Origin and stability of gravel beaches in Croatia: problems and solutions

1. Origin and stability of gravel beaches in Croatia: problems and solutions Dr. Kristina PIKELJ Faculty of Science, University of Zagreb, Croatia Forum Internazionale del Mare e delleCoste 10-13 October, 2018, Forte deiMarmi, Italy

2. Mediterranean • Touristic region • 50% of the coast is rocky Map of the Mediterranean and Black Sea (Furlaniet al., 2014)

3. Natural characteristics of the Croatian coast • Eastern Adriatic coast: • > 90% in carbonates – karstification and bioerosion dominate • ~6% in flysch* – mechanical weathering and wave action • Croatian Adriatic coast is mostly built in carbonates Political and simplified lithological map of the Eastern Adriatic coast (adapted from Pikelj & Juračić, 2013) *flysch - marl - siltstone - sandstone - breccia assemblage

4. 2 1 Dugi Otok Island St. Grgur Island 3 Dugi Otok Island Most common carbonate hard rocky coast – example of fault cliff (1), inaccessible carbonate coast (2), lithologically predetermined island shape (3), submarine spring-Vrulja Vrulja Bay 4

5. Natural characteristics of the Croatian coast • Lack of coastal processes • Low sediment supply • Beaches are exception • Estimation: • total beach length is ~ 5%(National report of the biological diversity , 2009; Pikeljand Juračić, 2013) • Small, pocket beaches • Gravel beaches • Exact number and length of beaches? Political and simplified lithological map of the Eastern Adriatic coast (adapted from Pikelj & Juračić, 2013)

6. Cres Island Krk Island Alluvial fans of recent and fossil flows or formed by wave action in previously weakened carbonates Orientation and dimensions influenced by lithology, karst geomorphology, valley/streams network, drainage area… Fossil beach sediment – geological and geomorphological heritage Istria Vis Island

7. Anthropogenic pressures www.novo.hr • High valued for geomorphological diversity, biodiversity • Mostly undisturbed and in natural state • Highly attracted by tourist • Rapid touristic development – last decade • Demands for beach capacities, accommodation… • Result? Environment degradation www.net.hr

8. Anthropogenic pressures Tourism in Croatia during the last 30 years: No of nights,arrivals and rooms Source: Croatian Beaureau of Statistcics www.novo.hr www.net.hr Structure of tourists by nationality

9. Anthropogenic pressures www.novo.hr • High valued for geomorphological diversity, biodiversity • Mostly undisturbed and in natural state • Highly attracted by tourist • Rapid touristic development – last decade • Demands for beach capacities, accommodation… • Result? Rapid environment degradation www.net.hr

10. Anthropogenic pressures • Environment degradation: • Beach enlargement • Artificial beach construction • Lack of sediment supply – quarried material used (non adequate grain size) • Beach nourishment without suitable environmental studies • Non adequate post-nourishment maintenance/monitoring • Uniform beach appearance • Decrease of coastal form diversity Senj Crikvenica

11. Anthropogenic pressures • Environment degradation: • Rapid urbanization • Massive construction • Sealing of the bedrock – disruption of sediment supply (if any) • Land use change • General loss of sediment on natural beaches Benchmarks used to reconstruct beach morphology in the 60s by means of repeat photography method (figures from: a) 1959, b) 1962, c) 1959) in comparison with actual situation (figures d), e), f ), g), h) from 2017) (Faivre and Micunovic, 2017)

12. Toward solutions… • Number of problems coincide with coastal development • No integrated system of beach management designed to evaluate beach environments (from all aspects; urgently needed) • General lack of data: • Coastal geomorphology • Beach dynamics • Coastal sediments… • Governance (and other) issues: • Coordination of governing bodies on all levels should be improved • Responsibilities of authorities should be cleared • Public awareness and participation should be increased • Enhanced dialogue and collaboration between all parties and stakeholders…

13. Toward solutions… • Ongoing monitoring in some municipalities • Ongoing data collection • Usage of state-of-the-art technology • Ground based and drone based photogrammetry proven to be applicable in coastal environments (cost effective, not time consuming…) • Smart pebbles…the next step • >6000 km of the coastline! • Comprehensive monitoring is challenging on operational and strategic level…and it will take some time… • To enhance initial “screening”, an intermediate step is proposed: • Integration of proven beach monitoring techniques into well-established bathing area water quality monitoring scheme (Ivanković and Pikelj, 2017; Pikelj et al., 2018)

14. Toward solutions… • Over 900 sea bathing areas are monitored • Coastal counties are responsible (Public health institutes) • National database; instantly available online • Future work: • Extension of the database and the monitoring scheme (only for beaches, not all bathing areas) http://www.izor.hr/bathing

15. Toward solutions… • Future work: • Additional education • Comprehensive historic data overview • Extended fieldwork • Benefits: • Identification of erosional hotspots • Once identified, targeted for the future site specific monitoring and management • Uniform methodology • BARE methodology for the comprehensive beach management in the future http://www.izor.hr/bathing

16. What about sediment?... • Local and insufficient river supply and sediment deprived shelf: • Lack of gravel sediment sources • Main challenge in beach erosion management • Production of gravel…?

17. Thank you for your attention! kpikelj@geol.pmf.hr