Nonlinear Interaction Between the Tide and the Storm Surge with the Current due to the River Flow in the Río de la Plata

DINÁPOLI, MATÍAS G.; SIMIONATO, CLAUDIA G.; MOREIRA, DIEGO

ESTUARIES AND COASTS

SPRINGER

Año: 2020

1559-2723

The Río de la Plata estuary (RdP) is characterized by the large flow of its tributaryrivers ( Q ), with an average of 22,000 m 3 s -1 and an inter-annual variability rangefrom 8,000 m 3 s -1 to 90,000 m 3 s -1 . In this work, the hypothesis that thecurrent due to that flow (CDR) interacts nonlinearly with both the tides and stormsurges is evaluated utilizing water level observations and numerical simulations. Twotide gauge time series gathered at the freshwater tidal zone (FTZ) of the RdP areanalyzed with the novel surrogate analysis. The analysis is applied for periods of high,medium and low Q . Results show that both interactions occur at the upper half of theFTZ and increase with Q . Harmonic analyses support the surrogate analysis?conclusions and show that tide-CDR interaction redistributes the energy among tidalharmonics, increasing asymmetry. Numerical simulations confirm that bothinteractions: ( i ) maximize at the upper half of the FTZ and decrease downstream;and ( ii ) they are modulated by Q ; a rise of about 14,000 m 3 s -1 (interquartilerange) can produce an intensification of 50% and 100% of the amplitudes of the tideCDR and surge-CDR interactions, respectively; and ( iii ) both interactions introduceasymmetries in the water level, with faster rises and slower falls; ( iv ) the quadraticbottom friction is the main source of both interactions; ( v ) tide-CDR interactionrepresents 12% of the water level associated with the tide, whereas surge-CDRinteraction accounts for 5% of the surge peak; and ( vi ) the interactions are significantin the upper FTZ because there, the magnitude of the currents associated with the tideand the surge are comparable to CDR; downstream, the channel widens and CDRdecreases.