Acta Geographica Sinica ›› 2015, Vol. 70 ›› Issue (5): 819-827.doi: 10.11821/dlxb201505012

• Orginal Article • Previous Articles     Next Articles

Temporal and spatial change of stream structure in Yangtze River Delta and its driving forces during 1960s-2010s

Longfei HAN1(), Youpeng XU1(), Liu YANG1, Xiaojun DENG1, Chunsheng HU1,2, Guanglai XU1,2   

  1. 1. School of Geographic and Oceanographic Sciences, Nanjing University, Nanjing 210093, China
    2. College of Territorial Resources and Tourism, Anhui Normal University, Wuhu 241000, Anhui, China
  • Received:2015-02-11 Revised:2015-04-12 Online:2015-05-20 Published:2015-06-11
  • Supported by:
    National Natural Science Foundation of China, No.41371046;The Commonwealth and Specialized Program for Scientific Research, Ministry of Water Resources of China, No.201201072, No.201301075;Natural Science Foundation of Jiangsu Province, No.BK20131278

Abstract:

Spatial and temporal variations of river systems in the Yangtze River Delta (YRD) during the 1960s-2010s were investigated based on streams derived from the topographic map in the 1960s, 1980s and 2010s. A list of indices, drainage density (Dd), water surface ratio (WSR), the ratio of area to length of main river (R), evolution coefficient of branch river (K) and box dimension (D), were classified into three types (quantitative, structural, and complex indices) and used to quantify the variation of stream structure. Results showed that: (1) quantitative indices (Dd, WSR) presented a decreasing trend in the past 50 years, and Dd in Wuchengxiyu, Hangjiahu and Yindongnan decreased by about 20%. Structurally, the Qinhuai river basin was characterized by a significantly upward R, and K value in Hangjiahu went down dramatically by 46.8% during the 1960s-2010s. A decreasing tendency in D was found to dominate the YRD, and decreasing magnitude in Wuchengxiyu and Hangjiahu peaked for 7.8%, and 6.5%, respectively in the YRD. (2) Urbanization affected the spatial pattern of river system, and areas with a high level of urbanization exhibited least Dd (2.18 km/km2), WSR (6.52%), K (2.64) and D (1.42), compared with moderate and low levels of urbanization. (3) Urbanization also affected the evolution of stream system. In the past 50 years, areas with high level of urbanization showed a compelling decreasing tendency in quantitative (27.2% and 19.3%) and complex indices (4.9%) and trend of enlargement of main rivers (4.5% and 7.9% in periods of the 1960s-1980s and 1980s-2010s). (4) Expanding of urban land, construction of hydraulic engineering and irrigation and water conservancy activities were the main means.

Key words: stream structure, spatial and temporal change, urbanization, Yangtze River Delta