Modelling fine-grained sediment transport in the Mahakam land–sea continuum, Indonesia

Abstract

Mahakam land-sea continuum, fine-grained sediment, finite element model, coupled

Tidal river dynamics: Implications for deltas

“…Resolution flexibility captures the multiscale nature of the nonlinear development of a tidal wave propagating from deep water into a tidal river. For example, the horizontal mesh resolution of the model by de Brye et al [], later used by Pham Van et al [, ], decreases from 10 km in the coastal ocean to 100 m in the upper reaches of the tidal river. Finite element and finite‐volume numerical methods are well established for hydrodynamic modeling purposes, yet it is only recently that such models have become a realistic option without having recourse to a high performance computing facility.…”

“…Using a finite‐volume model referred to as Delft3D Flexible Mesh [ Kernkamp et al , ] in a 2‐D mode, Achete et al [] took a first step toward the modeling of sediment dynamics and the associated ecological parameters in the San Francisco tidal wetlands. Flexible mesh numerical models have the promise to reproduce sediment transport in tidal rivers and the adjacent wetlands from source to sink [ Pham Van et al , ; Achete et al , ] and to allow coupling between processes governing flow, sediment transport, morphology, and ecology over a range of spatial and temporal scales.…”

Numerical Simulation of Water Renewal Timescales in the Mahakam Delta, Indonesia

“…with c k being an appropriate constant, and ∆ is the local characteristic length scale of the mesh. A value c k = 0.018 m 0.85 /s, which was calibrated from the best fit to the available salinity at 60 field sampling sites (see Figure 3) [42], is used to evaluate the diffusivity coefficient. The boundary and the initial conditions under which Equations (1) and (2) are to be solved are listed in…”

“…The latter is parameterized under the form of Equation 3, in which the local characteristic length scale of the grid is taken to be the distance between two channel cross-sections (i.e., 100 m). Equation 13is also solved the same way as governing equations in the 2D sub-domain (see details in [36,42]). A water parcel at open sea boundaries, which are located at the entrance and at the outlet of the Makassar Strait, is assumed to never return into the delta, and thus a value θ e = 0 is imposed.…”

“…A maximum value of 9 days is obtained in the main southern and northern fluvial channels (i.e., transect 1 and transect 2), while the maximum age is about 11 days in transect 3. A nonlinear increase of the age of water from the upstream to the downstream boundaries can be explained by the decrease of the flow velocity along the transects, which is due to changes in bathymetry, channel cross-section, tidal effects, and meandering and curvature of channels [36,42]. On the other hand, to investigate the effect of the tides on the water age, the standard deviation of the water age is also calculated at each location along the three considered transects, resulting in values lying between 0.5 and 4 days.…”