But as river cruising grows in popularity, many travelers are just learning how weather can affect these small-ship, inland sailings. It's important to understand the possible mishaps that can occur on any vacation so you can be prepared and make smart decisions.
Now don't get us wrong -- most river cruise vacations run smoothly, and when they don't, river cruise lines are often in a unique position to get travelers to the scheduled ports and sights, if in an alternate way. River cruise itineraries cover far less distance than ocean cruises, so it's often possible to reach destinations overland when passage by water is not possible. Your cruise line and ship's crew are prepared with Plan B (and even C and D) when weather events disrupt a sailing.
Here are the some of the most common "acts of God" that might affect your river cruise.
River cruise ships are built to strict requirements -- their height is determined by the bridges they must pass under, their width by the locks they must squeeze into and their draft by the depth of the river. However, these measurements are based on average water levels. When excessive rain raises water levels -- or worse, causes flooding -- riverboats might not be able to traverse certain stretches of rivers, either because they no longer can fit under bridges or because flooding makes it unsafe for the ship to moor.
High water is most common in the spring when rain and snow melt raise water levels, though summer flash floods are possible (though short-lived). Typically the highest water levels occur in April (either before itineraries begin or at the very start of the river cruise season), but as snow melt and spring rainstorms vary from year to year, sometimes high waters can affect cruises as late as May or June. The Danube and the Rhine between Cologne and Vienna are the most affected by high water; the Moselle is less affected, but low bridges means it doesn't take much to make a stretch of river impassable.
River cruise lines have two options when rivers become impassable. One is to turn the remainder of the cruise into a bus tour, with passengers reaching destinations by bus and overnighting in hotels -- alternatively, the ship can run day trips from a central docked location. The other is to swap ships. In cases where a line has two or more ships running the same river, often in different directions, passengers might be bussed around a high-water stretch and reboard a sister ship for the remainder of the sailing. As many riverboats are identical, or nearly so, passengers can usually reclaim the same cabin number on the new ship and not be too inconvenienced. Only in extreme circumstances -- such as the June 2013 flooding -- will river lines cancel cruises. (When water levels are just a tad too high, the ship's crew will fill ballast tanks to increase the ship's draft -- i.e., make it sit lower in the water -- to clear a bridge that's just inches too low.)
If you're concerned about high water, avoid spring cruises; if you do book one, consider a line that's experienced in land tours (such as Tauck or Scenic) or that has many ships running the same rivers (to facilitate swaps).
High water isn't the only water level to worry about. Low water means there is not enough water in a river to float a ship without it grounding. Low water is typically due to a drought and is most common at the end of a hot, dry summer, usually around late September/mid-October. The Elbe River, which has a low volume of water to begin with, is often the most affected by low water levels.
As with high water, river lines will either turn to busses or ship swaps to deal with impassable stretches of river. In instances where the water is just slightly too low, the crew will empty out ballast tanks or passengers might be offloaded to lighten the ship so it can pass a particularly low stretch and then be allowed to reboard when the ship is clear.
Fog will usually only have a minor impact on river cruises. All riverboats are outfitted with radar and can “sail blind.” A ship will have to reduce speed in thick fog, but most itineraries have a lot of wiggle room for late arrivals, and the day's tour should still run on schedule. Only in truly extreme cases will a river close, and then only for a few hours. The bigger issue will be if the fog prevents you from seeing the beauty of an especially scenic stretch of river or the view from a castle or promontory.
Fall is traditionally the season for fog, but it can happen any time of year.
All river ships are certified to sail in certain levels of wind. Typically, riverboats in Europe are safe in up to Level 6 winds. New ships, though, won't qualify for this certification until after a month on the water; they will be classified lower, often at Level 3. If a windstorm kicks up and wind levels exceed a ship's certification, it's effectively grounded -- forced to remain docked until the winds subside. In less extreme cases, wind can make it cold and unpleasant to lounge on the ship's sun deck, or if it's truly unsafe, the ship's crew will close the top deck and remove the furnishings. It's a minor annoyance -- unless it coincides with a day of scenic cruising you were eagerly anticipating.
High winds are most common near the Atlantic, such as the waterways of Belgium and the Netherlands, where winds blow off the ocean. The Rhone River can also experience strong winds in the summer. When high winds strand a ship, river lines will usually bus travelers to the day's destinations, either as day trips from the ship or canceling the sailing portion and employing hotel stays for the remainder of the cruise. Because wind levels can change throughout the day, your captain and cruise director might be making last-minute decisions on where to move the ship or how to handle tours.
--by Erica Silverstein, Features Editor, with information gathered from Rick Kaplan at Premier River Cruises and James Hill at GoRiverCruise.com