5-October 2008: Nature presents us with a tremendous variety of waterfalls. Indeed, no two waterfalls are exactly the same, and it's the main reason why you could be waterfalling your entire life and still have a completely different experience each time and see things differently than another waterfaller!There has been some effort in trying to categorize waterfalls. A couple of ways to classify waterfalls involve categorizing based on shape while there's another one involving the classification of waterfalls based on volume. Let's take a closer look at these methods. Have a comment or contribution?
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GEOMETRICAL CLASSIFICATIONEver since I was introduced to the notion of waterfall classification based on its geometry from reading Gregory Plumb's book about Waterfalls in the Pacific Northwest, I was intrigued by how he was able to categorize waterfalls based on some common features regarding shape. Of course, Plumb wasn't the only one doing this. There are numerous other people making categorizations based on geometry out on the internet. The big problem is that when you have criteria based on visualization and inspection, it's subject to interpretation. Therefore, there's bound to be disagreements and problems as well as inconsistencies within the categorical definitions themselves. Nevertheless, let's look into the types of geometrical classifications that are out there. Plunge: Waterfalls that drop vertically usually without touching the underlying cliff face fall under this category. As you'll see in the course "How Are Waterfalls Formed?", waterfalls typically well into the evolution of waterfall formation evolve into this category. Sometimes you can even go behind these types of waterfalls! Examples of this are Bridal Veil Falls near Raglan, New Zealand, Mangawhero Falls, Steinsdalsfossen, Nobe Young Falls, and Snoqualmie Falls.
Horsetail: Waterfalls that fan out as they drop into a steep slope but maintaining contact with the underlying cliff face usually fall into this category. The name of this category derives from the fact that some might observe the shape the waterfall under this circumstance resembles a horse's tail. In terms of waterfall formation and evolution, these types of waterfalls are either younger than the plunge types or the hard rock layer is steeply sloped. Examples of waterfalls in this category include Nevada Falls, Sanddalsfossen, and Manawaiopuna Falls.
Fan: Waterfalls in this category are quite similar to that of the Horsetail variety. They share the common characteristic in that the waterfall drops and slides along a steep slope while consistently maintaining contact with the underlying cliff. However, the difference is that the shape of the waterfall is such that it looks more like a fan (you know, the ones you see in Kung Fu movies or Asian women fanning themselves with) facing upside down. These tend to look more trapezoidal than their horsetail counterparts. Examples include Fantail Falls in New Zealand, Mokau Falls, Friaren, and Lower Falls or Enfield Falls in New York.
Punchbowl: This category of waterfalls is something I don't quite fully understand. Apparently, it describes the shape you get when you have a stream channeled into a narrow hanging gorge and shooting over a drop that results in a plunge pool resembling a punch bowl that you might see at a party. Honestly, I'm not sure if this is the correct interpretation, but I've seen this enough times in the literature to include it here and try to make it clearer for you. I somehow doubt I've succeeded in that though. Since I don't have a clear understanding of what exactly comprises waterfalls in this category, I can only take guesses. So here are my guesses at what could be examples: Devil's Punchbowl Falls in New Zealand.
Block: Sometimes called Rectangular waterfalls, these are the types of waterfalls that have what Julie and I consider the classic shape of the waterfall. Basically, you have a waterfall that resembles that of some rectangular shape. The underlying cliff face is usually a vertical wall. Sometimes waterfalls in this category end up being wider than its height. Usually, the wider the river that's plunging, the wider the waterfall and hence the fatter the rectangle. Examples of waterfalls in the block category include Marokopa Falls, Skógafoss, Niagara Falls, and even Victoria Falls!
Tiered: This category of waterfalls describes waterfalls that have more than one vertical leap or tier to it from the perspective of a singular vantage point. This definition could have problems as in the case of the Nevada Falls and Vernal Fall combo. But most waterfalls that get into this category have more obvious multiple tiers closer together such as Belmore Falls, Mitchell Falls, Gullfoss, and Sutherland Falls.
Segmented: This category of waterfalls involves the descending watercourse splitting up into two or more parallel segments or threads. Usually the cause of the split is some protruding rock in the middle of the watercourse before or during the course of the waterfalling cascade. The problem with this definition is that it's very subject to waterflow conditions and the segmented waterfall could easily degenerate into a singular waterfall with the smaller threads missing. Examples of this type of waterfall are Waipunga Falls, The Seven Sisters in Norway, and Glanni in Iceland.
Cascades: Waterfalls in this category basically descend along a sloped surface. From the standpoint of waterfall formation, the falls could be in the early phase of its evolution or the underlying hard rock layer is sloped and water is moving along it. Sometimes you get stepped formations if the individual tiers are too small to count as a tiered waterfall. Examples of waterfalls in this category include Chilnualna Falls and Tokopah Falls.
Chute: Waterfalls in this category are typically where its watercourse is forced into a narrow channel resulting in a violently pressurized ejection of water. I guess to some degree, you could argue these are more rapids than falls, but it's hard to tell when you have a noisy, frothy, white mess forcing its way through the narrow channel. Examples of waterfalls in this category include Murchison Falls and Barnafoss in Iceland.
Scree: Sometimes referred to as Talus, you could argue that waterfalls cascading over scree or talus should belong in the Cascades category. However, scree-type waterfalls flow over loose rock that has accumulated at the base of a mountain or cliff as a result of erosion. Often times cascades like this appear in combination with any of the other types of waterfall categories on this page, but there maybe instances where a watercourse just so happens to only fall over scree. Examples of this include Djúpavíkurfoss in Iceland and Vedalsfossen.
Slide: Waterfalls flowing over a relatively low angle slope falls under this category. Sometimes you get nothing more than rapids, but other times you get interesting waterslides. I guess you could argue that waterfalls in this category should belong in the cascades category, but if you think this category should exist, here are a few examples: Waterwheel Falls, Pywiack Cascade, and LeConte Falls.
Ribbon: This category is merely a toss in to encompass very thin or ephemeral waterfalls that have a very narrow stream but may fall over a long vertical drop resulting in its ribbon-like appearance. If you don't count ephemeral waterfalls as legitimate waterfalls, there are more consistent performers that fall under this category such as Fairy Falls in Yellowstone, Ribbon Falls in Yosemite, and perhaps even Manoa Falls and Pelverata Falls.
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WATER VOLUME CLASSIFICATIONRather than worry about the subjectiveness about a waterfall's shape, this is a more scientific approach to waterfall classification and it's completely based on how much water is present during the vertical drop of the waterfall. The following diagram (Figure 1) illustrates this principle. 
Figure 1: Visualizing the Beisel Waterfall Classification System; Don't worry if you can't follow the math. Just keep in mind that we have a logarithmic scale solely based on the volume of water present during the vertical drop of the waterfall
Filling in the numbers to arrive at a Beisel Rating from Class 0.1 to Class 10 is quite involved. First, you need to get streamflow data of the watercourse in question. Some watercourses have stream gauges measuring such data (many watercourses in the USA have this thanks to the USGS or US Geological Survey). Since waterflow tends to fluctuate throughout the year, you'll need to take an average over several readings at different times of the year.Second, you need to determine a waterfalls' vertical height. You can get this through the procedures described in the Waterfalls 101 article "How Do I Measure A Waterfall's Height?". Once you get the height number, you can calculate how much time a horizontal strip of water in the waterfall is falling from its top to bottom. Note that if you have a funky situation where the waterfall has a weird shape or it's sloping, you'll have to employ some trigonometry (explained in the height measurement article) and/or correlative measures to get the effective waterfall height. Once you have those parameters, you can run through the natural logarithmic calculations (rounding the result to the nearest tenth) to arrive at Beisel's Rating. Thus, miniscule waterfalls are either Class 0.1 or don't even get a Beisel Rating at all if the average volume is less than 1 cubic meter (to avoid a log of a negative number). Massive waterfalls obviously are closer to Class 9 or Class 10. I'm sure my brief explanation about Beisel's objective waterfall ratings system is incomplete. So to get all the gory details about this International Waterfall Classification System, you can read Beisel's book . Now there is some degree of subjectivity about a waterfalls' dimensions. For example, you could argue some of the Class 10 waterfalls that Beisel notes in his book are really more rapids than waterfalls. You could also nitpick about the accuracy of some of the stream flow numbers for many of the example waterfalls in his book . Nonetheless, the science behind his ratings remain sound and consistent.
Have Comments Or Questions?
Do you have comments or questions about the waterfall classifications described in this page?
Do you think we're missing any waterfall types?
Do you have examples you'd like to share?
We'd like to hear from you!
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