by Ensign Sarah Chappel, NOAA Ship Rainier
NOAA Ship Rainier recently surveyed Whale Passage, which separates Whale Island from Kodiak Island, Alaska. The area has never been surveyed with modern full bottom coverage methods, and some project areas were last surveyed by lead lines around a hundred years ago. The area frequently experiences 7 knot currents, making rocky or shoal areas particularly treacherous. Whale Passage is a high traffic area for fishing vessels, U.S. Coast Guard cutters, barges, ferries, and small boats, which is why updating the area’s nautical charts is so important.
Strong currents push around Ilkognak Rock daymark at the entrance of Whale Passage. (Photo by LTJG Damian Manda)
The dynamics of the passage and surrounding area create several challenges for the hydrographic survey teams. The local tidal and current models are not well-known. To resolve this, Rainier was instructed to install four tide gauges in the greater project area, compared to a typical requirement for one gauge. Two of these gauges are a mere 4.5 nautical miles apart, in and just outside of Whale Passage itself. Some areas are so narrow and experience such high currents that it is only possible to survey in one direction in order to maintain control of the launch. The coxswain must plan each turn carefully, to avoid being pushed into dangerous areas. Ideally, these areas would be surveyed at or near slack tide. However, the slack in this survey area is incredibly brief and the predicted slack periods did not match what survey crews saw in the field.
The bathymetry is so dynamic that, even in relatively deep water, boat crews must remain alert for rocks and shoals. The survey teams found several large rocks in locations significantly different from where they were charted. Furthermore, the presence of large kelp beds increases the difficulty of surveying: they can foul the propellers on the launches, add noise to the sonar data, and can also obscure the presence of rocks.
While the work within Whale Passage, and the neighboring Afognak Strait on the north side of Whale Island, is challenging, it is also high-value. In addition to correcting the positions of known rocks and hazards, Rainier and her crew found a sunken vessel. Most importantly, though, they found areas that were charted twice as deep as they actually are. When the chart reads 8 fathoms (48 feet) and the actual depth is only 4 fathoms (24 feet), commercial traffic utilizing the passage could be in serious danger of running aground. Thus far, Rainier has submitted two DTON (danger to navigation) reports for depths significantly shoaler than charted. These new depths are already published on the latest version of chart 16594.
Rainier‘s multibeam sonar data shows a sunken fishing vessel in the vicinity of Whale Passage.
NOAA Ship Rainier will continue to survey the vicinity of Whale Passage, as well as the waters near Cold Bay out in the Alaskan Peninsula, for the remainder of the survey season before heading home to Newport, Oregon.
NOAA Ship Rainier recovers a survey launch after a morning of surveying and data collection. (Photo by LTJG Damian Manda)
NOAA Ship Rainier had the wonderful fortune of cool, clear weather on March 13 as they fueled at the Navy Fuel Depot in Manchester, WA. This provided a clear view of Mount Rainier. However, it is even more rare that you would have three “Rainiers” all in view at once! At the pier you can see USNS RAINIER (on the left side of the pier), NOAA Ship Rainier (on the right side of the pier), and the iconic Mount Rainier in the background. Absolutely beautiful.
USNS RAINIER and NOAA Ship Rainier, with Mount Rainier in the background. March 13, 2014, photo courtesy of NAVSUP-FLC Puget Sound.
–By Christy Fandel, Coast Survey physical scientist
Have you ever wondered what lies beneath the charted soundings on a nautical chart? While surveying Alaskan waters during the 2013 hydrographic field season, collecting bathymetry to update NOAA’s nautical charts, hydrographers revealed many interesting geologic features on the seafloor.
NOAA focuses a significant portion of our ocean mapping effort along the Alaskan coast. The Alaskan coastline represents over 50% of the United States coastline and dated nautical charts are inadequate for the increasing vessel traffic in this region. NOAA surveys are essential for providing reliable charts to the area’s commercial shippers, passenger vessels, and fishing fleets.
This past season, NOAA-funded hydrographic surveys in Alaska revealed many interesting geological features on the seafloor. Three surveys, in particular, took place in southeastern Alaska in the Behm Canal, along the Aleutian Chain within the coastal waters surrounding Akutan Island, and around Chirikof Island.
These three areas were among the areas surveyed by the NOAA Ship Rainier and surveying contractor Fugro-Pelagos during the 2013 field season.
In May, hydrographic surveying conducted by NOAA Ship Rainier in the Behm Canal revealed two distinct geological features. In the northern region of the canal, scientists identified a long, meandering ancient river. This ancient submarine river is nearly 40 km in length with up to 50 m in relief. Further south, Rainier surveyed a large volcanic-like feature. The surveyed volcano appears to have a distinct caldera, or collapse-feature that most likely formed after the volcanic eruption.
Multibeam bathymetry of the northeastern portion of the Behm Canal shows a large, meandering submarine river. The cross-sectional inset highlights the relief of the channel, nearly 50 m, as shown by the red box.
Multibeam data acquired by NOAA Ship Rainier shows a large volcanic feature in the southern portion of the Behm Canal.
Directly following the Behm Canal survey, Rainier transited west to survey the coastal waters surrounding Chirikof Island. The acquired bathymetric data revealed a stark northeast-trending fault in the southeastern portion of the survey area. This surveyed fault is distinguished by a clear misalignment across the fracture.
The red box outlines the northeast-trending fault along the coast of Chirikof Island, shown with bathymetry acquired by the Rainier.
Concurrently, an Office of Coast Survey hydrographic surveying contractor – Fugro-Pelagos – was surveying off the western coast of Akutan Island. Fugro’s hydrographers identified a large volcanic feature within the acquired bathymetric data. The surveyed volcanic feature is believed to be either a volcanic vent or cinder cone volcano. The multiple circular rings outlining this feature may represent the successive lava flows that formed the volcano.
Multibeam bathymetry acquired by Fugro, around Akutan Island, shows a large volcanic vent or cinder cone volcano, marked by multiple circular rings that represent the successive lava flows that formed the volcano.
With the upcoming 2014 hydrographic field season quickly approaching, the number of geologic discoveries will only increase. Extending all along the Aleutian Chain, from Kodiak Island to Bechevin Bay, the planned surveys for the 2014 field season will surely reveal many interesting and previously unknown geologic features.
Cold Bay Elementary School students visit the NOAA Ship Rainier
On September 13, NOAA Ship Rainier began surveying Cold Bay, its fourth project of the summer. Cold Bay is a small town on the Aleutian Peninsula approximately 540 miles southwest of Anchorage, Alaska. The town currently has approximately 88 full-time residents and boasts an airport with one of the longest runways in Alaska.
On September 19, after deploying her launches for the day, officers and crew welcomed aboard the entire Cold Bay Elementary School – all eight students, teaching assistant Mrs. Lyons, and their teacher, Mrs. Burkhardt. The students are currently between fourth and seventh grade and go to school in a state-of-the-art, two-room school-house.
During the tour, the students learned about driving the ship and making nautical charts. They saw how sonars work, and they even used a sediment sampler to determine the seafloor composition.
The students were full of questions and enjoyed learning about life on a ship. They also captured the admiration of Rainier‘s commanding officer. “When Cold Bay residents describe their town, they can also boast of wonderful elementary school students who have a desire to explore new things,” explained Cmdr. Rick Brennan. “One of the great things about working on a NOAA ship is the opportunity to meet students like this. Combining our love of the sea with their enthusiasm for learning — that’s where America’s future hydrography starts.”
This student is ready to work!
The group examines bottom samples collected by the Rainier.
Cmdr. Rick Brennan explains how davits work.
- Cmdr. Brennan with friends — and potential future hydrographers.