In this note, we assess the validity of weak turbulence theory by numerical
ly investigating a three-parameter nonlinear dispersive wave equation. The
predicted power-law solutions are explicitly determined and then compared w
ith the numerical results. For both signs of nonlinearity, we show that the
weakly turbulent regime is strongly influenced by the presence of coherent
structures. These are wave collapses and quasisolitons. (C) 2000 Academie
des sciences/Editions scientifiques et medicales Elsevier SAS.