The line of the fastest flow along the course of a river. This usually crosses and recrosses the stream channel. Channel morphology can undergo rapid transitions along the thalweg, depending on changes in topography, bedrock structure, water, and sediment supplies; see Ramonell et al. (2002) Zeitschrift nf 192. For techniques to quantify thalweg profiles, see Bartley and Rutherfurd in F. Dyer et al. (2002).