Between 13 and 18 May 2014 a low-pressure cyclone designated Tamara and Yvette affected a large area of Southeastern and Central Europe, causing floods and landslides. Serbia and Bosnia and Herzegovina suffered the greatest damage, as the rain was the heaviest in 120 years of recorded weather measurements. By 20 May, at least 62 people had died as a result of the flooding, and hundreds of thousands had been forced from their homes. Towns of Obrenovac in Serbia and Doboj in Bosnia and Herzegovina account for most victims, after being inundated by several-meter high waters from nearby rivers.
Floodwaters caused over 2,000 landslides across Southeast Europe, spreading damage across many towns and villages. The rains activated torrents and mudslides, and subsequently several rivers in watersheds of Sava and Morava rose and flooded surrounding valleys. Official counts indicate that over 1.6 million people were affected in Serbia and Bosnia, after a week of flooding.
Assessments of the damage range up to €3.5 billion for Serbia, Bosnia and Herzegovina. Damage in Serbia, jointly estimated by EU, World Bank group and UN officials, stands at 1,55 billion euros. Officials in Bosnia stated that the damage could exceed that of the Bosnian War. The events initiated a large international aid campaign, with numerous countries, organizations and individuals donating humanitarian, material and monetary support for the affected areas.
Meteorological history
On 13 May, a low-pressure area formed over the Adriatic Sea, as polar air from Central Europe penetrated into the Mediterranean basin. The cold polar air mass met with humid subtropical air, leading to very low pressure. On 14 May, the low moved over Southeast Europe, becoming stationary. As a result, extremely heavy rain fell within the region; Serbia (in the area around Belgrade) and Bosnia were most affected. Serbian and Bosnian meteorologists named the formed cyclone "Tamara". On 15 May, the daily amounts of rainfall broke historical records in Belgrade (107.9 mm), Valjevo (108.2 mm) and Loznica (110 mm). By 15 May, the monthly rainfall in Belgrade had broken the historical record (175 L from 1897), reaching 205 L. By Saturday, May 17, the rain had subsided, and the weather gradually became warmer and sunnier, somewhat easing relief and rescue efforts. On 18 May, the cyclone moved further northwest.
The main flooding region was the watershed of the Sava river, which forms a border between Bosnia and Croatia, flows into Serbia, and drains into the Danube in Belgrade. On Wednesday, 14 May, heavy rainfall caused torrential floods across mountainous regions, which destroyed bridges and infrastructure, and caused numerous landslides. The deadliest impact occurred on Thursday, 15 May, when water levels in several right-bank tributaries of the Sava suddenly and uncontrollably rose at an unprecedented rate, flooding towns in their valleys. The Bosna river in central Bosnia completely flooded the cities of Doboj, Maglaj, Zavidovići and Šamac, while the Kolubara, near Belgrade, did the same to Obrenovac; those cities had the major share of victims. Subsequently, the Sava itself rose to record-high levels, threatening the cities of Slavonski Brod, Šabac and Sremska Mitrovica and numerous villages, but the damage was relatively contained as the population, helped by army and volunteers, strengthened flood defenses. Nonetheless, embankments gave way in several places.
Heavy rainfall was also experienced in the region on 3 and 4 May, affecting Romania, Italy and Bosnia. The event produced limited damage but left a number of flooding incidents and high rivers. A state of emergency was declared in parts of Bosnia by local government.
Hydrology
Though heaviest affected areas were in the valleys of the Sava and Kolubara rivers, the center of the flood was the drainage basin of the Bosna river and its mouth into the Sava. Water in the Sava then broke through the newly constructed embankment on the left bank in Croatia and flooded the Lower Syrmia region. The water then uncontrollably rushed into the Bosut river which flows back into the Sava in Serbia. In Serbia, the heaviest floods were in the Kolubara river basin where the major rainfall caused extreme torrents in the mountains, causing the hydrological coincidence, a fact that high tidal waves appeared simultaneously on both the left and the right tributaries of the Kolubara. Rivers of Peštan and Vraničina also spilled over, flooding the surface mine "Tamnava-Zapadna Polje", within the Kolubara mines (see Lake Paljuvi). The flooded mines captured 200 million m3 of the flood water.
Belgrade's Institute "Jaroslav Černi", funded by UNDP, compiled a study "Improvement of the water protection in the Kolubara drainage basin". Hydrological section of the report concludes that the cyclone caused the "continual rain of temperate intensity", which however lasted for too long (over three days). In May, the measured 48-hours rainfall was higher than the millennial rains in Loznica while the return period in Belgrade and Valjevo was 400 years. Return periods of the flow in the Kolubara was 120–520 and at the confluence into the Sava, when the Kolubara flooded Obrenovac and the mines, the discharge was 1,456 m3/s (51,400 cu ft/s). If the system against the floods was finished and functioning properly, and that mines and Obrenovac weren't flooded, the discharge would be 2,460 m3/s (87,000 cu ft/s).
In the drainage basin of the Bosna river in Bosnia and Herzegovina, the rains in some places were exceeding the return period of 5,000 years (Vidmar A., et al., "The Bosna River floods in May 2014", Journal on Flood Risk, p. 1–25). At the same time, during the massive overspill in the basin, the return period of the maximal discharge (4,121 m3/s (145,500 cu ft/s), 15 May 2014) was only 152 years and of the wave volume (1,463,000,000 m3 (5.17×1010 cu ft)) was 189 years. After the reconstruction of the flood in the controlled environment, it was concluded that the discharge of the Bosna at Doboj would be 5,000 m3/s (180,000 cu ft/s) on 16 May 2014. A discharge of the Sava, right after the mouth of the Bosna, at the Šamac bridge, was 6,000 m3/s (210,000 cu ft/s) on 17 May (Abdulaj R., et al., Velike vode donjeg toka rijeke Save tijekom svibnja 2014, Hrvatska vodoprivreda, 207, 14–16, 2014). Downstream, in Sremska Mitrovica in Serbia, the discharge of the Sava was 6,420 m3/s (227,000 cu ft/s) (Hidrološki godišnjak RHMZ Srbije za 2014).
If the entire flood control system in all three countries functioned, and that there were no overspills and floods, a hydrological coincidence of joining the highest Sava and Kolubara water levels would occur. That means that in Belgrade, downstream from the mouth of Kolubara into the Sava, the Sava would bring almost 9,000 m3/s (320,000 cu ft/s). The riparian zone along the Sava in Belgrade, called Savski Nasip and enhanced with the embankments, is designed for receiving 6,500 m3/s (230,000 cu ft/s), so the city would probably suffer a major damage. Additionally, due to the illegal construction of the houses in the Savski Nasip area, the riparian zone is being destroyed and its volume is reduced.
Affected regions
Serbia was the most severely affected, with several major cities in its central region completely flooded, and landslides in mountainous regions. Bosnia, in particular its Republika Srpska entity, was also inundated to a crippling extent. Eastern Croatia and southern Romania also experienced flooding and human victims, while Austria, Bulgaria, Hungary, Italy, Poland and Slovakia were affected by the storm.
Serbia
The city of Obrenovac was hit hardest by the floods, with an estimated 90% of the town flooded. During the night between 15 and 16 May, nearby Kolubara river, collecting waters from southerly mountains, suddenly rose several meters above its banks and flooded the city, catching the residents by surprise. The entire city was evacuated. During 18 May, the water level dropped, which enabled the evacuation of the citizens of Obrenovac to be carried out by trucks instead of boats. As of 20 May the total number of evacuated persons exceeded 30,000.
In Krupanj in western Serbia (located in a valley of several small rivers) torrents, mudslides and landslides devastated the infrastructure and destroyed dozens of houses. Because of road damages, the town was completely inaccessible for three days, and the road to Loznica was blocked until 18 May. Electric power was cut for almost the whole municipality. Around 500 houses were seriously damaged and at least 20 houses are completely uninhabitable Part of the village of Rebelj in Valjevo municipality was annihilated by landslides. In the Drina river valley, on the border with Bosnia, heavy rain activated landslides, cutting off several villages and closing roads. At Mali Zvornik, a giant hill threatened to slide into the river and cut its flow, endangering that town and Zvornik across the river.
Peak flood waters from Sava river hit Šabac on 18 May, but the embankments survived, strengthened by efforts of the army and several thousands volunteers. Flood waters on the river reached 6.3 metres (21 ft), the highest on record, endangering Šabac and Sremska Mitrovica on the left bank. In anticipation of the floods, a 7.3-metre-tall (24 ft) temporary embankment was erected.
Further east, along the valleys of Morava and Mlava rivers, city centers of Paraćin, Petrovac na Mlavi, Svilajnac and Smederevska Palanka were flooded.
During the flooding period, an estimated 300,000 households were left without electric power. Serbia's energy minister, Aleksandar Antić, had appealed to individuals to conserve power as best they can. The largest thermoelectric power plant in Serbia, TPP Nikola Tesla, which supplies close to 50% of electricity in Serbia, lies in the vicinity of Obrenovac, but was saved from danger. However, flood waters filled the largest coal field of RB Kolubara with 210 million cubic meters of water, more than the volume of Vlasina lake, and its pumping out took months, starting in September 2014. Further east, the thermoelectric power plant TPP Kostolac, which supplies 11% of electricity in Serbia, was threatened by floods from the Mlava river, but the water had not breached the innermost ring of defenses. During the floods, the hydro plants at Iron Gates reduced their production and opened the gates in order to lower the level of the Danube.
During the floods, transport across the country, particularly central and western parts, was interrupted or broken. 2,260 public, industrial and infrastructure facilities were flooded, and 3,500 roads were destroyed. The Belgrade–Bar railway was severed at several locations in western Serbia, and has been closed; basic reparations took about a month to complete, and afterwards the trains were forced to take a several-hours detour. Reconstruction of the section in the Gradac river canyon was finished in March 2015, allowing the trains to return to the original route.
Agricultural damage in affected areas was total, and the amount is yet to be determined. Thousands of cows, sheep, chicken and other domestic animals perished in the floods, and their corpses present a serious health risk for people who started returning and repairing their homes.
On 20 May, the Government of Serbia proclaimed 3 days of mourning. Serbian Prime Minister Aleksandar Vučić described the flooding as "the worst water catastrophe that has ever hit Serbia."
In a July 2014 report by the Government of Serbia, the total amount of damage in the country was estimated at 1.53 billion Euro. Of those, 810 million was attributed to direct damage, and 662 million to losses. Two thirds of the damage was attributed to the production sector (500 million direct and 569 million indirect), of which 228 million in the agricultural sector. Total damage on the housing was 227.3 million, while the infrastructure damage (transportation, communications and water management) was assessed at 192 million.
Bosnia and Herzegovina
Most of northern Bosnia was flooded, with the Bosna river valley hitting hardest. Other affected areas included the Sarajevo Canton and Tuzla Canton. Northern and northeastern Bosnia, including the region of Semberija, was also flooded. Rivers that flooded included the Bosna, Vrbas, Drina, Sana and Sava. A state of emergency was declared across the nation. Herzegovina in the south and central regions were not hit by floods.
The town of Maglaj experienced the average rainfall of two months in under 48 hours. In the city of Zavidovići, a footbridge was filmed being swept down the Bosna river and crashing into another bridge. In Sarajevo, the Miljacka river swelled almost to the level of city bridges. The entire hamlet of Parići in Hrasno Donje, municipality of Kalesija, was swept away by landslides.
As of 20 May, there were 24 confirmed deaths in Bosnia and Herzegovina: 17 in Republika Srpska and 7 in the Federation. At a press conference on 19 May, the Director of Police of Republika Srpska gave the names of 17 confirmed victims: 10 in Doboj, 2 in Šamac, 2 in Modriča and one each in Bijeljina, Vlasenica and Donji Žabar; an additional 7 persons are still listed as missing. Governments of the two entities jointly declared 20 May a day of mourning across the country.