Theoretical investigation on discharge induced river bank erosion

ABSTRACT

Bank erosion is incorporated in one-dimensional and two-dimensional horizontal models for river morphology. The banks are
assumed to consist of a fraction of cohesive material, which
becomes washload after being eroded, and a fraction of granular
material, with the same properties as the material of the bed. The
banks are taken to be eroded by discharge flow causing lateral
entrainment of lower parts of the banks and near-bank bed
degradation, both inducing mass failure of upper parts of the
banks.
Theoretical analyses
are performed in order to reveal the
influence of bank erosion on the morphological system. From an
analysis of characteristics of the one-dimensional model it is
concluded that generally river widths cannot be stabilized by
protecting certain carefully chosen bank section~ only, and that
computations of river planimetry can be decoupled from the
computations of flow and bed topography. A linear analysis of the
one-dimensional model is used to clarify the interactions between
bank and bed disturbances, whereas a linear analysis of the twodimensional model is used to demonstrate that the input of bank
erosion products decreases transverse bed slopes, but hardly
influences the wave lengths and damping lengths of flow and bed
topography in natural rivers with moderately migrating banks.