1. The role of episodic water level variations for the dynamics of Danube Delta coastal zone Sebastian Dan 1,2 and Adrian Stănică 1 1. National Institute of Marine Geology and Geoecology GeoEcoMar, Romania. 2. Delft University of Technology, Faculty of Civil Engineering and Geosciences, The Netherlands.

2. Outline: 1.Objective 2.Study zone 3.Methods - water level variations - aerial beach response 4.Results: - water level variations - aerial beach response 5.Conclusions

3. 1. Objective To identify the most vulnerable beach sectors to the water level variations induced by storm surges: - water level - aerial beach response

4. 2. Study zone Turkey Ukraine Russia BLACK SEA Danube Delta Bulgaria Romania

5. 10 km Sulina Sf. Gheorghe 2. Study zone Portiţa Inlet Canalul cu sondă Câşla Vădanei Zătoane Periteaşca -5m -10m Sahalin advance 5-10 m/year erosion up to 20 m/year migration > 20 m/year erosion 1 m/year 1 million m 3 /year

6. 3. Methods Water level variations: - numerical modelling. Process-based numerical model Delft-3D: - SWAN module waves; - FLOW module water level variations. Ten storm scenarios based on 10 years of wind records: - from north to south-west; - from 15 to 40 m/s; - one extreme case.

7. 3. Methods Aerial beach response: - extension of flooding – 10 profiles, 3 years (1995 – 1997) MSL Aerial beach Height 0.67 – 2.52 m Length 13.6 – 93 m

8. 4. Results Water level variations Sulina Sf. Gheorghe x10 6 4.98 4.97 4.96 4.95 4.94 4.3 4.4 4.5 4.6 4.7 4.8 x10 5 x coordinate (m) y coordinate (m) 50 45 40 35 30 25 20 15 10 5 0 (m) N wind direction: north wind speed: 40 m/s Water level variation expressed in centimetres

9. 4. Results y coordinate (m) Sulina Sf. Gheorghe 4.3 4.4 4.5 4.6 4.7 4.8 x10 5 50 45 40 35 30 25 20 15 10 5 0 (m) x10 6 4.98 4.97 4.96 4.95 4.94 x coordinate (m) wind direction: south wind speed: 30 m/s Water level variations Water level variation expressed in centimetres N

10. 4. Results Sulina Sf. Gheorghe c) y coordinate (m) x10 6 4.98 4.97 4.96 4.95 4.94 4.3 4.4 4.5 4.6 4.7 4.8 x10 5 50 45 40 35 30 25 20 15 10 5 0 (m) x coordinate (m) wind direction: north-east wind speed: 40 m/s Water level variations Water level variation expressed in centimetres N

11. 4. Results Aerial beach response

12. 4. Results Aerial beach response

13. 4. Results Aerial beach response

14. 5. Conclusions Variability of the water level variation along the Danube Delta coast due to change in the coast orientation. Largest rates of flooding: Sulina – Sf. Gheorghe area, already vulnerable. A catastrophic event (north-easterly wind, 40 m/s) would breach the dunes, with significant consequences: - input of the salt water in a fresh water environment; - destruction of infrastructure; - potential flood of parts of the Sf. Gheorghe village. The floodable inland areas are part of the DD Biosphere Reserve. Need for rapid intervention on the most vulnerable parts of the Danube Delta coast. Sulina Sf. Gheorghe Sahalin Portiţa Inlet -5m -10m

15. Acknowledgements EC FP6 no. 044122 project Concepts and Science for Coastal Erosion Management (CONSCIENCE) – numerical modeling. Romanian National Research Core Programmes (1984 – present) the field measurements.