Research: Forvie Sands

Dune evolution on Forvie Sands

Original text

The Sands of Forvie occupy an area about 1 x 3 miles, 15 miles north of Aberdeen. The unusual condition of sand blowing along the shore from a southern 'reservoir'. rather than inland from the sea, produces a succession of dune ridges or waves orientated at right angles to the coast rather than the more usual arrangement parallel to the shoreline.

Aerial photos and map, 1 & 2, show the orderly arrangement of seven almost parallel waves of sand moving approximately northwards, no: 1 being the oldest. Each wave consists of one or more U_shaped dunes side by side, and open to the 'dominant' wind. The orientation of the mobile dunes 4 - 7 can be mathematically related to frequency and velocity of Aberdeenshire winds. North of wave 4, where sand moves over ground 100 feet above sea level, the effects of winds from the land has resulted in a deflection in direction of sand movement, thus causing a clockwise curvature from the south to the north of the area.

The parallel waves vary in form. 4, 5, 6, 7 are mobile wandering domes of sands, sand at their foredge lapping forward at a rate of 1-50 yards per annum. While the main wave 'bow' moves at right angles to the 'dominant' wind, 'arms' of sand are held back by greater moisture and fixation, parallel to the 'diminanant' wind. Waves 4 - 7 represent the earliest and least colonized dune stage ~ the wandering dune, Fig:3.

Figure 3. Windward face of unfixed wandering dune, moving to left.

Leeward face of a similar dune at Culbin, advancing to the left