A lot of water collects from downspouts, patios, driveways, and sidewalks when it rains. This water may end up standing in yard or move in a wrong direction to cause unimagined destruction in foundations, gardens and storm drains. A rain garden will be helpful in calming surface runoff, filter the water and allow it back into the soil. Let’s look at how to build a rain garden in your yard.
What is a rain garden?
A rain garden is an area created in a yard to collect and filter rain water from hard surfaces before getting absorbed back into the ground. The swallow depression is planted with a variety of deep rooted plants that thrives in wet conditions to help in filtration and absorption of water back into the soil.
Rain gardens are ideally situated in low lying areas or naturally occurring depressions where water can easily move to after a downpour. However, the location should be at a distance from your house or foundations to avoid flooding problems.
In areas that are not sloppy, a French drain or a PVC pipe may be installed to channel water into the rain garden. It is normal for excess water to overflow the rain garden into the nearby storm drain but at least you will have directed it away from your properties.
Water collected in a rain garden is usually expected to seep into the ground within 24 hours in an area with well-draining soil. It can be unfortunate if water remains standing it this area beyond this duration since mosquitoes and other bugs can make it a breeding site. But with the right design, there should be not worry about mosquitoes.
Apart from managing the flow of surface runoff in your yard, a rain garden comes with other many benefits that include the following:
- Rain gardens adds to the beauty of a landscape by attracting butterflies, birds and other interesting wildlife
- Shrubs, flowers and grasses planted in a rain garden forms a spectacular feature in the yard
- It helps in tapping surface runoff, filter it and allow it back into the ground instead of causing pollution and damage to properties
- Reduces chances of fertilizers, pesticides and other gardening chemicals from getting into nearby streams, rivers or lakes
- Improves the quality of local water sources which serves as home to different aquatic lives
- Prevents flooding and issues of standing water in yard after a heavy downpour
How to Build a Rain Garden
With a hand hoe and a shovel you can completely built a rain garden without breaking a bank. Few things that may need you to get into your pocket include decorative rocks and a PVC pipe. A nearby university extension should recommend the best rain garden plants to use based on climatic conditions of your zone.
1. Choose an appropriate location
A low lying area would be great for a rain garden but there are few things you need to consider. The area should not be too close to your foundations. It is possible that the water can overflow and cause damages. Stay at least 10 feet from the house and at least 50 feet from a nearby septic system.
Call your municipality authorities to make sure they allow rain gardens in the region and also confirm that there are no underground utility running underway in your location. If the site is confirmed, test how the soil drains. Simply dig 8 inches hole in the ground, pour water and time how long it will take to disappear.
Measure how many inches of water has percolated in one hour. Any rate of above 0.5 inches of water per hour means that within 24 hours the soil will be able to drain at least 12 inches of water. This is a good rate for 18 inch deep rain garden. If the rate is lower than that, you have to make it even deeper to about 30 inches.
2. Determine and mark the size and shape
The size of your rain garden may depend on many factors like the amount of water collected, the average amount of rainfall in your area and size of your yard. Shape can be anything from oval, tear-shape, round or whatever design you like.
Once you have determined the shape and size of your upcoming rain garden, mark the outline with a spray paint. Also mark any area that need to be excavated for example where you plan to lay a PVC pipe that will channel water into the rain garden.
3. Start excavating the site
Begin by removing debris like stones or cutting sods of grass from the area using a hoe. Dig the soil using a hand hoe and shovel it onto a wheelbarrow for dumping or reuse. This will break you a sweat and I hope you remembered to protect your hands with a pair of work gloves. Alternatively, rent an excavator to save time.
Also dig a trench where you will lay a pipe that directs water from your surfaces or downspouts to the rain garden. If you plan to do a corrugation then make a slightly wider trench.
4. Lay the inlet pipe
Line the trench with stones to avoid soil erosion. In most cases a corrugated tubing is easier to work with but ensure that your pipe is not perforated. Lay your PVC pipe in place extending it few inches into the rain garden. Cover the pipe with sods or soil for growth of grass.
5. Fill the basin with rain-garden soil
Fill the excavated area with rain garden soil – usually a mixture of screened sand and compost. You can still reuse the native soil you excavated if free from clay but you have to mix it with compost. Simply make 2 scoops of your native soil for each scoop of compost and mix well.
6. Add rain garden plants
Get plants that thrives in wet conditions and grow them in your rain garden. You will also have to consider your area zone and drought conditions when ordering your rain garden plants. Aster, daylily, iris, bee balm, sedum, butterfly weed, coneflower and Artemisia are among the best plants to use but you can enquire more from your local extension office.
Plant your rain garden shrubs, native grasses and flowers as you would do in your garden and water them thoroughly until they establish. You can mulch around them to retain moisture during drought and also to prevent sprouting of weeds.
It will take about one year for your plants to fully establish. Before then, do not allow too much water to flood your young plants. You can control this by creating a notch into the berm to allow most of the water to flow out. Addition of decorative rocks at where water enters the rain garden will also protect your young plants from being washed away.
Outdoor structures and surfaces collect a lot of water during a downpour. Without any control measure, surface runoff may damage your properties or end up polluting the nearby water bodies. Building a rain garden is the easiest way to address this problem as it help in filtering the contaminated water before it safely seep back into the ground.