Coastal Erosion Monitoring Methods

Why Systematic Monitoring Matters

The Polish Baltic shore loses and gains sand on timescales ranging from single storm events to decadal trends. Distinguishing short-term variability from longer-term erosional trends requires sustained, spatially consistent measurement. Without a documented baseline, it is not possible to quantify the effect of storm seasons, assess whether engineering works have changed erosion rates, or inform decisions about where to invest in shore protection.

Poland's state coastal monitoring programme has been in operation in various forms since the mid-20th century. The data series collected by IMGW-PIB and, for geological aspects, by the Polish Geological Institute (PIG-PIB) now extend to decades at some sites, providing the empirical record that research institutions and coastal managers draw on.

Traditional Beach and Dune Surveys

The foundational monitoring method is the cross-shore profile survey: measuring the ground elevation along a transect running from a fixed inland benchmark across the dune, beach face and, where safe, into the nearshore zone. Profiles at fixed locations are re-measured at regular intervals — typically annually but sometimes seasonally at dynamic sites — to detect changes in the position of the dune foot, beach face gradient, and berm crest.

On the Polish coast, benchmark positions for profile surveys were established decades ago and are still in use at many stations. Measurements are taken with levelling instruments for precision work and increasingly with GNSS (Global Navigation Satellite System) receivers. A trained field team can survey a series of profiles in a single day of coastal access; the limiting factors are access permissions (particularly within protected areas), weather and the need to avoid active surf conditions that would compromise surveyor safety.

Photogrammetry and Aerial Survey

Aerial photography of the Polish coast has been carried out at irregular intervals since at least the 1950s for military and later civilian purposes. The overlapping photographs from these surveys can be used to construct photogrammetric models of the beach and dune topography. Comparison of models from different dates reveals shoreline migration rates and volumetric changes in the dune face — information not available from single profile surveys alone.

More recently, small unmanned aerial vehicles (UAVs, commonly referred to as drones) carrying compact photogrammetric cameras or LiDAR (Light Detection and Ranging) sensors have transformed the capability for high-resolution dune surveys at the local scale. A single UAV flight over a 1–2 km beach section can produce a point cloud or surface model at centimetre-scale resolution within a few hours. Research groups at the University of Gdańsk and Adam Mickiewicz University in Poznań have used UAV photogrammetry to document dune volumetric changes at sites including Łeba and Rowy.

Terrestrial Laser Scanning

Terrestrial laser scanning (TLS) places a stationary laser scanner at a known position and scans the dune or cliff face in front of it, producing a dense three-dimensional point cloud. The technique achieves millimetre-scale precision at distances of up to 300 metres. Its limitation is a restricted field of view: a single scanner position typically covers 50–150 metres of shoreline frontage, making it labour-intensive for longer coastal stretches.

TLS has been applied in Polish coastal research to quantify dune face erosion following individual storms and to measure the effect of artificial reef placement on dune accumulation rates. The detailed volumetric data from TLS surveys complement the broad-scale coverage from aerial photogrammetry.

Satellite-Derived Shoreline Change Detection

Multi-temporal analysis of optical satellite imagery — particularly from Landsat, Sentinel-2 and Planet Scope — allows automated or semi-automated extraction of the waterline or vegetation line as proxies for the shoreline position. Images from different years are analysed to compute rates of shoreline advance or retreat. This approach covers the entire Polish Baltic coast in a single analysis and is not subject to the logistical constraints of field surveys.

The primary limitation of satellite-derived shoreline data is the ambiguity in defining a consistent coastal reference feature. The instantaneous waterline at the time of image acquisition depends on tidal level and wave run-up, introducing noise into the signal. On the relatively microtidal Baltic coast (tidal range typically under 0.1 m), this is a smaller problem than on open-ocean coasts, but wave setup during wind events can shift the apparent shoreline by several metres. Filtering and calibration against ground-truth survey data are standard steps in Baltic shoreline change analyses.

The EUROSION project, a European Commission initiative, compiled multi-decadal shoreline change data for all EU Atlantic and Baltic coasts. Polish coastal scientists contributed data from the national monitoring system to this database, and the results are accessible through the EUROSION online tool.

Sea Level and Storm Surge Records

Erosion on a sandy coast is driven largely by extreme water level events. The IMGW-PIB operates a network of tide gauges along the Polish coast, with long instrumental records at stations including Świnoujście, Kołobrzeg, Ustka, Gdańsk and Hel. The Gdańsk tide gauge record extends to the 19th century and is one of the foundational Baltic sea-level datasets used in regional sea-level research.

Storm surge records from this network document the dates and magnitudes of events that exceeded critical water levels for dune overtopping. Research correlating these records with observed profile changes has shown that a small number of severe storms account for the majority of multi-year erosion at many Polish beach sites.

The Lubiatowo Research Station

The Institute of Hydro-Engineering of the Polish Academy of Sciences (Instytut Budownictwa Wodnego PAN, IBW PAN) operates the Coastal Research Station at Lubiatowo on the central Polish coast, roughly 40 km west of Gdańsk. The station has maintained a near-continuous programme of beach and nearshore surveys since the 1980s, making the Lubiatowo dataset one of the longest and densest monitoring records on the southern Baltic coast.

Data from Lubiatowo have been used in numerous peer-reviewed studies on beach morphodynamics, cross-shore sediment transport and the response of the beach system to storm sequences. The station also hosts instruments for wave measurement in the nearshore zone, complementing the morphological surveys with hydrodynamic data.

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References

• IMGW-PIB coastal monitoring reports. imgw.pl
• Pruszak, Z., Zawadzka, E. (2008). Potential implications of sea-level rise for Poland. Journal of Coastal Research 24(2), 410–422.
• EUROSION project coastal erosion data. eurosion.org
• IBW PAN Lubiatowo Coastal Research Station. ibwpan.gda.pl
• Rotnicka, J. et al. (2020). Impact of Sea Shore Protection on Aeolian Processes. Geosciences 9(4), 179. mdpi.com
• Polish Geological Institute – Baltic coast geology. pgi.gov.pl