Grassed Waterways: An Effective Water Quality Strategy

The following article by Jeffery Sanders, UVM Extension Agronomy Outreach Professional, was originally published in the October 2016 edition of Vermont’s Agriview.

While grassed waterways are nothing new in the world of soil erosion and water quality, their adaptation in the Northeastern United States lags far behind counterparts in other parts of the United States.  In the Midwestern corn belt where memories of the dust bowl and the severe erosion problems of the past are still in memories and family histories, the idea of taking care of erosion issues decisively and effectively are evident everywhere on the landscape.  We do not want the devastating loss of topsoil the Midwest experienced to be our fate in Vermont.  A plane ride over any corn belt state will provide ample evidence of the efforts to mitigate soil leaving fields through the implementation of different practices.  The one that is highly visible and effective is grassed waterways.

A grassed waterway is a simple structure designed to absorb energy from moving water while holding soil from eroding in areas where water is prone to moving in concentrated flow across crop fields.  The idea is that you fill gullies and flatten out slopes in an effort to remove energy from i.e. slow down the water as it moves across the field.  This area is then seeded down and left in a permanent state of vegetation.  The vegetation acts to hold soil particles from being mechanically lifted and moved off fields while also helping to reduce the speed of the water so it has less ability to cause erosion.  A well designed and implemented grassed waterway will keep water from moving down slope without concentrating the flow into a stream.  It will move the water off the field without allowing it to pick up enough energy to move soil.  Grassed waterways have been found to be very effective at reducing erosion in high risk locations on crop fields.

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Picture: Grass Waterway Cross-Section Diagram

While the idea of “giving up” productive ground to install a conservation measure seems foreign to many landowners in the Northeast, it shouldn’t be.  You can tell easily where grassed waterways would be an effective tool in a landowner’s toolbox for keeping soil on their fields.  Wherever you have gully erosion, not much is growing and it is wet and rough (from eroding topsoil), a grassed waterway may be able to fix your issue.  The productive ground in many cases is not all that productive because soils tend to be saturated with frequent water inundation which can prohibit quality crop growth.

In many cases grassed waterways do not need to be much wider than 20 feet depending on the situation.  The benefit to your field, equipment, and the environment easily offset any yield loss from not cropping that area.  Also, in some cases you could install grassed waterways wide enough to crop.  For example, a perennial forage could be seeded using a design which would allow the farmer to turn equipment within the boundaries of a grassed waterway.  The idea is not that you need tall vegetation but that you need a sod base or other vegetation with a good root system to help hold the soil.  If you are looking for the motivation to install one, but to date have just kept filling in that gully every spring, keep a few considerations in mind.

Here in Vermont with new regulations passed under Act 64, it is a violation of the law to have soil leaving fields in concentrated areas and entering waters of the state.  More importantly, it makes no business sense to allow this to happen.  The top six inches of top soil on your farm is the most important asset you have, so why let it leave your farm?  You have fertilized and cultivated the soil to grow your crop for your business.  Letting it go down the ditch is just bad business.

Furthermore, soil erosion creates sedimentation problems in ditches and creates additional work in the field to fill in gullies with more topsoil in an effort to prepare the field for planting.  If you think about the zone of influence, where the concentrated flow of water is causing problems on your field, it is probably larger than the entire grassed waterway would be. The amount of area you need to cover with soil “pulled” back into the gully to repair it just to have it wash out again is no doubt larger than the area of a grassed waterway, which would cure the problem.

Furthermore, soil erosion creates sedimentation problems in ditches and creates additional work in the field to fill in gullies with more topsoil in an effort to prepare the field for planting.  If you think about the zone of influence, where the concentrated flow of water is causing problems on your field, it is probably larger than the entire grassed waterway would be. The amount of area you need to cover with soil “pulled” back into the gully to repair it just to have it wash out again is no doubt larger than the area of a grassed waterway, which would cure the problem.

Installation of grassed waterways is a very cost effective method of addressing soil erosion on crop fields.  Many farmers already have the necessary equipment to move and shape the soil so that the grassed waterway will perform adequately.  In many cases a box blade and a Brillion seeder will make short work of a grassed waterway project depending on scale.  For larger gully erosion control, bulldozers are effective tools to move, shape, and level the contour.  Typical construction of a grassed waterway takes between one to two days.  NRCS has sample designs and job sheets that can guide a farmer through the installation for installing a grassed waterway without government assistance.  Google “NRCS grassed waterway design” and click on Engineering Field Tools (EFT) for more information or go to this webpage: http://www.nrcs.usda.gov/wps/portal/nrcs/detail/national/technical/engineering/?cid=stelprdb1186070.

Grassed waterways following NRCS design are built to have an average lifespan of 10 years and require little annual maintenance.  NRCS and the Vermont Agency of Agriculture Food & Markets (through its Best Management Practice (BMP) grant program) can also provide financial assistance.  Keep in mind, this may require a more detailed engineering effort depending on the project, but funds are available.

The Farmers Watershed Alliance was awarded a grant from the Lake Champlain Basin Program* to install three grassed waterway projects in the summer of 2016.  These structures were constructed and farmers are very happy with the results. The farmers were actively involved with the projects and worked with their selected contractors to ensure the installations where done in a manner that they could work with.   As the farmers are experiencing, it actually is a common sense solution to a common problem on many Vermont fields.

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Picture: Before construction of grassed waterway showing accumulation of snow in sloped area of field.

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Picture: After construction of grassed waterway showing an ideal stand of a conservation mix.

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*This project was funded by an agreement awarded by the Great Lakes Fishery Commission to the New England Interstate Water Pollution Control Commission in partnership with the Lake Champlain Basin Program.  NEIWPCC manages LCBP’s personnel, contract, grant, and budget tasks and provides input on the program’s activities through a partnership with the LCBP Steering Committee.  The viewpoints expressed here do not necessarily represent those of NEIWPCC, the LCBP Steering Committee, or GLFC, nor does mention of trade names, commercial products, or causes constitute endorsement or recommendation for use.
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