Infragravity Wave Propagation and Transport in a Small Estuary

Abstract This study investigates infragravity wave propagation in the Nilahue River estuary, a small Intermittently Open/Closed Estuary (IOCE) on Chile’s Pacific coast (34.48º S; 72.00ºW). The estuary, critical for ancient sea-salt production, experiences artificial breaching due to reduced river discharges and energetic swells that enhance sediment accumulation at the river mouth. Field measurements conducted in August 2023, during low river discharge, spring tides, and high swells, revealed that infragravity waves propagate at least 3 km upstream the estuary during flood tides. Data from acoustic Doppler velocimeters confirmed infragravity wave-driven scatterer fluctuations potentially affecting sediment transport dynamics. A second experiment conducted in July 2024 expands on these findings by incorporating turbulence, echosounder, salinity and turbidity measurements to improve our understanding of IG waves’ role in sediment transport and mixing in IOCEs.