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Subtle Precipitation
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Subtle Precipitation

When the opportunity to try something new came his way, Scott Cohen stepped up with an ingenious water-wall system that did more for his clients than he ever could have imagined.

When the opportunity to try something new came his way, Scott Cohen stepped up with an ingenious water-wall system that did more for his clients than he ever could have imagined.

This project started in a most unusual way, with the client telling me how little he liked the property he and his wife owned and that a move was likely in the near future. But in the meantime, he said, she wanted a pool.

So there I was, sizing up a challenging site and wondering if I really wanted to get involved. Sure, I’ve run into clients who get a bit cranky in the latter stages of a long project, but this gentleman was negative right off the bat and clearly thought we were both wasting our time in trying to dress up a what he saw as an awful, unsalvageable backyard.

Nonetheless, I saw potential – and, perhaps, an opportunity to work with an idea that had been rattling around in the back of my mind for a while. So before long, we at Green Scene Landscaping & Pools (Chatsworth, Calif.) had developed the design for a great little pool and an imaginative waterfeature – but really, was it going to be worth it?


The home sits at the bottom of a steep, two-to-one slope in Encino, Calif. When I arrived on site, there were three retaining walls rising up the slope – all made from braced railroad ties – to protect the home below from potential disaster. It was a late 1950s/early ’60s tract house, well maintained but in a tired style, and it was possible to understand why the clients might be inclined to cut and run.

The backyard itself was fairly small, but it was somewhat larger than a neighbor’s yard that had just been redone with a bland, lifeless, all-hardscape treatment that probably added to my clients’ pessimism about their own property. I told them not to worry, that they’d have a great pool, a large spa and – if they were willing to go along with me – an amazing water wall.

They seemed increasingly agreeable as the design took shape. As I explained to them, the swimming pool and its surrounding structures would replace all three of the ugly retaining walls and enable them to plant and beautify the slope in ways that had likely never occurred to them because they hadn’t wanted to do anything to compromise the old walls.

And the slope-containing functionality would be better than ever, I explained, because the revised soil-retention approach not only turned wood into concrete for the four-foot-tall bottom wall, but also reached six feet down into the soil at the bottom of the slope, with the new pool/wall structure forming a secure footing for the hillside.


It’s easy to understand how and why the homeowners could get discouraged about their backyard. The space included long, narrow sections that offered little hope, and the wider space beyond the impossibly shallow patio (and its lovely portable grill) directly confronted a steep hillside supported by a plug-ugly stack of railroad-tie retaining walls.

The back side of the wall was to be waterproofed with a hydrostatic-relief system in place, and we would include a new, thoughtfully engineered drainage system that would collect all water from behind the wall and allow it to flow safely around the pool, deck and house on its way to the street.

As for the pool and spa, they formed what I would call a nice little composition, with beautiful materials inside and out and a whole new look that transformed the backyard from “disaster in the making” to “gem set in a dramatic space” – pretty cool, if I do say so myself.

The pool is long enough for a bit of short-course lap swimming, while the spa is actually oversized and will hold a good number of family members or party guests. There’s a nice shallow lounging area, and the limestone decking connects the poolscape to a new outdoor kitchen that replaced a battered rolling barbecue.

Given the slope, it took us nearly six months to pull all of the required permits and gain all of the necessary approvals. By the time we began working on site, we were on track with a total redefinition of the outdoor space and had succeeded in driving visions of the neighbor’s drab hardscape almost completely from mind.


Then there was the fun part in the form of a new water wall that was to complete the adjustment of the outdoor environment.

For some time, I had been thinking about ways to replicate the experience of sitting and listening to falling rain from an up-close (but dry) perspective. Natural rain is generally not a steady pelting of a whole area: Instead, it moves in bands and waves across a space, falling heavily in one spot at any given moment before sweeping on to another, not necessarily adjacent spot.

I knew I could conjure the effect I was after using fountain equipment, but it would’ve cost tens of thousands of dollars to acquire the necessary valves, nozzles, switching systems and control units. What I had in mind as a budget alternative involved the repurposing of a manifold from an in-floor cleaning system – the unit that sends flows out to cleaning heads in a timed sequence to move silt, sand and debris to collection points.

By altering the regular circular sweep of a standard eight-port valve (made by Caretaker of West Valley City, Utah), I knew I could economically randomize the flow pattern and recreate the rain-simulating effect I was after. Now I just had to translate an idea that looked pretty good on paper into a flexible, working system.


Almost against their inclinations, we came up with a design that exploited the site’s full potential, inserting an engineered retaining wall that was effectively nine feet tall and including a huge slug of concrete that acts as a key to keep everything in place for the long haul. One big stretch of the retaining wall became a waterfeature in which we hooked up a rotary eight-port valve to send water down the wall as 16 random flows to mimic the sound and sense of real rainfall.

The water wall we’d designed stretched for 35 feet along the edge of the pool. To cover that much area, we set up split outlets for each of the manifold’s eight heads and mapped where we’d connect each of the 16 outlets at the wall to a four-inch pipe we’d use to distribute the water in a random pattern (see the illustration at right). We then took the 35-foot section of pipe and, using a drill press, cut quarter-inch holes with precise quarter-inch gaps between them.

The pipe isn’t pressurized by the 16 evenly spaced outlets at the pump speeds we tested, so the water introduced to the four-inch pipe drops to the nearest run of holes and flows out quickly, localizing a stronger flow to spans of about two feet across (or less) in each case. The flow through the eight-port valve is completely adjustable through use of a variable-speed pump, so the effect can be altered according to the clients’ desires.

As a result, with the pump at low speeds, the water flows out with the sort of random rainwater effect we were after. At higher speeds, the flow fills the four-inch pipe more or less completely, so the random look vanishes in favor of a strong, steady flow. Through experimentation, we found just the right flow to achieve my desired effect and identified it as one of the presets for the pump. The client can work around that target at will.

As for the wall itself, we surfaced it with stone pieces set with irregular profiles, adding dimension to the sound of the falling water and preventing any excessive monotony when the clients crank up the flow.


The thing about this rain effect is that it’s subtle. Because the flows are randomized at 16 places along the pipe, two at a time, it’s difficult to develop a sense of pattern that makes for the sort of mesmerizing experience found with, say, the side-to-side waves of the water wall at the Aria Resort & Casino in Las Vegas.

The intention here is more about integrating sight with sound: Cued by the noise of concentrated flows, the falling water attracts the focus of the beholder to a pair of specific areas for just a second or two before the sounds and visual effects jump to different spots. This is why the videos we’ve made are inadequate: It’s difficult to capture the subtly shifting flows with a typical camera and basically impossible to isolate the shifting sounds. In person, however, the waterfeature looks and sounds terrific.

The clients, thank goodness, were willing to come along on this experimental voyage and let me explore a new concept in water-wall “programming” – and the measure of its success brings a catch to my throat if not tears to my eyes: Their new backyard is so special that they’ve decided to stick around to enjoy it. Indeed, discussions about moving have been shelved indefinitely, and they credit the moods created by the water wall as the key to their change of heart about the place.


The resulting composition takes up a large portion of the backyard footprint, but it had to be substantial to fend off the looming hillside and will come into more complete balance with its surroundings once the plantings take hold and offer the watershapes a green backdrop. Best of all, the clients, initially skeptical beyond belief, have fallen so deeply in love with their new backyard (and its spacious outdoor kitchen and expanded seating areas) that they’re hanging in there on a property they were all ready to dump.

And there’s more: They love the shallow lounging area, the outdoor kitchen and the decks as much as they do the pool and spa, but their special favorite spot is the little in-pool table placed opposite the water wall: It’s the perfect place to relax with a glass of wine and listen to the rhythm of the falling rain.

Life is sweet.

Scott Cohen is president of The Green Scene Landscaping & Pools, a design/build firm based in Chatsworth, Calif. He provides consultation for clients nationwide and gives seminars on designing landscapes, swimming pools and outdoor kitchens in addition to being a construction defect expert witness. For more information, go to

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