Monitoring Coastal Dune Variations through Remote Sensing on the Southern Coast of Brazil

Frontal dunes protect the coast from storms and flooding and maintain stability in the coastal dune system. Increases and decreases in the size of dune systems can indicate instability in frontal dunes due to natural processes or anthropic and agricultural stresses. Using synthetic aperture radar (SAR) images, variations in the size of coastal dune fields were observed over an eleven-year period from 1996 to 2007 on a 70-mile stretch of the Southern coast of Brazil. Between 1996 and 2007 an overall increase in the area and width of coastal dune fields was observed, where large transgressive dune sheets spread landward due to increasing instability in coastal foredunes. This instability coincided with the cultivation of coastal land for rice and pine trees and increasing cattle ranching. Decreases in the dune field size occurred rarely, in small concentrated regions, and in more populated areas. Other areas, where the size of the dune field varied little, indicate that frontal dune systems were stable and that wind and sediment supply were favorable. Coastal dune systems increased in area and width along the majority of the coast between 1996 and 2007, as observed in radar images, most likely due to recent anthropic and agricultural stresses that increased the instability of the system.