Singapore Center for Global Environmental Sustainability

Singapore, Singapore

Singapore Center for Global Environmental Sustainability

Singapore, Singapore
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Costa D.,Singapore Center for Global Environmental Sustainability | Costa D.,National University of Singapore | Burlando P.,ETH Zurich | Liong S.-Y.,National University of Singapore
Environmental Modelling and Software | Year: 2016

Rivers and aquifers are mutually dependent components of the hydrological cycle, typically characterised by temporal dynamics that are a few orders of magnitude apart. This characteristic is often advocated to justify the use of independent single-system models to maximise the outcome for the available computational resources. However, the rapid increase in computational power presently provides means to explore new and more complex modelling schemes, which better reflect the complex physical reality. We present a new modelling framework, FLUXOS, developed from the full coupling of modified versions of state-of-the-art standalone river and groundwater flow and transport models. The model is validated against analytical solutions and applied to real world scenarios in the complex urban corridor of the Ciliwung River in Jakarta to show its flexibility for practical applications and its capabilities as an exploratory tool for realistic investigation of contamination sources and pathways determining non-linear behaviours of river-aquifer interactions. © 2016 Elsevier Ltd

Vollmer D.,Singapore Center for Global Environmental Sustainability | Vollmer D.,ETH Zurich | Prescott M.F.,Singapore Center for Global Environmental Sustainability | Prescott M.F.,ETH Zurich | And 4 more authors.
Landscape and Urban Planning | Year: 2015

Cultural ecosystem services are not easily integrated into planning decisions when rehabilitating urban rivers. Methods exist to characterize the value of these cultural services, but there are methodological challenges to obtaining this information and fitting it to a decision context, particularly when weighed against monetary costs and benefits. In a developing country, these challenges can be magnified and thus the value of cultural services is seldom considered. We illustrate this through a case study of a river in Jakarta, Indonesia, where plans call for widening the river channel, stabilizing the banks with concrete, and restricting access to the river. We employ a mixed-method approach of household surveys, a discrete choice experiment and ethnographic interviews, to ascertain historical and present uses of the river, and residents' preferences for future change to the river. We demonstrate that low-income residents value non- or indirect-use cultural services that the river corridor provides-services that would be lost under the current rehabilitation plan. By assessing residents' willingness to pay for cultural services, we can more easily compare these scenarios to the current plan. We also show how our mixed-methods approach to valuation can help frame and interpret quantitative results, so that decision makers have additional contextual information. We demonstrate that such approaches are feasible and sometimes necessary in complex, data-poor urban environments. © 2015 Elsevier B.V.

Prescott M.F.,Singapore Center for Global Environmental Sustainability | Prescott M.F.,ETH Zurich | Ninsalam Y.,Singapore Center for Global Environmental Sustainability | Ninsalam Y.,National University of Singapore
Sustainable Cities and Society | Year: 2016

Using the landscape as medium, we explore the relationship between residents and vegetation interaction, and spatial condition, of an urban riverine landscape in the Jakarta subdistricts of Kampung Melayu and Bukit Duri. These offer distinct examples of an urban riverine landscape within a growing megacity. Located on a peninsula of land called 'Kampung Pulo' the neighbourhood studied in Kampung Melayu has several distinctive elements (open spaces along the riverside, communal and private plantings, gentle sloping banks) that define the arrangement of this riverine landscape and influence its condition. In comparison, the neighbourhood studied in the nearby community of Bukit Duri, compressed between the railway siding of KRL-KRD Bukit Duri and the Ciliwung River, has limited river access and riverside open space, houses backing directly onto the river, and less vegetation. The landscape was used as medium to integrate local knowledge for the purpose of ecological design. Using an integrated mixed-methods approach including ethnographic surveys and interviews, and spatial mapping through drawings and image- and range-based modelling. The study discerned that differences in the landscape configuration of the two sites produced differences in resident interaction with domestic and riverine vegetation, and landscape condition. As such, the method is seen to be useful in providing valuable insights for the design of urban riverine landscapes. © 2015 Elsevier Ltd. All rights reserved.

Ninsalam Y.,Singapore Center for Global Environmental Sustainability | Ninsalam Y.,National University of Singapore | Rekittke J.,National University of Singapore
Sustainable Cities and Society | Year: 2016

The main objective of this paper is to propose a systematic fieldwork approach in order to describe the ground condition of dense urban riverine settlements. The proposed approach supplements aerial-view acquired digital elevation models that are unable to describe the ground conditions that are obstructed by urban and vegetative canopies. After three years spent developing this approach, we can compare and identify synergies between three ground-view acquisition methods: an action-, digital single lens reflex (DSLR)-camera, and terrestrial laser scanner (TLS). This paper consists of a two-part study, which uses the visual quality and accuracy of the data sets produced as criterion for appraisal. Although norms would suggest a hypothetical best operational workflow as an outcome of this paper, we instead argue that the identification of circumstances in which different methods are combined to complement the limitations of another is more beneficial. As such, through the appraisal of visual quality and accuracy obtained by the approaches described above we can draw better insights to make the most out of typically laborious fieldwork. Given the labour-intensive process, an economy of work is necessitated in order to capture the best description of landscape elements with the given equipment and time, allowing the greatest area of coverage. © 2015 Elsevier Ltd. All rights reserved.

Sun L.,Singapore Center for Global Environmental Sustainability | Sun L.,National University of Singapore | Sun L.,Massachusetts Institute of Technology | Axhausen K.W.,Singapore Center for Global Environmental Sustainability | And 3 more authors.
Scientific Reports | Year: 2014

Physical contact remains difficult to trace in large metropolitan networks, though it is a key vehicle for the transmission of contagious outbreaks. Co-presence encounters during daily transit use provide us with a city-scale time-resolved physical contact network, consisting of 1 billion contacts among 3 million transit users. Here, we study the advantage that knowledge of such co-presence structures may provide for early detection of contagious outbreaks. We first examine the â €œ friend sensorâ € scheme-a simple, but universal strategy requiring only local information-and demonstrate that it provides significant early detection of simulated outbreaks. Taking advantage of the full network structure, we then identify advanced â €œ global sensor setsâ €, obtaining substantial early warning times savings over the friends sensor scheme. Individuals with highest number of encounters are the most efficient sensors, with performance comparable to individuals with the highest travel frequency, exploratory behavior and structural centrality. An efficiency balance emerges when testing the dependency on sensor size and evaluating sensor reliability; we find that substantial and reliable lead-time could be attained by monitoring only 0.01% of the population with the highest degree.

Wang T.,Singapore Center for Global Environmental Sustainability | Belle I.,Singapore Center for Global Environmental Sustainability | Hassler U.,Singapore Center for Global Environmental Sustainability | Hassler U.,Institute of Historic Building Research and Conservation
Geomorphology | Year: 2015

Singapore's topography has been heavily transformed by industrialization and urbanization processes. To investigate topographic changes and evaluate soil mass flows, historical topographic maps of 1924 and 2012 were employed, and basic topographic features were vectorized. Digital elevation models (DEMs) for the two years were reconstructed based on vector features. Corresponding slope maps, a surface difference map and a scatter plot of elevation changes were generated and used to quantify and categorize the nature of the topographic transformation. The surface difference map is aggregated into five main categories of changes: (1) areas without significant height changes, (2) lowered-down areas where hill ranges were cut down, (3) raised-up areas where valleys and swamps were filled in, (4) reclaimed areas from the sea, and (5) new water-covered areas. Considering spatial proximity and configurations of different types of changes, topographic transformation can be differentiated as either creating inland flat areas or reclaiming new land from the sea. Typical topographic changes are discussed in the context of Singapore's urbanization processes. The two slope maps and elevation histograms show that generally, the topographic surface of Singapore has become flatter and lower since 1924. More than 89% of height changes have happened within a range of 20. m and 95% have been below 40. m. Because of differences in land surveying and map drawing methods, uncertainties and inaccuracies inherent in the 1924 topographic maps are discussed in detail. In this work, a modified version of a traditional scatter plot is used to present height transformation patterns intuitively. This method of deriving categorical maps of topographical changes from a surface difference map can be used in similar studies to qualitatively interpret transformation. Slope maps and histograms were also used jointly to reveal additional patterns of topographic change. © 2014 Elsevier B.V.

Vollmer D.,Singapore Center for Global Environmental Sustainability | Vollmer D.,ETH Zurich | Pribadi D.O.,TU Munich | Remondi F.,Singapore Center for Global Environmental Sustainability | And 3 more authors.
Sustainable Cities and Society | Year: 2016

Spatially explicit information on ecosystem services can be an important input to regional spatial planning, but must be framed in a particular social context in order to be useful. We present a case study in metropolitan Jakarta, Indonesia, where stakeholders are discussing a spatial plan to help mitigate flooding risk, conserve scarce agricultural land, and restore forests in the upper catchment areas. We demonstrate an application of a four-step spatial multi-criteria analytical (MCA) approach that involves scenario development, ecosystem service quantification and mapping, preference weighting, and optimization to maximize preferred ecosystem services while minimizing cost. We improve upon similarly-oriented MCAs by incorporating information on ecosystem service potential, supply, beneficiaries, and likely costs to conserve them, with the aim of assisting stakeholders in negotiating future land development. Stakeholder-weighted preferences provide information on potential areas of conflict or agreement, but the aggregated weights do not have a significant impact on the optimization model's outputs. Our results also reveal possible synergies between, for example, biodiversity conservation and erosion control, which are typically considered and planned for by separate stakeholder groups. We also find that if we include monetary estimates of flood damages by sub-basin and population data by groundwater basin, optimal solutions include more expensive interventions when compared to a model omitting this information. Overall, our approach offers a transparent way to collect and process relevant information on regional ecosystem services, and can be particularly useful in areas where land use is changing rapidly and land use controls are either weak or decentralized. © 2015 Elsevier Ltd. All rights reserved.

Vollmer D.,Singapore Center for Global Environmental Sustainability | Vollmer D.,ETH Zurich | Gret-Regamey A.,ETH Zurich
Global Environmental Change | Year: 2013

In many developing world cities, where municipal infrastructure lags urban growth, lower-income communities may compensate by relying on local waterways to meet basic needs for water, sanitation, and recreational space. Access to these environmental services is possible because residents settle in floodplains, but thus entails elevated exposure to several water-related hazards, especially flooding. We examine this complex relationship in the neighborhoods of Bukit Duri and Kampung Melayu on the Ciliwung River in Jakarta, Indonesia. Based on a spatially referenced household survey, we analyze and map the patterns of use of six environmental services provided by the river: direct sanitary use, recreation, harvesting plants, groundwater use, solid waste disposal, and sewage disposal. Using spatial interpolation and regression methods, we identify the most probable areas where services are being used and analyze possible influences on this behavior. We find that proximity to the river significantly influences households' behavior toward the river, as do infrastructure-related variables and neighborhing households' behavior, while household demographic factors appear less significant. These results indicate that many households rely on multiple environmental services, and that residents most reliant on these services are also at greater risk of water-related hazards, service disruption (e.g., a decline in water quality), and potentially, eviction. This pattern of floodplain development is prevalent in many low-income countries, and a better understanding of how informal settlements rely on environmental services can be used to assess their vulnerabilities and inform more sustainable courses of development. © 2013 Elsevier Ltd.

Medina S.,Singapore Center for Global Environmental Sustainability | Erath A.,Singapore Center for Global Environmental Sustainability
Transportation Research Record | Year: 2013

The number and the temporal and spatial distribution of work locations are crucial information for any transport demand model. To generate the initial transport demand of MATSim, an activity-based multiagent simulation framework, it is necessary to determine dynamic workplace capacities with high spatial resolution, either on a parcel or even a building level. Commonly applied methods to derive work locations are based on census of enterprises information, unemployment insurance database, or combined information of a building's gross floor area and individual work space requirements. As an alternative, the authors present a methodology that combines public transport smart card transaction data, travel diary surveys, and building information data sources. Work activities are detected from smart card transactions based on observed activity duration and start time and therefore related to public transport stops. To link the observed work activities to individual buildings, a linear programming optimization technique is applied that minimizes the walking time between public transport stops and potential work locations. The method classifies work activities in representative work schedules obtained by clustering methods. Information on maximum allowed building gross floor area derived from land use regulation is combined with estimates on individual work space requirements to ensure that buildings are only assigned with work activities according to their maximal capacity. To account for private transport based work activities, mode shares as observed in a travel diary are taken into account. To demonstrate the applicability, the proposed approach is implemented in Singapore and the results critically reviewed.

Karaman O.,Singapore Center for Global Environmental Sustainability
Antipode | Year: 2012

This paper is a critical engagement with immanentist approaches to cities. Geographers approaching the urban through an immanentist lens-primarily inspired by Gilles Deleuze's work-have called into question transcendent determination, namely the determination of material reality by an external and ontologically distinct substance. This has been an implicit assumption in approaches that reduce contemporary urban developments to "effects of globalization" or "impacts of neoliberalism". I identify two major shortcomings within the recent immanentist critique: first, their rejection of the notion of a structure in toto, and second, their noticeable silence on Louis Althusser despite his unique contribution to the question of complex causality and his shared trajectories with and influence on Deleuze. By using illustrations from the ongoing urban renewal program in Istanbul, I speculate on the ways in which an Althusserian notion of "immanent structure" could contribute to a better understanding of cities as multiplicities. © 2012 The Author. Antipode © 2012 Antipode Foundation Ltd.

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