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Erosion Control & Soil Conservation Erosion is the pervasive unravelling of the landscape that leads to broad-scale de-watering and ultimately desertification. Soil loss is perhaps the most serious threat that we face. Every lost grain of soil is a loss in the productive potential of the land. Erosion in drylands is especially serious since soils in arid environments develop at extremely slow rates. Erosion control in drylands is all about increasing the infiltration of runoff, producing soil and establishing diverse plant cover. We design and build carefully placed structures that dissipate the energy of water, capture soil particles and retain moisture. The protective environment created by these structures is ideal for the establishment of seedlings. As the plants mature they do most of the healing work by binding soil together and producing organic matter that continues to improve infiltration. By cultivating water in the landscape we aim to re-wet degraded drylands one drop at a time.
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Severe gully erosion is all too common in dryands. Deep gullies like this are the result of long periods of abusive land management practices that ultimately leave the landscape drier and less productive.
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This upland headcut was formed by the advance of gully erosion that started lower in the watershed. The headcut channelizes sheetflow and greatly increases the erosive energy of runoff that pours over the edge.
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The key to stabilizing this type of upland headcut is to reduce the erosive energy of the runoff it receives and to establish dense perennial vegetation that can bind soil particles together.
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This is the same headcut as above 1 year after treatment. The cobble mulch was made with small pieces of sandstone available nearby and the area was seeded with native grasses and wildflowers.
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Upland headcuts form an abrupt transition from sheetflow to channelized flow. Rock mulch slows runoff and prevents rills from forming upslope. Two years after treatment much of the once eroding face is colonized by vegetation.
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In-Channel headcuts are formed as bed erosion travels upstream. The face of the headcut forms a waterfall. The headcut will migrate upstream until it reaches the top of the watershed or a natural or manmade barrier.
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In-channel headcuts are different than upland headcuts and must be treated differently. Rock bowls form a plunge pool that dissipates energy and prevents scour. The rock work also helps to establish protective vegetation.
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This 2' tall headcut was treated with a rock bowl constructed from flagstone found nearby. The headcut is now held in place preventing further erosion of the upstream channel.
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This photo shows a rock bowl in action during a small runoff event. Notice how the plunge pool in the center of the structure converts one large drop off into two smaller ones. (Photo by Steve Vrooman)
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This modified bowl structure was constructed with woodchip and soil filled jute bags similar to compost wattles. While the materials are different the form is the same as a rock bowl.
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Regardless of the materials used it is essential to understand the form and function of erosion control structures.
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