We investigate the morphodynamics of river-influenced barrier basins numerically, with a particular emphasis on the effects of landscape and hydrodynamic settings. The simulated morphologies are qualitatively comparable to natural systems (e.g., tidal inlets along the East Coast of the USA). Model results suggest that the basin morphology is governed by the relative importance of tidal and fluvial forcing which is reflected, to the first-order approximation, in the ratio (r Q ) between the mean tidal and river discharge. In agreement with empirical knowledge, the model indicates that riverine influence can be neglected when r Q is larger than 20. On the other hand, the river may dominate when r Q is smaller than 5. Pronounced differences in morphodynamic evolution are observed for different landscape settings (i.e., initial basin bathymetries and river inflow locations), indicating their fundamental importance in governing the evolution of barrier basins. Model results also show that the addition of a river tends to compensate the flood dominance in the tidal basin. Overall, the river flow has limited influence on the volumetric change of tidal flats, while it plays a more important role in determining the depth of the tidal channels and the size of the ebb delta. The riverine sediment source appears to be more important in shaping the basin morphology when the fluvial forcing is stronger. Finally, we show that the presence of a large river in a tidal inlet system influences the performance of the widely adopted relation between tidal prism and inlet cross-sectional area.

The morphodynamic responses of tidal networks to anthropogenic reclamation and de-reclamation projects are investigated through a three-stage numerical simulation. In the first stage, the natural development of tidal networks is modelled in an open coast without any anthropogenic interventions. At the beginning of the second stage, parts of the computational domain are enclosed by sea dikes, which represents the implementation of the reclamation project. These sea dikes are removed or opened in the third stage to simulate the recovery of the tidal networks after de-reclamation. Each stage was set to last 100 years. The model results indicate that land reclamation can lead to three effects on tidal network morphology: (i) completely terminating the development of channels inside the projected area, (ii) hindering the development of the channel network in front of the dikes, and (iii) turning the channel direction near the corners of the dikes. When removing all the sea dikes, the previously reclaimed areas are quickly occupied by tidal networks. However, the morphology cannot be fully restored to its original natural state, although the entire reclaimed areas are returned. The effects of opening breaches are relatively slow, and tree-like network structures are formed inside the reclaimed areas.

A new methodology is developed to extract tidal network from hydrodynamic conditions, and use data derived from numerical modeling or field observations to test the hypothesis that tidal networks are characterized by scale-invariant properties. Different tidal network configurations have been obtained from long-term numerical simulations in an idealized basin. These simulations show the influence of hydrodynamic conditions (tidal range, TR) and sediment (grain size sediment, D 50 ) on the final configuration of the network. One of the signatures of scale-invariant behavior is related to the presence of a power law relationship in the probability distribution of geometrical characteristics. For each model configuration and field site, the probability distribution of drainage area and the drainage volume has been calculated, and in both cases tidal networks show scale-invariant characteristics. After assessing the sensitivity of the results, an energy expenditure analysis shows that tidal basins evolve toward a state with less morphodynamic activity, with a lower energy expenditure compare with the initial state.

Abstract. Long-term simulations (3000 yr) of an idealized basin using different tidal ranges (1, 2 and 3 m) and grain sizes (120, 480 and 960 μm) have been performed in order to cover a range of hydrodynamic and sedimentary conditions. Two different cell sizes (50 and 100 m) have been used to study the impact of cell size on tidal network development. The probability distributions of the drainage area and the drainage volume have been computed for every simulation (during an ebb and a flood phase). Power law distributions are observed in drainage area and drainage volume distribution. As an objective estimation of the exponent of a power law is an open issue, different approaches (linear binning, normalized logarithmic binning, cumulative distribution function and maximum likelihood) proposed by White et al. (2008) to estimate the exponent have been used to carry out a sensitivity analysis. Our findings indicate that although all methods results in high and significant correlation coefficients, more work is needed to develop a universal, objective estimation of the exponent.

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