A reduced-complexity model for river delta formation – Part 2: Assessment of the flow routing scheme

Abstract

Abstract. In a companion paper (Liang et al., 2015) we introduced a reduced-complexity model (RCM) for river delta formation, developed using a parcel-based "weighted random walk" method for routing water and sediment flux. This model (referred to as DeltaRCM) consists of a flow routing scheme as the hydrodynamic component (referred to as FlowRCM) and a set of sediment transport rules as the morphodynamic component. In this work, we assess the performance of FlowRCM via a series of hydrodynamic tests by comparing the model outputs to Delft3D and theoretical predictions. These tests are designed to reveal the capability of FlowRCM to resolve flow field features that are critical to delta dynamics at the level of channel processes. In particular, we focus on (1) backwater profile, (2) flow around a mouth bar, (3) flow through a single bifurcation, and (4) flow through a distributary channel network. We show that while the simple rules are not able to reproduce all fine-scale flow structures, FlowRCM captures flow field features that are essential to deltaic processes such as bifurcations and avulsions, the partitioning of flux between channels and inundated islands, and the instability of flux distribution at channel mouths which is responsible for mouth-bar growth. Finally, we discuss advantages and limitations of FlowRCM and identify environments most suitable for it.

How much subsidence is enough to change the morphology of river deltas?

“…The model resolves the depth-averaged flow field using a weighted-random-walk method and updates the bed elevation using phenomenological rules for sediment transport [Liang et al, 2015a]. The hydrodynamic performance of the flow routing scheme of DeltaRCM has been assessed against theoretical and high-resolution model results [Liang et al, 2015b]. The hydrodynamic performance of the flow routing scheme of DeltaRCM has been assessed against theoretical and high-resolution model results [Liang et al, 2015b].…”

Ice and Permafrost Effects on Delta Morphology and Channel Dynamics

“…Using the reduced complexity model of delta morphodynamics DeltaRCM (Liang, Geleynse, et al, 2015;Liang, Voller, & Paola, 2015;Liang, Kim, & Passalacqua, 2016;Liang, Van Dyk, & Passalacqua, 2016), we investigate the influences of permafrost and landfast ice on river delta morphology, growth, and channel dynamics. By simplifying physical processes for incorporation into this rule-based model (Murray, 2003), we gain insights into the processes and process interactions most important to Arctic river delta dynamics, which would be difficult to obtain through other methods (e.g., remote sensing or field observations).…”

Delta channel networks: 1. A graph‐theoretic approach for studying connectivity and steady state transport on deltaic surfaces

“…Several recent studies have focused on modeling delta growth and evolution with simple radially averaged models [Parker et al, 1998;Kim et al, 2009aKim et al, , 2009b, detailed hydrodynamic models [e.g., Edmonds and Slingerland, 2007], reduced complexity models [Seybold et al, 2007[Seybold et al, , 2009Liang et al, 2015aLiang et al, , 2015b, and laboratory experiments (see Paola et al [2009] for a review). Using such models for example, the effect of sediment flux and composition on the self-forming patterns of deltaic channels has been studied .…”