslines were collected in sets whenever both vessels were in simultaneous operation. The collection of crosslines in sets, while spreading sets out across the survey area for good distribution, led to incidental collection of additional crossline LNM beyond the required 8% of mainscheme. Crosslines were often collected while transiting across the survey area to reach a different survey priority such as bottom sample locations or infills, leading to crosslines that were diagonal to the direction of mainscheme lines. The crossline analysis was conducted using CARIS HIPS “Line QC Report” process. Each crossline (with all associated file segments) was selected and run separately through the process, which calculated the depth difference between each accepted crossline sounding and a "QC" BASE (CUBE-type) surface’s depth layer created from the mainscheme data. The QC surface was created with the same parameters and resolution used for the final surface, with the important distinction that the QC surface did not include crosslines so as to not bias the results. Differences in depth were grouped by beam number and statistics were computed, including the percentage of soundings with differences from the QC surface falling within IHO Order 1a. When at least 95% of the sounding differences exceed IHO Order 1a, the crossline was considered to “pass,” but when less than 95% of the soundings compare within IHO Order 1, the crossline was considered to “fail.” A 5% (or less) failure rate was considered acceptable since this approach compares soundings to a surface (instead of a surface to a surface), allowing for the possibility that noisy crossline soundings that don't adversely affect the final surface could be counted as a QC failure in this process. Lines selected as crosslines and their percentage (%) of soundings passing IHO Order 1a, sorted from highest passing to lowest, are listed below. Note that within the CARIS HIPS projects provided with the survey deliverables, lines used as crosslines have their "Line Class" attribute set to "Check", while all others have this attribute set to "Track". 0197-159-ASV-CW5-A1EW25440 -- 100.0% pass 1122-217-ArcticSeal-A-Overwatch -- 100.0% pass 1463-231-ArcticSeal-A1NS06240 -- 100.0% pass 1626-238-ArcticSeal-A-XL07 -- 100.0% pass 1628-238-ArcticSeal-A-XL08 -- 100.0% pass 1630-238-ArcticSeal-A-XL09 -- 100.0% pass 1631-238-ArcticSeal-A_XL10 -- 100.0% pass 0026_-_161-LC25-recon -- 100.0% pass 0176_-_215-LC25-A3XL -- 100.0% pass 0178_-_215-LC25-A3XL -- 100.0% pass 0179_-_215-LC25-A3XL -- 100.0% pass 0184_-_215-LC25-A3XL -- 100.0% pass 0303_-_216-LC25-A2Line -- 100.0% pass 0537_-_233-LC25-A5XL -- 100.0% pass 0745_-_235-LC25-A5XLLineL -- 100.0% pass 0220-159-ASV-CW5-A1-XL-002 -- 99.9% pass 0150-159-ArcticSeal-A1EW36720-Overwatch -- 99.9% pass 0170-159-ArcticSeal-A1-XL-001 -- 99.9% pass 1056-213-ArcticSeal-Seal-A-XL -- 99.9% pass 1632-238-ArcticSeal-A_XL11 -- 99.9% pass 0055_-_213-LC25-A3Line -- 99.9% pass 0177_-_215-LC25-A3XL -- 99.9% pass 0517_-_233-LC25-A5-XL -- 99.9% pass 0662_-_234-LC25-A5XLLineL -- 99.9% pass 2142-233-ASV-CW5-A-Infill-0045 -- 99.8% pass 0147-158-ArcticSeal-A1EW36720-Overwatch -- 99.8% pass 1855-251-ArcticSeal-A-Overwatch -- 99.7% pass 0780_-_235-LC25-A5XLLineL -- 99.7% pass 0296-160-ASV-CW5-A1-XL-004 -- 99.6% pass 0148-159-ArcticSeal-A1EW36720-Overwatch -- 99.5% pass 0180_-_215-LC25-sdg -- 99.4% pass 1374-213-ASV-CW5-A2-Shoreline -- 99.1% pass 0181_-_215-LC25-sdg -- 99.1% pass 0448_-_232-LC25-A3XL -- 98.7% pass 0283_-_216-LC25-A3XL -- 98.1% pass 0822_-_235-LC25-A5-XLL -- 98.0% pass 0637_-_234-LC25-A5XL -- 97.8% pass 0195-159-ASV-CW5-A1-Shoreline -- 97.7% pass 1372-213-ASV-CW5-A2-Shoreline -- 96.8% pass 0024_-_160-LC25-recon -- 96.4% pass 0539_-_233-LC25-A5XL -- 96.1% pass 0291_-_216-LC25-A3Line -- 96.0% pass 0196-159-ASV-CW5-A1-Shoreline -- 95.6% pass 0025_-_160-LC25-recon -- 95.3% pass 0192-158-ASV-CW5-A1-Shoreline -- 95.1% pass 0204-160-ArcticSeal-A1-XL-003 -- 93.2% pass 0284_-_216-LC25-A3XL -- 92.0% pass 0004_-_160-LC25-recon -- 69.7% pass 0282_-_216-LC25-A3XL -- 61.9% pass Results: Agreement between them mainscheme surface and crossline soundings is excellent. At least 95% of all crossline soundings compare to the mainscheme surface within IHO Order 1a for 45 of the 49 crosslines. The four crosslines with >5% failing soundings were in areas experiencing significant bottom change between the time of mainscheme and crossline collection. Refer to Separate II: Digital Data for the detailed Crossline QC reports. ERS via ERTDM 0.18 0.0 Arctic Seal 0 2.5 0 0.025 ASV-CW5 0 2.5 0 0.025 LC25 0 6.1 0 0.025 The uncertainty layer of the final surface was examined in CARIS HIPS software, as well as analyzed in Pydro QC Tools V3.10.9 Grid QA v6. Uncertainty of the final grid cells range from 0 to 2.22 m. Greater than 99.5% of grid cells have TVU falling within the allowable range by depth. The larger values were observed to be in areas of highly variable seafloor where many soundings of different depths contribute to the value a grid cell and result in a overall higher standard deviation for the final depth of the cell. This was most prevalent around abrupt shoals, sandwaves, and areas exhibiting bottom change. Despite the higher uncertainty computed for some grid cells, depths for all final grid cells are within specifications. Thousands of gridded nodes in the submitted grids contained Total Vertical Uncertainty (TVU) values of 0m, which HSD does not consider to be a valid value for vertical uncertainty. Calculating uncertainty from the contributing soundings' standard deviation is a valid method for computing node uncertainty per the HSSD, but it can result in grid nodes containing 0m TVU values. New grids were created in review so that TVU values were calculated from contributing soundings' vertical uncertainties instead of the standard deviation of their depths. This changed the range of values for gridded uncertainty, which now ranges from 0.36m to 1.15m. During field operations, effort was made to ensure sufficient overlap was achieved between this survey and any overlapping surveys for junction analysis. This included extending survey lines into overlapping sheets, and in some cases running survey lines along junction boundaries. The "Gridded Surface Comparison V22.1" utility within Pydro was used to compare survey junctions. The utility differences the surfaces from the two surveys and generates statistics that include the percentage of grid cells that compare to within allowable TVU for the depth. 4 m resolution surfaces were used for all comparisons. Overview of survey Junctions. Not shown is a minor junction with H13721 on this survey's SW corner. SupportFiles\H13714_Survey_Junctions.png H13715 40000 2023 TerraSond W Agreement between the two surveys is very good. The mean difference is 0.06 m with a standard deviation of 0.06 m. Greater than 99.5% of grid cells agree within allowable TVU by depth. H13721 80000 2023 TerraSond SW There was a very minor junction between these surveys, consisting of one swath of overlap. Agreement between the two surveys is excellent. The mean difference is 0.05 m with a standard deviation of 0.06 m. 100% of grid cells agree within allowable TVU by depth. H13441 40000 2021 TerraSond S H13441 was completed two years prior to this survey. A 4m resolution BAG surface (H13441_MB_4m_MLLW_1of1.bag) was downloaded from NOAA NCEI and used for this comparison. Agreement between the two surveys is excellent. The mean difference is 0.04 m with a standard deviation of 0.07 m. 100% of grid cells agree within allowable TVU by depth. H13440 40000 2021 TerraSond S H13440 was completed two years prior to this survey. A 4m resolution BAG surface (H13440_MB_4m_MLLW_1of1.bag) was downloaded from NOAA NCEI and used for this comparison. Agreement between the two surveys is excellent. The mean difference is 0.01 m with a standard deviation of 0.16 m. Greater than 99.5% of grid cells agree within allowable TVU by depth. In addition to the crossline checks which included inter-vessel comparisons, as an additional area-specific QC check, the depth data acquired by each vessel was gridded separately at 4 m resolution and differenced from each other. The ASV was compared to the Arctic Seal, as well as to the LC25. The ASV compared to the Arctic Seal to 0.07 m on average with a standard deviation of 0.14m. Greater than 99.5% of grid cells agreed within allowable TVU by depth. The ASV compared to the LC25 to 0.04 m on average with a standard deviation of 0.21m. 98% of grid cells agreed within allowable TVU. The relatively few grid cells with greater disagreement were examined and appear to be due to bottom change. In the case of the LC25, the largest disagreement is between recon lines run early in the project, and ASV lines run later in project in the area of the project (upper Kvichak Bay) showing the greatest amount of bottom change. The results of the difference between ASV and Arctic Seal depth data for this survey. SupportFiles\H13714_ASVvsSeal.png The results of the difference between Arctic Seal and LC25 depth data for this survey. SupportFiles\H13714_ASVvsLC25.png Along Track Gaps On all survey vessels, during rough weather conditions air bubbles would occasionally be forced under the multibeam sonar head and result in temporary loss of bottom tracking or "blowouts", sometimes resulting in along-track gaps. Note that data acquired early in the project (prior to JD168) on the Arctic Seal was most affected. On JD168 a 0.6 m extension was installed on the Arctic Seal's MBES pole to position the sonar deeper in the water column. This significantly improved data quality for the remainder of the project, though in adverse conditions air could still be forced under the sonar. In addition, intermittent sonar issues on the Arctic Seal late in project (approximately JD192 onwards), due to a possible sonar receiver issue, occasionally resulted in dropped pings. Too many consecutive dropped pings could result in an along-track gap. Along-track gaps, either from weather or sonar issues, were examined and normally only rerun when the along-track gap exceeded three nodes (12 m horizontal distance) for mainscheme lines in depths of 20 m or less. These were not rerun where they occurred on crosslines since there was ample crossline LNM for QC purposes. Final data is within specifications. Arctic Seal MBES Arm Issues The Arctic Seal's hydraulic MBES arm experienced movement that had the potential to adversely affect survey data. From approximately JD178 onwards the arm experienced intermittent hydraulic pressure drops which resulted in arm movement and therefore shifts in the sonar and IMU orientation relative to the POSMV reference frame. This was more prevalent in adverse weather when the vessel was experiencing above average roll conditions. A hinged joint in the MBES arm also experienced issues from JD178 until JD181. Co-location of the IMU and sonar mitigated most of the effects since mount movements were captured in the motion record and largely compensated for. However, some residual error remained as a result of shifts in the reference frame, which shows up periodically as a small roll bias in Arctic Seal data, apparent at crossline intersections. To reduce the effect, small roll corrections were systematically applied in the HVF at obvious change points, and all Arctic Seal MBES data was filtered with a 55 degree nadir filter to remove outer beams most subject to the error. Following these corrections, final data is within allowable TVU. More information on the issue and mitigation is available in the DAPR. GNSS Vertical Busts Although vertical agreement between overlapping lines is generally very good, normally within 0.10 m or better, vertical busts attributable to GNSS positioning error are apparent sporadically in the data set. Any that approached or exceeded allowable TVU for their depth were investigated and addressed in processing. Final data is within specifications. Sound Speed Error Sound speed error, which is characterized by a general upward or downward across-track cupping of sounding data that increases in magnitude towards the outer beams, is evident sporadically in the dataset. Profiles were taken frequently, approximately every two hours and whenever changing areas, but some residual error remains. In processing, beam filters were applied to reject outer beams greater than 65 degrees from nadir in order to reject soundings most subject to sound speed error. The effect on the final surfaces is relatively minor. Final data is within specifications. Bottom Change The seafloor in the area is dynamic due to the large amount of sediment deposition from the rivers draining into the area. The sediment is then readily transported by the strong tidal and river currents experienced here. In addition, part of the area is largely within channels of the Kvichak and Naknek Rivers. Sandwaves are present through most of the survey area, which is indicative of sediment movement. Data acquired distant in time, for example crosslines late in the job that cross mainscheme acquired earlier in the project, frequently show evidence of bottom change. Of particular note is the LC25 recon data collected in upper Kvichak Bay early in the job on JD160 and JD161, which often busts from mainscheme data collected later in the project, in some cases by up to 2 meters. Bottom change was observed nearly everywhere in the survey area. But the most extreme bottom change was observed in the upper Kvichak Bay ($AREAS polygon), especially in and near the channels heading up the Kvichak and Naknek Rivers. Some examples are shown below. In most cases of bottom change data was not edited to "choose" a bottom. An example of bottom change observed on this survey, viewed in CARIS HIPS subset mode, in the upper Kvichak Bay area. Position 58-47-01.9 N, 157-07-39.2 W. LC25 recon data collected on JD161 shows up to 1 m of vertical change from LC25 mainscheme collected on JD231. SupportFiles\H13714_BottomChangeExample1.png An example of bottom change observed on this survey, viewed in CARIS HIPS subset mode, in the southeast part of the bay. Position 58-28-28.6 N, 157-31-00.2 W. Arctic Seal and ASV data collected on JD158-159 shows up to 1 m of vertical change from ASV data collected on JD252. In addition note the large sandwave feature appears to have moved up to 50 m eastward over the 93 day period. SupportFiles\H13714_BottomChangeExample2.png Bottom Tracking Issues In the upper part of Kvichak Bay (specifically in the $AREAS polygon), the sonars on the vessels would sometimes track incorrect, or two bottoms, presumably due to a thick but soft "fluff" layer higher in the water column. This was in the deeper part of some of the channels. The likely cause is finer grain sludge or mud concentrating in the deeper parts of the channels but becoming diffused as it moves towards the bay and spreads out over a larger area. Shallower areas which were primarily sand did not have the issue, nor did the area further out in the bay. The deeper layer was assumed to be the actual seafloor because this layer would often show sandwaves while the shoaler layer would be uniform and featureless. The issue was first noticed in the LC25 on JD160/JD161 when crossing channels during the $AREAS polygon recon. The full range of possible tuning options on the sonar were attempted in order to improve tracking of the deeper layer, including extremes of power, gain, and pulse width. The best results, albeit with only marginal improvement, were achieved by operating the sonar at the lowest possible frequency, 200 kHz, instead of 400 kHz, which was the normal operating frequency for the sonars on this project. All data collection subsequent to the recon on the LC25 in this area was therefore collected at 200 kHz. However, even at 200 kHz the sonar return would be extremely noisy in these areas, and often still track the fluff layer, with only intermittent, near-nadir soundings (if any) reaching the deeper layer. To improve the number of soundings obtained on the deeper layer, the sonar rate on the LC25 was set to 15 pings per second instead of the default 10 when surveying in the $AREAS polygon. In data processing, soundings tracking the shoaler fluff layer were rejected where the two layers were clear, and sparse returns on the deeper layer accepted. This is evident in the data set as a swath reduced to little more than nadir on parts of some lines, as well as some along-track gaps where it the sonar simply could not acquire good seafloor. The issue was primarily on the LC25, though the ASV also experienced the issue on parts of some lines it acquired in the $AREAS polygon. The issue was brought to NOAA's attention in the H13714 Recon Report (included with the survey correspondence), with the expectation that some along-track gaps would likely be unavoidable due to the issue. An example is shown below. Note that the issue was also experienced on the nearby Egegik Bay survey (H13438) in 2021 and documented under its DR with similar results and outcome, as well as F00875 conducted in Nushagak Bay on this project. An example of double bottom tracking observed on this survey, viewed in CARIS HIPS subset mode, which was relatively common in channels of upper Kvichak Bay. Position 58-48-53.7 N, 157-11-04.4 W. A shoaler "fluff" layer is tracked about 1 m above true seafloor. The fluff layer has been rejected (gray),while true seafloor has been accepted (green). SupportFiles\H13714_BottomTrackingExample.png 2 hours Sound speed profiles or "casts" were normally acquired aboard the Arctic Seal while underway with a C-MAX Vigo profiling winch, which utilized a Valeport SWiFT sound speed profiler. Note that the ASV-CW5 was not equipped to collect sound speed profiles -- Arctic Seal sound speed profiles were used to correct all ASV sounding data, which was possible because the vessels always worked in close proximity to each other (usually within 2 kilometers). Sound speed casts were taken by hand deployment on the LC25 with a Valeport SWiFT sensor. Surface sound speed at the Arctic Seal sonar head was monitored continuously and a new cast was collected when the surface speed varied from the previous profile's speed at the same depth by greater than 2 m/s, leading to a cast interval of approximately 2 hours. Casts were taken as deep as possible. On survey lines with significant differences in depth, the deeper portion of the line was normally favored to ensure that changes across the full water column were measured. The cast data was used to correct the sounding data using the "nearest in distance within time" (set to 2 hours) within CARIS HIPS. Note that LC25 casts were placed within their own SVP file for CARIS HIPS processing and used only for correcting LC25 data. This was done so that LC25 casts would not be used to correct Arctic Seal or ASV data, and vice versa, since the LC25 usually operated at significant distance away from the other vessels. All equipment and survey methods were used as detailed in the DAPR. Complete Coverage Investigation Area Bottom Tracking The bottom tracking issue discussed previously also affected the Complete Coverage achieved in the area of two feature investigations. The area, shown below, was another area where a consistent seafloor could not be tracked. The sonar frequently tracked multiple bottoms in the deeper (approximately greater than 4 m) portion of the area, occasionally jumping between layers, tracking only one or the other. It is likely that portions of the final coverage are from the shoaler "fluff" layer, and not the deeper true seafloor. The area was reviewed and edited but not to the extent that rejected soundings would open holidays in the Complete MBES coverage. Area of Complete MBES coverage achieved within 200 m of feature investigations west of Naknek, approximately centered at 58-43-31.6 N, 157-05-15.9 W. The investigation area was in an area experiencing the bottom tracking issue, as seen in CARIS subset mode on the right, which shows multiple bottoms being tracked. SupportFiles\H13714_BottomTracking-Investigations.png Deviations from the Correction to Echo Soundings section of the DAPR are itemized below. Despite the deviations, final data is within specifications. GNSS Processing Exceptions: The following lines utilized Applanix Smart Base (ASB) processing instead of PPRTX to address GNSS vertical busts. LC25, JD213 - JD214, lines 0055 through 0184 LC25, JD233 - JD234, lines 0518 through 0691 Arctic Seal, JD162, lines 0240 through 0245 The following lines (or individual line segments) had altitudes loaded using CARIS Generic Data Parser (GDP) to address GNSS vertical busts that could not be repaired with other methods. GDP altitudes were smoothed, removing heave from the altitude data, therefore these lines were subsequently georeferenced with "GPS dynamic heave" set to "NONE". Arctic Seal, JD162, lines 0249 through 0250 Delayed Heave Exceptions: These lines also did not have delayed heave, therefore "Realtime" was used as the heave source. Arctic Seal, JD162, lines 0249 through 0250 ASV, JD161, line 0300, segment 2 Sound Speed Correction Exceptions: The following lines were sound speed corrected with nearest in distance within 3 hours (or 4 hours) instead of 2 hours. Arctic Seal, JD235, lines 1588 through 1591 (3 hours) Arctic Seal, JD236, line 1592 (4 hours) ASV, JD234, lines 2235 through 2236 (3 hours) LC25, JD160, lines 0003 through 0004 (3 hours) LC25, JD232, lines 0447 through 0452 (4 hours) LC25, JD235, lines 0734 through 0758 (4 hours) All sounding systems were calibrated as detailed in the DAPR. All equipment and survey methods were used as detailed in the DAPR. NOAA Extended Attribute Files V2023_1 The most current version of NOAA's Extended Attribute Files available at the start of survey operations was utilized for this project. H13714_MB_4m_MLLW_Final CARIS Raster Surface (CUBE) 4 0.0 27.588 NOAA_4m MBES Set Line Spacing H13714_MBAB_2m_400kHz_1of2 MB Backscatter Mosaic 2 0.0 27.588 N/A MBES Set Line Spacing H13714_MBAB_3m_LC25_200kHz_2of2 MB Backscatter Mosaic 3 0.0 27.588 N/A MBES Set Line Spacing H13714_MB_1m_MLLW_Final_1of2 CARIS Raster Surface (CUBE) 1 0.038 17.032 NOAA_1m Feature Investigation H13714_MB_1m_MLLW_Final_2of2 CARIS Raster Surface (CUBE) 1 2.842 7.072 NOAA_1m Feature Investigation The final depth information for this survey was submitted as a 4 m resolution CARIS BASE surface (CSAR format) which best represents the seafloor at the time of the 2023 survey. The surface was created from fully processed data with all final corrections applied. The surface was created using NOAA CUBE parameters and resolutions in conformance with the 2022 HSSD. The surface was finalized with a 0 to 80 m depth limit, "standard deviation" selected as the final uncertainty source, and designated soundings applied (if present). Horizontal projection was selected as WGS84 / UTM zone 4N. A non-finalized version of the CSAR surface is also included with the survey deliverables for reference. This does not have the "_Final" designation in the filename. Note that due to the 0 meter cutoff during finalization, a number of negative depths acquired during the survey--especially in upper Kvichak bay and the Naknek areas--are excluded from the final grid. This excludes data from the LC25 recon where the vessel crossed sandbars and flats at high tide. The negative depths are however still available in the non-finalized version of the grid. The Multibeam Acoustic Backscatter (MBAB) surfaces, produced with QPS Fledermaus Geocoder Toolbox (FMGT), are also provided. MBAB data for all vessels acquired using 400 kHz is combined in the 400 kHz mosaic. A separate 200 kHz mosaic was made for LC25 data collected at that frequency. NOTE: 1 m resolution surfaces are also provided to demonstrate that Complete Coverage was achieved where required in the vicinity of assigned or charted feature investigation locations. To create these, a 1 m resolution surface was first created over the general area of a feature investigation area. Next, this version was finalized in CARIS HIPS. Lastly, the finalized version was clipped using a Coverage Area polygon (cvrage object) so as to exclude area not surveyed to Complete Coverage standards from the 1 m surface. Note that finalized (but non-clipped) surfaces are included with the survey deliverables with "_F" designation in their filename. The HOB file used for clipping is included with the survey deliverables in the "Surfaces_Mosaics" directory. During review, new surfaces were created to address TVU values, as noted in comments in prior section B.2. Uncertainty. At this time, bathymetry for all 1m developments were gridded togather, resulting in only two grids submitted to the NBS and MCD: H13714_MB_1m_MLLW_Final and H13714_MB_4m_MLLW_Final. A waiver to HSSD Section 2.2 was was granted for this project. All products are submitted with horizontal positions as WGS84 instead of NAD83(2011). This was done to provide a consistent dataset from raw data, which was acquired in WGS84, through final processed data. See project correspondence for the waiver and additional discussion. Additional information discussing the vertical or horizontal control for this survey can be found in the accompanying HVCR. Mean Lower Low Water ERS via ERTDM OPR-R340-KR-23_AK_ERTDM_2023_WGS84(G2139)-MLLW_.csar All soundings were reduced to MLLW using the ERTDM WGS84 to MLLW separation model grid file provided by NOAA using ERS methodology. The uncertainty stated for the model in the Project Instructions is 0.18 m. Note all altitudes are relative to the WGS84 datum, therefore the WGS84 to MLLW ERTDM model was utilized to reduce soundings to MLLW. World Geodetic System (WGS) 1984 Projected UTM 4 Smart Base Applanix Smart Base (ASB) was used when necessary to address GNSS vertical busts. Any lines that used ASB were itemized earlier in this report. Post-processing of all navigation data for final positions was done in Applanix POSPac MMS (v8.9) software. Trimble PP-RTX was used as the primary processing methodology within POSPac, with any exceptions noted previously. Real-time positions were primarily RTK. Hemisphere SmartLink antennas on each vessel were set to receive the subscription-based Atlas H-10 service, which output RTCM corrections to each vessel's POSMV, allowing them to operate in RTK mode. This assisted with real-time positioning. However, all real-time positions were replaced in post-processing with PPK corrections, as described previously. The Wide Area Augmentation System (WAAS) was used incidentally for real-time positions as a backup when there were issues receiving RTK corrections. However, all real-time positions were replaced in postprocessing with PPK corrections, as described previously. The area is highly changeable, and changes are widespread versus the charts, especially in upper Kvichak Bay. US4AK3WW 90000 1 2023-10-12 2023-10-12 US4AK3XW 90000 1 2023-10-12 2023-10-12 US4AK3WX 90000 1 2023-10-12 2023-10-12 US4AK3XX 90000 1 2023-10-12 2023-10-12 US4AK3YX 90000 1 2023-10-12 2023-10-12 US4AK3XY 90000 1 2023-10-12 2023-10-12 US4AK3YY 90000 1 2023-10-12 2023-10-12 This survey found widespread and significant change from the charted data, especially in upper Kvichak Bay. In many areas, the bathymetry now bears little resemblance to what was previously charted. Two channels were surveyed in the upper Kvichak area: A western channel, corresponding roughly to what was currently charted as the "Albert Channel", and an eastern channel. The western channel was found to be the the most navigable. Both channels criss-cross what were previously charted as exposed shoals, and in same cases the channel is now where dry land was previously charted. Examples are of the area are shown in the images below. The Naknak area was more stable, with the charted channel still in the same general area. However this survey did find generally deeper depths than charted through the Naknek area. Examples are also shown below. No Danger to Navigation Reports were submitted for this survey. The lower part of the channel survey area. The locations of the surveyed channels are significantly different than what was charted. Soundings from this survey are in blue. All soundings in meters. SupportFiles\H13714_UpperKvichak1.png The upper part of the channel survey area, where the channels converge near Graveyard Point. The locations of the surveyed channels are significantly different than what was charted. Soundings from this survey are in blue. All soundings in meters. SupportFiles\H13714_UpperKvichak2.png The western part of the Naknek channel. The area was more stable than the other areas in Kvichak Bay, though this survey found generally deeper depths than charted. Soundings from this survey are in blue. All soundings in meters. SupportFiles\H13714_Naknek1.png The eastern part of the Naknek channel. The area was more stable than the other areas in Kvichak Bay, though this survey found generally deeper depths than charted. Soundings from this survey are in blue. All soundings in meters. SupportFiles\H13714_Naknek2.png Charted features that intersected the survey area were investigated and the results are available in the FFF. No uncharted features exist for this survey. No channels exist within the survey limits. All ATONs bordering the survey area were visually examined from the survey vessel while on site and determined to be on station and serving their intended purpose. Note however that light functionality could not be confirmed because operations were only conducted during daylight hours in this area. Applicable ATONs were the Naknek Entrance Daybeacon 1, South Naknek City Dock Light, and the Graveyard Point Light. Photos, if taken, are shown below. Per the HSSD, ATONs are not included in the FFF since they were observed to be on station. Photo of the Naknek Entrance Daybeacon ATON. SupportFiles\H13714_NaknekEntranceDaybeacon1.png Photo of the Graveyard Point ATON. SupportFiles\H13714_GraveyardPoint.png No Maritime Boundary Points were assigned for this survey. The Project Instructions required one bottom sample per 20 SNM of surveyed area, with at least two within the PRF $AREAS polygon. 15 were therefore acquired in this area, 5 of which in the $AREAS polygon. Bottom sample locations were chosen in regards to the acquired survey data backscatter, with one acquired near Naknek due to the likely use of the area for anchorage. Samples were examined, photographed, and then discarded overboard. Sand was the primary constituent of most samples, with gravel and pebbles commonly found as well. The image below shows their location within the survey area. Refer to the FFF for results. An overview of bottom sample results. SupportFiles\H13714_BottomSamples.png 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, or were discussed previously. No present or planned construction or dredging exist within the survey limits. Due the highly changeable nature of the seafloor in this area and the age of existing survey data, it is recommended that affected ENCs be prioritized for chart updates. The sooner the data is applied to affected navigation charts the greater this survey's value will be to mariners. The upper part of Kvichak Bay, roughly corresponding to the $AREAS polygon, is recommended for more frequent resurvey due to the extensive changes in bathymetry this survey found versus the chart, as well as changes observed during the course of this survey itself. As described earlier, the channels found and surveyed in this project bear little resemblance to those previously charted. It is likely that within a few years of this survey the channels will be substantially different. The area is navigated heavily during the salmon fishing season, and is regularly navigated by barges and other vessels heading up the Kvichak River. 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, Hydrographic Survey Project Instructions, and Statement of Work. 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, if any, noted in the Descriptive Report. Andrew Orthmann Charting Program Manager 2024-01-17 H13714 Recon Report 2023-06-14 Final Progress Report 2023-10-23 Survey Outline Submittal 2023-10-23 MMO Logsheets and Training Observer Logs 2023-10-23 NCEI Sound Speed Data Submittal 2023-12-01 Coast Pilot Review Report 2024-01-08