By Arno Timmer (The Netherlands)
A cross section of a coastal profile is a descending slope, often with upward deviations. The upward deviations are near shore sandbars and they majorly influence the energy and angle of waves that reach the shore. The dynamics of these sandbars have been studied intensely. The way they are studied changes with technology. Because of the increase in both temporal and spatial extent of the data, GIS offers an opportunity to study the sandbars over a large amount of time and a large spatial extent. This thesis proposes a method to identify sandbars along the Dutch North Sea coast, and calculates the volume, shape and movement within coastal areas and coastal regions. Sandbars are detected based on the direction of their slope, the aspect. The volume is calculated by summing the volume above the lowest point in the sandbar. Sandbar shape is quantified by calculating the basin elongation. The movement within a coastal area is calculated by using the average location of a sandbar in grid cells. All sandbar characteristics are compared among coastal areas and coastal regions.
The sandbar detection method influences the calculated volume and the identified shape. The volume is theoretically slightly under estimated, although the found volumes were close to the volume numbers found in literature. The theoretical underestimation is non-structural and depends on the slope of the shore. The shape of sandbars is found to be more elongated than round. The movement profiles identified in this research show a distinct spatial pattern within the studied coastal areas. The resulting cross shore movement is not significantly different from movements found in literature.