Modifications are made to the revised Morgan-Morgan-Finney erosion prediction model to enable the effects of vegetation cover to be expressed through measurable plant parameters. Given the potential role of vegetation in controlling water pollution by trapping clay particles in the landscape, changes are also made to the way the model deals with sediment deposition and to allow the model to incorporate particle-size selectivity in the processes of erosion, transport and deposition. Vegetation effects are described in relation to percentage canopy cover, percentage ground cover, plant height, effective hydrological depth, density of plant stems and stem diameter. Deposition is modelled through a particle fall number, which takes account of particle settling velocity, flow velocity, flow depth and slope length.

There are a variety of buffering features within the landscape that can be used to trap sediment and associated contaminants such as phosphorus (P), thereby helping to reduce sediment and P delivery to watercourses. Astroturf mats (n = 136) were placed within contrasting buffer features at nine sites [mid-field hedges (two sites), edge-of-field grass strips (six sites) and channel wetlands (one site)] within the River Parrett basin in England. Sediment was recorded on the mats at seven of the sites during the 18-month sampling period. At the other two sites either there was insufficient erosion or sediment by-passed the mats. At the seven sites where mats collected sediment, there was a considerable range in sediment deposition over the 18-month sampling period with site-average values (based on all mats at a site) ranging from 0.02 ± 0.06 to 1.15 ± 1.88 g cm )2 ; the average for all 136 mats was 0.41 ± 1.08 g cm )2 , or approximately 0.27 g cm )2 year )1 . Most of the sediment collected on the mats (n = 60) was sand-sized (>63 lm) material. The site-average total-P content of the <63 lm fraction of the deposited sediment ranged between 616 and 1938 mg kg )1 (average 890 mg kg )1 ). About half of all the mats that collected sediment were from the front of the buffers. Comparison of the sediment in the buffer features with topsoil from the contributing upslope fields suggests that the buffers trap coarser sediment with lower P concentrations, than the contributing topsoil. This suggests that the finer fraction, enriched in total-P, may be passing through the buffers towards river channels. Comparison between sites indicates that sediment deposition within buffers is greater at sites with steeper slopes, erodible soils and certain types of land use, such as maize for silage, reflecting the greater soil erosion and sediment transfers in these fields. The location and careful design of buffer features is a key factor in their effectiveness.

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Soil erosion involves a two‐phase process of soil detachment and transport, both of which require an energy input. Much of the energy of erosion derives from water or wind flow over the soil surface or is provided by gravity. Although reducing the energy of erosive forces is the most effective way of controlling soil erosion, one consequence of reducing energy may be the deposition of any material already eroded. As eroded sediment is often enriched with nutrients, organic matter, and contaminants preferentially adsorbed onto the sediment surface, sediment deposition may allow contaminant release into the environment. It is necessary, therefore, to reduce erosive energy at the source areas of sediment rather than after the sediment has been detached and transported.