Jetting Resources

Reading & Navigating Rivers

Author's Note: Photo's in this piece were not taken for Reading & Navigating Rivers. All shots need to be replaced with the topic of reading rivers in mind. A photo shoot is planned for Spring 2004, weather and river levels permitting. Thank you for your patience.    -chris gorsuch

Rivers present some of the best natural structures fishing has to offer. Long ledges, rocky points, swift rapids and deep pools are just a few of the favorite spots. Most, if not all of our Pennsylvania rivers offer plenty of these structures around every corner. It is getting to and from these structures that can be half the battle. Whether you are running rivers by prop or jet power, when it comes to navigating running water, the more you know, the better off you are.

To complicate matters, water levels in a river system can rise and fall with little warning, especially those rivers subject to dam releases. Unlike lakes, as the levels rise, the river takes on a completely different look, not to mention the increase in current flow. Many of us who run these waterways under power, tend to concentrate more on the perils of low water conditions and ignore those at high water stages. This is a mistake, as both of these stages require serious consideration.

While it is not likely that reading this will teach anyone how to run a jet craft and read rivers, it will open the door for some understanding and help eliminate common mistakes. If any statement is true, it is that nothing can replace experience and actual time on a river. Regardless how you chose to navigate rivers in the past, whether wading, paddling, or by prop; the lessons learned in these modes will help when you step into a jet rig for the first time. Those who wade, canoe or kayak, can usually read water very well. They have to, mishaps along the way have taught them to read water depth, understand current breaks, seek channels and above all else respect moving water. Like anything worthwhile, reading and navigating rivers in a jet craft takes some time.

Conclusion: Experience is the best teacher.

Understanding the impact of High & Low Water Levels.

Rainfall triggers small stream flooding. Run off from small streams can cause a river to rise for several days. Reservoir dams also periodically release large volumes of water. High water produces dangerous flow levels and can dislodge fallen trees, logs and other debris. The debris is a problem for a number of reasons, it may not always be easy to spot in stained water, and often catches on other structure, blocking channels and thoroughfares. This is a common sight in the spring and something to be aware of. Swift current alone in high level stages can cause navigational problems. I tend to keep closer to the shore's edge as the faster moving water tends to be in the center.

Low water conditions have their own hazards. Shallow riffles, narrow channels, rock ledges are just a few of them. Rock ledges and huge boulders have claimed more than crafts than any other hazard. The problem is not those rocks that protrude above waterline; it is those just under the surface. When the water level in a river drops, so does flow. The reduced flow leaves little sign as it rolls over rocks just a few inches below the surface. Speed and shallow water is a delacate balance. A jet powered craft needs to run at planing speeds to draft as little water as possible. To reach plane, you are nearing speeds of 18 to 25 mph and most crafts will push 30mph or better, at top speed. Knowing how low the water is can be a major success factor in running rivers in low conditions. Since inches count, knowing where the stage is can be very helpful.

The USGS United States Geological Survey home page can link you to a host of Basin Stations for nearly every river in the state of Pennsylvania.  Note the Web-Link on our Resources page

Conclusion: Understanding the Stage & Flow of a River is Key.

Just how much water is required?

There are many out there that will quote just how much water is required to run a jet powered boat. With factors, such as hull shape, length and width, I would rather stay away from a fixed depth. It is more important to understand what the hull an outboard jet is doing first, then draw your own conclusions as to the depth of water required.

Starting from an idle, a depth of 10 to 12 inches is often required. When throttling up to take off, the back of the boat drops some, as jet intake is drawing every bit of water it can. If you are too shallow, you will draw small stones or other debris into the impeller and lose power. This is best case; you could jam the impeller and shear the key, leaving you without power. When you are on plane, you are able to run in very shallow water and will not pick up stones because the boat is moving so fast, it has already moved beyond the stone before it lifts. Once on plane, it is running as skinny as the hull will go. Gradually coming on or off plane in shallow water only increases the risk of damage to the hull or intake.

Conclusion: Bring the craft on and off plane a quickly as possible.

This is one area where many misconceptions are born. Even a specific jet hull will find skinny water limitations at various depths. Truth is, the water depth you can safely navigate through, depends more on the river’s bottom structure than the amount of water available.

Shallow water in a river system is found in a number of different areas. One of the most common areas for shallows is riffle areas. At the end of most pools the river bottom slowly rises and the water begins to move more swiftly. This fast moving water carries away the sediment leaving a hard consistent bottom such as gravel, river stone or cobblestone. These areas are usually gradual rather than a sudden change in water depth.  When you run a jet hull through these areas (above), a high level of pressure is produced on  the bottom of the boat. The result is a lift in the hull as the water attempts to escape from underneath the bottom of the craft. The hull actually skims or hydroplanes on top of the water similar to car tires on a wet roadway. As with a car tire there is a point where the level of surface pressure decreases, such as deep puddle, where the tire will begin to plow rather than skim over the water.  With a jet hull, as you go from skinny to deep water, the overall drag increases and hull speed drops slightly.  Unlike a prop power, where the skeg, prop and cavitation plate lock you into the water, a jet craft performs better in shallows rather than in twenty feet of water.

A sudden depth change such as a rock ledge or boulder (above), just a few inches below the surface of the water has claimed more jet units than perhaps any other shallow structure. It is common to run through skinny water depths and never touch bottom, and then bump a rock ledge that is a full inch deeper than the riffle the craft just passed through. This is due to a combination of hull pressure and bow push.

Conclusion: Surface pressure decreases as the water depth increases.  The higher the surface pressure, the better the hull lift.

Reading Water:

Learning to read water is hard to explain in mere words. However, there are guidelines that can help. In many instances where there is a long straight stretch of a river, the deeper water channel tends to run midstream. Then as the river bends and turns, the deepest water tends to move toward the outside edge of the bend. This is due to the cutting power of the river at high water stages. This tends to be more consistant with small to medium rivers and less true with large wide rivers such as the Susquehanna. Structures such as hidden ledges that run both horizontal and vertical tough structures to navigate through, here are some suggestions.  

The same section of a river will often look completely different depending on the direction your heading. Running up river offers the best view of obstacles, while the down river run usually hides obstacles rather well. The two pictures below show my favorite spot on the river to take those new to jetting. While pictures rarely do justice, the river drops 3-feet in the matter of seconds and most of my passengers are left with their mouth wide open.

When possible, on new water, launch down stream and work the craft up river. There are two key reasons for doing this. First, it is easier to read the water running against the current. Boat control traveling up river is more forgiving. The craft is able to approach a potential problem area without fear of the current pulling the craft into or over the obstruction, throttle back and the current will move the craft away from the hazard. Second, should a mishap occur, the current will carry the craft back to the launch area.

 Conclusion: Use the current's force to your favor. 

Heading Up Stream:

Reading rocky terrain is easier when moving against the current. Obstacles are usually in full view because of the line of sight and the way the water spills below them. Those that are not above the water line usually have a telltale sign as the water passes over them. In these instances, navigate the craft between or around them giving as wide a birth as possible.

Rocky sections of the river may only have one or two channels that offer safe passage. Look for a small channel or break in a rock ledge. It may be visible in a number of ways, but if the shallow rocks are not above the water line, look for the “V” (above) where the smooth water is flowing and head into it.

Follow the “V” breaks moving down river. They indicate where the majority of the water is (above & below). Water that looks calm or placid when looking down through rough water usually indicates a large obstruction or short falls in a ledge area. Many make the mistake of heading towards this seemingly calm water and often become pinned against or slam into the obstruction. This looks completely different traveling up river, from that view, the point of the “V” looks far more calm and the area just below the obstruction looks as ominous as it really is. 

In rapid sections that are rated Class-I & Class-II ,the basic rule of thumb is to head for the smooth water flow when navigating up river (indicating the safe depth) and head for the rough water flow (indicating the safe depth) when navigating down river. This comes with practice and may not seem obvious until doing so, take one step at a time with your craft. Build your skills and extend your range as you go, ripping through Class I+ or II waters on your first outing is a mistake.

Reading water from different craft types also makes a difference. A Jet Craft with a good forward helm position will offer a better line of sight than most paddle craft. In a jet craft, the operator sits higher making a better angle of sight than from a canoe or kayak where the view is often just a few feet above the water line. Seeing channels and obstacles early adds additional time to counter and safely navigate rough water.

Written by Chris Gorsuch