The greatest difference between coastal boating and river boating is the constantly changing nature of inland waters.
Water depths never stay the same. Currents vary from fast to nonexistent. Channels change with shifting sand, silt and mud. And navigational aids move regularly.
Strong river currents create problems for both commercial and recreational boats. On some rivers like the Mississippi, currents reaching 8 to 10 miles per hour make it difficult for low-powered boats to get upstream.
Handling a boat in a strong current takes effort and practice. While heading downstream, skippers can lose partial control, putting their boats at the mercy of the current. The Navigation Rules give the right-of-way to vessels traveling downstream for this reason.
River depths vary depending on the amount of water coming from upstream. In droughts the water may fall too low to be navigable; in floods it may run high and strong and be littered with trees, logs and debris.
Detailed river charts are indispensable. The charts define safe channels with colored and shaded contour lines. Get accurate water depths by referring to daily river levels on weather forecasts and from local newspapers.
Stay within marked channels unless you are certain about the water depth and your boat’s draft. Don’t be tempted to take the shortest route between two points.
When the river is flooding, it can extend for miles beyond its usual banks, making it difficult or impossible to find the normal channels. Use common sense, handle your boat carefully, and make good use of charts and aids to navigation.
Logs sometimes float just under the surface of a river; at other times, they stand on end and float upright. Keep a lookout for debris because the part you do not see is often larger than the part you do.
Debris damages propellers, shafts, lower unit casings and hulls. If you hear or feel a thump, stop and check for damage. If you feel an unusual vibration, go slow until you determine its source.
Reading the river
A riverbank gives clues to the water’s depth. Along a steep bank, you can expect relatively deep water up to the shoreline. A long, gently sloping beach usually means that the water is shallow a long way from shore.
You can often tell shallow water by a difference in the water color, by ripples when the water is calm, or by a patch of quieter water in the midst of choppy water.
If you suspect shallow water, slow down to bare steerageway. Engage the propeller only as needed to maintain headway. You may be able to partially raise the propeller on an outboard motor or stern drive.
Check your wake to see if you are stirring up mud or sand. Place a lookout at the bow to measure the depth of water with a boat hook or weighted line.
To learn more, take USPS’ newest online seminar, Boating on Rivers, Locks and Lakes.