Rafting Education ep.3 River features


My name is Borislav Paunovski with Whitewater Rafting Education. In this episode we’re going to talk about River features. We’re gonna show you waves, currents, holes, eddies. Let’s begin! Rapids differ significantly in form depending on what causes them . Staircase – in mountain creeks the channel is wide as it is deep. Descending over drops with little pause in between Banks are usually steep and visibility is poor. The most popular rapids are pool drop. They form into the gorge of the river. Those rivers are wider than they are deep and tend to be calm after a rapid. The rocks narrow the flow and different hazards are formed. Confluence – strong eddie’s and whirlpools occur when two river channels join. Usually there is thick vegetation that reduces visibility. Compression – when big volumes of water are hitting a river bank or a straight wall, the water goes down and emerges in big boils. Big water and floods – the immense volume of water that runs will create a lot of surges and hydraulics. They will wash away trees and make hazards. A few things to keep in mind when we are dealing with a flooded river. Try to stay away from the current. You could get swept away. There’s no Eddie’s or places to exit. It’s like a big channel going down. A flush drowning can occur That means that you’re out of strength, out of power to fight to stay above the current and you can drown easily. Stay away from fallen power lines because they can be active. Try to wash your hands and body after you’ve been in such water cuz it can be contaminated. Man maid rapids are the most dangerous ones. They are caused by constructing dams, bridges or dumping waste or construction rubble into the river. There are different currents in the river. The main one is called the tongue of the river. This is the deepest channel that forms a v-shaped surface in the beginning of the rappid. Eddie – this is the current that moves in the opposite direction. It is a powerful swirl that forms behind big rocks, walls and causes water to reverse flow. We use the eddies as safe places to stop rest, wait for the others, get out of the river and scout what is comming ahead. Eddie line or Eddie fence. This is the friction line between the main current and the upstream Eddie. Usually we try to cross it as fast as possible. When there is a difference in the height, hence the name Eddie fence. A pillow or a cushion is when the downstream current hits a wall or an obstacle. Part of the water will go under and boil somewhere else. Another part will go up. If you see a pillow it means it’s safe. You can swim in it. You can play with it. If a pillow is missing it means there is an undercut somewhere there. An undercut rock occurs when a softer layer of rock under the water erodes away and forms a cave or a gap. Often those underwater spaces get choked up with branches and other debris. It is often difficult to escape from an undercut and they’re always best avoided. If the water level rises and water flows over an object a different sets of features are created. The water that flows over the rock will accelerate falling down and it will create a recirculation feature. The surface water of the downstream site will flow back into the obstacle. The reverse flow can be dangerous as it can cause an object to be stopped and recirculated in the hydraulic. The deeper water will still move downstream. The power of the hydraulic will depend on the volume of the water, the depth of the recirculating current, the shape of the riverbed and other features. If the recirculation is close to the surface and the majority of the water is moving downstream we may have impressive hydraulic, but it is unlikely to hold swimmers. Different holes can be formed. We call them smiling hole or face, frowning hole or a straight hole. A smiling hole or a face – if you look from upstream it will look like a smiley face. Usually those holes flush swimmers and boats downstream due to the downstream current at the sides. The hydraulic effect is stronger in the center and weaker at the ends. Frowning hole – if you look the feature from upstream It’ll look like a sad face. They keep swimmers and boats in and recirculate them back into the center. Hence the name keeper hole. A low head damn is a drop in the river that creates a hole that is perfectly straight the whole way across. It has a steep angle of entry and no way to escape from. Usually they are not quiet and difficult to spot from water level upstream. They are primary man-made but natural ones do occur. They hold boats and swimmers and are known to be drowning machines. A downstream V is formed in the deepest part of the rapid where water is channeled between rocks. It is easy to see because it is darker solid section of the current. The downstream V is often an indicator of a good line through a rapid An upstream V is created by water falling over or going around an obstacle. An upstream V is often an indicator of a hazard and should be avoided. The fastest part of the river is in the middle current that is 50 centimeters beneath the surface. On the sides and on the bottom of the river there is a friction with the rocks. On the surface wind can blow hence slowing down the current. Knowing that we can say that a swimmer in the water will travel faster than the boat on the surface We should always have that in mind when we are chasing a swimmer. Reactionary waves are also known as breaking waves. Formed by the water passing over an object. Their shape is Irregular . A diagonal wave is a wave that is at an angle to the main current. As with other ways diagonal waves are created by the rocks on the river bed. A rooster tail is a spray of water that fires up and out of the mains flow. Rooster tails are formed when fast-moving water passes over a rock causing a drastic change to the direction and water shoots up in the air. Haystacks are series of waves found on the rapid often referred to as a wave train. Haystacks tend to occur after a drop. They can vary in length, power and size and are often inconsistent, surging and breaking as they move around. Ledges are flat rocks that water flows over and drops. They often create a speed drop in the flow that causes a purover hole to form. In many situations a river or a rapid may have several ledges creating “Staircase rapids” with one drop after the other. Strainers are extremely dangerous. A strainer is an obstruction in a river that only limited amounts of water can pass through. A strainer can be anything from a tree that is stuck into some rocks to a car that someone may have dumped into the river. Okay, that was our third episode of White Water Rafting Education: River features. If you like to keep those videos up you can help us by donating. See the information in the link below. Stay tuned, have fun and see you on the river! You

2 thoughts on “Rafting Education ep.3 River features

Leave a Reply

Your email address will not be published. Required fields are marked *