Land Use/Cover Classification And Spatio-temporal Analysis In Qiantang River Watershed, Zhejiang Province

Qiantang River Watershed(QRW)is situated at the Yangtze River Delta where is one of the economically most developed areas.For the past decades,the economics and population of QRW have a swift growth,the land use/cover changes remarkably and the Gross National Product(GNP)increases substantially year by year.The area has becomes one of economic development fastest areas in China.However,soil and water resources have not been used and conserved properly in the course of economic development,which leads to the water quality declination and the environment quality deterioration.Previous research indicated that the proportion and changes of land use/cover in the drainage basin was the primary reason why the quality of water and soil declined and the ecological environment deteriorated.Along with the swift development of economy in QRW,there is an urgent need for us to utilize and manage the land resource scientifically and effectively.Therefore,using the remote sensing technique to classify land use/cover,to monitor land use/cover changes over space and time domains will have extremely vital significance to the sustainable development of QRW and even the entire Zhejiang Province.The paper found that the SAM method by integrating TM imagery and slope data was simple,efficient,and straightforward,and it had greatpotentials to be applied in the area with complex physiography and diversed land uses.Then using this method,the thesis studied the dynamics of land use/cover of QRW and performed spatio-temporal analysis for the land use/cover of the area in 1991,1997 and 2004,Which could convey substantial information for supporting the land use structure optimization and provide deep insight for the management of land resources in a scientific manner.The major results from this thesis were as follows:1.Land use/cover classification using multi-source data with SAMLand use/cover change is one of main causes and components of global change.It has been a great challenge for imagery interpreter that how to classify remote sensing imagery with high accuracy and apply in the area with complex physiography and diversed land uses.By using multi-source data with spectral angle mapper(SAM) algorithm,this study tested the effectiveness of these data.Fuyang City,Zhejiang Province was selected as the study site,while Yiwu City of the Province was as a verification site.Results showed that slope information provided the best assistance in land use/cover classification,comparing with other source data such as Elevation, Aspect,normalized difference vegetation index(NDVI),normalized difference water index(NDWI),normalized difference build-up index(NDBI)and normalized difference bareness index(NDBaI).In comparison with the result from TM data only,the classification accuracy with the slope information added increased by about 10%. The SAM method by integrating TM imagery and slope data is simple,efficient,and straightforward,and it has great potentials to be applied in other study areas.2.Land use/cover dynamic monitoring of Qiantang River Watershed in 1991,1997 and 2004With the classification scheme of by layers,regions and sub-region,the study areas were divided into 3 layers,16 regions and 87 sub-regions according to the local characters of geomorphology and landform.Land use/cover in 87 sub-regions of QRW in 1991,1997 and 2004 were classified with SAM from TM images and slope data.The classification results were assessed by the method of examining the random points and by the method of contrasting field-measured points.Both results of accuracy assessment showed that the classification accuracy of all three years were about 80%,with Kappa coefficients above 0.70.The main findings of land use/cover dynamic Of QRW in 1991,1997 and 2004 were:forest relatively invariant;paddy field decreasing, built-up increasing yearly;dry land/garden stable from 1991 to1997,while decreased significantly in 2004;and there was little change of water area in 1991 and 1997,whereas it increased in 2004.3 Spatio-temporal analysis of land use/cover dynamics of Qiantang River Watershed from 1991 to 2004Between 1991 and 2004,built-up was the hotspot type since its changing ratio was the largest;dry land/garden and water were the sensitive types of land since they changed frequently.The diversity of land use/cover kept increasing between 1991 and 2004,with the highest change from 1991 to 1997 in QRW.Land use/cover equilibrium kept increasing,while it was diminishing for some dominant types in QRW from 1991 to 2004.Nowadays,land use/cover of QRW has been gradually approaching the balancing point.Zhuji City and Yiwu City were the hotspot of land use/cover change from 1991 to 2004 in QRW.Zhuji City, Suichang County,Xiaoshan District,Fuyang City,Tonglu County and Yiwu City were the hotspots of land use/cover change from 1991 to 1997,while Xiaoshan District,Jindong District and Wucheng District were the hotspots of land use/cover change from 1997 to 2004.The gravity center of water and built-up shift dramatically.The gravity center of built-up drifted most towards northeast,while water towards southeast;The gravity center of paddy field,dry land/garden,forestland drifted slightly,and their directions were north,northwest,and southwest in sequence.