Formation of parabolic dunes from barchan and transverse dunes along Israel's Mediterranean coast

Abstract

The Mediterranean coastal dunes of Israel underwent a land-use change during the second half of the 20th century. Due to intense agricultural and pastoral activity, the coastal dunes were stripped of natural vegetation until the end of the first half of the 20th century. The barchan and transverse dunes were shaped by strong southwesterly winter winds. A decrease in human activity during the second half of the 20th century brought about a renewal of natural vegetation on the dune crest -the only area with neither erosion nor deposition. The establishment of vegetation on the crest changes the dynamics of these barchan and transverse dunes, so that not all of the sand eroded from the windward side is carried to the lee slip-face; some is trapped by plants. Consequently, there is a change in the shape of the windward slope from convex to concave, and the dune gradually becomes parabolic. In this study we trace the morphodynamics of the dunes by analysing 12 sets of aerial photographs, which were taken from 1944 to 1995. The average rate of advance of 15 dunes has decreased from 3Ð4 m a 1 to 1Ð9 m a 1 , while the vegetation cover has increased from 4Ð3 to 17 per cent during this period.

Remote sensing and spatial analysis of aeolian sand dunes: A review and outlook

“…For some dune fields, archival black and white aerial photographs have been used to great advantage, providing long temporal baselines and reasonably high spatial resolution (e.g., Gaylord and Stetler, 1994;Tsoar and Blumberg, 2002;Hugenholtz and Wolfe, 2005a;Marín et al, 2005;Levin, 2011). When the photos are converted to digital images and rectified they can be subjected to image analysis routines that generalize or classify the scene into the dominant surface covers.…”

“…In Israel, studies indicate a relation between dune stabilization in the second half of the twentieth century and concomitant changes in land management practices, particularly the suppression of various forms of disturbance (cutting of vegetation, grazing, and trampling: Tsoar and Karnieli, 1996;Tsoar and Blumberg, 2002;Kutiel et al, 2004;Seifan, 2009;Fig. 5).…”

“…Beginning with images from the early 1970s, remote sensing (RS) has revealed a rich diversity of dune field patterns on Earth, Mars, Venus, and Titan. The synoptic perspective provided by remote sensing imagery has, however, only recently stimulated a shift away from the singledune studies popularized in the 1980s and 1990s (Livingstone et al, 2007) towards dune field-scale studies that incorporate spatial analysis (SA) of boundary conditions, dune activity, dune patterns and hierarchies, and dune-dune relations (e.g., Tsoar and Blumberg, 2002;Hugenholtz and Wolfe, 2005a;Kocurek and Ewing, 2005;Mitasova et al, 2005;Ewing et al, 2006;Bishop, 2007;Wilkins and Ford, 2007;Ewing and Kocurek, 2010a,b;Hugenholtz and Barchyn, 2010;Kocurek et al, 2010).…”

Vegetation Against Dune Mobility

“…When the vegetation cover grows, barchans apparentely undergo a transformation into parabolic dunes with arms pointing upwind and partly colonized by plants (Fig. 1, top center-right), a metamorphosis that has been seen as the first step of dune inactivation [6,7,8,9].…”

“…Therefore, we introduce an heterogeneous seeding by allowing plants to germinate only where no erosion occurs, establishing a competition for their survival with the mobile sand. Such a scenario could for instance be the consequence of the cessation of human activity [9], an increase of the annual precipitation or a reduction of the wind strength in a dune field [7,20], all of them stimulating conditions for vegetation growth.…”