ZHANG Jinliang, LI Yan, BAI Yuchuan, XU Haijue, LUO Qiushi, HUANG Zhe

The sediment entering the lower Yellow River has been dramatically reduced, and the geomorphology has changed greatly during the operation of the Xiaolangdi (XLD) reservoir since 2000. However, the floodplain currently faces competition between land development and protection. This research presents a detailed investigation of the sediment temporal-spatial distribution and geomorphological evolution of the braided reach between Huayuankou (HYK) and Gaocun (GC) during 2000-2017, using digital elevation models (DEMs) and the historical bathymetry of the braided reach. During the implementation of the water-sediment regulation scheme (WSRS), the long-term low-concentration flow released from XLD leads to a fully scoured long channel, and effectively reduce the risk of floods on floodplains. However, the floodplains have gradually changed from sedimentation to erosion due to the continual construction of farm dykes and control works, land use changes and other forms of land disturbance, including water and soil conservation measures and climate change. The cumulative eroded volume was approximately 1137.3×106 m3 between HYK and GC from 2000-2017, of which 214.5×106 m3 originated from the floodplains. It is necessary to reconstruct the floodplain domain into different regions via mechanical dredging and other measures, and optimize the use of land resources.

Keywords: lower Yellow River, braided reach, sediment distribution, morphology evolution, floodplain re?construction