Investigating the Stability of Double-Inlet Tidal Systems Using a Process-Based Modelling Approach

Dastgheib, A.; Wulandari, A.S.R., and Ranasinghe R., 2018. Investigationg Stability of Double-Inlet Tidal System Using a Process-Based Modelling Approach. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 161–165. Coconut Creek (Florida), ISSN 0749-0208.Tidal inlet systems provide a dynamic connection between the ocean and water mass behind their barriers and are subjected to human intervention and natural changes. An understanding of the dynamic processes in tidal inlet systems is important for decision makers managing these areas. Most previous studies are focused on a basin connected to the ocean via a single inlet. But multi-inlet systems have more complexity than the typical single-inlet system, especially considering the interaction among different inlets. In this study, following the realistic analogue approach, we have adopted a morphodynamic process-based model (Delft3D) as a numerical lab and set up a model for a schematized double-inlet tidal system to investigate the stability of such systems. We have carried out a series of simulations and systematically changed the width and initial depth of the inlets and also the amount of sediment coming to the inlet due to littoral drift along the coast. Based on the result of these simulations, first, we developed "Escoffier" type stability curves for each inlet in every simulation. In the second step, we have fixed the cross-sectional area of one inlet and allowed the second inlet to evolve. We used the results of this set of the simulations to develop a 3D stability "Escoffier" curve as a function of the cross-sectional areas of both inlets and equilibrium velocity and identified stable and unstable equilibrium conditions. In the third step, to test these equilibrium points, we altered the stable system in seven different ways to show that the system goes back to one of these equilibrium conditions.