Abstract
This study analyzed relationship between deposition process of coarse particulate organic matter (CPOM) and flow structure around river bank in a gravel bed river. At first, the movement of CPOM behind the protrusion of a river bank was investigated. This field experiments revealed that the flow near the riverbed in main stream was entrained behind the protrusion of the bank and the flow near the surface behind the protrusion returned to the main streamline. Therefore, suspended materials near the riverbed in the main streamline are entrained and deposit at the center of circulation. Based on this result, litter patches were classified into several types by focusing on whether the litter patches collect suspended material or floating one. Then, deciduous leaves were collected from each litter patch, and type of tree, mass, decomposition rate, and attached macro invertebrates were analyzed. Consequently, following forming process of litter patches was clarified. The depth where CPOM suspended, which depends on type of tree, determines the place of CPOM deposition. Then, type of tree and physical environment of the litter patch determine the suitability of habitat for macro invertebrates. Finally the species and the number of macro invertebrate and the deposition period determine the decomposition rate of CPOM. Thus, the quality of CPOM is different among several litter patch types.
