Paleoflood records within Sikhote-Alin foothills during last 2.2 ka

Abstract

The periods of intensification of the frequency of severe floods in Late Holocene were reconstructed on the basis of a multi-proxy study of the section of paleo-bend deposits in the lower reaches of the Bikin River, which includes a peat bog, buried by floodplain loam. The peat bog was formed on the place of flood lake and is represented by interlayering of the layers with a different contents of mineral components, which brought during heavy floods. The criteria for the allocation of phases of abundant river flow were defined. Peat ash content, biostratigraphic data (diatom, botanical analyzes) and radiocarbon dates of the peat bog showed that the flood activity in the foothills of the Sikhote-Alin changed significantly over the last 2.24 ka. The most severe floods occurred in the Medieval Warm Period and warm phases of the Little Ice Age. Duration of periods with strong floods varied from 70 to 200 years. Synoptic situations leading to heavy rainfall were probably similar to modern ones. Strong floods began last 210 yr in the conditions of a trend for warming. Reduction of flood activity, as a rule, occurred in cooling. The intensification of fires took place in drier periods. The response of swamp landscapes to the passage of severe floods and fires has been established.