Terrain 3D modelling for the assessment of coastal change in beach and dune systems in Scotland

This paper describes how digital terrain models (DTMs) are derived from aerial photography to assess the rate of change during recent decades in some significant Scottish beach and dune systems. Two sets of metric photographs, at least twenty years apart, were available for each site to generate pairs of raster DTMs for each location. These three-dimensional models were then used to make comparisons of the coastal geomorphology at different dates. Planimetric change in the position of reference lines such as the zero-height above ordnance datum (AOD), the high water mark of ordinal spring tides (HWMOST), or the vegetation boundary, allowed the identification of sand bar development and changes in shoreline position. Volumetric analysis was carried out with geographical information system (GIS) techniques to assess the alteration of dunes, identify blowouts, and quantify rates of erosion and accretion. The availability of coastal sediments was interpreted as a key factor in the evolution of most beach and dune systems.