An inherent non-equilibrium sediment transport regime introduces autogenic processes, which can dynamically alter the base level of upstream reaches of a river. This affects safety of navigation and flood protection measures therein. An experiment has been conducted to investigate the characteristics of autogenic processes, such as:the formation mechanism, evolutional characteristics, fluctuations, and trends in a riverine environment. Wandering of depositional lobes, headward silting and erosion, channel switching, and avulsion have been observed in the experiment, and the growth and wandering of lobes controls the autogenic processes. An intrinsic threshold was found to affect the aforementioned autogenic processes. The results of the experiment showed that the critical sizes of depositional lobes, time period of fluctuations, power of headward waves, and fluctuations in upstream water-level differed with different inflow and sediment discharges. The inherent driving force and criticality of autogenic processes, and their inter-relationship with deltaic morphology, were discussed on the basis of the experimental results.