RIPARIAN VEGETATION SEED DISPERSAL AND SETTLEMENT ON BARE SANDBARS IN ALTERNATE AND BRAIDED CHANNELS.

Abstract

 To know the dispersal and recruitment characteristics of pioneer riparian vegetation that first invade bare sandbars after floods, seeds (particles) transported by the flow were investigated using laboratory flume experiments and numerical analysis. Seed dispersal was observed throughout the entire channel during the flood in both alternate sandbars and braided channels. In the case of alternate sandbars, seed settlement occurred locally at the edge of sandbars, during the period of discharge recession. On the other hand, in the case of the braided channel, even under high flow conditions, the main channel shifts and diverges on a small scale, resulting in advance and retreat at the sandbar edge. Therefore, unlike alternate sandbars, particles were widely settled on the braided bars. The dispersal and settlement of buoyancy seeds are strongly controlled by hydrograph shape, channel morphodynamics during floods, and seed dispersal timing rather than seeds characteristics itself (size and specific gravity, etc.), under the conditions of this experiment and numerical analysis.