Dridu Dam Failure Scenarios and Accidental Flood Wave

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

Dridu Dam

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

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

Break scenarios Breaking hydrograph in scenario 2 a 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

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

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

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

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

Input data Upstream boundary conditions Scen ario Maximum inflow discharge (m 3/s) Maximum Flood duration discharge of the caused by the breaking wave dam failure 1349 47 1 - 2 a 1280 2237 116 2 b 1330 2361 76 3 420 1398 144

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

Flood extention - Scenario 2 a

Flood extention - Scenario 2 b

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

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

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

Natural attenuation area downstream Dridu dam break section Stored water volume in the attenuation 6 m 3 area is of about 42 x 10 Flood extention limit in case of scenario 2 b High terrain elevations which determine a “bottle neck ” of the flooded area near Cosereni

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

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

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

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

Conclusions l l 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.