A simplified model approach to coastal idro-morphodynamical problems

A simplified model approach to coastal idro-morphodynamical problems

Biscayne Bay is located along the south Atlantic coast of the US, in the state of Florida. This area is prone to frequent flooding, and in particular the city of Miami, which is the major settlement and is characterized by a low-lying topography approximately 90% of the municipality lies below 6 meters above mean sea level; (Tompkins 2014). This, along with increasing sea level, with expected rises in between 15 and 30 cm through 2100 (following IPCC 2021 Report), frequent cyclone activity being magnified due to climate change related effects (Mendez 2023), and tidal excursion which can trigger nuisance flooding with relevant socio-economic impacts (moftakhari, 2018), pose significant threats to the assets of the city. De Leo et al (2022) showed a correlation of morphological change in the Biscayne Bay and the rising of the mean tidal range within the bay. This together with the observation of no sensitive change of mean tidal range in near points out of the Biscayne Bay (such as Miami Beach) completed our background.

The gap to fulfill was to demonstrate causation between the morphological change and the rising of the tidal range.

We utilize a reduced-complexity hydrodynamic model based on the de Saint-Venant equations, investigating two different
configurations aimed at reproducing both the historical layout of the bay and the modern one, which has been deeply modified by the development of the Miami harbor.

We assess tidal oscillations within the bay using a generalization of the Bruun [1978] approach for the computation of inlets flow velocity, first revisited by Marchi [1990] and later on by Tambroni & Seminara [2006]; the complete formulation of the generalized model is reported in the Appendix. The bay is modeled as a basin connected to the open sea through a number of inlets considered as straight rectangular flumes with specified lengths, widths, and mean depths. We assume that the dimensions of the basin and of the inlets are small compared to the tidal wavelength, enabling us to neglect any slope in the water level in the bay, which therefore oscillates rigidly.