The Huanghe (Yellow River) and Changjiang (Yangtze River) deltas: a reviewon their characteristics, evolution and sediment discharge during the Holocene

Citation
Y. Saito et al., The Huanghe (Yellow River) and Changjiang (Yangtze River) deltas: a reviewon their characteristics, evolution and sediment discharge during the Holocene, GEOMORPHOLO, 41(2-3), 2001, pp. 219-231
Citations number
62
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Earth Sciences
Journal title
GEOMORPHOLOGY
ISSN journal
0169-555X → ACNP
Volume
41
Issue
2-3
Year of publication
2001
Pages
219 - 231
Database
ISI
SICI code
0169-555X(20011115)41:2-3<219:TH(RAC>2.0.ZU;2-Y
Abstract
Today, Asian rivers play an important role in delivering sediment from the land to the oceans. However, past sediment discharge before human activitie s modified the landscape is not well known and is estimated to have been ro ughly one-third to one-half of the present level. Chinese rivers have been strongly influenced by human activities, and their sediment discharge has c hanged over the last 6000 years. For the study of the long-term human impac t on rivers and catchment basins, Chinese rivers provide excellent examples because continuous historical records are available. Here, the characteris tics, evolution and sediment discharge during the Holocene of the deltas of two large Chinese rivers, Huanghe (Yellow River) and Changjiang (Yangtze R iver) are summarized. The Huanghe and Changjiang deltas are different with respect to coastal env ironments, water and sediment discharge, the pattern of development of the delta lobe, thickness of Holocene sediments, and basal topography of the in cised valleys formed during the last glacial period. The Huanghe Delta is c haracterized by a high concentration of sediment, huge sediment discharge, thin Holocene deltaic sediments, a lateral delta lobe shift, and a steep lo ngitudinal profile in its lower reaches. The Changjiang Delta is characteri zed by a large water discharge, a large interseasonal water-level change, a tide-dominated coastal environment, continuous seaward progradation with i solated river-mouth sand bodies, thick Holocene sediments, and a deep-incis ed valley formed during the last glacial period. Based on the sediment volume of prograding deltaic sediments over the last 6000 years, the sediment discharge of Huanghe 1000 years ago is estimated t o have been 1 x 10(8) tons/year, 1/10 of the present level. An abrupt incre ase occurred at ca. 1000 years ago as a consequence of human activities on the Loess Plateau, especially involving cultivation and deforestation. More over, the estimated sediment load of Huanghe at Sanmenxia station prior to 1000 years was 2.7-4.0 x 10(8) tons/year, or about 20% (15-25%) of the pres ent level. Our recent study estimated that the sediment discharge of Changj iang before 2000 years BP was ca. 2.4 x 10(8) tons/year. Total sediment dis charge of both rivers before 2000 years BP is estimated to have been 3.4 x 10(8) tons/year, or only about 20% of the present level. Moreover, the tota l sediment load to the lower reaches is estimated to have been 5-6 x 10(8) tons/year, or one-fourth the present level. (C) 2001 Elsevier Science B.V. All rights reserved.