Short-term prognosis of development of barrier-type coasts (Southern Baltic Sea)

Abstract

The indiccatory forecasting of coastal zone changes is extremely important in view of proper management of this zone. Intense pressure on the development of coastal areas makes the importance of forecasting changes increased. The study presents prognostic variants (forecasts) for various development trends of the micro-tidal, wave dominated sea coast (Polish part of the Southern Baltic Sea) in the next 15 years. The main idea was to compare changes and to analyse them using various geoprocessing and statistical techniques based on the spatial analyses of different cartographical materials and extrapolation of historical trends. The basic premise for achieving this objective was to implement the problem-solving principle that makes the fewest possible assumptions. The performed works aimed at mapping the course of the shoreline at various time periods revealed significant changes in its location. All the presented forecasts (“shoreline extrapolation models” and “averaged shoreline changes model”) are characterized by certain volatility and specific features. In authors' opinion the “averaged shoreline changes model” is the most suitable for bulk visualization of shoreline changes. It averages short-term variables that can affect transparency of the image. It also allows avoiding the accumulation of errors that can have an imprint on shoreline variations. The largest forecasted shoreline changes may exceed 100 m. However, this value is highly controversial. The forecast based on the course of the dune base shows more stable situation and the expected changes have a marginal extent. The biggest differences between the two prognostic lines generated basing on the rate from periods 2010–2016 and 2001–2016 can reach up to 40 m. The “averaged shoreline changes model” (which in authors' opinion is the most suitable for bulk visualization) indicates the shoreline changes will affect the beach-wide part of the coast (up to almost 70 m). The biggest dislocation of shoreline will occur in the area of the most intense erosion (vicinity of 144–145 km and 155.5 km) and can affect the dune base.