Hydrometeorological risk phenomena in the Alba iulia – Turda Depression. Romania CĂTĂLINA MĂRCULEŢ1, IOAN MĂRCULEŢ2, 1. Institute of Geography, Bucharest, Romania 2. "I.L. Caragiale" National College, Bucharest, Romania e-mail: [email protected] Abstract In order to assess the vulnerability of communities to extreme hydrometeorological phenomena, observations on their onset and development should aim at quantifying intensity and frequency, also establishing and foreseeing possible damage. The present study focuses on a few atmospheric phenomena registered in the Alba Iulia – Turda Depression over the 2002-2006 interval, given that the damage incurred involved aspects of risk. Hazardous atmospheric phenomena, heavy rainfall in the main, led to other natural risks affecting both the environment and the socio-economic activity. Apart from atmospheric causes, the risk for other natural events are related to local particularities, e.g. lithological structure (sandy-clay substrate), landform (slopes and highly fragmented relief) and soils (little forestland and grassland due to human pressure – dominantly arable land and numerous human settlements). Houses and annexes, as well as socio-economic constructions were damaged, lots of animals and poultry perished, national, county, communal and forester's roads, bridges and foot-bridges were washed away or disaffected, crops were flooded, trees were brought to the ground, electrical and telephone networks were destroyed. Heavily affected were the road infrastructure, the hydroelectrical constructions the socio- economic units, the electrical and telephone networks and agriculture generally. The number of catastrophic situations, unusually high in 2005, represented 44% of all the interventions made over the past ten years to limit and remove flood effects. Negative hydrometeorological phenomena were found to occur mainly in summer, especially in June and July when torrential rains and floods are common. Significant damage is recorded also in spring (March, April), when snowmelt coupled with rich precipitation may trigger extensive flooding. Analysing the above situations we could say that most flood events were registered in small drainage basins and in torrential basinettes. Limiting the negative effects calls for the afforestation of slopes in the affected drainage basins, the construction of dams, the execution of works to consolidate or even change the direction of the roads running close to some watercourses. Key words: hydrometeorological risk phenomena, risk management, Alba Iulia – Turda Depression, Romania. Introduction A vast research programme within the International Decade for Natural Disaster Reduction (IDNDR) was implemented in the last decade of the 20th century. The programme, carried out under the UN aegis, had in view to contribute to diminishing the effects of natural disasters. The conclusion was that such interdisciplinary efforts should continue. As a result, the International Strategy for Disaster Reduction, put in place at the beginning of the 21st century, was aimed at intensifying multidisciplinary research efforts concerning the impact of hazards on society, this time with highlight on risk management instead of risk protection. The idea was to have risk prevention strategies included into sustainable development plans. Awareness of the fact that 90% of the natural hazards are triggered by weather, climate and water, made Disaster Prevention and Mitigation the theme of the 2006 anniversary of the World Meteorological Organization (WMO). The findings revealed that 65% of all natural disaster-induced economic damages registered over the 1992-2001 period were caused by hydrometeorological disasters. While natural hazards cannot be avoided, integrating risk assessment and early warnings into measures to prevent and reduce them may hinder risk effects from growing into disasters. _________________________________________________________________________________ BALWOIS 2008 - Ohrid, Republic of Macedonia - 27, 31 May 2008 1/7 Appraising the vulnerability of communities to extreme phenomena implies observations to enable quantifying the intensity and frequency of events, outline and predict damage. Therefore, systematic studies of meteorological observations on natural hazards and their impact represent a reliable risk management basis. Case-studies (2002-2006) In line with the introduction, the paper expounds on some hydrometeorological phenomena that affected the environment and society of the Alba Iulia – Turda Depression (a subunit of the Transylvanian Depression which lies in the central part of Romania) over the 2002-2006 period. • July 16-18, 2002 registered marked atmospheric instability manifest by a strong cyclonic activity due to a high temperature-pressure contrast between Mediterranean and Polar masses of air at the eastern periphery of the Azore Anticyclone. Central Europe was crossed successively by cold and warm fronts along a median line, starting from the Balkan Peninsula and moving northwards towards the Scandinavian Peninsula. This swift succession of front lines was felt also on the territory of the Alba Iulia – Turda Depression, unleashing heavy rainfalls, locally torrential, thunderstorms, gusts of wind and local hail-associated showers. The strong rainfalls enhanced run-off on slopes, floodwaves in catchments, entailing alluvial material and causing damage to households, roads, croplands, electrical and telephone lines, etc. Apart from atmospheric causes these risk phenomena were enhanced by the area’s lithology (sand- clay substrate), landforms (slopes and much fragmentation), soils and a reduced forest and grass cover, the consequence of human activity (mainly arable land use and lots of settlements). The quantity of rain fallen on those three days and registered by met stations and rain-gauge points stood between 36.7 mm and 69.6 mm. They represented 50-90% of the July average (observation points Ocna Mureş, Benic and Ighiu). The rains fallen within 24 hours reached 59.2 mm at Ocna Mureş, 44 mm at Benic and 30 mm at Ighiu. However, torrential local precipitation produced damages also in other localities than at the observation sites (Fig. 1). The losses incurred by these extreme phenomena at Aiud, Cugir, Livezile, Pianu and Stremţ amounted to 5,966,000,000 lei (ca. 180,000 €). • June 2, 2003, rain started pouring on Ţelna Village, Ighiu Commune between 16.00 p.m. and 17.20 p.m. Their torrential character (43 mm at Ighiu) entailed run-off on slope. One person caught in the events went missing. In 22 locations households, sheds, gardens, wells, cellars and kitchens were filled with flood-carried mud. Thunderstorms damaged the Ighiu substation and electricity supply was briefly cut (Fig. 1). • April 13-14, 2004, torrential showers formed floodwaves on the Mureş, Arieş, Ampoi, Geoagiu, Galda, Pianu rivers and their tributaries, run-off on slope and landslides. Heavy rainfall values averaged over 20 l/m2/24 hrs, with 42.8 at Sebeş, 38.4 at Ighiu, 32.0 at Benic, 31.9 in Alba Iulia, 30.0 at Teiuş, 28.2 at Blaj, etc. Water quantities were not excessive, but the intensity of precipitation led to channel waters swiftly rising and to overflows on most watercourses (Fig. 1), with violent manifestation of the floods on small streams, in particular. That water levels would rapidly grow over large areas was made possible also by the incipient stage of vegetation, the poor forest cover in the respective drainage basins, the steep slopes and the water- saturated soils. These violent phenomena reactivated and enhanced erosional processes and deposition of alluvia in channels. The outcome was damaged roads, bridges and foot-bridges, households, croplands, etc., most affected being the settlements of Sântimbru and Stremţ. • July 23, 2004. Torrential rains associated with hail fell in the Galda, Geoagiu and Ighiu drainage basins, totalling 41.0 mm/24 hrs at Benic, 40.0 mm at Ighiu, 41.0 mm at Bărăbanţ and 48.2 mm in Alba Iulia. As a result, level increases and overflows occurred on the small streams (without hydrometric control) and in the gully area of the Galda River basin. The floods carried big quantities of sediment, depositing it at the slope-foot of the limitrophe terrains and in stream channels. Bank erosion was also reactivated and amplified. At Galda de Jos, squally winds blew and hail stones of up to 10 mm in diameter fell; Benic, the most affected settlement, was hit by a 45 mm-long rain-and-hail storm that left 15 houses roofless, _________________________________________________________________________________ BALWOIS 2008 - Ohrid, Republic of Macedonia - 27, 31 May 2008 2/7 destroying almost all vegetable gardens and orchards; at Mesentea, Galda de Sus and Cetea, crops were washed away in proportion of 25%, 65% and 70%; 50% of the Galda de Jos vine culture was lost. The Galda de Jos hailstorm affected 50% of the 510 hectares of cultivated land (180 ha of orchard, 260 ha of cereal crops, 45 ha of vine culture and 25 ha of vegetables). Estimated losses were close to 3 billion lei. In Stremţ Commune, run-off on slope destroyed some 0.22 km of the County Road 750 C, estimated loss 50 million lei (Fig. 1). On that day, the Stremţ, Galda de Jos, Gârbova, Pianu and Şibot communes totalled a loss of 6,080,000,000 lei (ca. 140,000 €). • March 17-18, 2005. Sudden temperature rises associated with snowmelt increased water-flows up to flooding levels, affecting households and croplands. On March 15, a gradual warming process began, with a peak on