Quantification of openness and wave activity in archipelago environments

Abstract

Ecological and geomorphological processes in the littoral zone are greatly influenced by waves. Despite its importance wave exposure is not often quantified as a spatial parameter in coastal research. We present three GIS-based approaches for openness and wave exposure assessment in archipelago environments. First, we studied openness by fetch measurements: a theme map of sea area openness showing average fetch lengths for 1 km 2 study cells over the SW-Finnish archipelago area of 16 900 km 2 was produced. Second, we calculated wave exposure based on average wave power values for shoreline points to create a shoreline exposure classification within the same study areas. Finally, we made temporal graphs to study the variation in shoreline wave power and work at selected sites during a four-year period. The fetch and wave power calculations using GIS provide interesting possibilities for spatial studies concerning shoreline exposure in fragmented archipelago environments. Different kinds of numerical information of the shoreline exposure are required for diverse purposes in coastal regions: the average fetch maps assess effectively the sea area openness, and shoreline exposure and the temporal graphs quantify parameters relevant to littoral processes.