Standing water in a yard can lead to a number of problems. Puddles provide mosquito breeding grounds, and soggy areas on the lawn means that dogs and people are more likely to track mud into the house. Grass will not grow properly in lawn areas covered in standing water, leaving the area vulnerable to moss growth. Excess water can even lead to problems with your home's foundation. Standing water is usually caused by two common problems: poorly draining soil and low spots in the yard.
Poorly Draining Soils
Because the majority of water drainage on lawns typically occurs through the soil, soil type effects drainage. Loamy soils and sandy soils drain better than those heavy with clay. Clay traps water, whereas loam, and sand especially, are known for their sieve-like qualities.
If you have clayey soil the solution is to amend the soil with organic matter. This will break up those problematic clay barriers in the soil profile. Most commonly, this is done using compost, but there are also other ways to amend the soil in garden areas. For example, organic mulches, such as bark or wood chips, break down over time; as they do, they improve drainage in the ground under them.
Lawn areas are trickier: When the grass is in the way, it's hard to gain access to that clayey soil that you desperately need to break up. In extreme cases, you may need to remove your current lawn and start over again.
Thatch and Compaction
Clay isn't the only thing in the soil that keeps water from percolating downward and causing it to pool on the surface. Lawn thatch and compaction are also enemies of good drainage because they form barriers that trap water.
Depending on how severe your lawn-thatch issue is, there are two solutions:
- Dethatching (for mild cases): Removing thatch with a dethatching rake or a power dethatcher
- Core aeration (for severe cases): Aerating the lawn with an aerator tool or power aerator
Compaction occurs most often as a result of heavy foot traffic. Core aeration is one way to solve the problem, but a more permanent solution may be building a walkway to handle all that foot traffic.
There is a good chance that you have—or will have—standing water in your yard if your property lies at the foot of a hill and your region gets a lot of rain. You can also suffer from having low spots in particular areas of the yard, even if you don't live at the foot of a hill, where the terrain slopes down.
If a low spot is causing water to collect near your house, the first thing to do is correct the grading around your house foundation to prevent water from seeping through the foundation. This is more important than dealing with water pooling elsewhere in the yard.
There are two common ways to channel water away from a low spot or any area where water tends to collect. A French drain is a gravel-filled trench that slopes down toward a suitable exit point. Most French drains include a perforated plastic drain pipe, called drain tile, to move excess water quickly. An exit point for the water may be a storm drain—as appropriate—or a dry well installed on the property.
A dry creek is a path of gravel and rock that is made to look like a natural dry creek bed. These tend to be more aesthetically pleasing than a French drain but typically do not contain a drain pipe. Like a French drain, a dry creek can empty runoff water into a storm drain or a dry well.
It is important to make sure the runoff diverted by a dry creek or French drain does not end up on a neighbor's property: At best, the result would be ill will; at worst, you could be sued. If storm sewers run along your street, you may be tempted to channel the runoff in their direction. But doing so may land you in trouble with the authorities. Get permission first from your local Department of Public Works.
Unless you live in a rural area where there are no sidewalks, even directing runoff towards—but not into—the street is problematic. Channeling runoff onto a sidewalk can get you into trouble with the authorities because it makes the sidewalk slippery for pedestrians in winter once the water ices up. In summer, you may also make the sidewalk slick due to the formation of algae.
Usually, the best way to terminate a French drain or dry creek is with a dry well. A dry well is little more than a large, deep hole filled with rocks. The water collects in the well and gradually drains into the surrounding soil. Many dry wells include perforated plastic tubs that contain the rocks and help keep out soil, which clogs the rock and reduces its draining capacity.
When designing a dry well, err on the side of bigger rather than smaller, although you can always re-dig a rock pit later if you conclude that it's too small. A greater volume of runoff calls for a bigger rock pit, but volume is unpredictable because you never know how much rain you will receive in a given year. Four feet wide and deep is an average size for a dry well.