Uncertainties Resulting from Changes in River Form

Uncertainties resulting from flood-induced major changes in river form in some drainage basins are of such magnitude that many problems pertaining to the management of water and debris, the management of flood plains, and the effects of man's activities in the basins cannot be resolved except in a probabilistic or general way. For affected basins, major changes in channel form can cause significant differences in the hydraulics of floods, the surface runoff, recharge to aquifers, erosion rates, and sediment yields. Uncertainties develop for several related reasons. The capability does not exist to determine adequately whether a river is susceptible to a major change in form and to predict when a major river-form change will occur. The effects of a local change in river form in a drainage basin usually propagates along alluvium-filled valleys to other parts of the basin, but the propagation process is not understood.