Effect of Urban Expansion Intensity on Urban Ecological Status Utilizing Remote Sensing and GIS: A Study of Semarang-Indonesia

The rapid urban expansion will drive land-use conversion and cause substantial environmental and ecological impacts. The ability of remote sensing to record spatial and temporal data on the land surface with complete coverage has been proven effective for recognizing spatiotemporal changes in the regional eco-environment quickly. This study utilized Landsat TM / ETM + and Landsat-8 OLI remote sensing data to assess the effect of urban expansion intensity on the urban ecological status with the study area in Semarang, Indonesia. The method to measure urban expansion uses the urban expansion intensity index and to assess the urban ecological status using an integrated ecological index (IEI). The IEI generated from four parameters which include the degree of greenness (i.e. the soil adjusted vegetation index, SAVI), the moisture degree (i.e. the normalized difference moisture index, NDMI), dryness degree (i.e. the normalized difference soil index, NDSI) and built-up aggregation degree (i.e. the normalized difference built-up index, NDBI). Principal component analysis (PCA) is used to compress the four indicators to construct the index of ecological status and Pearson correlation analysis was used to determine the effect of urban expansion intensity on urban ecological status. The result showed that the urban land area increased by 38.98 km2 with an average expansion area of 3.9 km2 y-1 from 2005 to 2015. The index of urban expansion intensity during 2011-2015 increased about 2.1 times from 2005-2011. The pattern of deteriorating urban ecological status of the city of Semarang spreading towards the west, south, southeast, and east. The lowest integrated ecological index is in the central and northern parts of the city of Semarang. The extent of good and excellent urban ecological status continues to decline in a decade, on the contrary, the urban ecological status of poor and extremely poor increased. The negative linear relationship of the index of urban expansion intensity and urban ecological status shows that the intensity of urban expansion influences the urban ecological status in Semarang city. © Published under licence by IOP Publishing Ltd.