Solving Drainage Issues: Terracing

Last week I mentioned that in 2011 when Jack and I moved into our home, we discovered that several areas on our property needed drainage/water flow improvement. Professionals we consulted suggested catch basins with underground drainage pipes. While we had a catch basin installed in one area, in general, we preferred to use more natural landscaping techniques. In some areas, we mostly wanted to slow the water down so that it could be redistributed and used on our own property, rather than immediately sent to the sewer system. Of course, we needed any excess water directed away from our house. We decided we could solve most of these problems ourselves, using natural-looking methods like berms, dry stream beds, and terracing.

The first area we tackled was a side/back yard area that sloped away from our neighbor's mostly-concrete backyard toward our house. Here's a picture of the way that area looked when we moved in. The former owners had planted a small dogwood and there were a few azaleas and ferns planted here and there. Random stones were scattered around. The elevated area in front of the trees is an ivy-covered rock wall that was built by the former owner to hide an area where a drainage pipe was exposed.

Here's another "before" shot taken from farther back in the lawn.

In a heavy rain, water sheeted across the neighbor's concrete parking area and washed across the slope toward our house. We wanted to slow this water down to allow it to soak into the soil, while channeling excess away from the foundation of our house. To accomplish this, we decided to create a series of terraced beds bordered by short, dry-stacked stone walls.

Here's a recent picture of the the uppermost part of that area.

I would like to say that we began this effort with a full blown plan but, in fact, it "unfolded" as we went along. We first ordered two pallets of stone and built the beds closest to the neighbor's parking area. With practice, we got better at stacking the walls, and later walls we built looked better. We planted densely in this area to soften the hardscape and minimize bare ground.  When these plants mature in a few years, the walls will blend into the landscape.



The first obstacle that water meets as it comes off the neighbor's parking area is a thickly-planted bed of green liriope, bordered by a low stone wall. This grassy area both slows the water and controls erosion. We also brought in soil to decrease the slope within each bed. The combination of low walls, improved soil, and flatter terrain has slowed the speed of water flow, allowing more water to permeate the soil.

The following year, we started on the lower beds. The "sunken" pathways in the lower area serve as channels to direct any excess water away from our house. These pathways are actually at natural soil level but appear lower as a result of the slightly elevated beds that surround them. 

Although the terraced beds improved water retention in this area, the fact that the neighbor's adjoining area is nearly 100% concrete means that a lot of water is directed toward our garden in a heavy rain. The sunken pathways direct the water that can't be absorbed away from our house. We've tried using shredded bark and pine straw as mulch for these pathways, but both materials wash away in a hard rain. So, at least for now, the paths are not covered.


Another view of this area from a slightly different angle shows part of several flat stone paths that we created. These paths end with a slightly elevated border to maintain the flow of water inside the "sunken" pathway. The river rock (scattered in the path just below the flowerpot) are not a part of the path but were being temporarily stored there while we built a dry stream bed in another area. More on that in a later post.

To separate the lawn area from the garden, we decided to switch from natural stone to a single layer of retaining wall blocks. The blocks provide a more uniform surface for edging where the beds meet the lawn, and they are quicker and easier to put down. To make for a smoother transition to the natural stone, we extended the blocks up a bit into the garden area. 

For the most part, we were pleased with both the appearance and functionality of our terraced beds in this garden. However, in very heavy rains, a problem persisted in one area. I'll tell you how we handled that in the next post. Think "dry stream bed."