Experiments on the deterministic and non-deterministic effects of water inflow on sedimentary configurations during the lacustrine delta evolution

Abstract

The development of river-delta systems possesses some stochastic characteristics even under slow-varying external conditions. In this study, two sets of repeated physical modeling experiments were conducted to explore the deterministic and non-deterministic effects of the upstream river-inflow on sedimentary configurations in lacustrine shallow-water delta. The statistical analysis of the fluctuation characteristics of sedimentations indicated a commonness of the tendency of a quasi-deterministic mature state under the same sediment supply, and also deterministically, the average value, average amplitude, and average frequency of the geometrical characteristics of sedimentations were negative, positive, and positive correlated with discharge within the Runs-Averaged works respectively; non-deterministically, some outliers of average frequencies of the sedimental indicators revealed the variation of disturbance properties around the highly-active deltaic sections, and, the exceptional average amplitudes of both the indicator of sedimental height near the inlet and the indicator of sedimental width far from the inlet demonstrated the different modes of energy transformation during the process of systematic evolution. Furtherly within the Runs-Repeated works, in low-discharge cases, the unbalanced sediment transportation along the quasi-equiprobable anticlockwise-clockwise diverging directions from the polar perspective resulted in the remarkably negative relationships of both the average amplitude of the indicator of sedimental center and average frequency of the indicator of sedimental height versus the corresponding average values; in high-discharge cases, the uncertainties of the indicator of sedimental width always become prominent accompanied by the weakening of flow instability. This study innovatively interprets a new probabilistic way of understanding the deltaic sedimentations.