How to Find Waterfalls Using LiDAR
I cannot overstate how big a fan I am of using LiDAR data for locating new waterfalls. I even mentioned it a bit in a previous post about resources for waterfall hunters in Kentucky. Understanding how to use LiDAR maps is like a superpower for planning your backcountry adventures and, as we will see here, for finding new waterfalls.
I often get a lot of questions about how to do this, so in this post, I'm going to show you everything you need to know to get started using LiDAR mapping for locating waterfalls. I'll show you examples of how to read the maps, and I'll finish off by showing you, in detail, how I used these techniques to find two off-trail waterfalls in the Red River Gorge.
Screencast
I've also included a screencast version of this post for your convenience!
The Basics of LiDAR Mapping
Before we dive into understanding how to read a LiDAR map to locate waterfalls, we should first take some time to understand what LiDAR is.
LiDAR is short for Light Detection and Ranging. It's a technique for using light to take extremely accurate measurements of the surface of an object. It works by shooting a laser at the surface of an object and measuring how long it takes the light to reflect back to a receiver.
This technology has a whole host of useful applications. For our purposes, however, we want to focus on its applicability to making extremely accurate maps of Earth's terrain. In this application of LiDAR, a laser, usually mounted on an aircraft, is shot down at Earth's surface, and a receiver mounted on that same aircraft measures how long it takes for the light to reflect back. In doing this, you end up with an accurate measurement of the elevation of the point on Earth that the laser was shot at.
By continuously flying the aircraft over an area, you end up with a large number of highly accurate elevation measurements of various points on the surface. All of this raw data is what's known as a point cloud.
For our purposes, this raw point cloud data isn't terribly useful on its own. What we really want is a processed version of the data that removes measurements for things we don't care about (such as vegetation) and puts the data into a format we can better make use of.
The raw point cloud data is rendered into a Digital Elevation Map (DEM). A DEM is nothing more than an image that uses various shades of gray and black to represent the elevations from the point cloud data. You can, of course, generate these DEMs from raw point cloud data yourself, but it's a fairly obtuse and computationally expensive task. Luckily, most LiDAR data sources make the processed DEMs available for you.
An example of a LiDAR DEM.
As you can probably tell, this DEM is still not terribly useful to us on its own. What we really want is a rendered representation of the terrain that we can easily utilize for our backcountry adventures.
This rendered version of the DEM tiles is what's known as a Hillshade. Depending on your source for the LiDAR data, you may be able to get access to a pre-generated hillshade, or you may have to make one yourself from the DEM tiles themselves. Making these hillshades yourself isn't exactly difficult, but it's beyond the scope of this post. For the rest of this post, I'm going to assume that you have access to a hillshade.
An example of a rendered LiDAR hillshade.
Understanding how to Read a LiDAR Map
Now that we have a bit of background about what LiDAR is and the various forms the data comes in, let's take a closer look at how to use these maps.
These LiDAR hillshades are not any different than the hillshades that you can get on a lot of topographic maps. What's special about the LiDAR hillshades is the level of detail you get. With a typical topo map, you might get somewhere in the neighborhood of 25-foot accuracy for elevation measurements. With LiDAR, however, you get something more like 3-5 feet of accuracy (sometimes you get even better accuracy than this).
In other words, you're getting an extremely detailed picture of the terrain that allows you to resolve relatively small details, such as breaks in cliffs, roads, trails, and even logging roads that haven't been utilized in many years. The level of detail truly is remarkable.
Rather than try to describe how to use these maps, I think it's far more useful to look at some examples.
An Example of a LiDAR Map
For this example, we're going to be taking a look at the area around the Wildcat Trailhead in the Red River Gorge, Kentucky. Here's what the topo map for the area we're going to look at looks like:
Topo map of the Wildcat Trailhead area of the Red River Gorge.
And here's what the LiDAR for this area looks like:
LiDAR map of the Wildcat Trailhead region of the Red River Gorge
To get started, I want you to notice a few things on the topo map version. Specifically, I want you to make note of the following features:
Sky Bridge Road
The official Wildcat Trail
The unofficial Reffits Branch Overlook Trail
Mossy Falls
Features to pay attention to.
Now, let's take a look at these same features on the LiDAR map:
I think comparing these two maps makes it pretty easy to understand how to identify basic features on a LiDAR map. The more defined features, such as Sky Bridge Road (1) and the Wildcat Trail (2), are very clearly defined.
The other two features can be a bit trickier to spot, but you can still make them out pretty easily. In the case of the unofficial Reffits Branch Overlook Trail, you can see a faint line in the terrain from the unofficial trail. What's important to understand is that what you're looking at here is the actual depression in the Earth's surface from this unofficial trail being walked on. That's how detailed these maps are!
Finally, let's talk a bit about Mossy Falls (4). If you look at the surrounding terrain, you can see that we're looking at a small drainage. At the point marked Mossy Falls, you can see that there's a drop in the drainage.
In other words, we're following a wet-weather stream that has a drop in it. A.K.A. there's a wet-weather waterfall there!
Don't worry if this isn't completely clear just yet. We're going to look at more examples!
Some Obvious Waterfall Examples
Now that we've looked at an example, let's take a step back and consider an example that shows two obvious waterfalls. For this example, let's take a look at the Cumberland Falls region of Kentucky:
On this topo map, we can see the following two features:
Cumberland Falls
Eagle Falls
Let's take a look at the LiDAR for this same area:
The first thing you'll notice on this map is that both the Cumberland River and Cumberland Falls (1) are very clearly defined. Following the Cumberland River, the drop that forms Cumberland Falls is extremely obvious. Unfortunately, most waterfalls aren't this easy to spot, but the principles are basically the same!
Eagle Falls (2) is a bit more subtle, but still pretty obvious. I've highlighted the stream that Eagle Falls is on in blue to make it a bit easier to spot. If you follow that, you should be able to clearly see the drop that forms Eagle Falls. Take some time to study these features because this is a lot closer to what most waterfall are going to look like on a LiDAR map.
As a bonus, I've marked two additional features on the LiDAR map:
A bunch of very clearly defined boulders in the Cumberland River.
KY-90 – the road that's clearly marked on the topographic map.
For the case of the boulders (3), here's a small portion of a video I had on my phone of what this part of the river looks like:
A More Difficult Example
At this point, we've looked at two examples, both of which are quite simple. With these in mind, let's dive into a much more difficult example. This one is a lot more representative of what most waterfalls are going to look like on a LiDAR map.
Specifically, let's consider Fall Creek in Kentucky. Here's the topo map for the area we're going to look at:
I don't know about you, but I can't tell a whole lot about this region from the topo map alone. I certainly couldn't tell you that there's a waterfall here (spoiler alert, there are actually 4 waterfalls along this stretch of creek).
Now, let's take a look at the LiDAR:
One thing is for sure: we get a whole lot more information from the LiDAR map!
The first thing we can notice is that we can pretty easily make out Fall Creek itself, as well as a small side drainage that runs into Fall Creek. Here they are highlighted for you:
Take some time to make sure you can point these streams out on the map, as this is one of the most important aspects of being able to identify waterfalls on a LiDAR map.
Once you're comfortable identifying and following the stream on the LiDAR map, go ahead and see if you can identify the four waterfalls along Fall Creek. Here they are marked for you:
As you can see, some of these waterfalls can be extremely subtle and difficult to spot.
💡 This is a case where generating your own hillshade can be beneficial as you can control the direction of the light, which can make some features easier to see.
As a bonus, here are what I believe are two wet-weather waterfalls on the side drainage. I'm not certain about these as I haven't hiked that area before, but they certainly look like waterfalls on the LiDAR!
Using LiDAR to Find Two New Waterfalls in the Red River Gorge
As promised, here is a full, real-world example of how I used LiDAR data to find two previously undocumented waterfalls in the Red River Gorge.
I started this process by deciding that I wanted to look for waterfalls off-trail in The Gorge. I decided to take a look along Parched Corn Creek. More specifically, we'll be looking at the portion of the creek that's near the Wildcat Trailhead.
Here's the topo map of the region we're looking at:
And here's the LiDAR view of this area:
The process I use when doing this is to follow the stream, looking for potential waterfalls. In the case of this section of LiDAR, there are actually a ton of potential waterfalls, but most of them are on side drainages that would be extremely wet weather waterfalls.
For this trip, I wanted to focus on trying to find some more reliable falls that were more than just some side falls. Again, there are actually a few potentials that fit this criteria here, but we're going to focus on two of them.
In fact, you can pretty clearly spot these two waterfalls in this screenshot.
The two waterfalls on Parched Corn Creek.
Zooming in on this area, the two falls become even clearer.
Closer view of the two waterfalls.
Planning the Trip
Finding potential waterfalls is just the first part of the battle. Once you've found some candidates to check out, you need to figure out how you're going to get to them. Luckily for us, LiDAR is also great for figuring this out.
For this stage, I like to switch to CalTopo with the LiDAR set as a custom map layer to assist with planning. To start with, I like to add a marker to the map over the two candidate waterfalls on the LiDAR. I then switch back to the topo map view to start planning where I'm going to start the hike. Here's what the topo map of the area looks like with my two candidate waterfalls marked:
The two candidate waterfalls marked on the topo map.
With our candidate waterfalls marked, I can see a few potential places where I could start the hike from. One would be from Chimney Top Road (the gravel road on the left side of the map). Looking at the topo, however, it looks like there's a decent cliff line that I'd have to contend with.
Another good option is the trailhead along 715 (the Wildcat Trailhead that we looked at earlier). Just looking at the topo map, the cliff line through here looks a lot more manageable. So, let's go ahead and mark the trailhead as our starting point:
The updated top map with our starting point marked.
Now, I could plan a pretty reasonable route with just the topo map. In fact, there are a few places where it looks like it would be pretty easy to get below the cliff line, but we have LiDAR! This means that we can get a detailed look at what the cliff line looks like and find a good option to get below it. This is particularly useful when you're looking at trickier areas where you may have to search for a break in a large cliff line.
In general, I want to find a good way to get down in the creek. From there, I'll simply follow the creek to each of the waterfalls. Let's take a look and see what sort of options I have to get down to the creek:
Examining this section of the LiDAR, we can see that there are a few options to get down there, but I see a particular drainage that looks like it should get me down to the creek with minimal effort. I'll add a track on my map:
My proposed route down to Parched Corn Creek from the Wildcat Trail.
From here, it looks like it should be pretty easy to just follow the creek to both potential waterfalls. The only spot where I might have to deviate from the creek is at the first waterfall, where I might have to go up the bank a bit to get around the drop. Other than that, it looks like I should be good to just follow the creek. Adding that to my map, I get the following topo map to follow in the field:
The final route plan.
With this, we have everything that we need to actually get boots on the ground and see if what we've marked are indeed a couple of waterfalls. In this case, I can assure you that they are!
Resolution Falls. This is the first candidate waterfall that we marked on our map.
Jimmy Cracked Corn Falls. This is the second candidate waterfall that we marked on our map.
Just the Tip of the Iceberg
If you've made it this far, you should have all of the basics that you need to start using LiDAR to hunt for waterfalls yourself. This post just covers the tip of the LiDAR iceberg, though. There's a lot deeper that you can go.
If you get really deep down the LiDAR rabbit hole, you can start exploring more advanced topics such as generating your own hillshades from DEM tiles or even working with the raw LiDAR point cloud data itself. These are more advanced topics, but they can give you a lot more flexibility and can be, in my opinion, a lot of fun.
These are all out of the scope for this post, but I can certainly do more blog posts on this topic in the future if there's interest in it.
