Wild Ones   Camouflaged Drainage: Landscape Design With Nature in Mind  
Article and photos by Richard J. Ehrenberg

Autumn leaves

Autumn leaves blown in quickly break down to provide a medium for volunteer plants to move into. The speed of this process can be increased by the gardener introducing seeds and rooted seedlings.

Downspouts and gutters to catch rain water are automatically installed on new or remodeled buildings. Their purpose is to direct the flow of roof run-off away from entrances, from foundations, to prevent erosion, or to eliminate the splashing of mud onto siding. Placement of downspouts, however, can cause water problems in basements, or create erosion.

Getting the downspout water to flow away from the building foundation and toward a water garden, or into a natural landscape area, is the purpose of the drainage design I have constructed at my home. The design eliminates the gutter, downspout, and any horizontal downspout extension which is not in aesthetic harmony with nature.

A camouflaged drainage system has been constructed right next to and to the left of our front-door entrance. While the system is in full view for anyone coming to the front door, it is so well camouflaged with rocks, leaves, and moss, that none can discern its existence.

Fourteen feet of roof gutter and a corner downspout were removed, so cleaning this section of gutter every fall is now history. All the rainwater flowing off the roof on the left side of the front door now simply flows off the roof and splashes onto what appears to be rocks below.

Camouflaged drainage

This camouflaged drainage area is next to the entry. One might choose to quickly do an interplanting, or might keep the rocks clearly evident, removing leaves and volunteers.

The twenty-four feet of gutter located on the right side of and above the door remains. However, the downspout that served this section was also removed. It used to deliver the rainwater into an area where the soil had settled over the years. Since it could not drain away it would seep into the basement. With the downspout removed, rainwater now cascades out the end of the gutter, like a waterfall, into the same area, which now has a new drainage system. The water no longer seeps into the basement.

The secret to my drainage system consists of hidden, sloped, sheet-metal roofing which channels the rainwater away from the foundation.

The corrugated-metal roofing needed for this system can be purchased at a home supply center. The sheets come in widths of three feet and four feet, with widths of six feet, eight feet, and longer – and can be cut to your specifications. The sheets come in various colors, and I suggest green or brown to blend with nature in the event that a part of the metal shows through the camouflage. When laid on the ground the corrugated ribbing in the sheets should be oriented in the direction the water is to flow away from the foundation. If more than a four-foot width of sheeting is necessary, a second sheet may be laid parallel to the first and overlapped by about six inches to ensure that no water drains through before it gets to the end of the drain system. Note that fiberglass corrugated roofing is also available, and may last longer than metal since it is not subject to rusting.

Remember that water flows downhill and seeks the lowest point. It will not automatically flow from one sheet to the next if you have not provided an appropriate incline.

Prior to laying the corrugated metal sheeting in place, it’s necessary to create the appropriate topography with additional soil. Purchase, in bulk, a cubic yard of top soil or whatever is needed. Garden centers and some stone yards, but not discount stores which sell garden supplies, will sell in bulk, which is much less costly than soil in bags. Select a heavy soil which will provide a firm foundation, and prevent water from seeping back to the foundation. A light, airy soil full of rich humus will settle over time and undo the purpose of directing water down an incline and away from the house. Use as much soil as needed to fill any low areas next to the foundation, and to raise the soil level so that any water that falls next to the house will run downhill away from the house. An incline of at least a three-inch drop for each twelve inches of horizontal measurement is adequate, but of course can be steeper. Compact the new soil by walking on it, or by using a hand-held compacting device that may be rented.

After the incline has been con structed and extended out and away from the foundation as far as you determine is necessary to prevent water from seeping back, lay the roofing material on top, being sure to overlap secondary sheets by about six inches. Let it rain once or twice to see how well the rainwater runs away and toward where you want it to flow.

Once you have decided the system functions well, it’s time to camouflage the sheet metal by covering it with a single layer of stone. The stone has multiple functions: it stabilizes the sheet metal while hiding it and blending it into the background; and it serves as a surface on which friendly moss might grow.

The type of stone that you use should be natural to your area. For instance, here in the glaciated terrain of southeastern Wisconsin, you’ll have round-edged cobble-like stone. The last glacier did not pass through the southwestern corner of the state. Hence the use of straight-edged sandstone or limestone is more appropriate for natural landscaping. Unfortunately, garden centers don’t pay attention to regional differences. They provide white marble, pea gravel, and even volcanic rock for any and all landscaping, regardless of natural surroundings. The use of processed rocks which are crushed and sorted to produce a uniform size is artificial and does not fit into a natural landscape design, other than for use on paths, parking areas, and driveways.

Don’t just dump the stone from your wheelbarrow and walk away. The result will look like a new pile of discarded rocks. In addition, the weight of rocks piled high might crush the corrugated ribs on the metal sheets. (The ribs prevent the metal from sagging.). Starting at the bottom of the slope, field stone must be laid individually, next to each other, like pieces of a puzzle being woven together. This replicates what nature creates over a period of a thousand years at the bottom of a creek where water continues to move the stones until each one finds a niche and fits tightly into an overall pattern.

After the rocks are in place, nature will finish the camouflage. The leaves of autumn will find their place among the rocks with help from wind. Annual decomposition will control accumulation. Wait a few years and the moisture from splashing rainwater will help add the final touch of moss onto the rocks.

The rainwater from my house does not run into a specially designed water garden, or pool for birds to bath in, although it could. My front-yard forest simply absorbs the runoff and uses it in the natural process. At the end of the metal roofing I have planted mertensia (Mertensia virginica). Volunteers are common blue violets (Viola papilionacea), wild ginger (Asarum canadense), Dutchman’s breeches (Dicentra cucullaria), and pagoda dogwood (Cornus alternifolia). A few of the violets are even growing among the rocks where leaves have apparently decomposed to create a touch of soil. Various sedges would not be misplaced in this area.

I would invite anyone to come look at my drainage system, but fortunately it’s too well camouflaged to be able to see all of it.

Richard J. Ehernberg, of the Madison (WI) Chapter, is a landscape architect.

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Updated: Jul 28, 2009.