Tagged: Gully Erosion
April 18, 2017 at 7:45 am #941
Gullies: how to be rid of this pesky form of erosion.
Do you ever have an area in your field that just tends to gully out year after year, regardless of how many times you plow it shut or seed it down? If so, you may need a more “robust” method of dealing with that pesky type of erosion. Generally, when you are experiencing long term gully erosion in a field with active head cutting (the gully is advancing) it may be time for an engineered solution for the problem.
One the first tried and true methods of controlling gully erosion is simply installing a Grassed Waterway. This is a “sized” trapezoidal shaped channel excavated in place of the gully and seeded down. The channel is typically sized for the 10 year storm event and is big enough to handle that designed flow and slow the velocity down to a speed in which the vegetation can handle it and not erode. Seeding and vegetation establishment is the key to any Grassed Waterway, once you have a good seedling catch and grass becomes established, the waterway can handle the runoff that flows through it. Getting the seeding established is the tricky part; some folks seed perpendicular to the flow or serpentine through the waterway and even use erosion control netting and mulch to help get the seed established. Straw bales, rock checks and other methods across the flow path help the seed get established too.
Timing is everything for the construction of the grassed waterway. Spring and early summer is the best because it will allow for a long growing season for vegetative establishment. Late fall attempts usually result in reconstruction in spring so they are best avoided.
The Grassed Waterway can be crossed by equipment as they are shallow enough to drive through. On regular traffic pattern areas, a stone lined crossing should be planned to avoid damage to the waterway. This stone lined section should be made wide enough for all your equipment.
The vegetation needs to be periodically cut to maintain the design height of the grass. Too much vegetation will displace the runoff and cause it to run outside of the waterway and gully each side. Subsurface drain tile may be run alongside the waterway to help promote drainage and keep the waterway vegetation established. Grassed Waterways typically last about ten years before they fill up with sediment and vegetation and don’t handle the designed flows anymore. You know it’s time to replace the waterway when you see erosion occurring along the outside of the waterway.
Your local County Land and Water Conservation Department and or NRCS office is a great place to get technical assistance with this type of practice. They can complete a construction plan for you and help get it installed. They also may be able to offer cost share assistance.
April 20, 2017 at 10:28 am #944
Questions from the fieldParticipant
Drew, do you have advice on a method to replace a grassed waterway over 15 years old that has good sod establishment? Is there ways to manage the risk when tearing up and replacing a grassed waterway?
April 25, 2017 at 12:55 pm #947
<p style=”text-align: center;”>Gullies-How to Get Rid of that Pesky Form of Erosion</p>
<p style=”text-align: center;”>Without Using a Grassed Waterway</p>
In a previous article I discussed the need to address troublesome and re-occurring gully erosion with a more robust practice other than just seeding. I recommended a designed grassed waterway able to handle the designed flows and control these flows to a safe velocity. Well as we all know, waterways are hard to establish and do need to be replaced periodically. So when you’re dealing with a gully and don’t want to go to the trouble of getting a waterway established, you may want to consider installing a small berm with a surface inlet. This small berm with surface inlet is better known as a Water and Sediment Control Basin or a Grade Stabilization Structure. These types of practices are typically placed at the head of the gully, the idea behind them is to collect the runoff, hold it for a short period of time, then deliver it to a stable outlet via a pipe.
By collecting the runoff, storing it for a short period of time, and taking it to a stable outlet, you effectively cut the head off the gully and stop it from advancing. Small gullies can then be shaped and farmed through, larger gullies may be left and seeded over. The key is that these structures stop them from advancing through your field. There may be some cases, where these practices have to spaced in series through your fields, especially if you have a large watershed area. There may be two or more needed to control gully erosion in long gullies. They are similar to terraces, but used for gully erosion, not sheet and rill erosion, so they are generally bigger in size. These embankments can be narrow based and seeded down to permanent vegetation or broad base, and farmed over. They also work well at field edges, to intercept advancing gully erosion into you fields.
Outlets can be standard plastic surface inlets with PE tile or a Corrugated Metal Pipe (CMP) out letting to a stone lined channel with a pad to diffuse the energy of the water at the outlet end. The size and type of the outlet and the berm height all depends upon the size of the watershed area, how much space you have to store the runoff behind the berm, and how fast you want that runoff to be released.
The advantage to these types of practices is that they will last awhile, take up little cropland, do a great job in controlling gully erosion, and can be farmed over if desired. They also can be placed in areas of steeper slopes and irregular topography where you may not be able to get a waterway established. Cost is usually less than that of a grassed waterway. Maintenance is easy, just keep in inlets free and clear of obstructions, inspect the berm periodically to maintain designed heights, and control burrowing rodents.
Your local County Land and Water Conservation Department and or NRCS office is a great place to get technical assistance with this type of practice. They can complete a construction plan for you and help get it installed.
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