Danube Delta: A lost paradise

The Relief of the Danube Delta
is represented by a sequence of littoral plains continued towards the continental shelf of the Black Sea through a littoral front. As part of the littoral plain, there are two relief forms that make it stand out: levees and fields. Fluvial levees are relief forms obtained through the accumulation of alluvial deposits on both sides of the river's branches or on larger streams. They are alluvial ridges of tens km long, raised 1,5-2 m above the medium level of waters, very narrow (seldom over 100 m in breadth), tending to raise and extended laterally. By the lateral developing, banks juxtaposit, become higher, loosing their geomorphological character and developing into fluvial fields. Marine levees are long sandy ridges (up to 20 km) formed through the accumulation of sand on active riverside lines. When there is plenty of sand, the sandy ridges develop actively, juxtapositing and forming marine fields. Wind will carry on the subaerial moulding by the eolation of sand with the formation of dunes. A distinct relief form is thus obtained, the dune marine field, completely different from typical banks. The term swamp is frequently but improperly used, which term does not designate a relief form but an ecosystem. The deltaic plain borders on the abrupt regions on the Bugeac Plateau to the north, it advances up to the contact with the Razelm lagoon and the Peritesca canal to the south. Within the deltaic plain, during its evolution, two types of plains have distinguished: fluvial and marine. The fluvial deltaic plain stretches on 61% of the delta's area to the east bordering on the contact with the marine plain on the western line of the Letea field - the Raducu-Ceamurlia levees - the western border of the Caraorman field - the Ivancea levee - the western border of the Crasnicol field. The relief of the plain evolves on a stack of sand, sandy-clay and clay-sandy sediments having a fluvial origin accumulated under the river's control. The medium altitude of the whole fluvial plain is 0,6 m. deltaic plains are slightly divided into fragments by both streams, sahales and garle, and by the ridges of the fluvial levees. The medium relief energy is only 1,2 m, 6 m values occur due to damming workings. The typical soils are alluvial and gley soils alternating with histosoils and limnosoils. The salinity of the soils is weak. The marine deltaic plain stretches on 32% of the delta's area, bordering on the contact with the fluvial plain to the west and, to the east, bordering on the deltaic front. The relief displays an alternation of high marine fields (improperly called levees, as seen above) with low marine plains and it develops on a stock of sandy sediments with marine origin, mixed up with peat, biogen lacustrine sediments and fluvial sediments into the banks from the edge of the branches. The relief energy is on an average 3,5 m, the maximum value is 14,5 m due to the presence of the high dunes on the Letea and Caraorman fields. The carbonated or gleizated psamosoils, as well as the histosoils give the specific pedological note.

The salinity of the soils vary from very strong to weak. The secondary deltas of the Chilia and Sfantu Gheorghe branches represent the active part of the delta, where processes of advancing into the Black Sea take place; these processes have extremely different intensities, directions and rhythms as seen above. The lagoonal plain Razelm-Sinoe continues the deltaic plain southwards, forming together the Daanubian coastline of the Black Sea. The low lagoonal plain, mainly lacustrine, overlaps the Razelm,Glovitza, Zmeica and Sinoe basins, it displays an almost plane relief and the relief energy is maximum 3 m. The high lagoonal plain is made up of marine fields with very different altitudes and extensions and extensions formed through the development of marine sandy barriers. The littoral, deltaic and lagoonal plain connects the marine plain, the secondary deltas and the lagoonal plain with the continental shelf of the Black Sea, developing both subaerially and submarinely. The shore is the main element of the littoral front. From the north to the south there are marshy shores of the Chilia secondary delta and of the western Musura gulf, the deltaic barrier Ciotic and Zatonul Mare and Edighiol, the shore of the marine fields Chituc. Except the marshy shores, each type of shore has its characteristic beaches. The widest beaches are at Sfantu Gheorghe. The Sacalin Island is a barrier island formed at the mouth of the Sfantu Gheorghe branch in front of the secondary delta with the same name. At the beginning of the century (1902) there were a few sandy banks, which could barely exceed the sea level. A decade later, it gets the aspect of a barrier of 5 km long, which extends to the southwards and south-west with a medium rhythm of approximately 200m per year, at present time being over 20 km long and having an emerged area of about 6 km2. Unfortunately, these few years the northern part of the island has undergone a process of erosion, which has been destroying most of it. Thus, almost two km2 of the island where there was a field with big dunes and with special biodiversity, has disappeared.