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60 Ways Farmers Can Protect  Surface Water
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19. Install Grade Control Structures

Grade Control Structure Grade control structures drop water safely from one level to another, preventing it from gouging out gullies.

They can also help to control flooding and trap the sediment moving with runoff water. Grade control structures are typically built across an existing gully, a grassed waterway, or the outlet of a waterway. They come in three basic types: weirs, chutes, and pipes.

A weir A weir allows water to run over the edge like a miniature waterfall, dropping down onto a concrete apron. The apron safely absorbs the impact of the falling water and then the water streams to an outlet. Although weirs come in many forms, one of the most popular and cheapest of weirs is made of corrugated metal, with a concrete apron.
A Chute When the drop in grade is more dramatic, you can use a chute to prevent severe erosion. As the name implies, water moves down a chute made of concrete or lined with rocks or concrete blocks. The concrete block-lined chute is one of the most popular and economical of chutes.
Metal Pipe with Drop Inlet Like chutes, pipes are effective in handling water when the drop in grade is dramatic. They are designed to carry water through or under an earth embankment to a lower elevation. The inlet for pipes comes in two basic forms: a drop inlet and a hood inlet. With a drop inlet, water does just that—it drops down into the inlet and then flows through the pipe.
Metal Pipe with Hood Inlet With a hood inlet, water flows directly into the pipe; the end of the inlet either has a hood on the top or is cut at an angle so the top of the pipe acts as a hood. The hood allows the pipe to flow full of water and prevents the air above the water's surface from entering the pipe.

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