| Yangtze River Delta region is one of the highly urbanized areas, where the rapid expanding ofimpervious surface has became a more and more important factor effecting the river ecosystemhealth，so understanding the pressure response relationship between the impervious surface andriver ecosystem is of fully necessary for environmental planning and management．In this paper,a typical area of the Yangtze River Delta region–Shanghai was selected as the study area.Adopted typical sample analys is combined with GIS land use remote sensing interpretationmethods to determine the impervious area coefficient of Shanghai different land use, analysedthe characteristics of PTIA spatical distribution in Shanghai and explored the relationshipbetween PTIA and socio-economic driving force; Based on the CLUES model, explored thespatial driving force of impervious area distribution, simultaneous ly, made simulation andprediction of the spatial distribution pattern of impervious area; Then, further explored thenon-linear relationship between the impervious area and water environmental indicators with thecurrent focus, and determined the number threshold of impervious area affecting the waterenvironment.Some conclusions are drawn out:1) The PTIA of Shanghai is21.33%, and where is much higher in the central of city than thesuburbs.The PTIA in the central city is64.90%, which is3.37times than the PTIA of suburbs.PTIA that more than50%accounts for12.71%in Shanghai, and that more than30%accounts for25.72%.2) The impervious area coefficient of various kinds of land use types in Shanghai is different.The higher impervious area coefficient of industrial land and old-style residential is0.75and0.73, the lower impervious area coefficient of green parks is0.33. The order of impervious areacoefficient value is: road land and land for municipal facilities> industrial land> public buildingland> old-style residential> modern-style residential> villas> green parks> agricultural landand natural village house.3) The most significant socio-economic driving force of PTIA is population density, and with better performance in larger spatial scale. PTIA shows a more significant logarithmic relationshipwith population density, per unit land area of GDP and industrial output, of which populationdensity is the most significant impact factor. In addition, the relationship exhibits moresignificant at “city-district” scale than “city-suburbs” and “suburbs-town”scale, indicating thatdriving role in the larger spatial scale has better performance.4) More significant spatial driving force of TIA is the distance to sub-main road and sub-mainriver, and the distance to sub-main road has relative significance. The closer the distance tosub-main road, the more distribution of impervious area, the less distribution of permeable areaand water area.5) PTIA has threshold effect on the water quality, the jump point of PTIA is50%, andpreliminary propose that it can be used as urban planning and construction control indicators ofYangtze River Delta region in the future. It demonstrat that there is a clear non-linear relationshipbetween PTIA and water quality index, when the PTIA<50%, fluctuationof water qualityindicators (DO excluded) is not obvious, when the PTIA>50%, water quality indicators showsignificant upward trend, and the threshold effect50%of PTIA is clearly verified for theseindices. However，there is a simple linear relationship and not any threshold effect between PTIAand DO. At the same time，the results also prove that the scaling effect of the threshold effect isnot obvious in the100m~1500m five spatial scales. |
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