Ground deformation analysis of the Danube Delta using European Ground Motion Service products

The Danube Delta is Europe’s second-largest delta, with an area of more than 5000 km², and has undergone remarkable evolution during the Holocene. The Danube Delta is a UNESCO World Heritage natural reserve, renowned for its diverse and pristine fluvial, marine, and coastal landscapes. Besides its natural features, it has a complex and dynamic geomorphology developed on alluvial sediments transported by the Danube River and includes numerous lakes, fluvial levees, sand dunes, beach-ridge plains, barrier islands, spits, and extensive lagoons, which collectively serve as a preserved record of complex deltaic evolution. Moreover, geologically, the area is known for its position at the contact of two micro-plates (terranes) that accentuate and favour the displacements that add up to the area’s dynamics.

In this work, we aim first to identify areas with significant deformation in the Danube Delta and, second, to discriminate the origins of these deformations. Given its complex geology and geomorphology, the area is affected by both alluvial compaction from the fresh sediment load and by tectonic activity. To analyze this phenomenon, we are using the European Ground Motion Service (EGMS) products, which provide a large ensemble image of the delta’s deformations. The EGMS products enable land deformation monitoring along with other tools and instruments capable of detecting the displacements induced by various natural and man-made geohazards, including land subsidence, sinkhole detection, sediment compaction, volcanic activity, building and infrastructure tilting and sinking, landslides and many others. The EGMS products provide consistent, reliable InSAR measurements of ground deformation with millimetre accuracy and are continuously updated with newly processed data, depending on the programme timeline. These measurements include GNSS-calibrated full-resolution velocity and displacement time series for the ascending and descending orbits, and calculated displacement vectors in the vertical and E-W directions, resampled to a 100 x 100 m grid, which we used to detect large-scale deformations and analyze local, site-related deformations. The results indicate deformations up to 2 cm/year, detected locally, in the built-up areas and, especially, along the channelized Sulina distributary.