Obviously, we’ve been covering the living hell out of Ever Given’s obstruction of the Suez Canal for the last few weeks. But, we haven’t talked much about why the big boat got stuck in the first place. The consensus seems to be that a sandstorm with heavy winds played a starring role and the Suez Canal Authority blames human error or a technical failure. Here, the Practical Engineering YouTube channel is offering some additional information about some of the factors that were at play.
Ships traverse the canal with the help of Suez Canal pilots. These pilots help the ship’s crew navigate the canal, which sort of resembles a highway when everything is operating correctly.
The canal portion of the system runs about 213.36 m wide and 24.38 m deep. The Ever Given is about 60.96 m wide and fully-loaded, its draft (the amount of boat below the surface) is about 14.63 m. We know that the ship was at 85 per cent capacity at the time of the grounding, so it may have had a shallower draft. Either way, this isn’t a huge margin for error, especially when you consider the following.
Ships displace their own weight in water. This isn’t that big of a deal if the ship is small or is out on the open ocean. But it matters when a big ship is shoved into a confined space like the Suez where water is displaced up and around the hull, where it travels faster relative to the ship than the rest of the water in the canal. Bernoulli’s Principle states that an increase in speed of a fluid occurs at the same time as a decrease in pressure. This principle is also part of how aircraft wings generate lift.
Marine Insight has a good explanation of how these forces impact ships travelling in tight spaces.
When big ships like the Ever Given travel near a bank, fast moving water on the bank side can tug them toward that bank. That phenomenon is called Bank Effect. The fast moving water under the ship can also suck it down toward the bottom of the waterway, which is sometimes called the Squat Effect.
As the video explains, the basic phenomena are not exactly unknown and it’s not like the Ever Given is the only ship to have encountered them. What is interesting is that today’s gigantic ships behave differently in narrow/shallow waters than their smaller forbears do, and the impact of these forces on them isn’t actually all that well understood as this article from the Wall Street Journal explains.
The video shows that there’s a lot more to navigating the Suez than you might assume. Add in a strong crosswind or a mechanical failure and its easy to see how managing the incredible forces at work could get out of hand quickly. It’s not like you can just slam on the brakes when something starts to go wrong.