Riparian herbaceous cover is defined by NRCS as grasses, grass-like plants and forbs that are tolerant of intermittent flooding or saturated soils and that are established or managed in the riparian or transitional zone between terrestrial and aquatic habitats.
The riparian zone is the area adjacent to perennial and intermittent watercourses or water bodies, considered by NRCS to be a minimum of 1.5 times a stream’s with or 15 feet for other water bodies. For seasonal or short lived watercourses and water bodies, this zone extends to the center of the channel or basin.
Riparian herbaceous cover relies on grasses, sedges, rushes, ferns, legumes, and forbs tolerant of intermittent flooding or saturated soils established or managed as the dominant vegetation in the transitional zone between terrestrial and aquatic habitats. The riparian herbaceous cover provides habitat for wildlife, improves water quality by acting as a filter for sediments and pollutants in surface water run-off, stabilizes stream banks and shorelines, and increases soil biomass’ net carbon storage.
Land owners often use the riparian herbaceous cover practice to remedy damage due to the riparian area having been altered or converted to cropland, pasture, or other commercial/agricultural practices that have changed the native plant community. Proper application of riparian herbaceous cover requires research to select the appropriate perennial plants adapted to the riparian zone’s hydrological conditions and that provide the diversity required by the. When establishing a herbaceous cover practice the riparian zone must be protected from haying, grazing, or similar practices until the desired plant community is well established. After establishment of the herbaceous cover, land owners must use diligence in best management practices which limit haying, grazing, or similar practices, and avoid times when stream banks are vulnerable to livestock or mechanical damage.
Once established, riparian herbaceous cover has been shown to help reduce non-point source pollution from agricultural areas. Healthy riparian herbaceous cover has been shown to reduce the total weight of sediment and nutrients in run-off from agricultural fields by 50 to 80%. Research has shown other notable benefits of riparian herbaceous cover used as a filter for run-off including; reductions of total Phosphorous load of 50%, a 20 to 50% reduction of Ammonium, and about 50% reduction of the total Kjeldahl Nitrogen and Nitrate (R. B. Daniels and J. W. Gilliam 1996). Further improving or protecting water quality is benefited by increasing the minimum riparian zone to 2.5 times the stream width or 35 feet for water bodies. Management to control mass soil movement or concentrated flow erosion areas that may overload the riparian herbaceous cover’s filtering capacity prior to establishing a riparian herbaceous cover is also recommended.
Stream bank stability has been shown to greatly improve with a healthy riparian herbaceous cover as well. Research has shown mechanical effects of grass roots increasing soil strength and instances of up to a 70% improvement of stream bank stability (A. Simon and A. J. C. Collison 2002). Native or accepted, introduced herbaceous species with deep, binding root mass have been shown to be optimum for strengthen streambanks and improving soil health.
If conditions requiring riparian herbaceous cover exist, there are financial incentive programs which may cost-share the expenses of the additional requirements. Implementation of riparian herbaceous cover can be worked into an EQIP application package and may complement other conservation practices such as 580-Streambank and Shoreline Protection, 584-Stream Channel Stabilization, 382-Fence, 391-Ripariian Forest Buffer, 512-Pasture and Hayland Planting, 550-Range Planting, 393-Filter Strip, 472-Use Exclusion, 528A-Prescribed Grazing, or 314-Brush Management.
When performing a riparian herbaceous cover conservation practice there are several things that must be considered to achieve optimum results. When choosing herbaceous plants preference should be given to native, locally adapted species that provide full ground cover, however, a tame, introduced species suited for the location can often be used as well. Avoid plant species that may be hosts to undesirable pests. Control trees and shrubs that may have the potential of dominating the riparian zone, as there are few woody plants in healthy herbaceous riparian zones. Plant species diversity is crucial to maintaining a healthy habitat for wildlife in the riparian zone; special attention should be given to enhancing habitats of any possible threatened and/or endangered species; additionally consider seasonal changes and select plants accordingly. Be mindful of how this practice will compliment the function of surrounding ecosystems, paying attention to the locations natural features which should be used to frame the vegetative structure and composition, and complement those natural features. Finally establish alternate water sources and controlled access stream crossings for livestock to aid in maintaining a healthy herbaceous riparian cover.
In summary, riparian herbaceous cover is an important conservation and production practice that can be utilized in conservation programs. Riparian herbaceous cover is crucial to maintain a healthy stream system, by reducing sediment, nutrient, and pollution loads in run-off from agricultural production. Healthy riparian herbaceous cover also provides habitat for many different aquatic and terrestrial organisms. Careful selection of the proper deep rooting, native plant species, best suited for the riparian zone will provide the greatest benefits, filtering run-off, providing mechanical and hydrological stability to stream banks, and increases species diversity of the riparian zone. For more information contact your local County Extension Office or your local USDA Service Center.
Daniels, R. B., Gilliam, J. W. “Sediment and Chemical Load Reduction by Grass and Riparian Filters” Soil Sci. Soc. Am. J. (1996) 60: 246–251.
Simon, A., Collison, A. J. C. “Quantifying the mechanical and hydrologic effects of riparian vegetation on streambank stability” Earth Surface Processes and Landforms (2002) V. 27 I. 5: 527-546
– Lee Riley