Remote sensing-based artificial surface cover classification in Asia and spatial pattern analysis

Abstract

Artificial surfaces, characterized with intensive land-use changes and complex landscape structures, are important indicators of human impacts on terrestrial ecosystems. Without high-resolution land-cover data at continental scale, it is hard to evaluate the impacts of urbanization on regional climate, ecosystem processes and global environment. This study constructed a hierarchical classification system for artificial surfaces, promoted a remote sensing method to retrieve subpixel components of artificial surfaces from 30-m resolution satellite imageries (GlobeLand30) and developed a series of data products of high-precision urban built-up areas including impervious surface and vegetation cover in Asia in 2010. Our assessment, based on multisource data and expert knowledge, showed that the overall accuracy of classification was 90.79%. The mean relative error for the impervious surface components of cities was 0.87. The local error of the extracted information was closely related to the heterogeneity of urban buildings and vegetation in different climate zones. According to our results, the urban built-up area was 18.18×10 4 km 2 , accounting for 0.59% of the total land surface areas in Asia; urban impervious surfaces were 11.65×10 4 km 2 , accounting for 64.09% of the total urban built-up area in Asia. Vegetation and bare soils accounted for 34.56% of the urban built-up areas. There were three gradients: a concentrated distribution, a scattered distribution and an indeterminate distribution from east to west in terms of spatial pattern of urban impervious surfaces. China, India and Japan ranked as the top three countries with the largest impervious surface areas, which respectively accounted for 32.77%, 16.10% and 11.93% of the urban impervious surface area of Asia. We found the proportions of impervious surface and vegetation cover within urban built-up areas were closely related to the economic development degree of the country and regional climate environment. Built-up areas in developed countries had relatively low impervious surface and high public green vegetation cover, with 50-60% urban impervious surfaces in Japan, South Korea and Singapore. In comparison, the proportion of urban impervious surfaces in developing countries is approaching or exceeding 80% in Asia. In general, the composition and spatial patterns of built-up areas reflected population aggregation and economic development level as well as their impacts on the health of the environment in the sub-watershed.

Identifying Urban Flood Regulation Priority Areas in Beijing Based on an Ecosystem Services Approach

“…EconomicScore j (10) where EVI i is the economic vulnerability of subdistrict i and EconomicScore j is the economic vulnerability score of j pixel in subdistrict i. We assume that undeveloped land (forest, grass, and pasture) and cropland have relatively low vulnerability to flooding (score 1-3), whereas land with low-density (20%-50%) ISA, medium-density (50%-80%) ISA, and high-density (>80%) ISA have higher vulnerabilities (score 5-8) (Table A1).…”

“…Urban flooding has become one of the most severe natural hazards around the world, especially in coastal cities due to the increase of extreme precipitation events and the rise of sea level [3][4][5], and more than 600 cities worldwide face serious flood risks [6]. Specifically, the land surface in cities is continuously modified with impervious surfaces that do not allow water to permeate, and result in excessive flooding [7][8][9][10]. The flood regulation capability of river systems is also degraded in the urbanization process [11].…”

Coupling Relationship between Urban Expansion and Lake Change—A Case Study of Wuhan

“…Urban land is generally defined as all nonvegitative areas dominated by manmade surfaces (e.g., roads and buildings), including residential, commercial, industrial and transportation lands [27]. On the basis of the definition and most research practices [28][29][30], urban land is similar to an impermeable surface or a built environment. In this study, impervious surface area, lake area and lake fragmentation were used to measure the extent of urban expansion and lake change.…”

City-Level Comparison of Urban Land-Cover Configurations from 2000–2015 across 65 Countries within the Global Belt and Road

“…Currently, various built-up area definitions exist in the literature. From the land-cover perspective, the popular definition refers to built-up area as artificial impervious surfaces such as buildings, squares, pavements, and bricks [42,43], while this definition results in the built-up area discontinuity due to the lack of non-artificial land-covers. In the study, the built-up areas should contain artificial impervious surfaces and non-artificial land types (i.e., water bodies, bare soil, and vegetation) within the artificially digitized boundaries from 2 m Google images.…”