Diffusivelike buffering and saturation of large rivers.
We use mass balance data from Asian rivers together with a first-order diffusive simplification of the St. Venant-Exner equations to characterize river flood plain processes and discuss the reaction of a large model river to a hill slope supply of eroded masses. The simple analytical solution derived for the long-term profile of the river bed shows that (i) the system converges towards a state in which it reacts to perturbations in erosion of the landscape by small-amplitude oscillations around an average "stationary" state, (ii) to have an effective influence on the river plain profile, the perturbations need to have frequencies smaller than the characteristic frequencies of the river system, and (iii) this river buffering might be linked with a possible long-term saturation of the system carrying capacity.
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UFR des Sciences Physiques de la Terre, Université Paris 7, case 7011, 2 place Jussieu, 75251 Paris Cedex 05, France.