Remote Sensing Applications for the Urban Environment

George Z. Xian

• Publisher: CRC Press
• Year: 2015
• eBook ISBN: 9781498766494
• Topic: Technology & Engineering
• Subtopic: Civil Engineering
• Index: Technology & Engineering

Land use and land cover changes associated with increased urbanization have led to landscape and environmental changes throughout the world. Remote Sensing Applications for the Urban Environment places emphasis on the rapid development of worldwide urbanization and its impact on the environment, and reviews the assessment of urban land cover condit

Chapter 1

Introduction

Urban areas have experienced dramatic changes in both population and spatial extent over the past 50 years. More than 50% of the world’s population now lives in urban and suburban areas (UNFPA 2007). According to the UN Wall Chart of Urban and Rural Areas (http://www.unpopulation.org), the world’s urban population was estimated at 3.29 billion in 2007 and was expected to rise to 6.4 billion by 2050. The rural population was anticipated to decline slightly from 3.37 billion in 2007 to 2.79 billion in 2050. In 2007, 49% of the world’s population lived in urban areas. The world’s urban population reached 49.4% in 2007, resulting in more urban residents than rural residents in the world. The proportion of the world population living in urban areas is expected to rise to 69.6% by 2050. Much of the growth is occurring in the developing countries, where urban developments are significant. The speed and the scale of this growth continues to pose formidable challenges to individual countries as well as to the world community. Figure 1.1 illustrates variations of world population between 1950 and 2050 (United Nations 2012). Associating with these population changes are large and complex economic, social, political, and demographic changes, including the multiplication in the size of the world’s economy and a shift in economic activities and employment structures from agriculture to industry and services.

Figure 1.1

Urban and rural population between 1950 and 2050. (Modified from Figure 1, United Nations, World Urbanization Prospects. The 2011 Revision , United Nations, New York, 2012.)

In addition, more people are moving into urban areas in many developing countries. For example, in 2011, cities with fewer than 500,000 inhabitants accounted for about half of the world’s urban population, amounting to 1.85 billion (Figure 1.2). Cities with populations ranging between 500,000 and 1 million were home to more than 365 million people, equivalent to 10.1% of the world’s urban population. Taken together, cities with fewer than 1 million inhabitants account for 61% of the urban population. One of the most significant changes following this urban population trend has been the growth in the size and importance of cities whose economies increased and changed as a result of urbanization. Another change is the number of large cities that are now centers of large extended metropolitan regions.

Figure 1.2

Total urban population in millions by city size class in 1970, 1990, 2011, and 2025. (Modified from Figure 2, United Nations, World Urbanization Prospects. The 2011 Revision , United Nations, New York, 2012.)

Throughout the world, land use and land cover changes associated with increasing urbanization have had significant impacts at local, regional, and even global scales. Associated with urban growth is the expansion of urban land use that usually translated into a significant loss of natural resources in many countries. Urban land cover is also the physical manifestation of historical, cultural, socioeconomic, political, demographic, and natural conditions. Urban growth changes, land cover conditions, and urban infrastructure alter surrounding environments from natural to anthropogenic types. Landscape and environmental changes caused by urbanizations are significant in almost all urban areas. The most significant change in urban landscape is from natural to anthropogenic impervious surface. Such change brings evident impacts on water resource quality, air quality, ecosystems conditions, and even microclimate conditions. Evidence of the environmental impacts associated with urban growth have been reported by numerous researches, such as urban heat island (Oke 1973; Kukla et al. 1986; Quattrochi et al. 2000; Weng 2001; Voogt and Oke 2003), urban air quality (Nichol and Wong 2005; Lawrence et al. 2007; Xian 2007; Gurjar et al. 2008; Kanakidou et al. 2011), water quality (Ritchie et al. 2003; Carlson 2004; Jacobson 2011), and regional climate change (Landsberg 1981; Arnfield 2003; Shepherd 2005; Ren et al. 2011; Gago et al. 2013; Hebbert and Jankovic 2013; Janković 2013). Many new developments in urban areas require more pavements, which usually cause more surface runoffs. The runoff from impervious surfaces raises serious environmental concerns because of its impacts on surface water balance. Pollutants loaded with surface storm water runoff usually cause water quality problems and impact water supplies in many metropolitan areas (Matthews 2011). Generally, the impact of urban land use on environmental quality is much greater than its spatial extent would imply. Furthermore, urban land cover is an important component of regional and global environment. Urban growth can have significant impacts on ecological, biophysical, social, and climate conditions (Imhoff et al. 2004; IPCC 2007; Seto and Shepherd 2009).

A successful urban center has had to adapt to environmental conditions and available resources, although local resource constraints have often been overcome by drawing on resources from elsewhere. The growth of urban population over the latter half of the twentieth century has also caused a very large anthropogenic transformation of terrestrial biomes, although urban centers cover only a small proportion of the world’s land surface (Schneider et al. 2009). However, their physical and ecological footprints are much larger compared to their spatial extent.

Urbanization can generate both immediate and long-term influences on ecosystems in both obvious and subtle ways, often leading to unique biophysical characteristics in urban ecosystems (Alberti et al. 2003). For instance, urban development can change surface vegetation condition, and the effect of urbanization on vegetation cover depends on the form of urbanization and climate region. Low-density housing development may increase vegetation fraction and potential carbon uptake if lawns and gardens replace agricultural fields. Urban land use changes and changes in the number of people living in urban areas result in serious environmental and social problems and accelerate global environmental change (Grimmond 2007). The net ecological impact of urban centers includes the decline in the share of wild and seminatural areas. It has led not only to a decrease in biodiversity but also to fragmentation in much of the remaining natural areas and a threat to the ecological services that support both rural and urban areas (Revl et al. 2014).

Projections (Seto et al. 2012) suggest that, if current urbanization trends continue, global urban land cover will increase by 1.2 million km2 by 2030, nearly tripling global urban land area between 2000 and 2030. This would mean a considerable loss of habitat in key biodiversity hotspots through destruction of the green infrastructure, which is vital in helping areas adapt to climate change impacts (Seto et al. 2012); additionally, this loss increases the exposure of population and assets to higher risk levels. Monitoring urban developments and creating sustainable urban environments remain crucial issues in the future urban development agenda.

Driven by societal desires and continuous improvement in spatial, spectral, and geometrical (e.g., radar and lidar) resolutions in satellite and sensor technology as well as image processing algorithms, remotely sensed information has been widely used in terrestrial ecosystem research and application. Urban remote sensing has evolved from very coarse-resolution interpretation to high-resolution characterization. Remote sensing is widely used among urban planners for extracting biophysical information about the urban environment, including land cover and land use mapping, urban morphology description and analysis, vegetation distribution and characterization, hydrography, and disaster relief. These data are also widely used in the field of natural resource exploration and management. The use of this type of remotely sensed data is supported by the hypothesis that the surface appearance of a settlement is the result of the human population’s social and cultural behavior and interaction with the environment, which leaves its mark on the landscape (Patino and Duque 2013).

The use of remote sensing data is usually more suitable for measuring and monitoring urban environmental conditions than for urb...

Table of contents

• Foreword
• Preface
• Author
• Chapter 1 - Introduction
• Chapter 2 - Characteristics of Urban Landscape Feature in Local and Regional Scales
• Chapter 3 - Characterization of Urban Land Cover in a Moderate Resolution
• Chapter 4 - Regional and Global Urban Land Cover Characterizations
• Chapter 5 - Assessment of Water Quality in Urban Areas
• Chapter 6 - Natural Hazard Assessment for Urban Environments
• Chapter 7 - Air Quality in Urban Areas—Local and Regional Aspects
• Chapter 8 - Air Quality in Urban Areas— Global Aspects
• Chapter 9 - Urban Heat Island and Regional Climatic Effect
• References