ABSTRACT
Subsurface water flow in a gravel bar is closely related to the river environment and stream ecological system. In this study, we investigated the characteristics of subsurface water flow focusing on a gravel bar which has various heterogeneous effects, such as hydraulic conductivity and porosity of gravels, and bar shapes, during normal flow stage. A network of wells was established to measure water table elevations in gravel bars of gravel bed river in Tokyo, Japan. Hydraulic conductivity and porosity of subsurface layer were surveyed. The characteristic results of field survey suggested are: 1) the subsurface water almost stop flowing in downstream part of gravel bar based on the consideration of the relationship between the gravel ratio and hydraulic conductivity, and 2 ) the sharp reduction of subsurface water level at inflow side influenced by clogging of fine particles. These above mechanisms are verified using by experiments and the numerical simulation model. Thus, this suggested that the water exchange characteristics through both of surface and subsurface layer in the gravel bar are restrictive.
