Dridu Dam Failure Scenarios and Accidental Flood Wave Propagation 2010-428

1. Maria CHEVERESAN Nicolai SIRBU Dan STEMATIU Radu DROBOT Dridu Dam Failure Scenarios and Accidental Flood Wave Propagation 2010-428

2. Dridu Dam

3. Dridu Dam Height: 20 m Volume: 45 hm3 Purpose: - flood control - water supply for Urziceni town - irrigation of 17000 ha - safety discharge downstream

4. Break scenarios Breaking hydrograph in scenario 1 Progressive sliding of the downstream face of the promontory located on the left side of the concrete spillway

5. Break scenarios Breaking hydrograph in scenario 2a Overtopping of the left bank of the earth dam caused by a flood that can not be routed through the reservoir due to blocking of the gate

6. Break scenarios Breaking hydrograph in scenario 2b Overtopping of the left bank of the earth dam caused by a sliding of the downstream slope

7. Break scenarios Breaking hydrograph in scenario 3 Sliding of one of the bays of the concrete spillway section

8. Modelling steps • Calibration of the steady flow model on Dridu-Tandarei reach • Simulation of Dridu dam break wave propagation using an unsteady model

9. Input data Input data in Stereographic 1970 projection: • Cross sections on Ialomita river • Digital terrain model (DTM) on the area of interest • Dykes position and height • Ortophotos for the area of interest • Roughness coefficients depending on the land cover (Corine Land Cover) • Boundary conditions

10. Input data Upstream boundary conditions

11. Obtained results • Water levels in each cross section for each time step of the simulation • Discharges and velocities in each cross section differentiated between river bed, left and right overbank

12. Flood extention • Scenario 2a

13. Flood extention • Scenario 2b

14. Flood extention detail in case of scenarios 2a and 2b (1) Dyke between Dridu and Barbatescu is overtopped

15. Flood extention detail in case of scenarios 2a and 2b (2) Cosambesti, Marculesti si Bucu dykes are overtopped

16. Time until maximum of the flood occurs in 4 cross sections Flood hydrographs in Cosereni, Ciochina, Slobozia and Tandarei cross sections

17. Natural attenuation area downstream Dridu Flood extention limit in case of scenario 2b Dridu dam break section High terrain elevations which determine a “bottle neck ” of the flooded area near Cosereni Stored water volume in the attenuation area is of about 42 x 10 6 m3

18. Total, partial destruction or flood areas delimitation (1) • total destruction areas: • v x h > 7 m2/s and v> 2 m/s • Partial destruction areas: • 3 m2/s <v x h< 7 m2/s and v>2 m/s • inundated areas: • v x h< 3 m2/s and v<2 m/s where v – cross section average velocity; h – water depth in a point

19. Moldoveni contour limit Moldoveni Partial destruction area Total destruction area Inundaed area Total, partial destruction and inundaed areas delimitation (3) Total , partial destruction and flood areas distribution in Moldoveni

20. Inventory of the affected houses, agricultural land and forests (1):

21. Inventory of the affected houses, agricultural alnd and forests (2):

22. Conclusions • Moldoveni is completely affected by the Dridu dam break , having areas of 12,7 ha with total destruction and 5,2 ha with partial destruction and. The rest of Moldoveni surface is inundated • Partially affected settlements (less than 25% of their surface) from upstream to downstream are : Jilavele, Urziceni, Manasia, Alexeni, Brosteni, Ion Roata, Malu, Axintele, Barbatescu, Crasanii de Sus, Crasanii de Jos, Cazanesti, Ciochina, Piersica, Marsilinei, Andrasesti, Buesti, Poiana, Ivanesti, Ion Ghica, Ciulnita, Cosambesti, Marculesti, Gura Vaii, Bucu, Fratilesti.