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A RIVER ENVIRONMENT

A RIVER PADDLING ENVIRONMENT; RIVER FEATURES, HYDROLOGY AND DEVELOPING RIVER SAVVY
                                                                                                                             -- Jim Simmons

In our SWR workshops this instructional module is one of the most fun. Even for experienced boaters it highlights the selling point of the ongoing need for continued development of river savvy. In reviewing web forums, professional magazines, and internet 'talk' sites discussing river accidents, a primary reason for accidents is usually a lack of river savvy or not clearly understanding a river's behavior and its power. Just as with boaters who love rivers, generally all types of people want to be on rivers to have a good time because everyone enjoys playing in a river.

STREAM PARAMETERS
provide a point of reference for a river's action:
Water follows the path of least resistance and seeks the lowest level. The volume of the water is expressed as CFS (cubic feet second) and is determined by these factors--width of the river X depth of the riverbed X velocity of the current. Rivers are gravity driven and as the gradient increases (between two points) the current moves faster, a factor often misunderstood. When the river level rises the force of the water follows the exponential law; that is, the speed doubles and the force quadruples, etc. As the river narrows in places, the velocity must increase drammatically to accommodate the same amount of volume as when the river was moving at a wider section. This is what causes the big 'wave' action in narrower places, sometimes called 'haystacks'.

RIVER DYNAMICS
are a key ingredient to comprehending river behavior. Rivers have personalities just like people and a river's personality is determined by the following: a) volume of the flowing water, b) how fast the water moves, c) the gradient/elevation, and d) objects in the river and along the banks. Change any one of these and the river changes personality; it may go from one having a 'pleasant' demeanor to having a 'cranky' one. As mentioned, when the river rises the power of the current increases exponentially and the river carries more surface load. If we look at river dynamics in a different manner, we might even imagine that "rivers create beauty and the patterns and colors of a river are like a painting on a canvas; and river sounds mimic those of a symphony orchestra."

A river's action is just like Superman---powerful, relentless and predictable. If a stream is flooded it will predictably clear out anything in its path. Experienced boaters do not typically paddle on flooded rivers. Of all the natural disasters on planet Earth, flooding conditions and moving/swift waters kill more people and cause more destruction than any other disaster (cyclones, earthquakes, floods, hurricanes, typhoons, etc).

Surface loads the river 'carries along' includes floating debris, logs, flotsam and various objects that present danger to swimmers or to rescuers working in the river current. These can be on the surface, along the river bottom, or floating just under the surface where they cannot be seen and are a danger to rescuers working in the water. Rivers don't just flow straight ahead; things are happening under the surface, on the bottom, and along the banks. Understanding the river's behavior is critical when applying river swimming strategies (see the article on river swimming for a description of laminar and helical currents--two main concepts for self-rescue when floating in river current). Basically, still, slow, or dark and murky waters will run deep; while fast waters (like whitewater) will run more shallow as the current flows over rocks/boulders in a rapid.

Internationally, rivers fall into different classes of difficulty--I, II, III, IV, V, VI (consult the American Whitewater Affiliation webpage for a detail description of each class). Awareness of the characteristics of moving and swift water are crucial for paddlers and rescuers when helping others in a river environment.

MESMERIZING EFFECTS OF RIVER NOISE
It has been shown that rescuers (as well as paddlers and other river floaters) have found the sight and sound of powerful moving water to be monotonous, mesmerizing and thunderous enough to actually put a person in a trance like mental state. Such an environment can be quite unnerving! On some large LH dams rescuers even reported that the river sounds were hypnotic. An unwary person on a tube or in a recreational craft may believe (because of this hypnotic trance-like character) they can boat out of it quite easily. Individuals who have survived being trapped in a low head hydraulic or stuck in a whitewater situation, said afterwards "it didn't seem very deep...or high, I thought I could easily make it, etc". Thankfully, around the U.S., in both urban and rural regions, there are campaigns to warn citizens of the location and dangers of low head dams.

This 'hypnotic' phenomenon is absolutely why river swimming strategies and performing drills in the water during rescue workshops are so impactful for participants. It allows paddlers to build enough experience (in just one weekend) to become more comfortable with the mesmerizing effects that rivers create. This also builds self-confidence in personal rescue ability. *(see the article about River Swimming strategies).

NATURAL RIVER HAZARDS
usually present such characteristics as rocky, swampy, muddy, places with treacherous footing, places with dense vegetation, hydraulics, 'holes', strainers (fences, trees), boulder/debris sieves, cold water, high water, large waves, undercut rocks, 'holes', pourover rocks, ledges, entrapment possibilities, access points that may be strewn with debris and driftwood, and flooded conditions.

MAN-MADE HAZARDS
are the usual bridge abutments, low and high head dams (especially the older ones) flood channels and weirs, human debris left in the river, fishing spots where fishing tackle/lines/hooks were left, toxic wastes, etc., along with controlled substances that people may be using.

A) CHARACTERISTICS OF RIVER CURRENT. Skill in reading the river's surface features helps prevent mishaps and boating accidents; along with increasing paddling fun. Common river features develop as a river expresses its 'personality'. Yep, rivers have personality as was described and paddlers and rescuers should be thoroughly familiar with these features. A river releases energy as it reacts to obstacles in its path and creates a natural occurrence termed current DIFFERENTIALS. These differentials are variations in the course of the flowing water and typically create specific patterns. Whitewater boaters classify these patterns as 'river reading'. Differentials occur when currents of different speeds and direction exist adjacent to each other in a stretch of river, often flowing in opposite directions.

The following list describes common river features encountered as a river expresses its personality--
Downstream/Upstream V's and Chutes. Upstream V's form as water splits around an object (rock, bridge piling) and are to be avoided because of the obstruction. River chutes form between two upstream V's as the water is squeezed between the obstacles. It speeds up as it drops over the gradient and forms the classic downstream 'V' (eddylines on each side of the chute will merge into the point of the 'V' downstream). It is usually good strategy to follow a downstream V as it will be the deepest and clearest path (unless obviously blocked).

Eddies/Eddy Lines/Eddy Fences/Current Differentials. Many instructors and paddlers consider an eddy turn as a boater's most important defensive safety skill because it allows a paddler to exit the river current and stop. An eddy is formed as the main river current flows past an object such as a boulder. The water passing the boulder will circulate back upstream creating a parking place. When paddlers refer to "catching an eddy, they mean turning into that parking spot where the surface water is 'still' or even flowing upstream. Eddies also form along the river bank because of friction along the river bottom. Current differentials are also caused by various obstructions in the river such as sunken trees, tires, old drums, old autos and other debris left in the river. Current differentials that are moving very fast but in opposite directions can create eddy fences and elevated eddies that are harder to paddle through (Humongous on Ocoee Racecourse).

Standing Waves/Wave Holes. As the curent is constricted into a smaller space, it speeds up over the gradient and large waves pile up (as mentioned above). These large waves may actually be 'breaking' back upstream which can stop a swimmer or even a boat in midstream. In open canoes it is a good technique to 'quarter' the large waves to deflect water away from the boat. In self-rescue swimming, learning to match your breaths with breaking through the waves is important. Big, powerful waves can be very unpredictable.

Riverbends. A bend creates current characteristics that often get inexperienced boaters into trouble. Centrifugal force is at work with bends, which have accompanying cross currents and strong current differentials. Water piles up on the outside of the bend (high mountain side), creating eddies that collect flotsam, debris, sticks, sediments, trash etc. The river on this side is very deep and may cause undercuts in the rock face, or uproot trees that fall in to become strainers. The inside of the bend is usually the safer side and becomes more shallow near shore.

B) EFFECTS OF OBSTACLES IN THE RIVER
Ledges/Rock Gardens/Boulder Fields. Because a river doesn't necessarily flow over ledges in a straight ahead path boaters must learn to use boating techniques to negotiate ledges to locate the main current flow. This calls into play the skills of eddy turns, peelouts and valuable ferrying skills for working down a series of ledges. Rock gardens and boulder fields create many obstacles that must be negotiated because the best route is not always apparent.

Horizon Lines/Waterfalls. Horizon lines indicate a significant 'drop' in the river ahead. If uncertain of what is ahead, park your boat and scout from shore. Facetiously, if all your group sees ahead are the tops of trees downstream, it may very well be a waterfall or a low head dam. When in doubt, get out and scout!

Strainers and Sieves. Ranking third behind cold water and high water as the most frequent cause of river deaths strainers may be logs/trees, fences, old cars, or debris piles positioned in the main current. These allow water to flow through but will stop boats and bodies. Boulder sieves form in piles of rocks and look like a big cheese grater with holes. Boats, too big for an opening, may end up stuck in the sieve. The strainer drill, in which rescuers swim over a 10 inch diameter padded PVC pipe simulating a tree trunk, is one of the most impactful drills done during training drills.

Rocks/Pillows/Pourover Rocks. When reading river features just downstream of a partly sumberged rock will be a bump or a rising wave caused by the water flowing over the rock. If the rock is completely submerged a pillow forms just downstream. If the obstruction (rock, submerged tree) breaks the surface and is visible, a boater will know to avoid. Often, paddlers, not alert for these features may get sideways against a rock or a rock creating a pillow. This is termed 'broaching' and is high on the list of frequent mishaps. If there is enough of a cushion of water flowing against the obstruction the paddler may likely escape; if not, the boater may become broached sideways. Pourovers (water flow rather shallow over a flat type rock) won't usually 'keep' a swimmer in the hole downstream of it because body weight makes the swimmer sink into the aerated water, and the swimmer's momentum will cause her to exit downstream.

Holes/Hydraulics. If an underwater rock is large enough to rise above the surface, a 'hole' may form on the downstream side. As water passes over the rock a slight depression will form. The deeper this drop and the greater the volume and velocity of the flow the larger the hole will become--may form a hydraulic, or 'keeper'. The surface water downstream of the obstruction is flowing upstream to fill in the depression created by the force of the water falling over the rock ledge. This often traps an unsuspecting paddler. In whitewater terminology, holes may be termed either 'friendly' (good for playboating); or 'unfriendly' (boater may get trashed if in it).
Refer to the article on Low Head Dams for more details on hydraulics and keeper holes.

River reading, river savvy and knowledge of river hydrology are all valuable skills for more fully comprehending a natural river environment. Learn more each time you paddle, or even when spending time around a river setting.

Jim Simmons--4/28/2010; revised 3/2011
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