Extremely Shallow-water Morphobathymetric Surveys: The Valle Fattibello (Comacchio, Italy) Test Case

Abstract

A morphobathymetric survey has been carried out of a coastal lagoon south of the modern Po delta (Valle Fattibello, Comacchio). Acquisition of bathymetric data in such an extremely shallow water environment (more than 80% of the area lies between 0 and ) 1m ) faces technical difficulties that led to the development of ‘ad hoc’ solutions. Methods to obtain morphobathymetric and reflectivity maps of the lagoon are presented, including descriptions of data acquisition and processing. ‘Ground-truthing’ of the reflectivity data, provided by analysis of sediment samples, allowed description of the sediment distribution within the lagoon, and the imaging of sedimentary features. Combined analysis of morphobathymetry and reflectivity maps identified arcuate, sand-rich features not in equilibrium with the present-day ‘low energy’ regime of the lagoon. These features might constitute the substratum over which the lagoon system has been formed, not completely overprinted by anthropogenic and biogeochemical processes at the lagoon bottom.The system we have developed could be used on board remote-controlled or autonomous vehicles that could perform rapid, low-cost surveys and collect data useful for quantitative estimates of sedimentary dynamics. Rapidity and low-cost are important conditions for carrying out periodical surveys, and taking a series of ‘snapshots’ of the lagoon bottom. This would allow predictive geological models on sediment budgets of these complex environments, characterized by multiple sediment sources and sinks that are difficult to quantify.