ABSTRACT

In contrast to lakes, reservoirs, or wetlands, rivers are characterized by a unidirectional flow where the horizontal movement is the main forcing function. Rivers also have a strong interaction with the watershed receiving allochthonous material such as organic and inorganic suspended matter, leaves, fruits, and aquatic insects. The unidirectional flux controls the sediment deposition and the bottom structure. The physical characteristics that are important in rivers are the width and depth of the river channel, the current velocity and the roughness of the substrate, and the degree of meandering of the river. The declivity of the river is also important, because it determines the pattern of current velocity including the downstream transportation of the suspended material and organic matter (Barila et al. 1981, Drago and Amsler 1981, Drago 1989, 1990).