Natural conditions

The Kiliya Danube Delta is a young entity formed in the post-glacial period and is situated on novoevksynskyh clays caused by alluvial activity from the Davnodunayskoho estuary. The area is located within parts of Northern Dobruja, which is part of the Scythian plate and includes  parts of the north-western Black Sea and the Prydobrudzhynskoho deflection, which belongs to the East European platform (Zaritsky, 1989).

The secondary Kiliya delta   is the youngest natural  land in Europe, which emerged from the break in the Danube channel coastal sand ridges of Zhebriansky-Letya about 400 years ago on the shallow shelf of the sea.

The Stensovsko-Zhebryyanivski  (abbreviated as  SZHP) formed on the site of the accumulation of silt deposits, which began about 2 thousand years ago between native shores and the sandy Zhebriansky streak.

The delta region is characterized by large fluctuations of land due to the tectonic fluctuations of the Black Sea, including modern sea transgression (Bany, 1965). In the coastal area of ​​the DBR subsidence of 1-2 mm / year (Grew et al., 1990) and in the secondary Chilia delta - 1.8 mm / year. However, continuous alluvial deposits in the delta increase yearly by 2-3 cm (Bany, Buzetany, 1966).

The DBR area is located within the Danube-Dniester subregions and the Black Sea Lowland Plains. The surface of the subregion has a slight slope to the south and east of inclination relative to major tectonic blocks. Depth downcutting in the river and a tier-beam network is very noticeable and ranges from 5-10 to 20-30 cm.   In most low-lying coastal erosion surfaces, morpho sculpture is weakly developed, and the mouth of the sea floods watercourses or wetlands. At higher levels, beams with well developed valleys exist, their slopes are low, with rarely partitioned small ravines. There are also estuaries, lagoons and coves which are separated from the sea by sand and clay ravines.

On the surface, the delta seems almost horizontal, with a slight rise in the northern area. The highest of its parts are the pryruslovi ridges and the coastal spit islands with an average height of 0.5-1.0 m. The center of the islands are relatively flat with low relief lakes and channels.

The Pryruslovi ridge formed along the sleeves of the yerykiv. It is characterized by an asymmetric structure due to developmental activities of watercourses. The highest part of the ridge is located near the watercourses. Toward the center of the island they are falling, which defines the general relief as the last saucer visible. Formation of ridges are directly dependent on the magnitude of sediment, especially during floods, because of their capacity to hold deposits of silt and sand. This explains the much greater part of the ridges on the top of the islands (about 1.0-1.5 m) compared with the lower  area of the islands (about 0.5 m), where flooding is much weaker.
On riverine ridges coastal spits can be seen splaying out into the water. They are formed at some distance from the islands and are the result of interaction between the Danube waterways and the sea. At the initial stage (eg, spit bird) they have more or less significant increases in relief, and are small in length (up to 1.5 km). Coastal spits play an important role in shaping the freshened bays. Increasing in size, they are part of the shallow area separating uzmor'ya from exposure to sea water. They further connect  the upper section of the braid of riverine islands and the ridges formed bay, which gradually transforms into a semi-closed reservoir.  Along with the increase of sediments in the delta, there also seems to be a process of erosion in the coastal areas of the islands.

The Kili branch is the main channel of the Danube Delta for stock and morphometric characteristics. Below the Kiliya sleeves split into three separate parts: Babin, Solomon Chernovka and Direct - these are formed inside the lower delta.  The Marine Delta begins after breaking the sleeve marine ridges, Zhebriansky and Letya. Near  the 18th km of the Kili branch within Vylkove, the Belgorod sleeve departs, and the sleeve is then divided into the Kili Ochakovskiy and Starostambulski sleeves, the latter of which makeup the hydrological and morphological characteristics of the main sleeve. In turn, these sleeves are then divided into other sleeves of a lower order : Midday, Ankudinov, nimble, Vostochny, Limbaugh and others.

The processes   of the delta often affect diking of the coast which prevent the release of water on the broad floodplains, changing slopes, speed, and mode of movement of sediment, especially during periods of active formation of the channel and at the flood.

The marine part of the delta, which is the least disturbed by human activities, is formed by the interaction of large-scale river flows and sea currents. At the sea’s edges, the delta river flow is combined with the sea’s circulation and is dominant in the northwestern part of the Black Sea from the east to the west.   This process is accompanied by a marine estuary and its active extension.  The interaction of river flows and sea currents determines not only sea water regime but, to some extent, water regimes inside the upper and lower Kiliya Delta.

Some delta soils have formed in mineralized groundwater and near hruntotvornyh rocks (the northern part of the delta). Most recently these area s have been dominated by these types of soils: meadow, meadow marsh, swamp and salt marshes. In texture they are heavy and full of clay. In the coastal kosah region, soils are not developed and consist mainly of sand and shell deposits, sometimes with additions of plant residues.

Meadow marsh soils occupy areas with slope riverine ridges, formed in conditions of prolonged flooding (2-3 months) and permanent wetlands. The depth of the soil profile is 30-40 cm .

Wetland soils are formed on all low areas and flooding conditions of prolonged (3-4 months) and groundwater almost at the surface. In the presence of a peat layer they belong to the actual swamp and peat bog. Wetland soils where groundwater is found at a depth of 10-15 (25) cm are confined to the central part of the island. Saline soils are concentrated mainly in the northern and eastern parts of the delta, in depressions in areas under the direct influence of the sea. They are formed under conditions close to groundwater and observed at the surface and throughout the profile with a predominance of salts of chlorides and sulfates.

Saline soils are classified when soluble salts are found on the surface. Salt Flats occupy a small area and almost always form complexes with sod, meadow and marsh and mulovato-marsh soils.

In most of the SZHP sandy and clay soils are common, on the surface is a layer of dendrites, and under it lie the remains of reed - mostly dense plexus of its rhizomes, which promotes the formation of more or less powerful sediments.  In the Stensovsko floodplain sediments are characterized by slightly alkaline and alkaline reactions.

The formation of hydrochemical conditions in the Kiliya Delta is determined by all the processes occurring in the water of the river in its entirety and in its catchment area (Diamonds, Maistrenko, 1961 Diamonds, 1962, Anak, Zhuravleva, 1987; Linnik et al, 1989 , Jacyk et al, 1993).

Water quality is influenced by factors of natural and anthropogenic origin. A major role in this process of waterworks.