The Danube's flow capacity at Patlageanca is 6470 sq m/sec the same with Volga's flow capacity. The branch with the biggest flow capacity is Chilia: 58%, followed by Sfantu Gheorghe: 23,2 % and Sulina: 18,8%. The biggest lacustrine complex is Razim-Sinoe, laying its territory over 700 sq m, and joining together Razim, Sinoe, Zmeica and the Golovita lakes.
The Danube Delta is a plane region - an alluvial plain in continuous formation in which the Chilia plain, the continental ridge Stipoc and the bank ridges Letea and Caraorman arise, a few meters higher, witnessing the erosion of the Baragan plain. On the last two, Letea and Caraorman, formations of forests appeared. 20% of the Delta territory is under the zero level of the Black Sea, and 80% is above this level. The highest bank ridges are Letea=12 m and Caraorman. The depth of the three arms is also of great importance: Chilia - 39 m and Sfantu Gheorghe - 26 m, Sulina - 18 m and 34 m at Tulcea. The average altitude of the delta is of +0.52 m and the depth in the lacustrian depressions do not exceed 3 meters.
The Delta has two different kinds of bank ridges: sea bank ridges, perpendicularly on the Danube's branches and river bank ridges, all across the Danube's branches and the main brooks.
The bank ridges on the sea shore, in the east of the Danube Delta, namely Letea, Caraorman, Saraturile, Crasnicol, stretch for 27,000 hectares of surface. The bank ridges along the river, which stretch for 20,000 hectares, go along the branches of the Danube, the main brooks broadening towards the top of the Delta, resembling to 2-5 m tall alluvial fields.
The continental lowlands are witnessing the erosion of Bugeac Plain and are formed of loess deposits. The marsh lands are covered with water and paludal vegetation and stretch for approximately 67% of the surface. The lakes are placed in depressions set under 0 meter in the West (the fluvial Delta) and under 0,5 m in the East (the sea Delta), where they form lacustrian complexes. Among the biggest lakes in the Delta we can mention: Dranov - 2,170 ha, Rosu - 1,445 ha, Gorgova - 1,377 ha, Lumina - 1,367 ha, Isac - 1,100 ha, Merhei - 10,507 ha, Furtuna - 997 ha.
The branches, brooks and main canals cover a surface of measuring around 9,900 ha, among which the best known are Lopatna, Pervolovca, Sontea, and among the canals - Litcov, Sireasa, Eracle, Mila 35.
The floating reed islets are a sight for sore eyes, the vastest floating reed islet being placed in the Rosu-Puiu-Lumina lacustrian complex. A floating reed islet is a mixture of roots, common reed, herbs, soil and organic remains agglomeration, these islets particular evolution turning into a very dangerous one when it comes to block certain navigation canals.