According to UNESCO estimates, thereare as many as 3 million shipwrecks spread across the ocean floors, and agreat many of those reside in coastal regions, where they posesignificant danger to passing ships. New research has found that itmight be possible to spot coastal shipwrecks by searching for plumesof sediment in imagery collected by NASA's Landsat 8 satellite.
The risk posed by shipwrecks to passingvessels is significant, so much so that in 2012, the Council ofEurope's Parliamentary Assembly recommended that North Atlanticwaters be mapped and monitored. The problem is, that while knowingexactly where each and every sunken ship resides would certainly beadvantageous, the actual process of mapping them out isn't all thateasy.
In the past, researchers have usedlidar (which uses pulses of light to measure distance) to map coastalregions, and sound-based methods such as echosounders can be used indeep water. But the cost involved in blanket-mapping regions usingsuch methods is too high to make them practical options.
Now, a team of researchers from theRoyal Belgian Institute of Natural Sciences, Ulster University inNorthern Ireland and the Flemish Agency for Maritime and CoastalServices, has turned to freely available Landsat data to help providea cost-effective widespread solution.
The research focused on a coastal areanear the Belgium port of Zeebrugge, making use of data from apreviously conducted echosounder survey of the region to pinpointfour fully submerged shipwrecks. They then used 21 Landsat 8 images,combined with tidal models, to map the sediment plumes that extendfrom the wrecks.
Of the four wrecks, the two that hadsignificant portions of their structure unburied were found to createeasily trackeable sediment plumes. Studying the data, the researchersconcluded that pits in the structures fill with sediment during calmperiods, with that sediment thensurfacing and forming detectable plumes during flood and ebb tides.
While the researchers were looking atknown shipwrecks during the study, they believe that theirmethodology could be used in reverse to identify uncharted wrecks, bypicking out sediment plumes and tracing them back to their source. In the long run, it could provide an effective means of mapping coastal regions, without the need to conduct expensive surveys.
The findings of the work are publishedonline in the Journal of Archaeological Science.
Source: NASA