Rain Garden
How to reduce stormwater runoffs
Winter season is rolling in and even if Southern California doesn’t need to worry about east coast weather conditions, it still rains during those winter months, a lot. What should we do with all the rain water on the streets, in our backyards and properties that runs in streams and overflowing our drain systems or ending up in our favorite shopping mall parking structure (yes I am talking about Fashion Valley)? Remembering those summer months when drought was a real big problem and now we are moving to the other extreme, too much water? This seems to be a funny little joke that nature likes to play on us every year over and over….but hold on, the joke is no longer on us….RAIN GARDEN is the answer to end this viscous cycle that we are literally “running” in.
What is a Rain Garden you might ask, sounding like a fancy add on to your backyard design but hold on, it is such a simple, economic and beautiful system that takes advantage of all those runoffs.
A rain garden is simply a depression in the landscape that collects stormwater runoffs. Roof, sidewalk or driveway runoff is directed towards the landscaped area rather than to all the Strom drains that will only lead back into the ocean and pollute the water and natural habitats. By directing the runoff to those landscaped areas (which could be easily built in your backyard/side yard/front yard) the rain water infiltrates through the soil. This process will do so much good to your environment by removing the sediment of bacteria, mimicking the natural absorption and pollutant removal abilities of a forest or meadow. It can absorb runoffs actually even more efficiently- as much as 30% - 40% more than a standard lawn. By capturing rainwater in a rain garden, holding it, and then slowly releasing it into the soil, the rush of runoff from a large storm can be slowed and most importantly cleaned - quickly, neatly and naturally.
If you aren’t convinced by now that these rain garden are simply amazing, here are the main bullet points (you might especially value the last one):
Filter pollutants from runoffs
Recharge groundwater
Conserve water
Protect guts, ponds and coastal waters
Remove standing water in your area
Reduce mosquito breeding
Increase beneficial insect that eliminate pests
Create habitats for birds & butterflies
Reduce potential of home flooding
Survive that nasty drought season
Less garden maintenance (and more savings in your pocket)
Aaand here it comes: Enhance your properties overall value!!
Lets jump to the question that by now probably popped into your head:
Can I and how can I get myself one of these beautiful ran garden systems?
Everyone who has some kind of outside space/lawn can integrate a rain garden into their design and it does not need to become an expensive add on but a beneficial solution.
First Step: WHERE to put your rain garden. This is incredible important to find the right area since your property already has some kind of existing drainage pattern (even if you can’t visibly see it), and it would make the most sense to take advantage of that and safe yourself some extra work. Find your runoff spots from your roof, any surrounding areas and notice low spots on your property. If these water collecting low spots are away and downhill from your building foundation, they will be a good place for your rain garden.
If you are planning on building your own rain garden make sure to double check with utility companies that there aren’t any undergrouns=d wires, cables or pipes in the proposed area before you start the process.
Some main rules:
Any rain garden should not be within 10 feet of your buildings foundation
Make sure to avoid any underground utility lines
Best location is exposed to partial or full sun
Rain garden should be located at least25 fee from a septic system drain field
Let’s talk about the rain garden size that works best in your yard, a little bit of math (don’t worry any calculator can do that job for you) is required:
To determine the best size for your garden, estimate the volume of water that would flow off the roof and down the spout that feeds it during a 1-in. rainfall (the rainfall from an average storm). To do this, calculate the rough area of the roof that drains down the spout. For example, in a 2,400-sq.-ft. rectangular home with a downspout at each corner, you’d have approximately 600 sq. ft. of runoff going to each downspout. Multiply by rainfall depth (1 in., or 1/12 ft.) to get the volume of water—50 cu. ft. in this case. If your soil porosity can handle a 6-in.-deep (that is, 1/2 ft.) garden bed, dividing by 1/2 ft. gives you a 100-sq.-ft. (10 x 10 ft.) garden size.
Now don’t stress out on getting the exact to the inch measurements, it is ok to vary the size of your garden. Keep the calculation as a fair guideline in mind since you want to avoid to overflow your garden or not give it enough water exposure.
Once you've identified the new garden's location and size, remove the sod and dig a shallow depression approximately 6" deep. Slope the sides gradually from the outside edge to the deepest area. Use the soil that you remove to build up a slightly raised area on the lowest side of the garden. This berm will help contain the stormwater and allow it to percolate slowly through the rain garden. If your rain garden is no more than about 6" deep, stormwater will usually be absorbed within a one- to seven-day period.
The downspout from your roof or sump pump outlet from your basement should be directed toward your rain garden depression. This can be accomplished by a natural slope, by digging a shallow swale, or by piping the runoff directly to the garden through a buried 4" diameter plastic drain tile.
After all that work is done (let’s hope you have a lot of willing helpers if this is a DIY project or an amazing company just like ours wink wink to build your Oasis) let us move to the fun part, the plant selection:
Native plants are the ideal choice for rain garden. Southern California has a ton of beautiful, colorful plant selections that require little care. Make sure to mix native grasses and sedges in with your wildflowers to ensure the garden has a strong root foundation for growth and to resist all kinds of weather circumstances. New plants should be watered every other day for the first two weeks until they are well established, After that your garden should thrive and bloom beautifully without additional watering.
