Spatially, DIVA works on a database of linear coastline-segments. A polygon of the global coastline is divided into segments of coast with a homogeneous socio-economic and bio-physical characteristics. To do so, the polygon is cut at all positions where one of the underlying raster layers (coastal morphology, tidal type, population density, etc.) or polygon layers (country, administrative unit) change. The global default database of DIVA contains 12,148 segments. This technology can be downscaled to a finer resolution. On regional or national level often more detailed versions of the digital coastline as well as of the underlying bio-physical or socio-economic layers are available. Thus, local versions of the DIVA database can be developed. Downscaling has been applied for several countries and regions (Croatia, Tunisia, China, Maldives, German Baltic Sea coast, Emilia Romagna coast).

Fig.1 – The coastal segments of the global database for Germany and neighboring areas (left) and the digital coastline of Croatia (right). Global version in white and downscaled version in red. While the global version provides 29 segments for Croatia, the downscaled version provides 1,560.

For each segment a (stylized) model of the coast is populated with data from various sources. For example, to compute flooding impacts, areas and population numbers on different elevation levels are needed. Digital Elevation models, digital gridded population data and night-time illumination data are used to compute current exposure to extreme water levels (flood events).

Fig.2 – Digital elevation data (upper left, red: area below 2.5m, grey: area from 2.5m to 10.5m, blue: area above 10.5m above sea-level), current annual subsidence rates (upper right, blue=0 mm/year and red = 3 mm/year), digital population data (lower left, the darker the color the higher the population density) and night-time illumination data (lower right, the lighter the color the brigther the night time illumination) for the mekong delta in Vietnam.