The morphodynamics of super- and transcritical flow

摘要

The fluvial regime prevails in most of the alluvial rivers, during most of the time. However, drastic alterations in river morphology happen during floods: the velocities increase, with possible appearance of supercritical regime. Intense erosion and deposition may disrupt the river feature forming a sequence of breaks in bottom slope. The common Saint-Venant-Exner approach may fail in reproducing such intense transport and also in properly handling the discontinuities in regime. The influence of the hydraulic regime on the solid discharge is analyzed and a two-layer model is proposed, able to cope with intense transport or severe transients. Some results are presented as well in uniform conditions as in dam-break modeling. The model is also promising in modeling the generation of antidunes. Moreover the two-layer approach helps to correctly pose the boundary conditions in morphodynamics, above all if transcritical flow is expected.