Impact Of Urban Growth Research Articles

Urbanisation and Food Insecurity Risks: Assessing the Role of Human Development

The phenomenon of rapid urbanisation across the world has become a topic of increased scholarly inquiry. Yet, little attention has been paid to how urban growth affects countries’ food security and whether this association is modified by a country's level of development. The present study aims to fill this lacuna by examining the association between urbanisation and food security applying statistical modelling. The analysis uses country-level data, from the World Development Indicators and the United Nations’ World Urbanization Prospects. Using a Food Insecurity Risk Index (FIRI) as the outcome variable, the results confirm a significant negative impact of urban growth on food security at the country level. It further finds that rapidly urbanising countries with the lowest levels of human development are most at risk of food insecurity.

English

Urban ecological systems are characterized by complex interactions among institutional, socio-economic and environmental variables. These interactions often generate complex human-dominated landscapes, which significantly influence effective functioning of local and global earth ecosystems and the services they provide to humans and other life on earth. Changes in ecological conditions that result from human actions in urban areas ultimately affect physical morphology and structural outlook as in the case of the study area. Using Survey Research Design (SRD) via questionnaire administration, observation and personal interview and photo-snaps for data collection, authors investigate the impact of urban growth on the environment as occasioned by the existence of a university; essentially, the effects that the growth has on the ecological system of the community. Findings in the study revealed that urban development affects the spatial heterogeneity of the landscape; especially the patterns of variation in land cover and changes in land use over time. The authors propose that effective monitoring agent to guide the direction and coherence of development in the study area is needed to forestall the haphazard pattern of development that is rampart in the area. Also, a comprehensive master plan is needed for the area coupled with provision of essential services like power supply to facilitate adequate and regular electricity supply in the area. Key words: Urban growth, land-use changes, EKSU.

Assessment of Impact of Urbanization on Groundwater Resources using GIS Techniques- Case Study of Hyderabad, India

Hyderabad is one of the fastest growing Indian megacities which have significant impact on itsenvironment. The surface and groundwater resources are severely affected by uncontrolled expansion anddensification of the city. For the better understanding, recovery and to prevent future deterioration of thesesignificance resources, it is necessary to have knowledge of the impact of urban growth in various ways onenvironment. Historical groundwater level and quality data obtained from different sources as well as by fieldstudy data is used for this analysis. In some cases missing data points were interpolated and verified byproviding certain criteria. The map of rate of groundwater level change per year showed the locations ofrecharge activity by sewage and other effluents as well as overexploitations by industrial and some uppermiddle class residential areas. The results obtained from groundwater quality analysis are then compared withthe BIS (Bureau of India) as well as WHO (World Health Organization) standards for drinking water. It hadbeen observed that many water samples had heavy metal elements and bacterial formation above permissiblelimits and it is not suitable for drinking purpose. The water samples obtained from locations which do notqualify for drinking water use according to WHO as well as BIS standards are identified. These results are thenoverlapped with map of rate of groundwater level change to establish the relation between urban groundwaterrecharge and its effect on groundwater quality.

Urban dynamics, landscape ecological security, and policy implications: A case study from the Wuhan area of central China

Monitoring of urban growth and the characterization of its patterns in the Wuhan area of central China from 1988 to 2013 was performed using an integrated approach of remote sensing (RS) and geographic information system (GIS) techniques and statistical methods. We also undertook a qualitative analysis of the impact of urban growth on landscape ecological security. The results showed that the Wuhan area was in a rapid process of urbanization between 2000 and 2011, with an average urban growth rate of 10.666km2/a and 2.969km2/a in the surrounding region and city proper, respectively. An aggregated pattern was the primary growth type in the whole study area, while linear and leapfrog patterns mainly occurred in the surrounding region. Rapid urban growth has aggravated the landscape fragmentation and has led to considerable declines in ecosystem services. A Pearson correlation analysis was used to qualitatively explore the relationships between the urban growth patterns and the factors associated with ecological security. It was found that the ecosystem fragmentation and ecosystem services were correlated with the urban growth rate, the three types of urban growth, and the compactness of the urban form. Of the three growth types, the leapfrog growth pattern destroys the integrity of water bodies, thereby preventing the connection of lakes to the main surface water network, and thus results in increase fragmentation and reduction of ecosystem services. Although the land-use policies implemented in Wuhan during the study period have promoted the development of the local economy, they have failed to protect the ecosystem. Urban growth speed should be effectively controlled because natural resource protection is as important as, and even more important, to some extent, than encouraging extensive economic development. This research has highlighted the importance of the joint application of urban growth quantification and the monitoring of the changes in the factors associated with ecological security in landscape planning.

Geospatial scenario based modelling of urban and agricultural intrusions in Ramsar wetland Deepor Beel in Northeast India using a multi-layer perceptron neural network

In recent decades, the world has experienced unprecedented urban growth which endangers the green environment in and around urban areas. In this work, an artificial neural network (ANN) based model is developed to predict future impacts of urban and agricultural expansion on the uplands of Deepor Beel, a Ramsar wetland in the city area of Guwahati, Assam, India, by 2025 and 2035 respectively. Simulations were carried out for three different transition rates as determined from the changes during 2001–2011, namely simple extrapolation, Markov Chain (MC), and system dynamic (SD) modelling, using projected population growth, which were further investigated based on three different zoning policies. The first zoning policy employed no restriction while the second conversion restriction zoning policy restricted urban-agricultural expansion in the Guwahati Municipal Development Authority (GMDA) proposed green belt, extending to a third zoning policy providing wetland restoration in the proposed green belt. The prediction maps were found to be greatly influenced by the transition rates and the allowed transitions from one class to another within each sub-model. The model outputs were compared with GMDA land demand as proposed for 2025 whereby the land demand as produced by MC was found to best match the projected demand. Regarding the conservation of Deepor Beel, the Landscape Development Intensity (LDI) Index revealed that wetland restoration zoning policies may reduce the impact of urban growth on a local scale, but none of the zoning policies was found to minimize the impact on a broader base. The results from this study may assist the planning and reviewing of land use allocation within Guwahati city to secure ecological sustainability of the wetlands.

Impact of urban growth-driven landuse change on microclimate and extreme precipitation — A sensitivity study

More than half of the humanity lives in cities and many cities are growing in size at a phenomenal rate. Urbanisation-driven landuse change influences the local hydrometeorological processes, changes the urban micro-climate and sometimes affects the precipitation significantly. Understanding the feedback of urbanisation driven micro-climatic changes on the rainfall process is a timely challenge. In this study we attempt to investigate the impact of urban growth driven landuse change on the changes in the extreme rainfall in and around cities, by means of sensitivity studies. We conduct three sets of controlled numerical experiments using a mesoscale atmospheric model coupled with a land surface model to investigate the hypothesis that the increasing urbanisation causes a significant increase of extreme rainfall values. First we conduct an ensemble of purely idealised simulations where we show that there is a significant increase of high intensity rainfall with the increase of urban landuse. Then four selected extreme rainfall events of different tropical cities were simulated with first current level of urbanisation and then (ideally) expanded urban areas. Three out of the four cases show a significant increase of local extreme rainfall when the urban area is increased. Finally, we conducted a focused study on the city of Mumbai, India: A landscape dynamics model Dinamica-EGO was used to develop a future urban growth scenario based on past trends. The predicted future landuse changes, with current landuse as control, were used as an input to the atmospheric model. The model was integrated for four historical cases which showed that, had these events occurred with the future landuse, the extreme rainfall outcome would have been significantly more severe. An analysis of extreme rainfall showed that hourly 10-year and 50-year rainfall would increase in frequency to 3-year and 22-year respectively.

Ulating Hydrologic Impacts of Urban Growth Using SLEUTH, Multi Criteria Evaluation and Runoff Modeling

Research on the sustainability of future urban environments has shown not only the value of simulation modeling, but also the strength of coupling their forecasts together into loosely integrated models. In this research we propose a way to improve modeling of urban futures by using enhanced land use change modeling as an input to a hydrological model. Our forecasts of hydrologic impacts are based on the L-THIA model, but this model is sensitive in turn to the land uses associated with urbanization, especially impervious surfaces and other urban uses. In order to improve the performance of the SLEUTH land use/cover change model, we modified one of that models inputs using multi-criteria evaluation (MCE). The data basis for the modeling used land cover classes mapped for the years 1987, 1992, 2000 and 2005 in the Gorgan Township of northeastern Iran using Landsat TM and ETM+ remotely sensed images. A hybrid unsupervised, supervised and on-screen classification method was used to generate land use/cover maps of the area. To test the value of enhanced modeling, we compared the results from three model forecasts of the year 2040, an original SLEUTH forecast, an urban suitability-informed SLEUTH forecast, and a hydrologic plus urban suitability-informed SLEUTH forecast. As a control, we also used standard MCE to forecast urban growth for the year 2040. The integrated model comparison was made based on two future urban landscape descriptors: (1) potential surface runoff volume; and (2) landscape metrics. Results indicate that the integrated modeling approach produces a land use arrangement through SLEUTH that can be better directed towards higher land suitability and more favorable hydrologic conditions. The results for the combined hydrologic plus urban suitability-informed SLEUTH modeling were superior to the other three methods in terms of lower potential for runoff volume generation and more sustainable landscape metrics of shape, size and proximity. We demonstrate that the self-organizing cellular automata method behind SLEUTH is capable of better informed land use planning when compared to the simple MCE method. The approach can also be improved by using suitability layers for other land use practices to achieve a more comprehensive land use plan.

Modeling of urban growth dynamics and its impact on surface runoff characteristics

Modeling urban growth and generating scenarios are essential for studying the impact and sustainability of an urban hydrologic system. Urban systems are regarded as complex self-organizing systems, where the dynamic transitions from one form of landuse to another occur over a period of time. Therefore, a modeling framework that captures and simulates this complex behavior is essential for generating urban growth scenarios. Cellular Automata (CA)-based models have the potential to model such discrete dynamic systems. In this study, a constraint-based binary CA model was used to predict the future urban growth scenario of the city of Roorkee (India). A hydrologic model was applied on the simulated urban catchment to study its hydrologic response. The Natural Resources Conservation Service Curve Number (NRCS-CN) method, which is suitable for ungauged urban watersheds, was adopted to determine the impact of urban growth on the quantity of storm water runoff over a period of time. The results indicate that urban growth has a linear relationship with peak discharge and time to peak for the catchment under investigation.

An Assessment of the Growth of Ile-Ife, Osun State Nigeria, Using Multi-Temporal Imageries

This paper examined the use of GIS and Remote Sensing in monitoring the growth and development pattern of Ile-Ife, Osun State, Nigeria over a period of 21 years with a view to predicting its direction of growth. In effect, the study sought to identify and explain the rate and extent of changes in the study area between 1986 and 2007; measure the rate of urban growth in the study area between 1986 and 2007; assess the impact of urban growth on land use patterns; and predict the trend of urban growth in the study area. Data for the study were generated from both primary and secondary sources. Remote Sensing Imagery of Landsat TM 1986, Landsat ETM 2002 and ALOS 2007 were used to measure the extent of growth and to show the effects of this growth on other Land use/Land cover types. Multi-temporal approach was adopted for the study to detect the changes in the imageries. Pixel analysis was employed to identify and compare the type, nature, trend and magnitude of change that occurred in the study area within the slated dates. The observed land use/land cover and population were projected to the next 15 years. The results showed the growth of Ile-Ife and its effects on other land use classes. Pixel analysis revealed that changes occurred in the magnitude and rate of urbanization in the study area between 1986 and 2007. The results were discussed mainly focusing on the trend of urban growth expansion and its effect to the Environment natural resources, farmland and food security and its contribution to climate change. Its implications to urban planning were also discussed and the recommendations made.

Urbanization and climate change impacts on future urban flooding in Can Tho city, Vietnam

Abstract. Urban development increases flood risk in cities due to local changes in hydrological and hydrometeorological conditions that increase flood hazard, as well as to urban concentrations that increase the vulnerability. The relationship between the increasing urban runoff and flooding due to increased imperviousness is better perceived than that between the cyclic impact of urban growth and the urban rainfall via microclimatic changes. The large-scale, global impacts due to climate variability and change could compound these risks. We present the case of a typical third world city – Can Tho (the biggest city in Mekong River Delta, Vietnam) – faced with multiple future challenges, namely: (i) the likely effect of climate change-driven sea level rise, (ii) an expected increase of river runoff due to climate change as estimated by the Vietnamese government, (iii) increased urban runoff driven by imperviousness, and (iv) enhancement of extreme rainfall due to urban growth-driven, microclimatic change (urban heat islands). A set of model simulations were used to construct future scenarios, combining these influences. Urban growth of the city was projected up to year 2100 based on historical growth patterns, using a land use simulation model (Dinamica EGO). A dynamic limited-area atmospheric model (WRF), coupled with a detailed land surface model with vegetation parameterization (Noah LSM), was employed in controlled numerical experiments to estimate the anticipated changes in extreme rainfall patterns due to urban heat island effect. Finally, a 1-D/2-D coupled urban-drainage/flooding model (SWMM-Brezo) was used to simulate storm-sewer surcharge and surface inundation to establish the increase in the flood hazard resulting from the changes. The results show that under the combined scenario of significant change in river level (due to climate-driven sea level rise and increase of flow in the Mekong) and "business as usual" urbanization, the flooding of Can Tho could increase significantly. The worst case may occur if a sea level rise of 100 cm and the flow from upstream happen together with high-development scenarios. The relative contribution of causes of flooding are significantly different at various locations; therefore, detailed research on adaptation are necessary for future investments to be effective.

Assessing urbanisation effects on rainfall-runoff using a remote sensing supported modelling strategy

This paper aims at developing a methodology for assessing urban dynamics in urban catchments and the related impact on hydrology. Using a multi-temporal remote sensing supported hydrological modelling approach an improved simulation of runoff for urban areas is targeted. A time-series of five medium resolution urban masks and corresponding sub-pixel sealed surface proportions maps was generated from Landsat and SPOT imagery. The consistency of the urban mask and sealed surface proportion time-series was imposed through an urban change trajectory analysis. The physically based rainfall-runoff model WetSpa was successfully adapted for integration of remote sensing derived information of detailed urban land use and sealed surface characteristics.A first scenario compares the original land-use class based approach for hydrological parameterisation with a remote sensing sub-pixel based approach. A second scenario assesses the impact of urban growth on hydrology. Study area is the Tolka River basin in Dublin, Ireland.The grid-based approach of WetSpa enables an optimal use of the spatially distributed properties of remote sensing derived input.Though change trajectory analysis remains little used in urban studies it is shown to be of utmost importance in case of time series analysis. The analysis enabled to assign a rational trajectory to 99% of all pixels. The study showed that consistent remote sensing derived land-use maps are preferred over alternative sources (such as CORINE) to avoid over-estimation errors, interpretation inconsistencies and assure enough spatial detail for urban studies. Scenario 1 reveals that both the class and remote sensing sub-pixel based approaches are able to simulate discharges at the catchment outlet in an equally satisfactory way, but the sub-pixel approach yields considerably higher peak discharges. The result confirms the importance of detailed information on the sealed surface proportion for hydrological simulations in urbanised catchments. In addition a major advantage with respect to hydrological parameterisation using remote sensing is the fact that it is site- and period-specific. Regarding the assessment of the impact of urbanisation (scenario 2) the hydrological simulations revealed that the steady urban growth in the Tolka basin between 1988 and 2006 had a considerable impact on peak discharges. Additionally, the hydrological response is quicker as a result of urbanisation. Spatially distributed surface runoff maps identify the zones with high runoff production.It is evident that this type of information is important for urban water management and decision makers. The results of the remote sensing supported modelling approach do not only indicate increased volumes due to urbanisation, but also identifies the locations where the most relevant impacts took place.

Urban Industrial Composition and the Spatial Expansion of Cities

This paper uses a computable general equilibrium model with integrated commercial and residential land data to estimate the impact of urban growth, both in sector origin and growth mechanism, on urban spatial expansion, measured by density (population, employment, and commercial), residential lot size, and urban land conversion. The results demonstrate that specific sectors and individual growth mechanisms have unique impacts across the spatial expansion measures in both sign and magnitude; therefore, local policy makers should carefully consider the uniqueness of their city in terms of their geographic surroundings and mixture of urban growth before implementing or emulating other cities’ policies. (JEL R11, R14)

The impact of urban growth on regional air quality surrounding the Langat River Basin, Malaysia

Studies of air quality were carried out in the towns of Kajang, Nilai and Banting in the Langat River Basin, southern region of Kuala Lumpur to determine the status and trend of air quality. The determination of air quality was based on several parameters such as suspended solids with diameters less than 10 μm (PM10) and gaseous pollutants of sulphur dioxide (SO2), nitrogen dioxide (NO2), ozone (O3), and carbon monoxide (CO). Primary concentration data of air pollutants were compiled through fieldwork studies and combined with secondary data obtained from the regular monitoring data as collected by Alam Sekitar Malaysia Sdn. Bhd. (ASMA) on behalf of Malaysian Department of Environment (DOE) at their stations in Kajang and Nilai. Results showed that the average concentrations of PM10, SO2, NO2, O3, and CO at all sampling stations were still below the permissible values recommended by the Malaysian DOE. The level of gaseous pollutants of NO2, O3, and CO was recorded at statistically higher levels (p < 0.05) than values recorded at the control station at Pangsun Recreational Area. These pollutants were suspected to have originated mainly from exhaust systems of motor vehicles. Data for the years 1996 to 2006 as obtained from ASMA showed long-term air quality trends of increasing O3 and NO2 concentrations in Kajang whilst concentrations of PM10 recorded at both Kajang and Nilai stations were mostly expected coming from transboundary sources especially biomass burning and the development activities around the study areas.

Systems dynamic model to forecast salinity load to the Colorado River due to urbanization within the Las Vegas Valley

This study evaluates the impact of urban growth in the Las Vegas Valley (LVV), Nevada, USA on salinity of the Colorado River. In the past thirty eight years the LVV population has grown from 273,288 (1970) to 1,986,146 (2008). The wastewater effluents and runoff from the valley are diverted back to the Colorado River through the Las Vegas Wash (LVW). With the growth of the valley, the salinity released from urban areas has increased the level of TDS in the wastewater effluents, ultimately increasing the TDS in the Colorado River. The increased usage of water softeners in residential and commercial locations is a major contributor of TDS in the wastewater effluents. Controlling TDS release to the Colorado River is important because of the 1944 Treaty signed between the USA and Mexico. In addition, the agriculture salinity damage cost for the Colorado River has been estimated to be more than $306 a million per year using 2004 salinity levels. With the expected growth of LVV in coming years the TDS release into Lake Mead will increase over time. For this purpose, it is important to investigate future TDS release into the Colorado in anticipation of potential TDS reducing measures to be adopted. In this research, a dynamic simulation model was developed using system dynamics modeling to carry out water and TDS mass balances over the entire LVV. The dynamic model output agreed with historic data with an average error of 2%. Forecasts revealed that conservation efforts can reduce TDS load by 16% in the year 2035 when compared to the current trend. If total population using water softeners can be limited to 10% in the year 2035, from the current 30% usage, TDS load in the LVW can be reduced by 7%.

Assessing the Environmental Impacts of Urban Growth Using Land Use/Land Cover, Water Quality and Health Indicators: A Case Study of Arequipa, Peru

Problem statement: This research assesses the direct effects of urban expansion on land cover/use, river flow, water quality and the indirect effects of these variables in the rate of gastrointestinal disease in people in Arequipa, Peru through the combined use of satellite remote sensing and geographic information systems. Approach: It also uses information about demographic changes, hydrologic data and land cover change in the Arequipa region for the last 17 years. The goal is to understand the relationship between urbanization, water quality in the Chili River and incidence of gastrointestinal diseases. Results: Landsat imagery was used to determine this relationship and to extrapolate business as usual trends into the future ten years from now. Results indicate that there has been notable urban growth and a loss in volcanic material land and cropland between 1990 and 2007, as new urban developments have appeared in these areas. The population expansion over volcanically active area is particularly troubling since it poses a potential human health risk. We also model a business as usual scenario out to the year 2020, which shows continued loss of these land use types and serves as a warning for land managers to consider alternate policies. Conclusion/Recommendations: The analysis also shows a direct correlation between urbanization with the decrease of water quality and the increase in the incidence of gastrointestinal diseases.

The impact of urban growth on commuting patterns in a restructuring city: Evidence from Beijing

AbstractOur existing knowledge of the links between urban growth and commuting patterns are dominated by cases from developed countries. This paper examines the impact of urban growth on workers' commutes using the case of Beijing, which is undergoing rapid economic and spatial restructuring. The results of an analysis of household survey data show that clustered and compact urban development in planned sub‐centres is likely to reduce suburban workers' need for a long‐distance commute to the city centre when the workers' socio‐economic characteristics, the level of transport accessibility and household preferences for residential location are taken into account. Workers employed in the manufacturing sector tend to have shorter commutes and travel within the planned suburban sub‐centres. This reveals that the decentralization of employment in the manufacturing sector provides more opportunities to enhance the spatial matches between household residential and job location choices. Household preferences for residential location have an effect on commuting patterns, and high‐income workers are likely to accept longer commutes in order to fulfil their residential preferences. Dramatic urban restructuring, in conjunction with changes in lifestyle, is creating new commuting patterns in the rapidly growing cities of China.ResumenEl estado actual del conocimiento sobre los vínculos entre el crecimiento urbanístico y los patrones de desplazamiento al trabajo está dominado por ejemplos de países desarrollados. Este artículo examina el impacto del crecimiento urbano en los desplazamientos al trabajo en una ciudad como Pekín, la cual está siendo objeto de una rápida reestructuración económica y espacial. Los resultados del análisis de datos de un muestreo de hogares mostró que es probable que un desarrollo urbano compacto y agrupado en torno a sub‐centros planificados a propósito de este modo reduzca la necesidad de largos desplazamientos al trabajo hasta el centro de la ciudad, si se tienen en cuenta las características socioeconómicas de los trabajadores, la facilidad de acceso a transporte y las preferencias de cada hogar en cuanto a la zona residencial. Los trabajadores empleados en el sector manufacturero tienden a realizar desplazamientos más cortos y a viajar dentro de los sub‐centros suburbanos planificados. Esto revela que la descentralización del empleo en el sector manufacturero proporciona más oportunidades de mejorar la correspondencia espacial entre la elección de la zona residencial y la del puesto de trabajo. Las preferencias familiares en cuanto a la zona residencial tienen un efecto en los patrones de desplazamiento al trabajo, siendo más probable que los empleados con ingresos más altos estén dispuestos a realizar desplazamientos más largos a cambio de satisfacer sus preferencias residenciales. Una dramática reestructuración urbana, junto con cambios en el estilo de vida, está creando nuevos patrones de desplazamiento al trabajo en las ciudades chinas de rápido crecimiento.

An Expert System Applied in Construction Water Quality Monitoring

Problem statement: An untoward environmental impact of urban growth in Malaysia has been deterioration in a number of watercourses due to severe siltation and other pollutants from the construction site. Water quality monitoring is a plan for decision makers to take into account the adverse impacts of construction activities on the receiving water bodies. It is also a process for collecting the construction water quality monitoring, baseline data and standard level. Approach: In recent years, expert systems have been used extensively in different applications areas including environmental studies. In this study, expert system software -CWQM- developed by using Microsoft Visual Basic was introduced. CWQM to be used for water quality monitoring during construction activities was designed based on the legal process in Malaysia. Results: According to the water quality monitoring regulation enacted in Malaysia, construction activities require mandatory water quality monitoring plans duly approved by Department of Environment before staring activities. CWQM primarily aims to provide educational and support system for water quality monitoring engineers and decision-makers during construction activities. It displays water quality monitoring plan in report form, water sampling location in GIS format and water quality monitoring data in graph. Conclusion: When the use of CWQM in construction water quality monitoring becomes widespread, it is highly possible that it will be benefited in terms of having more accurate and objective decisions on construction projects which are mainly focused on reducing the stormwater pollution.

Impacts of urban growth on forest cover in Istanbul (1987–2007)

This article reports findings of a study that examined the impacts of urban growth on forest cover in Istanbul between 1987 and 2007. Four Landsat images from 1987, 1990, 2000, and 2007 were classified with maximum likelihood supervised classification method by using ERDAS IMAGINE 9.1. Forest and urban areas were given highest importance in the classification, while other land-use characteristics, like agriculture and bare soil, were grouped into a third class as others. The study revealed that rapid increase in population and accompanying unplanned urban growth in Istanbul resulted in significant changes in land use after 1987. Urban areas have expanded 87.9% from 1987 to 2007, while forest areas declined 5.4% in the same period. One of the most significant results of the study was that total forest areas in Istanbul have increased 0.3% between 2000 and 2007. This suggests that progress has been made in Istanbul not only in having sustainable urban growth, but also in preserving, restoring, and even expanding forest areas, especially after the year 2000.

Impact of Urban Growth on Surface Climate: A Case Study in Oran, Algeria

Abstract The authors develop a land use map discriminating urban surfaces from other cover types over a semiarid region in North Africa and use it in a land surface model to assess the impact of urbanized land on surface energy, water, and carbon balances. Unlike in temperate climates where urbanization creates a marked heat island effect, this effect is not strongly marked in semiarid regions. During summer, the urban class results in an additional warming of 1.45°C during daytime and 0.81°C at night relative to that simulated for needleleaf trees under similar climate conditions. Seasonal temperatures show that urban areas are warmer than their surrounding areas during summer and slightly cooler in winter. The hydrological cycle is practically “shut down” during summer and is characterized by relatively large amounts of runoff in winter. The authors estimate the annual amount of carbon uptake to be 1.94 million metric tons with only 11.9% assimilated during the rainy season. However, if urbanization expands to reach 50% of the total area excluding forests, the annual total carbon uptake will decline by 35% and the July mean temperature would increase only 0.10°C relative to the current situation. In contrast, if urbanization expands to 50% of the total land excluding forests and croplands but all short vegetation is replaced by native broadleaf deciduous trees, the annual carbon uptake would increase by 39% and the July mean temperature would decrease by 0.9°C relative to the current configuration. These results provide guidelines for urban planners and land use managers and indicate possibilities for mitigating the urban heat.

Environmental impacts of urban growth from an integrated dynamic perspective: A case study of Shenzhen, South China

China is home to one-fifth of the world's population and that population is increasingly urban. The landscape is also urbanizing. Although there are studies that focus on specific elements of urban growth, there is very little empirical work that incorporates feedbacks and linkages to assess the interactions between the dynamics of urban growth and their environmental impacts. In this study, we develop a system dynamics simulation model of the drivers and environmental impacts of urban growth, using Shenzhen, South China, as a case study. We identify three phases of urban growth and develop scenarios to evaluate the impact of urban growth on several environmental indicators: land use, air quality, and demand for water and energy. The results show that all developable land will be urban by 2020 and the increase in the number of vehicles will be a major source of air pollution. Demand for water and electricity will rise, and the city will become increasingly vulnerable to shortages of either. The scenarios also show that there will be improvements in local environmental quality as a result of increasing affluence and economic growth. However, the environmental impacts outside of Shenzhen may increase as demands for natural resources increase and Shenzhen pushes its manufacturing industries out of the municipality. The findings may also portend to changes other cities in China and elsewhere in the developing world may experience as they continue to industrialize.