THE INFLUENCE OF EVALUATION METHOD OF FLOW RESITANCE AND POROSITY ON 2D RIVERBED VARIATION CALCULATION IN GRAVEL-BED RIVERS

Abstract

 This study focuses on "riverbed environment" which is the foundation of the stream ecosystem in the upper and middle reaches. This study aims to develop a numerical simulation model that can directly evaluate habitat of organisms dependent on riverbed at the same time as calculating flow and river bed variation in reach scale by changes in flow rate and sediment supply from upstream. The Nays 2D solver of iRIC which is one of the general horizontal two - dimensional riverbed variation solver was improved, and the improved model coupled with the grain size distribution, flow resistance, porosity was implemented. Reproduction calculation of the past representative meandering flume experiment was carried out, validation was performed on riverbed topography and mean grain size distribution on the surface. As a result, it became possible to obtain the information necessary for habitat evaluation of the riverbed, but also the precision of riverbed variation calculation itself improved, especially on the sorting phenomenon.