Satellite data detects shipwrecks

The European researchers have found a way to use freely available Landsat satellite data to detect shipwrecks in sediment-laden coastal waters.

The study, conducted in a coastal area off of the Belgium port of Zeebrugge, relied on a detailed multibeam echosounder survey of wreck sites, previously conducted by the Flemish government. This part of the Belgian coast is strewn with shipwrecks, in often sediment-laden waters. The researchers started with the known location of four fully submerged shipwrecks.

Using 21 Landsat 8 images and tidal models, the researchers mapped sediment plumes extending from the wreck locations. They found that the two ships with substantial portions of their structure unburied created sediment plumes that could be traced downstream during ebb and flood tides. The researchers postulate that the exposed structure of these ships created scour pits that then fill with fine sediments during slack tides (the period of relatively still currents between ebb and flood tides).

These scour pits then serve as sediment repositories from which sediments are re-suspended during flood and ebb tides. When these sediments reach the surface, they create their telltale plumes. Uncharted shipwrecks could be located by using the researchers' methodology in reverse - ie mapping sediment plumes during various tidal stages and then following the plumes upstream to their point of origin.

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