Anthropogenic interventions and hydrological-risk phenomena in the fluvial-maritime delta of the Danube (Romania)

The Danube Delta represents the most important wetland of Europe and the manifestation area of periodical spring-summer floods. The hydrotechnical works executed in the Danube Delta between 1950 and 1990 were meant to protect the localities against floods and to facilitate the fluvial transport. For rapid access to the locality of Caraorman (for the exploitation of quartziferous sand) and to the Rosu touristic complex, the Crisan-Caraorman channel was oversized (12 km long, 60-70 m wide, with a maximum depth of 4-6 m). The access mouth of the channel in the Sulina arm and the outlets towards the Black Sea of the deltaic lacustrine complex were poorly designed. The aggradation of the channel determined the increase in the solid discharged carried by the water and the accentuation of the alluvia accumulated in lakes. To facilitate the transit of the fluvial waters towards the Black Sea, a weir was built at the mouth of Lake Rosulet (1.20 m r MNS). Unfortunately, the weir is too high, and the water level within the lacustrine complex increases alarmingly during floods. This is why the locality of Caraorman - situated 25 km away from the Black Sea - becomes flooded. That is, there is an increase in the phreatic level (the localities of Sulina and St. George are also affected but not to the same extent). The topographic and bathymetric measurements and the precise positioning of the targeted critical points (GPS) served as the methods for investigating the deltaic area affected by flooding. The causes of the backwater floods were identified, and the measures of an adequate management plan were set out. To eliminate this impediment, alterations to the hydrotechnical works must be made as follows: reducing the height of the existing weir and building two other weirs with lower crests; dredging the secondary channels and the lacustrine cuvettes; and using shallow-draft ships. The lack of funds and the apathy of the habilitated institutions delays the implementation of the necessary measures. (c) 2014 Elsevier Ltd. All rights reserved.