The slower the boat travels, the closer to the wind it has to point in order to avoid being pushed into the leeward shore. (assuming it doesn't have significant

The slower the boat travels, the closer to the wind it has to point in order to avoid being pushed into the leeward shore. (assuming it doesn't have significant thrust-vectoring capabilities at both the bow and the stern which as far as I can tell seems to be the case for large cargo ships) Because the boat is longer than the canal is wide, for any nonzero perpendicular wind speed there is a minimum boat speed below which it would not be able to avoid running aground. The solution is to either not permit such large ships to transit the canal during high wind events or to send them with enough tugboats to counteract the force of the wind.