Information and Knowledge Management using ArcGIS ModelBuilder

Using Geographic Information to Assess Urban
Environmental Indicators in the City of Lisbon
Teresa Santos, Ségio Freire and José António Tenedório
e-GEO, FCSH, Universidade Nova de Lisboa, Portugal
teresasantos@fcsh.unl.pt
sfreire@fcsh.unl.pt
ja.tenedorio@fcsh.unl.pt
Abstract: Cities are complex and dynamic systems that reproduce the interactions between socio-economic and
environmental processes at a local and global scale. This complexity constitutes a significant challenge for urban
planning. One effective source of information about the urban environment is remote sensing data. Sealed
surfaces generate intense rainwater run-off which the drainage network cannot accommodate, thus promoting
flooding events. Mapping urban flood risk implies knowing the spatial distribution and extent of the pervious and
impervious areas in the city. These are important variables for planning, mitigation, preparedness and response
to potential events. Green areas are an important land use in urban areas, performing relevant environment
functions, such as improving urban climate, reducing atmospheric pollution, providing amenities, aesthetical
benefits and a good environment for urban populations. However, the urbanization process generally occurs at
the expense of agricultural or forested areas, thus contributing to degrade the urban environment quality. The
present case study addresses the quantification of impervious land at the city scale through remote sensing data.
A methodology for generating a large-scale Land Cover Map for the city of Lisbon, Portugal is proposed. The
data source is Very-High Resolution (VHR) IKONOS pansharp image, from 2008, with a spatial resolution of 1 m,
and a normalized Digital Surface Model (nDSM) from 2006. The methodology was based on the object-based
extraction of features of interest, namely: vegetation, soil and impervious surfaces. After deriving the land cover
information from remote sensing data, several applications can be implemented. Indicators on land sealing area,
quantification of green area, or the available vacant soil in the city, are ecological measures that can be used as
tools for cities to assess and communicate different environmental risks, and promote strategies and measures of
sustainable urban development and disaster risk management. It is demonstrated that using a methodology
based on large-scale geographic information, quick updating of detailed land cover information is possible and
can be used to support decisions in a crisis situation where official maps are generally outdated, or to evaluate
the quality of the urban environment.
Keywords: very-high resolution satellite image, impervious mapping, soil sealing, Lisbon, IKONOS, LiDAR
1. Introduction
Regular updates of land cover status and land cover condition are required to improve our
understanding of nearly every aspect of the changing environment, including fluxes of water, carbon
dioxide and other trace gases, changing coastlines and their influence on marine resources,
biodiversity, land and soil resources use intensity, or urban patterns of environmental significance
(CEOS 2010). The present study demonstrates that automatic classification of remote sensing data
allows creating spatial knowledge, which can be implemented to support decision-making, identifying
major areas for policy intervention. Integrated environmental information based on urban indicators
allows for policy monitoring and evaluation.
Land impermeabilization is a direct result of urban development. The occurrence of surfaces
impenetrable by water like roads, buildings or sidewalks, induces changes on the natural environment
like the decrease in water quality, fish\animal populations or groundwater reserves, and increase in
habitat fragmentation, flooding events or urban heat island effects. Consequently, the amount of
impervious surface area is a good measure of environmental quality.
Several methods can be used to estimate the percentage of impervious land at different landscape
levels. Maps with the spatial distribution of the city’s land cover can be very helpful in reporting areas
which are more vulnerable and where negative impacts of urbanization should be minimized.
One obvious source of information about the urban environment is remote sensing data. The
constantly increasing availability and accessibility of modern remote sensing technologies has
provided new opportunities for a wide range of urban applications such as mapping and monitoring of
the urban environment (land cover, land use, morphology, urban structural types), socio-economic
estimations (population density), characterization of urban climate (microclimate, human health
conditions), analysis of regional and global impacts – (ground water and climate modeling, urban heat
islands) or urban security and emergency preparedness (sustainability, vulnerability) (Esch 2010).
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