data for “Morphodynamic differences of migrating and non-migrating mid-bars in the Jingjiang Reach in the middle Yangtze River over 1960-2018”
Description
Abstract：Mid-channel bars are prominent geomorphic components in alluvial rivers, yet our understanding of morphological dynamics of migrating and non-migrating mid-bars remains incomplete. Therefore, we selected the Jingjiang Reach of the middle Yangtze River to elucidate their morphodynamics of migrating and non-migrating mid-bars by topographic data in 1960~2018. The results indicate that under natural conditions, migrating and non-migrating mid-bars exhibit periodic dynamic adjustments with migrating mid-channel bars being more variable than nonmigrating mid-channel bars. Migrating mid-channel bars are characterized by alternate erosion and deposition and non-migrating mid-channel bars are characterized by unchanged size and position. After the Three Gorges Dam (TGD) operation, both migrating and non-migrating mid-channel bars have experienced scouring and erosion, whereas migrating mid-channel bars have experienced severe scouring and shrinkage. Migrating mid-channel bars are characterized by surficial erosion, and non-migrating mid-channel bars are characterized by lateral erosion. Natural hydrological regimes controlled rich sediment supply was responsible for the periodic morphodynamic adjustments in the pre-TGD period. Changes in flow and sediment regimes within the effective flow range is responsible for this erosion adjustments of migrating mid-channel bars in the post-TGD period, while changes in flow-sediment regime and vegetation status are responsible for lateral erosion of non-migrating mid-channel bars. Before the dam construction, the increase in bar top elevation and relative height of nonmigrating mid-channel bars were caused by sediment deposition on bar crest; after the dam construction, the increase in relative height was caused by channel incision. The elevation reduction of migrating mid-channel bars caused by altered flow and sediment regimes makes it difficult to determine the change in relative height.