Yokohama typhoon collision
Following two incidents of large vessels hitting major road bridges, Japanese authorities are now insisting masters declare how they intend to set and manage their ship’s anchors.
In September 2019, the 103m (338ft) cargo ship Bungo Princess was at anchor off Yokohama in Tokyo Bay, at night, when a typhoon warning was issued. As the typhoon closed in, with strengthening winds and worsening sea conditions, the ship began to drag its anchor, despite having its engine set full ahead, and it eventually collided with a major road bridge.
The vessel sustained damage to its bulbous bow and along the starboard side of its hull. A lifeboat and cradle, installed just below the bridge on the starboard side, were also torn off.
The road bridge, meanwhile, sustained damage so severe to its structure and road lighting fixtures that it had to be completely closed for eight months whilst repairs were carried out.
Gouges and abrasions were also sustained along a concrete seawall adjacent to the bridge.
Fortunately, no injuries were reported amongst any of the ship’s 17 crew members.
Bungo Princess was at anchor off Yokohama in Tokyo Bay (Credit: Shutterstock)
Loss of control
That morning, Bungo Princess’ master had dropped the ship’s starboard anchor in 23m (75ft) of water, letting out seven shackles (192m/630ft) of anchor chain, before making further preparations, along with his crew, to see out the incoming heavy weather.
The vessel’s ballast water tanks were also full at the time, with its draft approximately 4.7m (15ft) at the bow and 5.3m (17ft) at the stern.
By the early evening, with the typhoon quickly approaching, the master let out an additional shackle of anchor chain and ordered the main engine to be put on a one-hour standby.
Two hours later he received a call from the local port authorities asking him to check his anchoring arrangement and to be alert to any anchor drag. During the checks the master realised his ship had, indeed, begun dragging its anchor in the 60-knot winds. He engaged the engine, increasing slowly to full ahead, and tried to keep the ship’s bow pointed upwind.
However, despite all efforts, the vessel was now being pushed towards the lee shore by the intensifying wind. Shortly afterwards, after finally admitting that he had completely lost control of his vessel, the master radioed the local port authorities to ask for tug assistance. Unfortunately, the sea conditions had deteriorated so badly that it was, by now, too unsafe for any of the tugs to come out. Thirty minutes later Bungo Princess collided with the bridge.
A recently published accident investigation report by the Japan Transport Safety Board (JTSB) found that Bungo Princess’ master had decided against using two anchors at the time of the incident because he believed that multiple anchors in storm conditions might cause further operational problems, such as tangled chains or reduced manoeuvrability. He also believed that the total of eight shackles of anchor chain would be sufficient to maintain his position. He then, according to the report, failed to use the engine to try and overcome the ship’s induced swinging motion and was not sufficiently aware of the fact that once full-scale anchor dragging at a constant speed begins, it becomes very difficult to overcome.
Of the 24 ships anchored in the area that night, three dragged their anchors.
Princess Bungo (Credit: @punipcruises)
The JTSB report cites data published by the Japan Meteorological Agency (JMA) that shows wind speeds that night reached more than 80 knots, creating sea swells in excess of 6m (20ft) — making it the most powerful typhoon to hit the region in more than thirty years.
It also cites research, again published by the Japan Meteorological Agency, that indicates how climate change — including rising temperatures and heavier rainfall — has become more and more common and is predicted to become even more serious in the near future.
The increasing frequency of anchor dragging accidents in vital commercial waters has forced the Japan Coast Guard to issue a public awareness statement to the shipping industry which recommends that vessels are moved outside of Tokyo Bay during severe storms.
In September 2018, in a very similar incident, the 90m (295ft) oil tanker Houn Maru dragged its anchor during a typhoon in Osaka Bay, causing it to collide with the main access road bridge to Kansai International Airport. In response, the Japan Coast Guard identified 40 locations in sea areas around the country, containing important transport and utility facilities, in which they implemented special storm weather anchoring restrictions.
A special ‘Reinforced Dragging Anchor Prevention Area’ was also immediately set up in Tokyo Bay following the Houn Maru incident to prevent any damage being caused to LNG berths. Harbour masters around the country are also now insisting that ships confirm their anchoring arrangement so that they can help provide guidance or assistance if required.
Read the full Bungo Princess accident report.
Dennis O’Neill is a freelance journalist specialising in maritime.