Build a Backyard Waterfall and Stream

This cascading stream flows into a gravel bed, not a pond, so it stays clean with little maintenance.

Step 1: Overview

We've all stopped, gazed and listened upon encountering a rippling brook or waterfall—to soak up the serenity that nature provides. But where is that spot when we need it most? Since you probably can't drive and hike to a tranquil location after a hard day's work, you can use this project to help you recreate these all-too-fleeting moments in your backyard. And you can build your stream in two weekends.

We designed this stream to eliminate the filtering and cleaning maintenance that comes with ponds. The trick to low maintenance is to let nature (layers of gravel and stone) filter the water, using an underground sump at the lower end to catch the filtered water before pumping it back up to the top of the stream. All you have to do is occasionally add water to replace what evaporates—and rainfall may handle this task for you. In this story, we'll show you how to slope the stream, lay the liner and install the pump and the catch basin as well as landscape the stream. We'll help you plan the ideal location and size of your stream, and tell you how to select liners, pumps and stone. We won't get into kits that are available either on-line or at home centers. We chose to build our system with parts and components that are readily available and less expensive than kits. They'll give you more flexibility to design the stream that best fits your yard.

You can complete this project successfully even if it's your first water feature. But it's heavy work. The only special tools you'll need are a strong wheelbarrow (one with pneumatic tires is best) and a two-wheel ball cart for moving and placing heavy boulders.

CAUTION

Although these pools are shallow, they can be a drowning hazard for small children. Check with your local building department for local regulations. And be watchful of toddlers.

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Step 2: Select a location

Sit in a favorite spot and visualize where a stream with waterfalls would fit into your landscape—perhaps near a patio or deck.

Planning elements to consider:

Foundation
If your soil is easy to dig, then excavate the entire project. If digging is difficult, build your stream above ground with stones for the base.

Slope
Very little slope is needed (minimum 2 in. drop per 10 ft. of stream). For faster moving water or taller waterfalls, make the grade steeper (which also adds more sound).

Size
Plan your stream size first to determine how much water the lower basin and upper pool must hold when the pump is off. Figure 5 gallons per linear foot of flowing stream (2-1/2 ft. wide x 3 in. deep). Our lower basin (40 gallons) and upper pool (240 gallons) easily held our 75-gallon stream capacity.

Sound
For a babbling brook sound, use a waterfall height of 2 to 4 in. To drown out street noise, use 10-in. and greater waterfall drops. More waterfalls equals more noise.

Location
Waterfalls should be visible from your favorite deck, patio or inside-the-home chair. Consider a location near the bedroom if you like the sound of running water at night; you can always turn it off if it's too loud or distracting. Make sure your pump location (lower basin) is close to an electrical source, and that you can reach the stream with a garden hose to add water as needed. For our site, we wrapped an S-shaped stream next to a ground-level deck built into an existing perennial garden. We varied the height of the four waterfalls and the width of the stream to give it a more natural look and sound. Plus we added a ball valve to the return water line so we could speed or slow the flow rate, and control the sound level.

Figures A-C: Stream and Waterfalls Layout

Use these illustrations to help you plan your water feature.

Figure A: Stream layout Figure A: Stream layout
Figure B: Upper pool Figure B: Upper pool
Figure C: Lower basin Figure C: Lower basin
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Step 3: Order Stone

When you start your stone search, look under “Rock,” “Quarries” or “Sand & Gravel” in the Yellow Pages or online. Call to check prices and types of stone available. Go visit dealers to get exactly what you want, plus you can select specific colorful accent boulders and flat stones for the waterfalls—then have it all delivered. Some quarries will even bag the stone by type and size (for a fee), and these palleted bags take up less space on a driveway, as opposed to piles of gravel and boulders.

For gravel (3/4-in. to 2-in. stones), figure you'll need 1/2 ton per 10 ft. of stream, plus we used 1 to 1-1/2 tons for the upper pool and lower basin. For basic field boulders (6 in. to 24 in.) to line the stream banks, figure 3/4 ton per 10 ft. of stream. Add 1-1/2 to 2 tons more of larger 12-in. to 24-in.boulders for the upper pool and lower basin. Because we built the top half of the stream above ground, we used 3-1/2 tons of extra boulders.

If you want specialty colorful accent boulders, expect to pay premium prices. Avoid limestone, as it can encourage algae growth.

CAUTION

A few days before you plan to dig for your stream, call 811 to have underground utilities in the area located and marked.

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Step 4: Map the stream and start digging

After all the stone and gravel arrive, map out your design and mark it with spray paint (Photo 1).

We built the upper half of the stream and two waterfalls above the ground, then carved the lower half of this 15-ft. stream out of the soil (Figure A). Pick whichever technique works with your soil and go with it. Either way, keep the ibuprofen handy to soothe those sore lifting and digging muscles!

Next, dig the lower basin for the sump basin and surrounding stone and gravel. Dig a square hole at least 2 ft. wider than the basin diameter and 6 in. deeper than the height. It should be at least a foot wider than the stream.

Simultaneously, build a ring of stone for the upper pool foundation and the stream banks (Photo 2). Place 12-in. tall stones flat side up (if possible) so the next layer of stone will fit more securely on top (Figure B). Use a rubber mallet to pack dirt and gravel tightly around the stones to hold them in place.

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Step 5: Complete the lower basin first

Use a 2-in. hole saw bit and drill holes every 4 in. in the bottom third of the pump basin (Figure C and Photo 3). Repeat the process with a 1-in. hole saw bit for the middle third, then use a 3/8-in. bit for the top third.

Remove sharp objects from the bottom of the basin, then lay in the underlayment and liner. Calculate the size carefully and cut the underlayment first. Then cut and fit the liner so it is tucked in all corners and extends about 2 ft. out of the hole in all directions. With the pump basin in place, insert the pump, connect the water line and lay it in place to ensure it will reach the top of the upper pool. Add layers of stone around the basin and top with the lid (Figure C and Photo 4).

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Step 6: Dig out (or build) a long staircase

First, at each waterfall location, dig down to the approximate depth of the drop you desire or build up the fall if you're working above grade. This gives you a streambed depth target. Now move to the bottom of the stream and carve a 2 to 3-1/2 ft. wide streambed 6 to 8 in. deep, sloping upward as you dig upstream to meet that streambed depth target at each waterfall (Photo 5). Then dig out shallow pools below waterfalls as needed (Figure A) to slow the water flow.

Since we built above ground for the upper section of the stream, we next added a level row of stones for waterfalls No. 1 and 2 (Photo 6). Pick the height you desire. Use 6- in. tall stones to frame the banks. Also finish compacting a gravel and dirt mixture to the inside and outside of the upper pool stones. Then tamp down the upper pool area and the streambed.

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Step 7: Lay the liner and position waterfall stones

Position the fabric underlayment and liner to extend from the lower basin to the upper pool, with slack at the base of each waterfall, because placing boulders can stretch and rip a tight liner (Photo 7). Place decorative boulders at the side of each waterfall, and add an extra piece of rubber liner underneath each heavy stone to protect the base liner. For stable, above-ground stream edges, backfill the edging stones with a gravel and dirt mixture and compact it (Photo 8). Next, lay the final piece of underlayment and liner in the upper pool so it tucks in at all corners and extends 2 ft. out in all directions. There's no need to tape the liners to each other; just make sure the top liner overlaps the liner underneath it by 1-1/2 to 2 ft. Then add the top layer of stones around the upper pool.

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Step 8: Add spill stones and foam the gaps

Once you place the decorative boulders at the waterfall locations, place all the flat spill stones. Apply black expanding foam sealant, designed for ponds and waterfalls, to the underside to adhere them to the rubber liner. Now fill all gaps with stones to force water to go only over the waterfall (Photo 9). Then apply foam sealant to all sides and to the underneath of each spill stone to create a good seal (Photo 10). After the foam has dried for 30 minutes, take your garden hose and run water down the stream. Look for any water trails (leaks) along the spill stone edges and underneath. Fill any leaks with more foam and repeat until all water goes over the top of the spill stones.

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Step 9: Add gravel and clean the stream

The final construction step is to place steppingstones in the middle of the stream to make it inviting for people, birds and pets. Then carefully layer in gravel to cover any exposed liner (Photo 11).

Spray down the entire stream area with a garden hose nozzle until the water level rises above the gravel in the bottom basin. Now power up the pump and direct the pump hose away from the stream. Keep washing down the stream and rock until the water from the pump hose runs clear. Then insert the pump hose into the upper pool (make sure it is hidden), and finish your stream by trimming and covering any rubber liner that shows (Photo 12).

Now it's time to take that favorite seat, with a cold beverage in hand, and relax to the soothing sounds of your new stream.

Pump Sizing

Submersible pumps are rated by gph (gallons per hour) at a specific discharge height (known as head or lift). To calculate the gph you need, figure 150 gph for each inch of your widest waterfall. Next, to figure the head/lift you need, calculate the distance your water line travels from the pump to the upper pool (measure vertical and horizontal; 10 ft. of horizontal distance = 1 ft. of vertical rise). Look for a high quality pump (bronze, brass or stainless steel; not a cheap sump pump) that can exceed the gph and lift you need.

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