Remember how much fun it was as a child to redirect the flow of water in a small creek or a muddy water seep after a rain storm? It’s a fascinating effort, and it can consume hours of a child’s time. This childhood fascination has turned into a passionate profession for many of you reading this article — and for me as well.
I speak for myself, and perhaps for many of you, when I say that the most enjoyable and rewarding aspect of water feature construction is building waterfalls and streams. There are so many material variations available that each waterfall or stream I build is unique unto itself. In my search for the perfect natural stone, I might find an unlimited variety of shapes, structures, textures and markings. They seem to call out, “Hey! Over here! Pick me! I’d be perfect in a waterfall!”
Seeing that very first trickle of water emerge from a shadowy area and flow over a virgin waterfall stone is almost a spiritual experience for me. The anticipation grows as I watch the water flow increase, change direction and finally drop off the edge of a weir. As the flowing water begins to build and work its way down the rock formations, you can actually see the intricate character of the rock surfaces affecting the direction and visual nature of the water. This is also the time of reckoning when hopefully the water volumes, visual appearance and pleasant sounds meet or exceed my and my client’s expectations and goals. This effort and passion to control and manipulate the water flow explains why, when considering waterfall and cascading stream design, I focus on two critical factors: visual and audible presentation.
Visual: Manipulating Moving and Falling Water
When I started building waterfalls, I just assumed that I would easily see the falling water, and it would be an awesome display. Disappointment with some of the visual results challenged me to understand how to manipulate the water. I quickly realized two things. First, only a portion of the water in the waterfall was actually falling — the rest was clinging to and running down the face of the waterfall. Second, the water that was actually falling was difficult to see because it was clear — so transparent, in fact, that I could look directly through the falling water and see the rocks behind it.
Another key factor in maximizing water visibility is the need to ensure that the water leaves the weir edge abruptly, suddenly free-falling rather than clinging to vertical rock surfaces. The sharper the weir edge, the more water will actually separate from the weir edge. The smoother and rounder the weir edge, the more water will cling to the weir and ultimately run down the face of the waterfall.
Another technique and term Anthony Archer-Wills and I use in making water more visible in streams and areas immediately upstream of waterfall weirs is brimming. We elevate the water surface in a stream or waterfall rather than hide it in a ditch. This brimming effect allows the water to be easily seen and gives the feature a unique and desirable appearance.
Audible: Developing, Controlling and Projecting Sounds
There are three aspects of waterfall acoustics that I focus on: pitch, volume and the projection of sounds away from the waterfall.
[box] Construction of four large waterfall features is taking place above, left, with the larger boulders being set first. These boulders sit on a fiber-reinforced concrete pad poured on top of the pond liner. This large commercial entry waterfall weir rock is being set in place, and its position will be adjusted by using heavy-duty concrete blocks. Once the position is confirmed and adjacent boulders are set, concrete and rebar will be used to permanently secure them together.[/box]
When discussing the audible aspect of waterfalls with my clients, I prefer to use the term “sound” rather than “noise,” because it places the perceived deliverable — that is, what they will hear — in a more desirable, positive and up-sellable manner. Clients will be receptive and willing to pay for added value in their future water feature when you use desirable, descriptive words relating to soothing sounds, peace and tranquility, rather than annoying, agitating words such as “noise.” Traditionally, clients are open and willing to invest more into project enhancements when they fully understand the details and options that are part of a high-quality, well-designed water feature.
In situations where there are annoying or distracting local noises, such as car traffic or airplanes overhead, the waterfall pitch can be tuned to mute or minimize them. I’m certainly not saying that we want to add so much waterfall sound or volume that we overpower the local noise. Instead, this is a situation where we want to encourage the human ear and subconscious mind to pick up the ever-changing melody of cascading waterfall sounds. The closer we can tune the water-generated sound, or pitch, to match the local noise, the greater chance we have of the subconscious mind focusing on the more pleasant, melodic and ever-changing soothing sounds. Typically, it is the medium and higher-pitch sounds that will assist with muting traffic and aircraft noise.
Pitch is the highness or lowness of a sound. Low, medium and high-pitch sounds are quite easily developed in a waterfall or stream by simply changing the depth of the water that the falling water is impacting. If water flows over a weir and falls onto a hard surface of rock, it is going to generate a high-pitch sound. Water falling into a deeper pool of water will generate a lower, bass-pitch sound. It is most desirable to provide a mix of pitch, and the conflict created upstream of the weir will help ensure that the sound is melodic and ever-changing. The best way to experiment with this pitch control is to begin by placing your hand, palm-up, deep into a basin where water is falling. As you raise your hand and reduce the depth of the water, you will begin to hear a distinct change in pitch. Too much high pitch, like the sound of a smoke detector, can be agitating rather than soothing. On the other hand, too much low-bass pitch negatively impacts the ability to have a conversation and can cancel out the human voice as well as the sounds of birds and wildlife nearby. Preferably a good variety of constantly changing, melodic sounds and pitch is the best place to start, and then you can tune the waterfall to more specific client needs.
Volume of sound is typically a function of water mass and velocity. The higher the water column is falling and the tighter, denser the water column is, the greater the sound volume will be at impact. If, on the other hand, the same volume of water and height was used but the water was spread out, making the water column less dense, the sound volume would be reduced.
Another aspect to take into consideration is the multiplying factor of reflected sound. Constructing a waterfall or cascading stream in a densely landscaped environment minimizes the likelihood that the generated sound will be reflected off the soft leaves, groundcover and curved branches. Conversely, where there is a concrete driveway, flagstone patio, stone veneer or large windows facing the water feature, the sound dynamics can change remarkably. Since the waterfall sounds cannot be absorbed by concrete, stone or glass, the sound is reflected back into the living, relaxing space and can be overwhelming unless understood and controlled.
Projecting sound from a waterfall is similar to how music is projected from an outdoor orchestra or band shell. The music is reflected off the curved, semi-overhanging, seashell-looking structure and is focused toward the audience, which can enjoy the balanced acoustics without any reflected sound. Similarly, in waterfalls, we typically have an overhanging weir supported by a curved or irregularly-shaped rock formation, which I call the echo chamber. The easiest way to detect an echo chamber in natural or man-made waterfalls is to look for shadows within the overhanging structure. These shadows, or caves, could be small or large, and there could just be one or a multitude of recesses within the waterfall structure. It is the orientation and shape of the caves, or echo chambers, and their proximity to the impacting water, which will determine where sounds are projected. To encourage sound to travel to specific areas around the water feature, such as toward a more distant viewing area like a bedroom, kitchen or living room window, the orientation of the falling water, as well as the curve or curves within the echo chamber, can be focused on specific locations.
So when you’re ready to experiment with the entire waterfall or cascading stream package, keep in mind three important details. First, make the water visible and easily seen from various viewing areas. Then, generate melodic sounds with varying pitch and volume. Finally, project the sound to the various interaction locations. This may take some time to master, but it will enhance your clients’ enjoyment, fulfill your creative passion and make your work even more remarkable and memorable.
David B. Duensing, a long-time industry expert and educator, created Aquatic Construction Services, LLC in 2006 specializing in combining natural stone, living water and his clients’ dreams to build unique and exceptional aquatic features throughout the Americas, the Caribbean and abroad.