Submarine geomorphology of tidal channels in the northern Venice Lagoon, Italy

The morphodynamics of coastal tidal wetlands and salt marshes are closely tied to the tidal channel networks that link these ecosystems to the sea. Tidal channels, shaped by strong currents and dynamic bathymetry, are vital for sediment transport and key ecological functions in coastal environments. They act as pathways for sediment, nutrients, and organic matter, supporting the health and resilience of tidal wetlands. These networks provide essential ecosystem services, including erosion control and habitats for fish and shellfish, which are crucial for biodiversity and fisheries.

However, tidal wetlands face growing threats from human activities. Dredging disrupts sediment transport and alters flow patterns, leading to habitat loss. Increased navigation accelerates bank erosion and raises water turbidity, degrading habitat quality. Coastal infrastructure, such as seawalls and dikes, further fragments these ecosystems, disrupting natural hydrological processes. Climate change exacerbates these pressures through rising sea levels and more frequent storms, accelerating wetland degradation.

Understanding the geomorphology and sediment dynamics of tidal channels is critical for managing these ecosystems, to mitigate natural and human-induced changes, enhance biodiversity, and promote sustainable management. Geomorphological studies often rely on satellite imagery and aerial surveys to analyze channel morphology and path changes. Seismic surveys and laboratory experiments contribute to understanding large-scale and fine-scale geomorphic processes. However, few studies employ high-resolution multibeam echosounder systems to document the detailed underwater morphology of tidal channels, with limited work on their three-dimensional structures.

This study aims to deliver a detailed 3D mapping of the seafloor morphology and sediment distribution in the tidal channels of the northern Venice Lagoon (Italy), one of the most studied coastal lagoons globally. While many studies have explored the migration and evolution of Venetian tidal channels, fewer have focused on high-resolution 3D mapping of their underwater features. We conducted morphometric analyses and classified channel substrates by means of high-resolution multibeam echosounder data validated with grab samples and video footage. The approach integrated bathymetric derivatives, expert geomorphic interpretation, and supervised classification of acoustic backscatter to produce a comprehensive understanding of tidal channel features.

The findings reveal fine-scale details of tidal channel seafloor geomorphology, providing new insights into their structure and functioning. This research enhances our understanding of tidal channel dynamics and offers valuable information for preserving and managing these critical ecosystems effectively.