The use of buffer features for sediment and phosphorus retention in the landscape: implications for sediment delivery and water quality in river basins.

There is 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 were placed within contrasting buffer features at nine sites within the River Parrett basin in England. Mats collected sediment at only four of the sites during the sampling period due to limited erosion and/or sediment bypassing the mats at most sites. For those sites where mats collected sediment, which tended to be either grass strips and/or hedges at mid- or bottom-field locations, there was a considerable range in sedimentation with average values for the sites ranging from 0.07 to 9.1 g cm -2 (average for all mats = 1.7 g cm -2 ). Most of the sediment was sand-sized material (average for all mats: %sand = 82%, d 50 = 123 μm). The site-average total-P content of the <63-μm fraction of the deposited sediment ranged between 559 and 1185 mg kg -1 . Comparison between mats located at the front and back of one of the sites shows that more sediment was trapped at the front than at the back, although the particle size and total-P content were similar at both locations. The results suggest that different types of buffers are more effective than others in reducing sediment and P delivery to watercourses, and that the strategic location and careful design of buffer features is a key factor in their effectiveness.