MACROINVERTEBRATE ASSEMBLAGE OF AN AGRICULTURALLY IMPACTED STREAM

(www.interscience.wiley.com) DOI: 10.1002/rra.1063regions (Brookes, 1988). Channelization decreases habitat for aquatic organisms by increasing peak stream flows and reducing benthic substrate heterogeneity (Brookes, 1988). The lateral area over which stream flow can dissipate is reduced when a straightened channel is disconnected from its floodplain (Simon and Darby, 2002). Consequently, stream energy is forced vertically down and peak discharges increase, resulting in channel incision and stream bank erosion (Simon and Darby, 2002). Sediment from overland runoff and within-channel erosion buries natural rocky substrates and storm flow events wash woody debris and leaf packs downstream, destroying habitat for aquatic organisms. Furthermore, as incised channels erode, infrastructure and farmland are lost by widening of stream banks (Baumel et al., 1994). In response to deteriorating conditions of streams, many rehabilitation projects use in-stream structures such as boulder weirs, artificial riffles and flow deflectors to increase habitat heterogeneity andEFFECTS OF GRADE CONTROL STRUCTURES ON TH