Into the Drink...and Out Again (hopefully)
Part II: It's Only Water

The bottom surface of a stream or river is obviously affected by the geology of the area (for example, it will be unusual to find a rocky bottom stream in the Mississippi lowlands, ) it is also greatly affected by the current. A swift flowing current will tend to sweep fine silty particles downstream, leaving heavier sand and rocks. The fastest streams will often have large rocks and boulders on the bottom, as smaller ones get pushed along. Where the current slows, the lighter, smaller particles will drop out and collect. For our purposes (getting across...) the firmer the bottom, the better (no wise cracks here...). A mud bog or silt hole underneath a slow flowing stream or a beaver pond is no easier to get across than a bog or silt hole without the water on top, and it's usually a lot worse. The banks of the river, and the area surrounding it will usually tell you a lot about what is under the surface. If the river is surrounded by a gravel flood plain, then you can expect that the bottom will be of similar composition. The same applies if the surrounding banks and river bed is sandy. If the stream flows through an area of thick rich topsoil, there is a good chance the bottom will be soft organic material.

Sometimes a jaunt down the middle of the stream will yield an easier crossing than trying to go straight across. Note the calm smooth water to the right of the rigs. This is a deeper area. The rough choppy nature of the water from the vehicle left, shows that it is shallower. Although hard to make out in the picture, the stream narrows to less than a fifth of it's former width, as it curves off to the left ahead of the front rig. As it does so the channel deepens and the current picks up. By following the gravel bar as this rig is doing, a posibly hazardous crossing is reduced to little more than hub depth.

In a case like this, take a good look at the exposed material at the banks, below the level of the surrounding topsoil. You will often find that under a shallow layer of rich soil there is a rocky or sandy layer. The water may be flowing across this or similar layers, resulting in a firmer bottom surface than you might expect. Especially if the current is fairly swift.

Careful visual inspection of the water surface can often tell you a lot about the bottom. A smooth calm surface will usually be (relatively) deep. If there are slight indications of upwelling current, it is even more likely to be deep, and probably relatively soft as well. Riffles and splashing are of course indications of shallow water. Standing waves and ripple patterns show larger obstructions under the surface. A section of calm smooth surface becoming rippled and dancing on the downstream side usually indicates a ledge or other rapid transition from deep to shallow.

While this crossing is wide and swift, the fairly calm water and exposed rock for the majority of the distance show that it is not deep. Again, the detail in the picture is not good, but ahead of the rig, the water is much faster, with small standing waves. This shows that there is a deeper channel just to the front of the vehicle.

A "V" shaped area of standing waves surrounded by riffles or splash zones will be a deeper current channel in between shallow areas. A smooth, calm area along side the main current flow will be deep and possible soft, while a riffled but fairly calm area along side the main current will be shallow and more likely solid.

Note that most of these indicators apply much more to swifter flowing water over fairly firm bottom. In a slow moving sandy or muddy bottom stream the surface will usually be pretty uniform, and the profile of the bottom will be a gentle slope in and out of the deepest area, which will usually be at the center of the stream. If there is evidence of cut bank however, then expect a steep drop below the surface as well. Trees right to the edge of the water, and overhanging it tend to indicate a sharp bank edge too. While these types of streams are less likely to have boulders and holes, they are more likely to contain submerged logs and other snags.

The clarity of the water can make it easier or harder to read the nature of the bottom, and to detect characteristics which may not affect the surface.

The outside of a bend in the river will almost always be deeper and faster moving than the inside of the bend. The bank and the underwater profile is usually much steeper as well.

A river or stream that has wide nearly flat banks will usually have a steep step down, either just before the water, or just after entry. A stream at the bottom of a steep valley or ravine which drops right to the banks will usually have a fairly flat bottom (aside from boulders and obstructions).

Although this small stream is easily forded by a stock FJ40 in this shot, on our next trip out it was a different story. Note the steep banks on each side, and the narrow stream bed. Afterr several days of steady rain, the water was running about 4 feet deep, and erroding away the banks as well. Fortunately the slope is fairly mild, so the current was not extreme. It took about 4-5 hours of clawing, jacking, recovering, winching and bashing to get the first of 3 well prepared rig through the water and up unto the near side bank. Once that was done, the others were an easy task, but it was a long wet and cold affair for such a puny looking water course.

The banks will, as mentioned before, tell you a good bit about the nature of the bottom, and the profile as well. They are a concern all on their own however. Carefully look the banks over, to ensure that an entry can be made into the stream without wedging the nose of the rig against the bottom, or dropping nose first into a hole deep enough to drown the engine. Make sure that the line you select to cross the current brings you out at a point where you can climb over the bank to exit the water. If this is not possible, look to see if you will be able to make your way up or down stream to a suitable point, or if it will be feasible to leave the vehicle in the water while you rig up a winch to get over the bank. Pay attention to both the angle of the banks, and the type surface, and don't forget that on the way out, your tires will be wet, and water will be pouring off of your rig. It will be a muddy slippery exit if you have to claw your way up a dirt incline.

In this shot the glacier pictured is about 4 miles away. The outflow crosses in front of the ice over a wide plain of gravel. Due to the heat of the sunlight, the meltwater volume increased greatly during the daylight hours, creating a surge of higher water which works it's way down the river. Timing your crossing to coincide with the lower water levels can ease the difficulty significantly, as both water depth and current speed drop off.

You may have noticed that I haven't mentioned anything much about current yet. I've saved the best for last. Many people underestimate the current. If the water is very shallow then it is no factor at all. But with any depth, current becomes a serious thing. And of course the deeper the water, and/or the faster the current, the more hazardous it is. Water pushing against your rig can exert an incredible amount of force. Water flowing around tires sitting on, or crawling over a sandy bottom, can scour the material right out from under the tires, sinking the rig firmly into the bottom. Water rushing under and around your rig and create turbulence and actual lifting force which will float it free of the bottom, even though it would have remained firmly planted in calm water. When combined with a rough and rugged bottom which can cause any given tire to be unloaded as it comes down off of an obstacle, this can be even more serious.

This is a classic example of a slow current and a soft bottom. As is usually the case, the water is less than crystal clear. A water proof ignition would have probably allowed this rig to continue across this sandy Florida channel. Of course simply getting mired in the sand is a problem too. At least the water was nice and warm...

Current washing against the vehicle will raise the level of the water on the upstream side potentially overcoming your waterproofing efforts if you have not allowed for this. It can also impose much higher power requirements if you have to work your way upstream, rather than simply moving across the flow. Stating any kind of combination of current/depth levels as being safe or unsafe is impossible.

As you can see, with this many variables, every water crossing which is difficult to require any consideration, is going to be at least a little different from every other one. With all of these factors in mind, and some experience in "reading" the water, most crossings can be made with little delay. The approach to getting across any given river or stream will vary, often even from the approach that was best the last time you were there. There have been occasions when it took us hours of multiple attempts, winching, and even slight vehicle damage to cross a stream which earlier in the day was forded in less than a minute. Water levels and flow speeds can change from month to month, day to day, or even in an afternoon, depending on the climate and weather conditions.

Seen from 1000 feet up the hillside, and a distance of 3 miles and more, the sunlit East Fork of the Knik River below looks pretty small. When you are picking your way across the multiple and everchanging channels in the waning light it doesn't feel so insignificant. The meandering course, and braided flow offers an excellent chance to practice "reading" the water. Doing it at night can be a real thrill.

Often the nature the bottom of a crossing, and any underwater hazards can only be determined by first walking and wading the crossing. Don't be afraid of getting a little wet. Many people will urge you to always wade a crossing first when in doubt, but my experience has been that this is generally best used in water with minimal current. A beaver pond, or slow placid stream is a situation where this approach works well. In a faster flowing stream or river however, you will often find that your vehicle is easily capable of forging ahead through current that would knock you off you feet with the slightest misstep. In these kind of situations I prefer to examine the crossing as thoroughly as possible from the shore, and then slowly edge out into the flow with one of the vehicles. A slow forward pace will usually allow you to back out of any hole or rut before you drown the rig.

This is an example of a stretch which lends itself to wading first. There is no current, the water is slightly murky, and there is a good chance of holes and ruts below the surface. An inspection on foot can prevent a lengthy, wet and muddy chore of vehicle recovery.

Of course a slightly faster pace will often carry you through the hole and up the other side before the water has a chance to climb within the sheltered engine compartment and drown the rig. This call has to be based on experience and personal technique preferences. Anyway, consider which rig has the best chance of getting across, and which will be the easiest to recover in the event that it doesn't make it across (along with considering which is the best suited to perform the recovery from the shore). If the crossing is narrow enough, we will sometimes hook one or two 150 foot lengths of cable to the back of the rig entering the water, and lay it out on the ground to be pulled in after it. Then if the rig gets bogged down in a soft bottom, or swamped in a hole, it can be quickly recovered with little difficulty. For wider crossings this will not work of course, but you can often move the recovery rig out into the water a bit as well (or simply use more cable).