Research On The Influence Of Landscape Pattern Changes Of Hangzhou On The Hydrological Process Of The Grand Canal(Hangzhou)

The hydrological process of the the Grand Canal(Hangzhou)is of great significance to the rain flood safety in Hangzhou.Based on the theory of pattern-process in landscape ecology,this paper studies the influence of landscape pattern changes of Hangzhou on the hydrological process of the canal.The studying area,determined by the range of the canal water network,is the northern part of Qiantang River in Hangzhou.First,we calculate some landscape pattern indexes through five landscape type maps in the 1980 s,1995,2000,2005 and 2010.Based on the maps and these indexes,we then analyze the landscape pattern changes of the studying area.Next,we use the data of the characteristic water level during 1981-2010 of the Gongchen Bridge station as the hydrological indicator and analyze the trend of the hydrological process of the canal.Through statistical method,we study the potential correlation between the two aspects and find the landscape pattern characteristics which are significantly related to the hydrological process.The research findings are as follows:(1)In addition to the area index,the characteristics of the landscape pattern such as shape,aggregation index also have influence on the hydrological processes,and thus cannot be ignored.(2)The landscape pattern in the northern part of Qiantang River in Hangzhou has changed with the process of urbanization.The main changes are as follows: the area and dominance of cultivated land are declining,instead,the two indexes of construction land continue to increase;the connectivity of construction land is increasing,at the same time,the fragmentation of cultivated land is increasing too;the fragmentation and complexity of the landscape as a whole are on the rise.(3)The lowest water level has a great response to the change of landscape pattern,which shows a significant upward trend over the past 30 years.This is closely related to the following landscape pattern changes: the declining of the cultivated land area;the tendency to be complex in shape of cultivated land;the increasing of construction land area,largest patch area and its aggregation;the increasing of the fragmentation and complexity of the overall landscape.The highest water level is greatly affected by precipitation,and it is also affected by the water landscape pattern such as its area,edge,shape and aggregation.(4)The impact of landscape pattern on hydrological process is limited by precipitation,and the effect of landscape pattern on hydrological process is more prominent when there is less precipitation.The response of the lowest water level to the landscape pattern changes is greater than the highest water level.Finally,based on the correlation between landscape pattern and hydrological process,this paper proposes some suggestions for the restoration of natural water circulation in cities.On the small scale,change the hydrological characteristics of the construction land from impermeable to permeable.On the large scale,consider the influence of the spatial distribution of different landscape types on the hydrological process.This paper can provide a theoretical basis for the solution of waterlogging problems in Hangzhou and for the construction of sponge cities.