How the water reacts when in a rapid.
lets explore how water reacts when in a rapid. To do this we are going to look at; how a rapid is formed, rapid classification, types of rapids, fluid dynamics and the features the water creates when in a rapid.
How rapids are formed
Factors that contribute to the formation of a rapid are: water, gradient, volume of water, and constriction. usually two or more factors are put together in the creation of a rapid
Water:
If there is no water, there is no river, therefor no rapid.
If there is no water, there is no river, therefor no rapid.
Gradient:
Sudden or constant change in elevation creates rapids. A topographic map, guide book, local knowledge are all factors in determining what the river, and its rapids may look like. At least one, or all of the aforementioned items should be used. When using a topographic map count the number of contour lines that cross the river, and how close they are together. then take into account what your maps elevation is in (written somewhere on the map). This will give you an idea of what the river may look like. More gradient generally means steeper rapids. A river's elevation drop that is steady, will be more continuous then one that drops with less. |
Volume:
measured in CMS (cubic meters per second) or CFS (cubic feet per second). This is the amount of water that passes by you every every second.
measured in CMS (cubic meters per second) or CFS (cubic feet per second). This is the amount of water that passes by you every every second.
Volume plays an important role in the creation of rapids. A shallow mountain creek that drops at 50 meters per kilometer with a volume of 10 cms will look different then a river that drops at 5 m per kilometer with 1000 cms.
On the flip side if the shallow mountain creek that drops at 50 m per kilometer, and that normally has a volume of 10 cms now has 50 cms We no that it will look very different. |
Constriction:
Some times wide river meets a constriction such as; a landslide, a canyon or human made obstacles. The sudden narrowing increases the waters speed and can create a rapid.
Some times wide river meets a constriction such as; a landslide, a canyon or human made obstacles. The sudden narrowing increases the waters speed and can create a rapid.
A rapid
When add you to water: gradient and constriction you get a rapid. Each of the factors that contribute to the creation of a rapid (gradient, volume and constriction) always interact with each other. You will often find all of them working together not only to create a rapid but within a rapid as well. These factors help to create river features, a topic we will discus latter on.
When add you to water: gradient and constriction you get a rapid. Each of the factors that contribute to the creation of a rapid (gradient, volume and constriction) always interact with each other. You will often find all of them working together not only to create a rapid but within a rapid as well. These factors help to create river features, a topic we will discus latter on.
Rapid classification
Rapids are classified or graded 1-6, with 6 being the hardest. This is an international grading system, the exception is the Grand Canyon of the Colorado where the grading system is 1-10. In grading a rapid orally we say "class...." or "R....". When writing, we write "C...." or "R....". C: class R: rapid. Both are correct. I will be using the word class to describe the grading system.
The grading system it's self is fine, the issue is that of human interpretation in the form of: experience on a variety of different types of rivers, gradient and volume.
The grading system it's self is fine, the issue is that of human interpretation in the form of: experience on a variety of different types of rivers, gradient and volume.
In short a paddler who paddles class 3 and occasional class 4 pool and drop may struggle on continuous class 3 white water because they are not used to be constantly on there toes. The fault is not the classification but the paddlers experience. Human error can also play in to the description continuous means. Is it a continuous section of class 3 white water for 1 km? Or 2 class 3 rapids inter spaced by class 2 white water. This is where it gets really complicated. Class 3 big water is different from a class 3 creek, but it is still class 3. Therefor it is important to paddle a verity of different rivers and volumes in order to better understand the grading system.
International and different area paddling:
When paddling international, or for that matter a different area in your country (my country, Canada, has so much white water that is so diverse you can paddle a completely different style of river 200 km away or 2000 km away) always 'check your self before you wreck you self'. Always dial your self back a full grade. In the case of international travel you may be not used to the food or water (shiting yourself every 5 minutes), or the method of travel (have just been scared for your life because of the roads or traffic), your bed is not your bed (you may have slept funny or not slept at all) Take a moment and get comfortable with your surroundings before you jump back into the swing of paddling.
When paddling international, or for that matter a different area in your country (my country, Canada, has so much white water that is so diverse you can paddle a completely different style of river 200 km away or 2000 km away) always 'check your self before you wreck you self'. Always dial your self back a full grade. In the case of international travel you may be not used to the food or water (shiting yourself every 5 minutes), or the method of travel (have just been scared for your life because of the roads or traffic), your bed is not your bed (you may have slept funny or not slept at all) Take a moment and get comfortable with your surroundings before you jump back into the swing of paddling.
Rapid Classification
Swift:
Moving water
Moving water
Class 1
No obstacles, no need to navigate
No obstacles, no need to navigate
Class 2:
Small obstacles that may or may not need to be avoided, Some white water skill required
Small obstacles that may or may not need to be avoided, Some white water skill required
Class 3:
Obstacles in ones path, may require significant maneuvering, white water skill required and white water rescue and first aid skills recommended
Obstacles in ones path, may require significant maneuvering, white water skill required and white water rescue and first aid skills recommended
Class 4:
Mandatory navigation around obstacles that may pose danger to ones health, significant maneuvering required. Advanced white water skills, rescue and first aid skills are required
Mandatory navigation around obstacles that may pose danger to ones health, significant maneuvering required. Advanced white water skills, rescue and first aid skills are required
Class 5:
Complex and mandatory navigation and maneuvering around obstacles. Failure to navigate correctly will pose a danger to your life. Expert white water skills, rescue and first aid skills are required.
Class 5.1-5.5
Used in Canada and the United State's east side as a way to further break down Class 5. Each decimal added is a full white water class. This has not taken off around the world because of its complexity. One can also use class 5+ to describe this
Complex and mandatory navigation and maneuvering around obstacles. Failure to navigate correctly will pose a danger to your life. Expert white water skills, rescue and first aid skills are required.
Class 5.1-5.5
Used in Canada and the United State's east side as a way to further break down Class 5. Each decimal added is a full white water class. This has not taken off around the world because of its complexity. One can also use class 5+ to describe this
Class 6:
Not passable. When a Class 6 rapid or section has been successfully navigated it may or may not be downgraded to Class 5 (5+)
Not passable. When a Class 6 rapid or section has been successfully navigated it may or may not be downgraded to Class 5 (5+)
+ / -
Some times a rapid can be a little harder or a little easier. However It dose not warrant the next full grade. People some times add a + or - sign to the grade to convey this.
Some times a rapid can be a little harder or a little easier. However It dose not warrant the next full grade. People some times add a + or - sign to the grade to convey this.
Types of rapids
There are three different styles or types of rivers. They are: boulder gardens, slides and waterfalls, and big water. Each have there own unique characteristics. Some rivers are mashups of two different styles, some rivers have all three. Being acquainted with all three styles is important for your personal progression and ones ability to interpret the rapid classification system.
Boulder Gardens
When a glacier receded it left boulders in the river of varying sizes. A land slide (human or natural) added randomly placed boulders in the river. Or a dynamic powerful river constantly bringing rocks down from the mountains, After the yearly flood the rocks settle, only to move again the next year.
When a glacier receded it left boulders in the river of varying sizes. A land slide (human or natural) added randomly placed boulders in the river. Or a dynamic powerful river constantly bringing rocks down from the mountains, After the yearly flood the rocks settle, only to move again the next year.
Slides and waterfalls
A slide is when water moves thinly over the bed of the river. It is called a slide because your boat 'slides' over the rocks. Picture a play ground slide. These can be any where from 1 to 89 degrees.
A water fall is when the water enters the vertical realm and your boat is now airborne.
On some rapids the slides and waterfalls meld into one, or the rapid is so complex that you can have both.
A slide is when water moves thinly over the bed of the river. It is called a slide because your boat 'slides' over the rocks. Picture a play ground slide. These can be any where from 1 to 89 degrees.
A water fall is when the water enters the vertical realm and your boat is now airborne.
On some rapids the slides and waterfalls meld into one, or the rapid is so complex that you can have both.
Big water
Big water characterized by large Standing waves. Rapids are deep, and have powerful under currents (described bellow).
Big water characterized by large Standing waves. Rapids are deep, and have powerful under currents (described bellow).
Fluid Dynamics
In order to have a better understanding of how the water reacts when in a rapid, and the features it makes. One must understand what the water is doing, both on the surface and below.
The flow of water in a river is a sandwich of different layers; surface flow, laminar flow, helicoidal flow, bottom flow.
Surface Flow is the top layer. It is the slow moving aerated water at the top. When you are paddling in a rapid, this is the area you will spend most of your time. It is slow moving because of the friction against the air and the next flow.
Laminar flow or linear (straight) flow is the second layer. It is the fast moving water that if you have ever directly jumped into white water, or capsized from your boat. You have most likely felt your self being swept-ed away. this is that layer. It is fast because of minimal friction.
Helicoidal flow is responsible for everything that we see on the surface; waves, boils ext. as the water moves down hill it is pushed up by hitting objects off of the bottom. The larger the features we see on the surface the deeper the river.
The Helicoidal flow hits the laminar flow bellow it and is pressed up, it in turn pushes the surface flow up creating what we see on the surface. Laminar flow or linear (straight) flow is the tertiary flow. It is a fast flowing layer at the bottom of the river it is relatively unhindered as it moves in a straight line up and over any undulations and rocks on the river bottom. As it follows over these undulations it pushes the helicoidal flow upward.
Bottom flow like the surface flow encounters friction between the bottom of the river and the laminar flow above. This friction makes it slow moving.
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Holes
Types of holes
There are three different types of holes, they are: smiling holes, frowning holes and ledge holes
Smiling holes are generally considered 'good' holes. This is because exit points face downstream, making it easier to release from the hole.
They are called smiling holes because if you put two 'eyes' down stream of the hole it looks like a smile :) from upstream. Frowning holes are generally considered 'bad' holes. this is because the exit points face upstream, making it harder to release from the hole.
They are called frowning holes because if you put two 'eyes' down stream of the hole it looks like a frowning face :( from upstream. Ledge holes look like a ledge and depending on the circumstances can be very bad. The worst, the low head dam (called a drowning machine) is bad because there are no natural exits except the bottom. It is often very hard to exit because one must crawl along the river bed to get out (self rescue), or someone must rescue you via shore, water or both. These holes (often called weirs) do appear naturally, and are blocked of on ether side by rock or water. Ledge holes can also be angled meaning they have one release point angled down stream.
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Escape artist
Entering and exiting holes preferably in your boat
Big Hole flushes
This is a planned technique. You may decided to implement this as part of your line, or mid line realize you need to implement this. If mid line, one can flip over so as to minimize above water surface area that the air rated water can hold on to.
The Idea when flushing through a big hole is to catch the helicoidal flow and allow it to push us as deep as possible so it (the helicoidal flow) pushes us out, or pushes us into the deep laminar flow at the bottom of the river. As you can imagine it would be less then ideal to be in stuck in the slow moving aerated water at the top of the hole. The top Laminar flow dose push out, however its not ideal.
Determining whether passing through the hole is a viable option is usually pretty evident when scouting the hole. Can I see water exiting the hole? How much is exiting? If the answer to these questions is positive then one may opt to go for the flush. If not, one may decide that the best line is walking around.
Stuck in a rut? er... a hole?
so you're stuck in a hole eh! Here are a few ideas on how to get your self out before swimming. One of the most important skills as paddlers - both canoe and kayak, is spending time in a hole. As paddlers we are often scared of holes as they are taught to us being dangerous areas. So when you're stuck in a hole eh! Here are a few ideas on how to get your self out before swimming. One of the most important skills as paddlers - both canoe and kayak is spending time in a hole. As paddlers we are often scared of holes as they are taught to us being dangerous areas when we are first learning about white water. Each hole has it's own personality. In order to have a better understanding of the personalities out there, you need to get in to the holes them selves. n we are first learning about white water. Each hole has it's own personality. In order to have a better understanding of the personalities out there, you need to get in to the holes them selves.
Rodeo:
Play, and surf your way out, by cartwheeling, throwing ends and loops (yes you can loop a creek boat). By doing this you limit the amount of surface area that is in the hole making it easier for your boat to catch any water that is traveling downstream.
Play, and surf your way out, by cartwheeling, throwing ends and loops (yes you can loop a creek boat). By doing this you limit the amount of surface area that is in the hole making it easier for your boat to catch any water that is traveling downstream.
Submarine:
The idea is while you are upside down to catch any down stream current that is deep bellow the surface. When you are upside down reach down with your paddle in order to try and catch any water that is exiting the hole.
The idea is while you are upside down to catch any down stream current that is deep bellow the surface. When you are upside down reach down with your paddle in order to try and catch any water that is exiting the hole.
waves
Waves are created when the water (helicoidal flow) hits the bottom of the river and bounces up. the more time it takes for the the helicoidal flow to hit (and push up) the laminer and surface flow the larger the waves. Thus if you see very big waves odds are it is deep. The flip side is true as well, if you see lots of short choppy waves its shallow.
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Types of waves
There are many different types of waves, and lots of nomenclature to describe them. I have condensed waves into two major groups; standing and breaking waves.
Standing waves:
Also know as hay stacks (large pointed waves) or ocean waves (usually describing large rolling waves). Standing waves can be large green waves - referring to the face of the wave, and the lack of foam on top. Or have a small crown or crest of of white foam. Breaking waves
A breaking wave is when the crest of the wave becomes so large and heavy that it 'breaks' or falls down into the trough. some times the foam pile can be so large that it is in the trough its self. The difference between a breaking wave and a hole is that a hole is constantly recirculating on its self. breaking waves can be powerful enough that the can stop and surf your boat if you do not have enough speed, however there is no re circulation. It is always building and breaking. |