The studied area is located in Hungary, one of the deepest parts of the Carpathian Basin. Körös Rivers (it means Fekete-, Fehér-, Kettős-, Sebes-, Hármas-Körös) is belonging to Tisza river drainage basin that is the second main watercourse in the country. The Körös catchment area is 27,537 km2, but 53% is in Romania, and 47% is in Hungary. Vast areas of the Hungarian Plain were flooded by the Paleo-Tisza and its affluents; and the river itself had not fix bed. The settlements were threatened by the enormous flood hazards returning year by year. The flood control has a long history in Hungary, because barrages were already built in 1613 along Tisza and other rivers. The real work started (with mapping) when a big flood was happened in the Körös–Berettyó region, in 1816. The Körös river regulation plan was made by M. Huszár, who distributed the work, and gave the depth and width of the bed, barrages distance and dimension. He determined the width of the active floodplain: by Hármas-Körös 379 m, by Kettős-Körös 246 m, by Sebes-Körös 246 m, by Fekete-Körös 190 m, by Fehér-Körös 114 m. The river regulation of the Danube and Tisza, and their affluents, was the most important reform in the remaking of nature in the 19th century Europe. These impacts were filled the requirements of the era’s economic and social assumption. Low and a high water level database were made for the time interval between 1907 and 2006 with two water gauges in case of analysing the regime of Hármas-Körös River. The low water level had occurred in winter time (57%) in Gyoma (first water gauge), the lowest was -116 cm on 3rd August in 1930. The highest water level had happened in the first five month of the year. The highest water level was 918 cm on 9th July in 1970. The biggest difference was 943 cm in 1919. In Kunszentmárton (second water gauge) the lowest water level had happened in winter time (69%) as well, and the lowest water level was -240 cm on 24th August, 1946. The highest water levels occurred in January, March, April, and May. The highest water level was 1041 cm on 21st April, 2006. The biggest difference was 1134 cm in 2006. We are dealing with measurements of alluvial deposits of floodplain, as well. The sampling was made at the Hármas-Körös River in Takács-zug. The aim of the study to find out the amount of flood deposits on the floodplain after the river regulations. Geomorphological mapping was made near Kunszentmárton and Öcsöd in scale 1:10 000. The new map demonstrates some paleodrainage system of the study area. The thickness of alluvial deposit is increased with 150–180 cm after the river regulations on the study area. The greater part of mapped area is high floodplain; a low floodplain is deepening into this, which was perhaps a fossil riverbed. This low floodplain was occupied by Körös River. The deposits of the last few year of the 20th century could be easily recognized; it is 5–13 cm by floods.