Bioswale Solving erosion problems With natural Elements

Steep hillsides with limited top soil and plantings are vulnerable to erosion during heavy rainstorms. This beautiful slate staircase created access up the slope, but didn't include any erosion control. Planting the slope and inserting garden borders around plantings helped. But the homeowners dump truck load of expensive planting mix wouldn't last long once the winter rains hit.

This slate staircase adds practical beauty to a house built on a slope and provides access to a lower parking area.

After watching the hillside transform into a waterfall during a particularly heavy rainstorm, the homeowner quickly realized more erosion work needed to be done. Not only had the storm eroded the hillside, but the water had begun to undermine the foundation for the staircase. A 6 x 8 bio-swale would easily handle the 1800 gallons of water that funneled off the roof from the homes' rain gutters during a moderate storm. This design diverts the water directly from the rain gutter into a holding pond where it will then percolate back through the soil to recharge the aquifer.

This design includes five trenches, about four inches a part, dug five-six inches deep and cut perpendicular to the hillside. The trenches were then filled with pea gravel. On the right in this image there is a mulched berm, spanning about three-feet wide and about 18 inches high. The perimeter of the bio-swale is finished with plastic bender, secured with 10-inch stakes.
A bio-swale looks like a decorative landscaping feature, but works hard to capture, divert, hold and percolate rain water that flows from rain gutters and other flood prone areas, eliminating flooding and saving foundations. Cross-cut trenching, varying rock sizes and concave 'pond' area eventually cause the water to seep back into the water table.
Copper rain chains replaced traditional piping allowing for easy maintenance.
Rain chains divert water just as efficiently as traditional piping, but their open design allow for easy removal of debris.
"Bio" in the term bio-swale refers to the plantings that surround the rock 'pond.' These plants can handle dry, summer conditions and months of soggy soil during winter months. Landscape fabric covers the trenching system and a layer of metal screening, secured with metal stakes pins the landscape fabric in place and works to keep gophers from disturbing the rocked area. Inexpensive bags of drain rock were layered above the metal screening and landscape fabric, then more expensive bags of "Mexican Beach Pebbles" combined with large cobbles and rocks from a local quarry stabilize the basin.
During summer, the bio-swale provides an attractive dry stream focal point coming up the stairs and through the windows along this eastern wall of the house.
During winter months the bio-swale works efficiently to channel water and eliminate erosion issues. An overflow drain was placed on the downhill side of the bio-swale to guide excess water down a lower, trenched drainage path. This second trenching system looks like the continuation of the dry stream bed and curves naturally down the slope.
A four-inch perforated drain pipe was installed in a 6-inch deep channel connected to the rain chain area. Plantings and large cobbles shaped like a dry stream bed hide the drainpipe while connecting the roof run-off to the bio-swale below. In heavy storms the bio-swale looks like a pond, but typically drains within about 30 minutes of rain events.
A "bluestone" bridge and a Buddha transform what had been homeowner headache into a place of meditative tranquility.

This project can be completed in a long weekend for less than $500 and can eliminate costly erosion damage while helping to recharge underground aquifers during heavy rain events. So if you are looking to locate a peaceful meditation area in your garden, consider finding your Zen by building a bio-swale.

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