Post a comment on the text below

River modification accelerated in the twentieth century, largely associated with the intensification of agriculture, when many rivers were straightened, deepened and widened to facilitate catchment drainage and to prevent local flooding (McCarthy 1985; Brookes 1988). Instream gravel deposits and most instream woody debris were often dredged from such rivers, further reducing their physical heterogeneity (Swales 1989; Brookes 1988). The characteristic longitudinal and lateral sediment deposition pattern of actively meandering channels was then replaced by a more uniform and diffuse deposition of finer material in constrained channels. The physical complexity of natural marginal and riparian habitats was also usually greatly simplified. Water quality changed to reflect a greater input of nutrients and organic material from more-intensively managed catchments (Sweeting 1996; Riis & Sand-Jensen 2001).