Urban Areas Of Region Research Articles

Assessment of air pollution tolerance and anticipated performance index of roadside trees in urban and semi-urban regions.

Rapid urbanization and rising vehicular population are the main precursors in increasing air pollutants concentration which negatively influences the surrounding ecosystem. Roadside plants are frequently used as the barrier against traffic emissions to minimize the effects of air pollution. They are, however, vulnerable to various contaminants, and their tolerance capacity varies. This necessitates a scientific inquiry into the role of roadside plantations in improved urban sprawl planning and management, where chosen trees could be cultivated to reduce air pollution. The present study assesses biochemical and physiological characteristics to evaluate the air pollution tolerance index (APTI) in Ranchi, Jharkhand. The anticipated performance index (API) was assessed based on calculated APTI and socioeconomic characteristics of a selected common tree species along the roadside at different sites. According to APTI, Mangifera indica and Eugenia jambolana were the most tolerant species throughout all the sites, while Ficus benghalensis and Ficus religiosa were intermediately tolerant towards air pollution. The one-way ANOVA shows no significant variation in APTI throughout all the sites. The regression plot shows the positive correlation of APTI with ascorbic acid among all the parameters. According to API, the Mangifera indica, Eugenia jambolana Ficus religiosa and Ficus benghalensis were excellent and best performers among all the sites. So, the air pollution-resistant tree species can be recommended for roadside plantations for the development of green belt areas in urban regions.

Evaluation of Flood Mitigation Effectiveness of Nature-Based Solutions Potential Cases with an Assessment Model for Flood Mitigation

In recent years, climate change has been widely discussed around the world. The Intergovernmental Panel on Climate Change (IPCC) published the Sixth Assessment Report (AR6) in 2021, which stated that with the intensification of global warming, heavy rainfalls are becoming more severe and frequent. Economic development in recent years has also caused the proportion of impervious areas in urban regions to increase with the advancement of urbanization. When the two aforementioned factors are coupled together, the result is faster surface runoff speeds and reduced infiltration rates, which in turn result in worse flooding. Thus, water disaster mitigation is becoming a topic of great importance to developed and developing countries. This study examined five Nature-based Solutions (NbS) cases (A, B C, D, E) for the Nangang river in Taiwan. Case A is to design levees with a 100-year return period flood design standard. Under steady flow conditions, floods can be smoothly discharged downstream without any significant inundation in most situations. Case B and C used gabions with a 10-year return period flood design standard and discontinuous levees with a 25-year return period flood design standard, respectively. Though neither case is as effective in flood mitigation, both cases B and C can still reduce inundation from the flooding disaster relatively well. Case D is to dredge local areas of the main channel, but the steady flow simulation showed little flood mitigation effect. Case E is the implementation of “Room for the River”, and employs main channel dredging and floodplain land grading to increase flood conveyance capacity. Case E provides good flood mitigation.

What explains the regional variation in the use of general practitioners in Australia?

BackgroundRegional variation in the use of health care services is widespread. Identifying and understanding the sources of variation and how much variation is unexplained can inform policy interventions to improve the efficiency and equity of health care delivery.MethodsWe examined the regional variation in the use of general practitioners (GPs) using data from the Social Health Atlas of Australia by Statistical Local Area (SLAs). 756 SLAs were included in the analysis. The outcome variable of GP visits per capita by SLAs was regressed on a series of demand-side factors measuring population health status and demographic characteristics and supply-side factors measuring access to physicians. Each group of variables was entered into the model sequentially to assess their explanatory share on regional differences in GP usage.ResultsBoth demand-side and supply-side factors were found to influence the frequency of GP visits. Specifically, areas in urban regions, areas with a higher percentage of the population who are obese, who have profound or severe disability, and who hold concession cards, and areas with a smaller percentage of the population who reported difficulty in accessing services have higher GP usage. The availability of more GPs led to higher use of GP services while the supply of more specialists reduced use. 30.56% of the variation was explained by medical need. Together, both need-related and supply-side variables accounted for 32.24% of the regional differences as measured by the standard deviation of adjusted GP-consultation rate.ConclusionsThere was substantial variation in GP use across Australian regions with only a small proportion of them being explained by population health needs, indicating a high level of unexplained clinical variation. Supply factors did not add a lot to the explanatory power. There was a lot of variation that was not attributable to the factors we could observe. This could be due to more subtle aspects of population need or preferences and therefore warranted. However, it could be due to practice patterns or other aspects of supply and be unexplained. Future work should try to explain the remaining unexplained variation.

A Temporal Distribution Method of Probable Rainfall for Planning a Storm Sewer Network in an Urban Area

Recently, rainfall runoff models have been introduced for planning a storm sewer network in an urban areas because they can calculate the flood hydrograph as well as peak flow. This would solve the flood problem for the entire watershed. While a rainfall hyetograph is an essential input to a rainfall-runoff model, there is no proper guideline for an urban area on how to obtain a rainfall hyetograph from a temporal distribution of probable rainfall. The purpose of this study is to suggest an appropriate method for temporal distribution of probable rainfall for a storm sewer network. Thus, Huff’s quartile method, which is widely used in practice, and the alternating block method (ABM), which is known to be reasonable for planning medium- or small-scale drainage facilities, were compared. The two estimation results were used for the comparison: the probable rainfall amounts by duration; the peak flows from arbitrary watersheds. The results showed that the ABM was more appropriate than the Huff method from three perspectives: reproducibility of actual rainfall phenomena, accuracy of peak flow estimates for small drainage areas in urban regions, and consideration of continuity for the storm sewer network. These results may contribute to enhance planning methods for a storm sewer network in urban areas. Keywords: Temporal Distribution, Rainfall, Storm Sewer Network, ABM, Huff

Determining potential planting areas in urban regions.

Impermeable surfaces are getting larger in Turkey, as they are in most parts of the world as urban sprawl increases. The increase in impermeable surfaces leads to air pollution, floods, and overflows due to changes in urban landscapes and ecosystems. In order to prevent such damages, impermeable surfaces must be reduced by the means of urban afforestation. The main purpose of this study is to determine which areas are suitable for urban afforestation, and thus to improve the ecological conditions of the city. Accordingly, the study adopts a method that takes urban density into account. Satellite image classification, canopy measurement and determination of potential afforestation areas have been performed within the boundaries of Bartın Municipality. The IKONOS satellite images have been taken as a base for the study, which has been carried out via ENVI, GIS, and SPSS techniques and Tree Canopy Cover. By excluding the too-small spaces within the study area, as well as the ones too close to infrastructural facilities, I have been able to identify potential planting areas using GIS-based decision-making mechanisms. The existing trees and other plant covers have been noted in order to plan the potential plant cover.Considering the locational suitability of the planting areas and the canopy of the trees, the planting areas have been set out using three grid types: 15×15m (large tree), 10×10m (medium tree), and 5×5m (small tree). A total of 29,773 potential trees have been planned for. After corrections, the potential canopy cover has been calculated to be 0.71km2. Of the potential trees, 93.34% are small, 5.23% are medium, and 1.43% are large trees. If the potential planting areas determined in this study are forested as calculated, the canopy in Bartın city will increase by approximately 2%. In the city, where impermeable surface areas have expanded because of rapid urban sprawl, this new increase will make an important contribution to the improvement of the city's ecosystem.

Air Quality in Association With Rural Coal Mining and Combustion in New South Wales Australia.

Rural areas may face under-recognized threats to air quality. We tested 2 hypotheses that 1) rural areas in New South Wales, Australia, would have better air quality than metropolitan Sydney, and that 2) the rural Upper Hunter region characterized by coal mining and coal combustion would have worse air quality than other rural areas of the state. We analyzed 2017 daily mean values for New South Wales, Australia, for particulate matter (PM2.5 and PM10), sulfur dioxide (SO2 ), nitric oxide (NO), nitrogen dioxide (NO2 ), and NOx (sum of NO and NO2 ). Forty-six air monitoring stations were grouped into 6 rural and urban regional areas. Linear regression models examined pollution levels in association with rural and urban regions and meteorological covariates. Findings show that daily mean pollutant levels in the rural Upper Hunter were the highest of all regions, and were significantly higher than metropolitan Sydney, with and without control for weather conditions, for every pollutant. For example, daily mean PM2.5 was 8.64 µg/m3 in the rural Upper Hunter, compared to 7.23 µg/m3 in metropolitan Sydney. Results highlight the need to consider both urban and rural sources of pollution in air quality studies, and appropriate policy steps to address likely rural air pollution from coal mining.

Urban Modality

This thesis proposes a framework for evaluating the mobility potential and performance of urban areas in the city region, as an instrument to support urban development that contributes positively to regional sustainable mobility objectives. The research takes a quantitative approach, modelling and measuring the characteristics of a city-region and of its individual urban areas, in terms of travel patterns and socioeconomic characteristics of the resident population, and in terms of built environment characteristics. It then explores how the built environment defines the affordances of urban areas for travelling by particular modes of transport, i.e. its walk-ability, cycleability, drive-ability and transit-ability, by developing a typology of what I call their ‘urban modality’. And finally the work combines this typology with the socio-economic characteristics of urban areas to determine their sustainable mobility potential and performance. It focuses on the case of the Randstad region of the Netherlands and its VINEX neighbourhoods, which are an emblematic example of new urban areas created under a policy programme with sustainable mobility objectives. A key stance in this work is the understanding that the location of an urban area in the region can be indicative of its population’s travel patterns, because the built environment (infrastructural) and socio-economic characteristics are interrelated and present strong regional spatial patterns. What types of urban areas support sustainable travel patterns, and what are their spatial characteristics? How do new neighbourhoods compare to the best performing urban areas, and to other areas of the same ‘modality’ type? These are some of the questions addressed in this study. There are two main contributions of this research: the methods for building and analysing integrated multimodal network models, and the framework for contextual performance evaluation using urban area typologies. The integrated multimodal network model combines the various mobility infrastructure networks and the buildings’ land use to create a detailed description of the region, using open spatial data and open source Geographic Information Systems (GIS) technologies. The network model’s spatial analysis covers local urban form indicators, such as street layout, network density and land use mix, as well as regional indicators of multimodal accessibility and network configuration (its structure), to give a holistic profile of urban areas across modes and scales of travel. The analysis results go through exploratory data mining and classification procedures to identify urban form typologies of urban areas. It is shown that there is a relation between this ‘urban modality’ of urban areas and the travel patterns of their residents, measured as a set of sustainable mobility indicators related to mode share and distance travelled. For this reason, ‘urban modality’ offers the possibility for ex-ante evaluation of sustainable mobility potential of planned urban areas. Furthermore, when combined with the socio-economic profile of the resident population, ‘urban modality’ defines a context for the ex-post evaluation of sustainable mobility performance of existing urban areas. The evaluation of suburban areas together with the more central historical urban areas gives invariably a high score in sustainable travel to the central areas, and rates the suburban areas negatively. On the other hand, the evaluation of sustainable mobility performance in the context of suburban areas of the same type allows the finer distinction of underperformers that have scope for improvement, and overachievers that provide examples of (relative) success. This contextual evaluation can become a decision support instrument for “hard” and “soft” planning measures involving sustainable mobility targets. Applying this method to the set of VINEX neighbourhoods of the Randstad leads to the conclusion that despite being planned following the same policy objectives, the neighbourhoods have different types of ‘urban modality’, thus present different levels of sustainable mobility potential. Neighbourhoods identified as underperformers within their context can be targeted for soft measures related to transport services, technology and individual attitudes to travel, to fulfil the potential of their ‘urban modality’ type. However, if this potential is not deemed satisfactory or if they already overachieve, only by retrofitting a set of infrastructure and land use characteristics will lead to a different ‘urban modality’ type, and a change in potential. Such a change can be lengthy, costly and sometimes impossible to implement ex-post. The thesis is based on a collection of published articles in peer-reviewed academic publications, with the first and last chapters providing an overview of the research and of its findings, and defining the main narrative thread.

Urban Modality

This thesis proposes a framework for evaluating the mobility potential and performance of urban areas in the city region, as an instrument to support urban development that contributes positively to regional sustainable mobility objectives. The research takes a quantitative approach, modelling and measuring the characteristics of a city-region and of its individual urban areas, in terms of travel patterns and socioeconomic characteristics of the resident population, and in terms of built environment characteristics. It then explores how the built environment defines the affordances of urban areas for travelling by particular modes of transport, i.e. its walk-ability, cycleability, drive-ability and transit-ability, by developing a typology of what I call their ‘urban modality’. And finally the work combines this typology with the socio-economic characteristics of urban areas to determine their sustainable mobility potential and performance. It focuses on the case of the Randstad region of the Netherlands and its VINEX neighbourhoods, which are an emblematic example of new urban areas created under a policy programme with sustainable mobility objectives. A key stance in this work is the understanding that the location of an urban area in the region can be indicative of its population’s travel patterns, because the built environment (infrastructural) and socio-economic characteristics are interrelated and present strong regional spatial patterns. What types of urban areas support sustainable travel patterns, and what are their spatial characteristics? How do new neighbourhoods compare to the best performing urban areas, and to other areas of the same ‘modality’ type? These are some of the questions addressed in this study. There are two main contributions of this research: the methods for building and analysing integrated multimodal network models, and the framework for contextual performance evaluation using urban area typologies. The integrated multimodal network model combines the various mobility infrastructure networks and the buildings’ land use to create a detailed description of the region, using open spatial data and open source Geographic Information Systems (GIS) technologies. The network model’s spatial analysis covers local urban form indicators, such as street layout, network density and land use mix, as well as regional indicators of multimodal accessibility and network configuration (its structure), to give a holistic profile of urban areas across modes and scales of travel. The analysis results go through exploratory data mining and classification procedures to identify urban form typologies of urban areas. It is shown that there is a relation between this ‘urban modality’ of urban areas and the travel patterns of their residents, measured as a set of sustainable mobility indicators related to mode share and distance travelled. For this reason, ‘urban modality’ offers the possibility for ex-ante evaluation of sustainable mobility potential of planned urban areas. Furthermore, when combined with the socio-economic profile of the resident population, ‘urban modality’ defines a context for the ex-post evaluation of sustainable mobility performance of existing urban areas. The evaluation of suburban areas together with the more central historical urban areas gives invariably a high score in sustainable travel to the central areas, and rates the suburban areas negatively. On the other hand, the evaluation of sustainable mobility performance in the context of suburban areas of the same type allows the finer distinction of underperformers that have scope for improvement, and overachievers that provide examples of (relative) success. This contextual evaluation can become a decision support instrument for “hard” and “soft” planning measures involving sustainable mobility targets. Applying this method to the set of VINEX neighbourhoods of the Randstad leads to the conclusion that despite being planned following the same policy objectives, the neighbourhoods have different types of ‘urban modality’, thus present different levels of sustainable mobility potential. Neighbourhoods identified as underperformers within their context can be targeted for soft measures related to transport services, technology and individual attitudes to travel, to fulfil the potential of their ‘urban modality’ type. However, if this potential is not deemed satisfactory or if they already overachieve, only by retrofitting a set of infrastructure and land use characteristics will lead to a different ‘urban modality’ type, and a change in potential. Such a change can be lengthy, costly and sometimes impossible to implement ex-post. The thesis is based on a collection of published articles in peer-reviewed academic publications, with the first and last chapters providing an overview of the research and of its findings, and defining the main narrative thread.

Urban Modality

This thesis proposes a framework for evaluating the mobility potential and performance of urban areas in the city region, as an instrument to support urban development that contributes positively to regional sustainable mobility objectives. The research takes a quantitative approach, modelling and measuring the characteristics of a city-region and of its individual urban areas, in terms of travel patterns and socioeconomic characteristics of the resident population, and in terms of built environment characteristics. It then explores how the built environment defines the affordances of urban areas for travelling by particular modes of transport, i.e. its walk-ability, cycleability, drive-ability and transit-ability, by developing a typology of what I call their ‘urban modality’. And finally the work combines this typology with the socio-economic characteristics of urban areas to determine their sustainable mobility potential and performance. It focuses on the case of the Randstad region of the Netherlands and its VINEX neighbourhoods, which are an emblematic example of new urban areas created under a policy programme with sustainable mobility objectives. A key stance in this work is the understanding that the location of an urban area in the region can be indicative of its population’s travel patterns, because the built environment (infrastructural) and socio-economic characteristics are interrelated and present strong regional spatial patterns. What types of urban areas support sustainable travel patterns, and what are their spatial characteristics? How do new neighbourhoods compare to the best performing urban areas, and to other areas of the same ‘modality’ type? These are some of the questions addressed in this study. There are two main contributions of this research: the methods for building and analysing integrated multimodal network models, and the framework for contextual performance evaluation using urban area typologies. The integrated multimodal network model combines the various mobility infrastructure networks and the buildings’ land use to create a detailed description of the region, using open spatial data and open source Geographic Information Systems (GIS) technologies. The network model’s spatial analysis covers local urban form indicators, such as street layout, network density and land use mix, as well as regional indicators of multimodal accessibility and network configuration (its structure), to give a holistic profile of urban areas across modes and scales of travel. The analysis results go through exploratory data mining and classification procedures to identify urban form typologies of urban areas. It is shown that there is a relation between this ‘urban modality’ of urban areas and the travel patterns of their residents, measured as a set of sustainable mobility indicators related to mode share and distance travelled. For this reason, ‘urban modality’ offers the possibility for ex-ante evaluation of sustainable mobility potential of planned urban areas. Furthermore, when combined with the socio-economic profile of the resident population, ‘urban modality’ defines a context for the ex-post evaluation of sustainable mobility performance of existing urban areas. The evaluation of suburban areas together with the more central historical urban areas gives invariably a high score in sustainable travel to the central areas, and rates the suburban areas negatively. On the other hand, the evaluation of sustainable mobility performance in the context of suburban areas of the same type allows the finer distinction of underperformers that have scope for improvement, and overachievers that provide examples of (relative) success. This contextual evaluation can become a decision support instrument for “hard” and “soft” planning measures involving sustainable mobility targets. Applying this method to the set of VINEX neighbourhoods of the Randstad leads to the conclusion that despite being planned following the same policy objectives, the neighbourhoods have different types of ‘urban modality’, thus present different levels of sustainable mobility potential. Neighbourhoods identified as underperformers within their context can be targeted for soft measures related to transport services, technology and individual attitudes to travel, to fulfil the potential of their ‘urban modality’ type. However, if this potential is not deemed satisfactory or if they already overachieve, only by retrofitting a set of infrastructure and land use characteristics will lead to a different ‘urban modality’ type, and a change in potential. Such a change can be lengthy, costly and sometimes impossible to implement ex-post. The thesis is based on a collection of published articles in peer-reviewed academic publications, with the first and last chapters providing an overview of the research and of its findings, and defining the main narrative thread.

Performance of Permeable Block Pavements in Accelerated Pavement Test and Rainfall Simulation

As industrialization advances, the increase in impermeable areas in urban regions has changed the water circulation system. Hence, many environmental issues such as heat islands and city floods have arisen. To solve this issue, related research with a high budget allocation is currently being carried out. A method of addressing this issue is to utilize permeable block pavements. The bearing capacity and hydrological efficiency of permeable block pavement with different base types was evaluated in this study using two accelerated pavement testings (APTs). Rutting was evaluated by performing a comparative analysis in each permeable block pavement. Furthermore, the hydrological characteristics were reviewed through a rainfall simulation experiment. The results of APT show that performance of permeable block pavements varies depending on the base type and traffic volume. Based on the result, it was demonstrated that the permeable block pavement is applicable for a vehicle road as well as the sidewalk. In addition, it was demonstrated that this pavement can improve the water circulation system.

Review and Research Needs of Bioretention Used for the Treatment of Urban Stormwater

The continued development of urban areas in recent decades has caused multiple issues affecting the sustainability of urban drainage systems. The increase of impervious surface areas in urban regions alters watershed hydrology and water quality. Typical impacts to downstream hydrologic regimes include higher peak flows and runoff volumes, shorter lag times, and reduced infiltration and base flow. Urban runoff increases the transport of pollutants and nutrients and thus degrades water bodies downstream from urban areas. One of the most frequently used practices to mitigate these impacts is bioretention. Despite its widespread use, research on bioretention systems remains active, particularly in terms of mix design and nitrogen treatment. Recent research focusing on bioretention is reviewed herein. The use of mesocosms provides the ability to isolate particular treatment processes and replicate variability. Computational models have been adapted and applied to simulate bioretention, offering potential improvements to their operation, maintenance, and design. Maintenance practices are important for sustained operation and have also been reviewed. Predicting maintenance is essential to assessing lifecycle costs. Within these research areas, gaps are explored, and recommendations made for future work.

Geospatial analyses to prioritize public health interventions: a case study of pedestrian and pedal cycle injuries in New South Wales, Australia

Pedestrian and pedal cycle injuries are important causes of child morbidity and mortality. The combination of Bayesian methods and geographical distribution maps may assist public health practitioners to identify communities at high risk of injury. Data were obtained on all hospitalizations of children from NSW (Australia), for pedestrian and pedal cycle injuries, from 2000-2001 to 2004-2005. Using Bayesian methods, posterior expected rate ratios (as an estimate of smoothed standardized hospitalization ratios for each injury mechanism) were mapped by local government area (LGA) across the state. There were over 7,000 hospitalizations for pedestrian and pedal cycle injuries. High risk LGAs accounted for more than one third of hospitalized pedestrian and pedal cycle injuries in NSW. LGAs at high risk for pedestrian injury tended to be urbanized metropolitan areas with a high population density, while high risk LGAs for pedal cycle injury tended to be either in urban regional areas, or on the margin of urbanized metropolitan areas. Geospatial analyses can assist policymakers and practitioners to identify high risk communities for which public health interventions can be prioritized.

Status of MSW management system in northern India-an overview

Many Indian cities are facing serious problems in managing solid wastes with rise in population and urbanization. This article assesses the existing state of municipal solid waste management (MSWM) in northern India with the aim of identifying the major obstacles to its efficiency and the prospects for improvisation of the solid waste management system in the region. The existing solid waste management system in the region is found to be highly inefficient. Primary and secondary collection, transportation and open dumping are the only activities practiced that too in a non-technical manner. Many cities in region face serious problems in managing solid wastes. The annual waste generation increases in proportion to the rises in population and urbanization. This paper systematically assesses the obstacles in the existing solid waste management system in the urban areas of region and also tries to assess the potentials for its improvisation.

An Examination for Efficient Applicability of the Land Readjustment Method at the International Context

Land readjustment (LR) is an important technique for urban land development in both developed and developing countries. This technique is used for both development of new areas and reorganization of structured areas in urban regions. The efficient application of LR may provide a planned urban development, production of a serviced urban plot, a supply of technical infrastructure and service areas for public use, a significant ease in the solution of ownership problems, the supply of subdivisions with good standards, the possibility of readjustment of land ownership and plot borders, and other benefits. However, the efficient application of LR is contingent on certain basic conditions. In this article, the basic conditions are defined and examined for the successful and efficient application of the LR method within the frame of international literature. The provision of benefits expected from LR rests on the availability of LR models that include the foregoing basic conditions.

Vibrio parahaemolyticusO3:K6 Epidemic Diarrhea, Chile, 2005

<i>Vibrio parahaemolyticus</i>O3:K6 Epidemic Diarrhea, Chile, 2005

Measuring Sustainable Accessibility

Transport is one of the most significant sources of unsustainability in urban regional areas. This challenge is stimulating urban planners and decision makers to incorporate the concept of sustainability into their policy design at various levels. Despite its successful implementation in several sectors and wide recognition in academic and professional debate, sustainability is still not that evident in day-to-day regional planning practice. Interpretable measures integrating accessibility and sustainability and linking them with policy-making practice are relatively scarce. This paper aims to take some steps toward measuring sustainable accessibility, which in turn is intended to help regional planners define the potential problems and design possible alternatives at the strategic planning level for a sustainable regional transport and land use system. The proposed methodology for such measurement consists of the concept of conflicts in the planning process, job opportunity modeling, and sustainability and spatial conflict analysis. The Amsterdam urban region in the Netherlands is taken as a case study. Sustainable accessibility is measured in an integrated geographic information system environment, followed by corresponding policy implications for strategy design. The experimental study demonstrates that the indicator of sustainable accessibility can be incorporated into the process of strategic policy design.

Automatic determination of imperviousness in urban areas from digital orthophotos

Determination of impervious areas in urban regions is the most labour-intensive part of data acquisition for rainfall-runoff modelling in urban hydrology. This paper presents an automatic determination method of imperviousness from aerial photographs. The colour, CIR (colour infrared) aerial photographs and orthophotos used have a ground resolution of 25 to 75 centimetres. A maximum likelihood classification algorithm was applied to assign each pixel to a surface category. Classification results were then then overlaid with the subcatchments to determine the imperviousness of each subcatchment. Classification and overlay were carried out with the raster-based GIS IDRISI. The method was tested on various catchment areas, and the results compared with data obtained from manually digitised surfaces. Accuracy of the estimated imperviousness for the entire catchment areas was within 10 %. The deviations for individual subcatchments were much higher. Equivalent results were obtained for colour and CIR photograplhs. A combination of both spectral ranges resulted only in a slight improvement. Consequently, this does not justify the additional costs of the second image. The developed method is an interesting alternative for use on large catchment areas where manual digitisation is very time-consuming and, thus, expensive.

Automatic determination of imperviousness in urban areas from digital orthophotos

Determination of impervious areas in urban regions is the most labour-intensive part of data acquisition for rainfall-runoff modelling in urban hydrology. This paper presents an automatic determination method of imperviousness from aerial photographs. The colour, CIR (colour infrared) aerial photographs and orthophotos used have a ground resolution of 25 to 75 centimetres. A maximum likelihood classification algorithm was applied to assign each pixel to a surface category. Classification results were then overlaid with the subcatchments to determine the imperviousness of each subcatchment. Classification and overlay were carried out with the raster-based GIS IDRISI. The method was tested on various catcbment areas, and the results compared with data obtained from manually digitised surfaces. Accuracy of the estimated imperviousness for the entire catchment areas was within 10%. The deviations for individual subcatchments were much higher. Equivalent results were obtained for colour and CIR photographs. A combination of both spectral ranges resulted only in a slight improvement. Consequently, this does not justify the additional costs of the second image. The developed method is an interesting alternative for use on large catchment areas where manual digitisation is very time-consuming and, thus, expensive.

Sentiment and Symbolism as Ecological Variables

SYSTEMATIZATION of ecological theory has thus far proceeded on two main premises regarding the character of space and the nature of locational activities. first premise postulates that the sole relation of space to locational activities is an impeditive and cost-imposing one. second premise assumes that locational activities are primarily economizing, fiscal agents.' On the basis of these two premises the only possible relationship that locational activities may bear to space is an one. In such a relationship each activity will seek to so locate as to minimize the obstruction put upon its functions by spatial distance. Since the supply of the desired locations is limited it follows that not all activities can be favored with choice sites. Consequently a competitive process ensues in which the scarce desirable locations are preempted by those locational activities which can so exploit advantageous location as to produce the greatest surplus of income over expenditure. Less desirable locations devolve to correspondingly less economizing land uses. result is a pattern of land use that is presumed to be most efficient for both the individual locational activity and for the community.2 Given the contractualistic milieu within which the modern city has arisen and acquires its functions, such an economic ecology has had a certain explanatory adequacy in describing urban spatial structure and dynamics. However, as any theory matures and approaches a logical closure of its generalizations it inevitably encounters facts which remain unassimilable to the theoretical scheme. In this paper it will be our purpose to describe certain ecological processes which apparently cannot be embraced in a strictly analysis. Our hypothesis is that the data to be presented, while in no way startling or unfamiliar to the research ecologist, do suggest an alteration of the basic premises of ecology. This alteration would consist, first, of ascribing to space not only an impeditive quality but also an additional property, viz., that of being at times a symbol for certain cultural values that have become associated with a certain spatial area. Second, it would involve a recognition that locational activities are not only economizing agents but may also bear sentiments which can significantly influence the locational process.3 A test case for this twofold hypothesis is afforded by certain features of land use in central Boston. In common with many of the older American cities Boston has inherited from the past certain spatial patterns and landmarks which have had a remarkable persistence and even recuperative power despite challenges from other more land uses. persistence of these spatial patterns can only be understood in terms of the group values that they have come to symbolize. We shall describe three types of such patterns: first, an in-town upper class residential neighborhood known as Beacon Hill; second, certain sacred sites, notably the ' See Everett C. Hughes, The Ecological Aspect of Institutions, American Sociological Review. I:i80-9, April, I936. 2This assumption of a correspondence between the maximum utility of a private association and that of the community may be questioned within the very framework of marginal utility analysis. See particularly A. C. Pigou, Economics of Welfare. Second Edition, London: 1924, Part II, ch. 8. For a clear presentation of the typical position see Robert Murray Haig, Towards an Understanding of the Metropolis-the Assignment of Activities to Areas in Urban Regions, Quarterly Journal of Economics. 40:402-34, May, 1926. 'Georg Simmel, Der Raum und die ru cf. Hughes, op. cit.