What is considered a Waterfall?

Ah.  The crux of any argument regarding what is the true tallest waterfall on the planet.  There have been many discussions among the die-hard waterfall lovers on the internet regarding this topic, all of which have shown that we can't all agree on what makes a waterfall legitimate. 

In part, this is because there is no international standard as to how high, or how steep a waterfall must be before it is considered a waterfall.  In our years of research, we've come up with plenty of data which illustrates that the lack of a standard to judge whether a section of stream can be considered a waterfall or not creates many problems.  Some of the tallest waterfalls on the planet are measured in ways that include long stretches of stream which really don't have any similarity to falling water at all, and vice versa, there are hundreds, if not thousands, of legitimate waterfalls on earth that aren't recognized as legitimate waterfalls because they aren't steep enough.

So, after many discussions between the two of us, as well as with the community when situations arose, we decided to put this page together to outline what we consider legitimate waterfalls.  This is by no means meant to establish a standard to be used world wide, since most people will agree to disagree on certain subjects, but this format can be used to 1) further understand the partitioning of the waterfalls on this website, and 2) to help to illustrate and reaffirm the discussions which never seemed to reach a general consensus.

Vertical Height

Since waterfalls are most commonly measured by their vertical drop, we'll start with this subject.  For the purposes of this website, we currently only list waterfalls which drop at least 300 feet, or have a large volume and drop at least 32 feet.  This does not encompass all the waterfalls in the world by any stretch of the imagination.  Waterfalls of largely varying height can be found in the same local areas, but the starkest differences come when comparing regions of great relief to regions of little or no relief at all. 

Take Washington, Vermont and Michigan for example.  Washington, having the most heavily glaciated mountains in the lower 48 states, possesses thousands of waterfalls, some among country's most spectacular, reaching as high as 2500 feet.  Vermont has a similar density of waterfalls, due to the rolling topography, but because of the lack of relief, comparatively, the waterfalls aren't nearly as tall or dramatic.  Michigan, to further illustrate, has very few waterfalls, the tallest of which drops a staggering 100 feet (note the sarcasm).

Many of the largest waterfalls in Washington State are not officially recognized, often because of their more remote wilderness locations.  In retrospect, some of the smallest recognized waterfalls in Washington would have a hard time standing their ground against some of the modest waterfalls in Kansas.  Likewise, even some of the most well known waterfalls in Kansas would not even be regarded as legitimate in Vermont or Washington.

The point here is that if there is a visible vertical drop, somebody, somewhere might view it as a waterfall.  It all depends on what kind of topography that person is acclimated to.  There is no set standard for how tall a waterfall must be.  We both feel, and use as a standard on our own websites, that generally anything over 10 to 15 feet tall is legitimate enough to warrant mention.

Verticality / Slope

The next big issue is the slope of a waterfall.  Few people argue that a true freefalling waterfall can't be considered a waterfall.  Questions start to arise when the waterfall skips down a pitched formation in a non-vertical fashion.  Some people consider such occurrences"cascades" rather than waterfalls.  As we see it, all cascades are waterfalls (but not all waterfalls are cascades).  This can be clearly shown by observing some of the waterfalls in the world which are attributed as being "(whatever) Cascades" rather than "(whatever) Falls".  Silver Cord Cascade in Yellowstone National Park in Wyoming is a perfect example.  Though the falls are nearly vertical, the official name suggests the falls are cascades.

Like the height of a waterfall, the slope of a formation which can be legitimately considered a waterfall can vary depending on the region.  In the plain states, a stream flowing across a smooth bedrock sheet in the streambed can be considered a noteworthy feature, but in some place like the California Sierra Nevada, where sloping granite waterfalls are common, there are many many features which aren't given much attention because of the lack of a defined free fall.

For the purposes of this site, as well as our individual sites, the general requirement is that there is a section of noted agitation of the stream, followed on either side by a section of little agitation, in comparison.  Further, we generally require waterfalls to be in constant contact with bedrock (if not freefalling) in order for it to qualify for this website.  Steep cascades which descend over rocky stretches of stream are not counted.  Which brings us to the next section.

Bedrock versus Talus

There are many instances among the world's largest waterfalls where non-bedrock cascades are considered to be part of a waterfall.  The most outstanding of these occurrences is American Falls at Niagara Falls.  The river free falls for about 100 feet, before cascading another 60+ feet through large boulders which have cleaved off the cliff face.  This, in our opinion, is a questionable practice.

The requirements for inclusion in our database state that, with a very few exceptions (Niagara being one), waterfalls which end with steep cascades through large boulders or talus will be measured to the end of the bedrock descent, and not to the bottom of the talus field, unless that talus field lies in between two sections of bedrock descent.

What this breaks down to is illustrated below.  Figure 1 shows a waterfall with no talus below, and were it entered into the database, the height we list for the falls would reflect the total height.  Figure 2 shows a waterfall with a long section of talus below it.  While some might consider this part of the waterfall, when entered in the database, the height listed will take into account only the marked portion of the falls.  Figure 3 shows a waterfall which possesses a section of talus cascade between two bedrock-based descents.  Because the bedrock descents are close enough together, they are often considered part of the same waterfall, so logically, the talus slope in between should also be considered part of the falls.  The height shown in the database would reflect the marked portion of the falls.

These guidelines are significant, because they affect and apply to many well known waterfalls of the world.  Angel Falls, first and foremost, has an initial drop of 2,648 feet, followed by a talus slope, which, for all intents and purposes, does not resemble a waterfall no matter how it is sliced, followed by a bedrock cascade of approximately 100 feet.  Because of the bedrock cascade below the talus slope, the height of the falls is commonly thought of as 3,212 feet (though we have had many second thoughts as to whether the two legitimate tiers are too far apart to be considered part of the same waterfall).  Another outstanding example is Norway's Vedalsfossen.  The falls begin with a plunge of 656 feet (200m), followed by another 1400 feet of steep cascades down a bouldery slope.  While the slope is rather steep, it does not resemble a legitimate waterfall, and since there is no vertical portion of the falls below the slope, we do not count the final 1400 feet of the stream as part of the waterfall.

Volume

The issue of volume is pretty self explanatory.  Usually, the question is either "How much volume must a stream have", or "How many days out of the year must a waterfall flow"...to be considered a legitimate waterfall?  Well, few will question whether or not waterfalls which only flow when it rains heavily, such as some of those seen in the fjords of New Zealand, are truly waterfalls.  Usually, this question applies to whether a waterfall is significant enough to be thought of as one of the world's tallest.  It is true that some of the waterfalls we have presented on this website don't flow for the majority of the year, but it is also true that they are significant enough to warrant attention. 

Where you draw the line is up to you.  We typically examine each instance on a case by case basis, largely based on totally subjective observation.  The biggest issue with limiting the amount of seasonal waterfalls included is that several of the world's most famous waterfalls would be stricken from the database.  Many of those in Yosemite National Park, including Yosemite Falls and Ribbon Falls, as well as major waterfalls in Europe affected by hydroelectric facilities; Tyssestrengene, Mongefossen, Mardalsfossen in Norway; Cascata del Serio in Italy; and some of the large waterfalls in southern Asia and the tropical Islands such as Hawaii, which depend largely on the rainy season; Nohkalikai and Nohsnighiang Falls in India for example, would have to be excluded completely because they don't flow all year long, even though there is absolutely no doubt of their impressiveness.

Measurement

Now, the question, taking all the previous information into account is "What is considered the top and what is considered the bottom?"  Well, the answer is, it varies on a case by case basis.  If you're lucky, you'll have some obvious way of determining where the top and bottom of the falls lie, such as a distinct knickpoint at the top of the falls, and a large pool at the bottom of the falls, or lakes immediately above and below the falls.  In many cases, this isn't possible.

As we're not trying to establish a standard here, our criteria, both on a personal basis and for this website, works as follows:

The top of the waterfall must be at a distinct transition between a relatively shallow pitched section of stream and a relatively steeply pitched section of stream.  This is usually accompanied by an increase in velocity, agitation and aeration of the water, causing it to turn frothy, if not white.

The bottom of the waterfall, if not vertical or nearly vertical must be at the end of a distinct stretch of bedrock based cascades.  If the bedrock terminates and a talus slope begins, the waterfall will end at the beginning of the talus slope.  If the waterfall transitions from a steep pitch of bedrock to a shallow pitch of bedrock in a concave manor, with a slope decreasing in a near exponential fashion, the bottom of the waterfall is considered to be the point at which the stream is no longer agitated to the point of aeration, or to the point where the bedrock ends.

Exceptions to these requirements may be made on a case by case basis if it is determined to be necessary.