CONTROLLING EROSION

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Rills. The easiest way of stopping a gully is to catch it early. Whenever you see small rills (or channels), get right to work. Use a mattock or a hoe to break them up. Work in some compost or rotted manure, if you can, and rake the area smooth. Then treat the area as you would for sheet erosion — seed it, mulch it, or possibly use brush mats or contour trenches.

Gully monsters. A neglected rill may grow up to be a monster gully. In the next two pages I'll tell you how to go about fighting and conquering gullies. It's a long, complicated fight, but very much worth the trouble. We no longer have fire-eating dragons, but we do have land-eating gullies to fight. Just to make sure you can find your way through the following instructions, here is an outline of the battle plans.

[1] Stabilize the gully bottom. The bottom is more important than the sides. If the gully continues to dig deeper, no matter what else you do, the sides will cave and slump. You've got to prevent the gully from getting any deeper, and you should even attempt to build up the bottom.

[2] Grade the walls of the gully to their angle of repose — the angle at which they will no longer slump or slide.

[3] Stop or reduce the flow of water entering the gully.

[4] Plant an immediate cover of grasses and legumes that will hold everything together for a season or two.

[5] Plant a permanent cover of native shrubs, trees, vines, and grasses that will eventually stabilize the area, perpetuate themselves, build up soil fertility, encourage wildlife, and completely restore the land.

Check dams. The way to stabilize the gully bottom and build it up again is with check dams. Please don't be intimidated by the thought of building a dam. You're not going to be competing with Grand Coulee or Aswan. In fact, your check dams won't even hold any water. They are merely obstructions that will slow the water down. And the best of all possible obstructions (as we all know from our various misadventures in life) is a big mess. Basically that is what a check dam is: a big mess of brush or perhaps straw packed into the bottom of the gully, with a simple structure to hold it all in place.

Why a check dam works. I think we all have an intuitive sense of why a check dam works: A slow-moving stream carries far less silt and does far less damage than a raging torrent. But to understand how dramatically true this is, you might want to consider a few hard-core engineering facts. If you reduce the speed of the flow of water by one-half, here (according to certain laws of hydraulics) is what happens:

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