Translation and dispersion of sediment pulses induced by an extreme rainfall in mountain rivers

Understanding linkage between channel process along a river course and hill-slope process with lateral sediment sources can be significant for management of sedimentary systems. The linkage that is characterized by distribution of storm-induced sediment in a river channel is often expressed as sediment pulse (wave). This paper examines the propagation of sediment pulse formed by storm-induced sediment flow in two river channels of Southern Hokkaido, and classifies the patterns of sediment pulse based on difference in the distribution of accumulated sediment volume. Longitudinal changes in sediment volume along a river channel were modified to a sediment mass curve. Auto-correlation and cross-correlation analyses were employed for examining sediment mass curves. The sediment pulses demonstrated with sediment mass curve was classified to four patterns, such as decreasing, increasing, intermediate and periodic types. Decreasing type along a transport-limited channel and increasing type along a supply-limited channel were dominated. Periodic type was not influenced by sedimentary link between channel and hill-slope but independently occurred by available sediment along a channel. Furthermore these types of sediment pulse were resulted to be influenced by channel with, channel slope and (quasi-) stream power. Although the highest peak of sediment pulse has been demonstrated at the channel reach with wide section and/or gentle slope, it has shown dispersed and lower peak at the channel reach with larger stream power