Back when my house was built in 2003, the city I live in required (and still does) that the grading of the lot must include a drainage pond – a place for collecting rainwater that comes off of the rooftop of the house during a rainstorm. It is designed with a low area near the back of my half-acre lot and has a concrete block and gravel dam at the downhill end. The dam is one concrete block high and about 10 feet in length. Once the level of water fills the “pond” area and reaches the height of the dam, the water then continues to flow downhill and off the property. This essentially helps to capture some of the rainwater allowing it to sink into the ground rather than cause a runoff problem. And, it works really well during a rare (I live in the desert, and California is in a severe drought) cloudburst. It is especially good that it works given the fact that my house is the only one new enough on my block to have these “pond” requirements. The water that comes off of all the rooftops uphill from my house runs off of their lots and straight into mine.
So, most of the time this “pond” area is completely dry and unused. For several years I thought this was a big waste of land that could be used for something useful or productive. Last year I made the decision to add more raised beds to my organic veggie garden, and this was the area that I would put them. I just needed a plan/design that would keep the beds and plants safe in the event of the area flooding during a storm, yet not prevent the “pond” from doing its job.
On June 12, 2015, the setup was tested when a cloudburst (yay, free water) occurred right over the area. It poured for over an hour and dumped well over an inch of rain, probably closer to two inches. I discovered about half way through that my rain gauge had been knocked over, so I set it back up and it still measured nearly an inch when it was over. I spoke with some friends in nearby areas and none had anything more than a drizzle. My garden area not only survived, it pretty much went unscathed!
So what is that I did when I built the garden to withstand so much water?
I created eight raised beds, each measuring eight feet by four feet and eight inches high. With the beds being placed uphill from the dam area, the eight-inch height would allow the area around the beds to fill with water, but the excess water would escape over the dam before it would go over the tops of the beds. Between each bed, I attached two-by-four boards at ground level. These served to divert the flow of water around the garden area so that the pathway materials would not be washed away when a deluge of water came rushing through. The setup would divert the water around the garden, while allowing it to come slowly into the pathways from the downhill end.
The vegetable plants got a little extra water during the deluge, but since the water was not able to wash everything away, the plants did very well. The native soil is very sandy, so it was only a short time before the ponded water around the beds had completely drained into the ground.
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