Morphodynamics of channel networks in tide-influenced deltas

Abstract

Deltas formed and change by erosion and sedimentation of sand and mud driven by river flow, ebb and flood. Deltas often have channel networks where the upstream river channel splits in several places, known as bifurcations, into two downstream channels. At bifurcations, river flow and the tides distribute sediment over the channel network and determine the development of the entire delta landscape. In most situations in river bifurcations, one of the two downstream branches fills in and is abandoned. For bifurcations with a large influence of the tides, the distribution of flow and sediment is complex and less well understood than in river-dominated bifurcation. This thesis improves our understanding of the morphodynamics of tide-influenced bifurcations. A novel one-dimensional (1D) numerical model was developed to simulate morphodynamics in tide-influenced river networks. The results of the 1D model are validated by a well-established two-dimensional model. The outcomes show that: (1) with tides, channels are less likely to fill in and be abandoned than in river-dominated bifurcation system, and (2) in channel networks with multiple-bifurcations, the final morphological equilibrium strongly depends on the initial conditions, meaning that the delta development is a complex result of the river- and coastal processes and the history of the system.