Terrace Maintenance and Contour Farming

by Susan J. Francis, Civil Engineering Technician
Natural Resources Conservation Service (NRCS)
Lakin, Kansas

Terrace maintenance is critical in any dryland farming operation. Whether you have level storage terraces and diversions or a gradient structure, poor maintenance can have results that are worse than having no structure at all. Overtopping and breaks can often cause a great deal of erosion. When either of these occurs, water that was stored in the length of the terrace becomes a concentrated flow going through the narrow break. Concentrated flow causes gully erosion which eventually cannot be farmed across. This can have a domino effect if the problem starts at the top of the hill.

Breaks and overtopping can occasionally be caused by unusually large rainfall amounts. However, more often than not, the trouble starts with lack of maintenance. Sediment that has accumulated in the terrace reduces on the storage capacity. Each terrace is designed to handle the runoff from the determined interval above it. When the actual storage area is less than the calculated storage area, there is not room for accumulated water. Ridge height and outlet elevation are also important considerations in the storage area. Ridge height can be compromised by tillage operations that go across the ridge rather than parallel with it. Sweeping straight up and down the hill or even at an angle to the terrace can easily loosen the top four to six inches of soil on the top of the ridge. A hard rain immediately after this will move this same amount of soil from the ridge. It does not take very many times before you have a considerably shorter ridge height. At the same time, sediment is filling the channel.

Modern technology has given us Global Positioning Systems (GPS) guidance systems. These have become common place in many areas with the hope of using less seed, fuel, and time. This will be a great advantage; however, a producer also needs to consider the terrace system when setting a path with the guidance system. Remember that those pretty, straight tillage marks go right over the top of the terrace ridge. You could be damaging a structure that should have a 20-year life span!

For more information about terrace maintenance and contour farming, please contact your local Natural Resources Conservation Service office (NRCS) or conservation district office located at your local county USDA Service Center.

For more information about NRCS programs, visit the Kansas NRCS Web site at www.ks.nrcs.usda.gov.

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Last Modified: 12/10/2008