Changes In Wetland And Floodplain Sedimentation Processes In The Middle Reach Of The Amur River Basin

Remarkable land-cover changes have recently occurred in the Amur River Basin. In particular, cultivated area has increased in China, while deforestation has advanced in Russia. It is possible that these land-cover changes will affect the hydrologic environment of the Amur River and the movement of material through the river. We reconstruct historical environmental changes in the Amur River Basin using floodplain sediments. We focused on the Sanjiang Plain in Northeast China, which is on the middle reach of the Amur River. We investigated sediment profiles on the floodplains of the river and its tributaries from outcrops or sediment cores obtained by hand boring. These confirmed recent coarsening of fluvial deposits at many locations on the floodplain, along the Amur, Songhua, and Ussuri rivers. Here, silt-clay layers were covered by 30-70 cm-thick sandy deposits. We postulate that the grain size coarsening of the floodplain deposits ensued from an increase in peak discharge and coarse material supplied by farmland expansion and forest reduction.