ABSTRACT
Geomorphic thresholds may be studied in two crucial ways. The first is the establishment of domains for particular processes, within which that process is dominant. The second important aspect of thresholds is the nature of the transition between domains of dominance. This chapter reviews the properties of dominance domains and the nature of transitions at thresholds in general terms, before examining the hillslope/channel threshold in more detail. The measure of geomorphic effectiveness is generally sediment transport, which tends to act as a common unit in much the same role as the flow of money in economic systems. In the thresholds and dominance domains, there is implicitly a steadily changing process rate as environmental factors change. The model developed is for creep, wash, and solution processes, which are thought to dominate in the determination of drainage density in areas where slopes are below landslide thresholds.
