Friday, May 29, 2020

Sheet-flow Erosion/Gully Repair

At this 6 acre rural property heavy storms cause rain water to sheet-flow from large neighboring properties, following the natural contour of the land. Run-off travels across an open field, then decends downhill in a torrent. Over time the resulting erosion has carved a 25' deep gully, which is in danger of reaching the water table and destabilizing the house foundation.

My design solution uses large scale swales and hugelkultur berms to intersect water flow, enabling the ground to absorb it before reaching the hillside.

Long logs, recently cut from trees located too close to the house, were transported to the site and placed in a series on contour, perpendicular to the water flow.

Swales were dug at the uphill side of the logs. The displaced soil was dumped on top of the logs to construct huge planting berms, or hugelkultur. Swales were filled with wood chips, leftover from the tree cutting. 

The fence line  (where the sheet-flow first enters the property) was planted with water-loving native trees to provide a suntrap, a windbreak and privacy. The entire site is protected by a deer fence.

Small check dams were built in the gully to slow water flow. Its banks were planted with red twig dogwood live stakes to stabilize the soil.

The 2 largest swales, seeded with native flowers, act as huge rain gardens. After a storm they absorb the bulk of the water in about 2 days, recharging the water table.

The berms located in the shade of the adjacent forest were planted with native shrubs. Those located in full sun were planted the first season with a soil boosting seed mix, and the next with perennial edible berries and fruit trees. 

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