Water Qual. Res. J. Canada, 2006 • Volume 41, No. 3, 275–282 Copyright © 2006, CAWQ 275 Effectiveness of Vegetative Filter Strips in Removal of Sediments from Overland Flow Bahram Gharabaghi, 1 * Ramesh P. Rudra 1 and Pradeep K. Goel 2 1 School of Engineering, University of Guelph, Guelph, Ontario N1G 2W1 2 Water Monitoring Section, Ministry of the Environment, 125 Resource Road, Etobicoke, Ontario M9P 3V6 Many forms of natural heritage manifested as streams, rivers, ponds, lakes and wetlands play an integral role in maintaining natural beauty, health and a high quality of life. Agricultural intensification in southern Ontario has contributed to elevated sediments, nutrient and bacteria levels in water bodies. Vegetative filter strips (VFS) are control measures that can partially remove sediments and pollutants adhered to sediments from overland runoff before entering water bodies. The objective of this study was to determine the effect of vegetation type, width of the filter strip, runoff flow rate and inflow sediment char- acteristics on effectiveness of the VFS in removing pollutants from runoff. The results show that sediment removal efficiency increased from 50 to 98% as the width of the filter increased from 2.5 to 20 m. In addition to the width of the filter strip, grass type and flow rate were also significant factors. This study indicates that the first five (5) metres of a filter strip are crit- ical and effective in removal of suspended sediments. More than 95% of the aggregates larger than 40 μm in diameter were trapped within the first five metres of the filter strip. Key words: vegetative filter strips, water quality, stormwater management * Corresponding author; bgharaba@uoguelph.ca Introduction The Clean Water Act and the Nutrient Management Act passed recently in the Ontario legislature have put in motion a massive science-based effort to better under- stand and protect our drinking water sources. Sediment, nitrogen, phosphorus and bacteria are primary pollu- tants associated with surface runoff from agricultural fields (McLeod and Hegg 1984; Edwards et al. 1983). Environmental concern related to nutrient loss and appearance of sediments and sediment-bound contami- nants at higher than recommended levels in water sys- tems can be addressed by adopting better management options. Major investments are being made in Ontario to control point and non-point pollution sources. During the recent past, vegetative filter strips (VFS) have become an important best management practice (BMP) to control pollutant transport by stormwater runoff and are used widely in the United States to enhance the quality of stream ecosystems (Schellinger and Clausen 1992; Mickelson and Baker 1993; Chaubey et al. 1994; Patty et al. 1997; Egball et al. 2000; Fajardo et al. 2001; Boyd et al. 2003). Numerous studies have clearly advo- cated the effectiveness of vegetative filter strips as the first defense mechanism in the multi-tier approach of reducing pollutant transport from agricultural fields. Dickey and Vanderholm (1981) studied feedlot runoff and found that VFS can remove up to 95% (on mass basis) of nutrients and oxygen-demanding materi- als from the incoming runoff with concentration reduc- tions of up to 80%. However, Dillaha et al. (1988) observed a significant reduction in the sediment trapping efficiency of VFS when flow regimes changed from uni- form to concentrated flow. Lammers et al. (1991) also observed similar results in a survey of buffer strips in Virginia and concluded that buffer strips were not very effective when water collects in natural drainage ways prior to crossing the buffer strips. Chaubey et al. (1994) observed a mass reduction of total suspended solids (TSS) and total phosphorus (TP) in surface runoff by 66 and 27%, respectively, with a 4.6-m wide filter strip. They also observed an improve- ment in the ammonia and P removal from swine lagoon effluent with an increase in filter strip width. Such reduc- tions can be attributed to a decrease in flow velocity and the retarding effect of vegetation; however, the reduc- tions in the concentration of soluble pollutants were not as significant (Edwards et al. 1996; Srivastava et al. 1996; Robinson et al. 1996; Lim et al. 1998). Schmitt et al. (1999) suggested that VFS were more effective in the reduction of particulate pollutant concen- tration but have less effect on the concentration of solu- ble pollutants. They investigated the performance of dif- ferent filter strip widths and concluded that filter strips of 7.5 and 15 m in width can result in 76 and 93% sedi- ment removal efficiencies. Oelbermann and Gordon (2000) evaluated the per- formance of the VFS by comparing the pollutant con-