Topo maps are only one method we use to determine a waterfall’s height. This is a frequently used method as we don’t get out as much as we’d like.
We also use clinometer/rangefinder combos.
Google Earth’s elevation data has recently been shored up, and is getting alarmingly accurate.
We’ve never used the rock drop method as it would be completely indifferent to anyone that might be below.
Plumb lining is only worthwhile on vertical waterfalls, and most waterfalls aren’t totally sheer in nature.
Bryan and I are currently buried in a massive revision of the WWD. We are well aware of the many differing opinions on height, specifically how it relates to the perceived top and bottom of a waterfall.
We’ve AGONIZED over the best way to determine height, and have reluctantly arrived at the conclusion that no matter how detailed or mindful we try to be, people are always likely to interpret a waterfalls “legitimate” height based on their own feelings.
The new revision is still going to list height as we see it (our views are described in detail on this page: http://www.worldwaterfalldatabase.com/measurement.php ), and highest individual tier, but we’ve got a lot of additional information regarding the hydropotential height figure, MOH (meters of head), which is how many European waterfalls seem to be named. We also intend to devote a lot more explanation to how we spot the top and bottom of each fall.
New Zealand’s Browne Falls is a great example. We’ve seen tight aerial photography that shows considerable aeration and agitation of the water pretty much as it leaves the lake. From the exit of the lake, it is continually falling all the way to the sound. The elevation of the lake is 2744′, thus our height figure is the same. The original height figure I saw many years ago was 2019′, but looking at the falls, I can’t see a 700′ chunk that I’d choose to omit. This reinforces my theory that 10 people will see a waterfall 10 different ways.
Obviously, you’ve spent a lot more time in the field than we have, and until one of us wins a lottery, or gets a huge inheritance from an unknown rich relative’s estate, we are limited to our annual safari. What we all share is a love (perhaps obsession, that wouldn’t be unfair…) of the subject matter. Either way, we all have a lot of happy memories and many photos of a subject we all hold dear.