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Title: SEDIMENT CONTROL AND LANDSCAPE MODIFICATION WITH GRASS HEDGES

Author
item Dabney, Seth
item Meyer, L
item McGregor, Keith

Submitted to: Management of Landscapes Disturbed by Channel Incision Stabilization Rehabi
Publication Type: Proceedings
Publication Acceptance Date: 3/7/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: Grass hedges are narrow (3 to 5 ft wide) strips of stiff, erect, grass planted near to or on the contour of fields. They serve as a guide for contour cultivation, slow down and spread out surface runoff to let suspended sediment settle out, and reduce growth of small gullies. This paper illustrates the effectiveness of grass hedges in sediment control and landscape modification by reviewing previously published results from flume and plot studies and presents new results from an ongoing field study. Flume studies, using flow rates typically found in fields where runoff from up to 5 acres is concentrated, showed that hedges can trap most of the sand and silt-sized sediment in runoff. Hedges located at the downslope end of 72-ft long erosion plots with 5% slope trapped about 70% of sediment eroded by natural rainfall. Switchgrass (Panicum virgatum L.) is a large-stemmed warm-season grass native to Mississippi that can be successfully used to form grass hedges. Five years after switchgrass hedges were planted in a 20-a field farmed in soybean, corn, and wheat, slopes between hedges had flattened enough to reduce future erosion rates. Slope within 50- ft wide cropped intervals between 4-ft wide hedges was reduced from 9% to 7% as a result of surface lowering immediately below hedges plus increases in elevation immediately above hedges. Erosion and deposition by runoff plus movement of soil by tillage both contributed to these changes. Grass hedges are an inexpensive biological conservation technology that can help control erosion on cropland and keep pollutants out of surface waters

Technical Abstract: Grass hedges are narrow (~1 m) strips of stiff, erect, grass planted near to or on the contour of fields. They serve as a guide for contour cultivation, retard and disperse surface runoff, cause deposition of eroded sediment, and reduce ephemeral gully development. This paper illustrates the effectiveness of grass hedges in sediment control and landscape modification by reviewing previously published results from flume and plot studies and presents new results from an ongoing field study. Switchgrass (Panicum virgatum L.) is a large-stemmed warm-season grass native to Mississippi. In flume studies with flow rates per unit width from 0.005 to 0.04 m**3sec**-1m**-1 , switchgrass hedges trapped 100% of sediment coarser than 0.25 mm. Miscanthus hedges located at the downslope end of 20-m long plots with 0.05 m/m grade trapped about 70% of sediment eroded by natural rainfall. Five years after switchgrass hedge establishment in a 10-ha field within the Hickahala and Senatobia Demonstration Erosion Control project (DEC) watershed, landform changes were large enough to alter future runoff and erosion patterns. Grade of 15-m wide cropped intervals between 1-m wide hedges was reduced from 0.09 m/m to 0.07 m/m as a result of surface lowering immediately below hedges and on the shoulders of swale areas combined with increases in elevation immediately above hedges.