Download
1 / 27
270 likes | 285 Vues
Effects of Extreme Hydrological Phenomena on the Danube River – Calarasi-Harsova Sector between 2003 and 2006. Author: Salajan Lidia, Hydrologist, National Institute of Hydrology and Water Management. Lower Basin of the Danube. Old Danube. Borcea arm.
E N D
Effects of Extreme Hydrological Phenomena on the Danube River – Calarasi-Harsova Sector between 2003 and 2006 Author: Salajan Lidia, Hydrologist, National Institute of Hydrology and Water Management
Lower Basin of the Danube Old Danube Borcea arm
Short presentation of the Calarasi-Harsova sector from the geomorphologic and hydrographic point of view • This sector is part of the Eastern Romanian Plain, made up of very old crystalline schist (Protorosoic and Paleosoic), and represents a small tectonic plate situated in a slight subduction under the Carpathian Arch plate. • At the end of Pliocene and Quaternary, sands, gravel and loess were deposited. Specific to the Bărăganul Ialomiţei are the flat stretches covered by loess,cove microrelief and tabular plains of lacustrian origin. • This flat plain has mean altitudes of 10-100m and has 2 terraces, an arid climate with scarce precipitation amounts and frost during the winter. It has steppe vegetation and a relatively rare population, gathered in the valley. • From the hydrographic point of view, in this sector, the lower Danube splits into 2 branches: eastwards – the Old Danube, and westwards – the Borcea Branch, which passes through Feteşti and meet again at Harsova.
Satellite analysis of rainfall for the month of August 2003 for the Danube basin
Analysis of the situation on the Călăraşi-Hârşova sector of the Danube river in 2003 • The minimum flow in 2003 recorded the lowest discharges in the last 100 years, as a result of a prolonged drought, due to an air mass of African origin which remained over Europe, with frequent temperatures exceeding 35°C and the lack of precipitation over a very long period of time. • Droughts are detemined by the negative anomaly of the precipitation amounts compared to the climatologic norm within the non-periodic climatic variations, pointing out the driest months or years. • The hydrological drought is dure to the absence of precipitation and high temperatures which lead to an accentuated evaporation of watr from the rivers and lakes and to the decrease of the ground water levels.
Analysis of the situation on the Călăraşi-Hârşova sector of the Danube river in 2003 • The extremely low values of levels and discharges during the interval July-September 2003, determined the shutting down of the nuclear reactor in Cernavoda. • The reactor of Unit 1 of the Nuclear-Electric Power Plant of Cernavoda was shut down on 23 August 2003 and restarted on 16 September 2003. At the Cernavoda hydrometric station, on 23 August 2003, the recorded level was of -187cm, and the discharge of 200 cm/s. • The shutting down of the reactor led to the decrease of energy in the national energetic system, affecting the population and the national economy. • On 24 August 2003, the Danube’s discharge reached a minimum of 1640 cm/s when entering the country (Bazias sector), a value which has not reached since the beginning of the observation period (1840). • Following the evolution of the characteristic levels over the year 2003, it can be noticed that the flood from the spring-summer period is missing, the levels decreasing continuously.
Variation of the levels recorded at four hydrometric station in 2003
Variation of the discharges recorded at four hydrometric station in 2003
Minimum values of the levels and discharges recorded at the Calarasi hydrometric station in 2003
Analysis of the situation on the Calarasi-Harsova sector of the Danube river in 2006 • The floods on the Danube river in 2006, were due to the meteorological and hydrological situation in the catchment during the previous months (February, March) and the sudden snow melting in the upper and middle basin of the Danube, starting with the first decade of March. • This one, together with the liquid precipitation fallen over extended areas in the basin, in April, generated significant increase in discharges at the entry in the country (Baziaş sector)and downstream Portile de Fier, and led to the exceeding of the Attention Levels and the recording of historical discharges in April (16000 cm/s). • From the analysis of the monthly characteristic levels and discharges it can be noticed that high flood of spring-summer is very well emphasized with maximum values recorded in April. • The flood on the lower Danube in 2006 over the interval March-June had the largest discharge receorded over the period 1840-2006. The duration of the high flood was the longest in records, with a return period of 100 years.
Analysis of thesituation on the Calarasi-Harsova sector of the Danube river in 2006. • In order to avoid the flooding of the downstream towns (Cernavodǎ, Feteşti, Galaţi, Brăila) controlled breaches were executed. Thus, on the lower Danube sector (Călăraşi-Hârşova) the follwing breaches were executed: • - On 15 April 2006, 19:00 hrs. a controlled breach was made in the Facaieni section on the Borcea branch to mitigate the flood; • - On 17 April 2006, at 18:00 hrs. a controlled breach was executed in the Călăraşi-Răul section; • - On 22 April 2006, at 17:00 hrs. a breach was made in the Oltina section on the Old Danibe due to thebreaking of the defense dyke. • As a result of these exceptional discharges on the lower Danube in Romania, caused by the breaking of dykes followed by the overflowing in unfitted areas, led to the evacuation of 15.834 people, 154 localities were affected, 1.774 houses were flooded, 443 of which being completely damaged and 134 close to collapse.More than 4.700 households annexes, 64.350 ha of agricultural land, 6,8 km of national roads and 593 km county and village roads were also affected.
Variation of the levels recorded at four hydrometric station in 2006
Variation of the discharges recorded at four hydrometric station in 2006
Satellite analysis of rainfall for the month of Decembre 2006 for the Danube basin
Breahs realizated on the Danube river – sector Calarasi-Harsova (2006)
Assessment of flood effectson the Danube river in 2006 – Călăraşi – Hârşova sector On theCălăraşi-Hârşova sector, the consequence of the Danube’s high waters, according to a statement of the General Inspectorate for Emergency Situations (GIES), caused the following damage: - in the Călăraşi county 1625 ha of agricultural land, hayfields and pasture were flooded, 154 household annexes, 4 houses were damaged and 6 people were evacuated from 8 localities; - in the Feteşti municipality, the Danube overflew the first and the second defense dykes in the Buliga and Parcul Trandafirilor areas. The first defense line deteriorated due to the strong vawes, enabling the overflowing of water over the crowning of the dyke. 500 ha of pastures and 80 ha of agricultural land were flooded, from which 30 ha of orchards; - In the Giurgeni village, at the mouth of the Ialomita river into the Danube, the remuu phenomenon maintained and together with the humidity excess coming from infiltrations (125 ha ouside the localities), 33 households were affected by infiltrations and the water covered a surface of 6000 m2;
Assessment of flood effectson the Danube river in 2006 – Călăraşi – Hârşova sector • In the Stelnica village, 30 ha of pastures were flooded bewtween the dyke and the river bank, 15 households and a surface of 1,8 ha of agricultura land were also flooded; • - în the Vlădeni village, a surface of 420 ha of pastures on the right bank of the Ialomita river was flooded; • - in the Constanţa county, 151 houses were damaged, 324 household annexes were flooded, as well as 3500 ha of agrucultura land and 2.320 ha of pasures; • The most serous problems were in Ostrov, where 52 houses and 125 households were damaged, 3 wills became unusable, the headquarters of 2 institutions and economic agents became also unusable and 60 inhabitants were evacuated. In Oltina, 127 people left their homes. În the 12 localities, 25,5 km of roads, 1,5 km of railways, 9 bridges and footbridges were affected by floods.
Waters flooding the road in the Vlădeni village, Ialomiţa county
Solutions proposed for re-development on the Danube River - Romanian sector • Technical solutions which will be taken into consideration for the rehabilitation of the Danube River, such as:carrying out of cascading polders: • 1. Creation of cascading polders in the already flooded endyked precincts taking into account the large level difference of 2-2.5m between the upstream head and downstream head of the precincts. It is recommended that the selection of the polders should be made as follows: • a. Upstream the confluence of the Jiu river and Olt river with the Danube river in order to attenuate the peak of the flood wave in the upstream sector of the Danube river and reduce the pressure on the dykes on the downstream sector; • b. The polders will be executed near important defense-against- floodobjectives so that the effects would be maximal taking into account the very large volume of the high flood in the Danuberiver compared to the volume of water these polders could store;
Solutions proposed for the re-development of the Danube River on the Romanian Sector It is proposed that cascading polders should be executed in the precincts of the following flooded areas: Rast – Bistreatu-Nedeia, Dabuleni – Potelu-Corabia, Spantov-Manastirea. It will also be taken into account the execution of a polder in the endyked section of Borcea de Sus, as well as in the area created between the longitudinal dykes on the right side of the Danube river on the Galati-Braila sector. • The execution of ring dykes along the Calarasi Raul and Facaieni-Vladeni localities, or, as an alternative solution the relocation of certain localities, function of the social and economic implications, and not last, the reduction of freedom space of the rivers,according to a Ministry of Environment and Forests’ decision.
The controlled breach executed in the Calarasi – Raul section
