Based on river structure data in 1960s

1980s and 2009

the change characteristics of river structure of urban central area in Hangzhou City of Zhejiang Province nearly 50 years were analyzed with river density

water surface ratio

development coefficient

river network stability

connection rate and practical combination degree from aspects of quantity

structure and connectivity features. Results showed that:(1) The length and area of the whole river network showed a decreasing trend except that in the secondary river in 1960s-1980s had a small increase. River density and water surface ratio showed decreasing trends since 1960s.(2) Compared with 1960s

development coefficient of river network increased in the secondary river and reduced in the tertiary river in 1980s

which decreased in 2009

the river stability also decreased.(3) River connection rate and practical combination degree decreased

which made the river connectivity decrease slightly in 1960s-1980s. While in 2009

the river connection rate and practical combination degree decrease dramatically

the river connectivity also decreased distinctly

which made the flood risk increased simultaneously.