I recall hearing a business maxim some years ago: “What gets measured gets done.” In other words, if there is no standard by which to measure something, it becomes a low priority. Unfortunately, this seems to be the case with soil erosion.
For years, resource professionals have had the RUSLE2 soil erosion model to predict the amount of sheet and rill erosion that occurs on a farm. Sheet and rill erosion is caused by a shallow sheet of rainwater that runs across the land. This picks up and transports soil particles already detached by a raindrop splash or by soil disturbances such tillage operations. Because there was a way to estimate sheet and rill erosion, soil scientists set standards, or benchmarks, for it. Using the RUSLE2 model, soil scientists developed the standard for “T” or the “Tolerable soil loss” level. This “T” is the erosion level that Natural Resources Conservation Service (NRCS) encourages farmers to achieve. The tolerable soil loss for most soils in the Midwest is set at 5 tons/acre/year. As with all standards, experts argue whether it should be higher or lower but the fact remains, resource professionals and farmers have a method to estimate how changes to farming practices impact soil erosion. In other words, we can set standards and measure progress.
Unfortunately, the same cannot be said for ephemeral gullies. Ephemeral gullies are defined as small channels eroded by concentrated flow that can be easily filled by normal tillage, only to reform again in the same location by additional runoff. Ephemeral gully erosion is far more visible than sheet and rill erosion and everybody can see it is occurring. But still, resource professionals have no method to predict the amount of ephemeral gully erosion that occurs at a field level. Ephemeral gully erosion is believed to be at least as significant as sheet and rill erosion in terms of sediment delivered from cropland to streams, rivers, and lakes. In fact, a special report written jointly by the USDA Agriculture Research Service (ARS) and NRCS emphasized the need to focus on ephemeral gully erosion. This report estimates that 40 percent of watershed sediment yield can be attributed to ephemeral gully sources (Bernard, 2009).
To date, there is no model similar to RUSLE2 that can be used to estimate or predict the level of ephemeral erosion occurring in a farmer’s field. Therefore, ephemeral erosion has always been the ugly step sister to sheet and rill erosion. With no way to predict ephemeral gully erosion, it has received far less attention, and no standard for ephemeral gully erosion reduction has ever been set.
After all of these years, finally, USDA-ARS is developing a model that can be used to measure ephemeral erosion. Dr. Seth Dabney is working to develop a model that can be used to predict the location and the amount of ephemeral erosion. Hopefully, resource professionals will take notice of Dr. Dabney’s work and get serious about measuring and reducing ephemeral erosion.
Not having an ephemeral gully erosion calculator is a disservice to all of those working to protect natural resources. Remember, precision conservation is about applying conservation practices in the right place, at the right time, and at the right scale so we can solve the right problem. How can resource professionals be expected to apply the right practice if they don’t know how much ephemeral gully erosion is occurring? In some cases, we have been applying practices to reduce sheet and rill erosion when we should have been looking at ephemeral gully erosion.