Alaska’s Kuskokwim River is both unpredictable and essential. Shifting sandbars, variable tides, and seasonal ice dramatically reshape the waterway, requiring frequent updates to the navigational channel. It remains a lifeline for communities like Bethel, Alaska. NOAA’s Coast Pilot describes the waterway as a “maze of shifting sandbars…and blind channels” with navigation conditions that can change daily.
Currently, the U.S. Coast Guard maintains over 50 aids to navigation, or ATONs, along the river to guide vessels. Mariners use these ATONs to travel safely through the channels. The Coast Guard Cutter Aspen requested support from NOAA to provide updated bathymetric data to help them to validate and adjust ATONs–a mission critical function to ensure safe navigation for vessels traversing one of the state’s most dynamic and economically vital waterways.
Coast Survey has a select group of hydrographers specially trained to deploy with portable survey equipment on vessels of opportunity and complete missions in challenging and remote areas. This group is referred to as the Mobile Integrated Survey Team (MIST) and the portable equipment that is stored in ready-to-ship cases is referred to as the MIST kit. The Kuskokwim River survey request was a mission perfectly suited for MIST operations. For this mission, the team was comprised of personnel from the Navigation Response Team located in Gulfport, MS. Upon arrival at Coast Guard Cutter Aspen, in Homer, Alaska, the team quickly went to work installing a multibeam echosounder and associated equipment on one of the Aspen’s small boats. When the installation was complete, the team had all the tools necessary to record the highly accurate and precise depth measurements that the mission required.
The mission
First, the team met the Aspen in Homer, AK where they installed the equipment on one of the two small boats the Aspen carries.
“The OPS officer LTJG Liam Long set us up for success, having the MIST kit cases staged in a covered garage with the trailered Vessel of Opportunity making for a safe and efficient assembly of the kit.” said LTJG Robert Sobelsohn, Officer in Charge of Navigation Response Team Gulfport. “Operating in an unfamiliar survey area to us, with USCG Coxswains new to Hypack and a dual mission of ATON deployment and hydrographic survey posed initial challenges that were quickly overcome through effective communication, on the job training, and shared expertise.”
An 11-day transit from Homer brought them to the Kuskokwim River. The heavy sediment load in the Kuskokwim River that makes it such a dynamic and highly changeable area, also makes it difficult and time consuming to make potable (drinkable) water without clogging the ship’s filters. Because of this, the first day of operations was delayed while the ship made enough water to prepare for the extended journey.
The Coast Guard maintains buoys in the mouth of the river. The team began survey operations near Buoy 8, where shoaling was suspected. The small boat traveled ahead of the Aspen, identifying water deep enough for the Cutter to safely navigate through and determining the extents of the bar that had formed. While LTJG Sobelsohn operated the equipment on the small boat, John Gray, Physical Scientist stayed aboard the Aspen to process the data in real-time, providing his expertise in interpreting the data to the Aspen crew. The team concluded operations near Buoy 10/11, returning the boat to the Aspen and anchoring overnight.
On the second day of survey operations, the team continued to work with the cutter, moving upstream and identifying deeper water to support improved buoy placement. The Gulfport team surveyed areas near the proposed placement of Buoys 29, 36, 37, and Buoy 45.
While the Aspen was servicing those buoys, a tugboat hailed the crew and thanked them for the updated buoy placement at the Buoy 8 and 9 bar–placed the day before and already making navigating the river safer.
The third and final day of surveying brought the small boat to some of the northernmost aids to navigation in the river, buoys 62 and 63. These buoys are a gated pair that tells mariners that safe water lies between the buoys. The team, while surveying the area near the 2024 buoy placement location, determined the Coast Guard should move the gate further north for 2025. The small boat and NOAA team aboard helped place those initial buoys for the gate.
After that, the NOAA team traveled back to port aboard the Aspen, which stopped to reposition five buoys that had already moved off their station in the previous two days from the strong currents of the river. The team disassembled the MIST kit while the Coast Guard small boat was secured to the top bridge deck of the Aspen. In this position, the MIST kit hung over the side of the Aspen many levels above the water, not for those afraid of heights. The forecast was predicting high winds and large swell during the transit back to port, so the team had to move quickly to stow away the MIST kit before leaving protected waters.
“After previously sailing on NOAA Ship Fairweather as a Deck Watch Officer charting Alaskan waterways, it was a privilege to explore an area of Alaska that I did not have much experience with, and work with an incredibly welcoming crew while on project. The quick turnaround from data acquisition to processing and interpretation of the data from John Gray to the bridge crew maximized the success of the trip while pressed up against a tight schedule.” said LTJG Sobelsohn.
In total, the MIST was able to collect 44.6 linear nautical miles of survey data.
The 2025 Kuskokwim River Survey was a success in both updating critical ATON positions and demonstrating the value and challenges of rapid, targeted hydrographic surveys in extreme environments. The collaboration between NOAA and the Coast Guard highlights the importance of adapting tools, timelines, and strategies to support mariner safety in one of the most unpredictable and essential waterways of Western Alaska.
Charting
Cartographers in Coast Survey applied all the updated buoy positions from the U.S. Coast Guard on NOAA’s Electronic Navigational Charts (ENCs), the backbone of nautical navigation. Beyond those, much of the Kuskwoskim River remains uncharted.
What is charted primarily comes from NOAA’s National Ocean Service’s three-year effort (2009 to 2011) to survey the River using multiple survey platforms utilizing both single-beam echosounders and multibeam echosounders. One of the many reports from this effort noted, “The River is a highly changeable area. Severe bank erosion was evident during field operations, and changes in bottom depth and topography were common over the course of the survey” (Chief of party, Andrew Orthmann, TerraSond Ltd, H12167, Descriptive report, 2010). Due to this actively changing landscape, keeping nautical charts up to date remains a challenge.
About the Mobile Integrated Survey Team
Coast Survey maintains a mobile integrated survey team, or MIST kit, for deployment on a Vessel of Opportunity Platform (VOOP). The MIST kit is a modular system that can be used to collect seafloor imagery and depth soundings. The MIST kit fits in the back of a pickup truck and can typically be shipped to anywhere in the U.S. or its territories. The system includes a mounting pole designed to fit a wide range of vessels such as a USCG trailer-able aids to navigation boat, a rigid inflatable boat, or a USCG launch. In general, a VOOP should be a non-privately owned vessel platform provided by state, local, and other federal agencies—ideally operated by a government entity capable of assuming liability for any damages caused by installing equipment onboard. Read our Captain of the Port’s Guide or contact your region’s navigation manager to learn more.