02 Fakultät Bau- und Umweltingenieurwissenschaften
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Item Open Access Infrastructure cost implications of urban forms in developing countries : an analysis of development patterns in Ghana(2012) Adaku, Ebenezer; Siedentop, Stefan (Prof. Dr.-Ing.)The interdependency or relationship between infrastructure costs and urban form has been an important issue in town and regional planning over the years. Debates have generated among practitioners and theorists for over three decades now as to which development is the most cost efficient. However, the conclusions are still fuzzy and not clear, partly, because both practitioners and theorists often deliberately or unintentionally gloss over the realistic impacts of alternative development patterns in their submissions. Interestingly, most planning authorities rarely know and consider the costs of alternative development patterns in their decision making process. Besides, studies on infrastructure costs efficiency of alternative developments have constantly focused on developed countries without any attention to developing countries. This study then sought to contribute to the debate from developing countries’ perspective – using Ghana as the reference point – by analysing the effects of urban forms on infrastructure costs from both developing and developed countries’ points of view; determining the urban form that is infrastructure costs efficient as well as recommending to planners and policy makers in developing countries, possible areas in the development process, where infrastructure costs could be reduced. In approaching the study, both qualitative and quantitative methods were employed. The qualitative approach deals with the literature review of urban sprawl, particularly its general impacts and influence on the costs of infrastructure. Again, the phenomenon of urban sprawl is situated in the context of both developing and developed countries with differences and similarities of attributes in the different economic regions of the world ascertained. The literature review, further, focuses on how infrastructure costs relate to urban forms as well as analysing how the urban structures (with respect to social and spatial distributions) in both developing and developed countries affect infrastructure costs and financing. The conclusions of the literature review form the bedrock of the investigation and further reinforce the isolation of the effect of urban configuration on infrastructure costs. A graph theoretic tool, by means of AutoCAD, was employed for further isolation of the effect of urban configuration on infrastructure costs. Pattern classification – to delineate the primary urban patterns – coupled with agreement in literature on historical and current urban patterns gave rise to four hypothetical residential neighbourhood patterns – tributary, radial, grid and hybrid patterns. The four hypothetical patterns held all other factors constant and isolated the effect of street patterns and density on the capital costs of roads, water and electricity distribution networks. The study found out that, generally, the major factors that drive the current urban development patterns – urban sprawl – in developed countries have reached, relatively, higher levels of development in comparison with developing countries. Therefore, developed countries have higher urban dispersion potential and hence higher infrastructure costs vis-à-vis developing countries. The phenomenon also occasions a shift from intra-city to inter-city infrastructure costs concerns in the case of developed countries while in developing countries, emphasis is on intra-city infrastructure costs concerns with respect to urban forms. Again, the phenomenon of urban sprawl is perceived to be occasioned by market distortions and failures. The market distortions and failures leading to urban sprawl are deemed to be anchored in the cost-sharing scheme of infrastructure financing. Hence, the externalities and market failures associated with the cost-sharing scheme (which induces urban sprawl) could be dealt with so as to ensure more efficient urban forms through marginal costs pricing of infrastructure. The phenomenon of urban sprawl albeit evident in developing counties (particularly Ghana), does not fit exactly into the developed countries’ scheme of urban sprawl – both in causes and impacts. Besides, the urban structures of both developing and developed countries are different and have different implications on the costs of infrastructure development and financing. The study also found out that there is a relationship between urban forms and infrastructure costs. However, the relationship is not a single relationship but rather a multiple one. The intrinsic purpose of these relationships, as claimed by studies in developed countries, is independent of the socio-economic situation of any particular region. Hence, this relationship is presumably applicable in developing countries as well. It has also been shown in this study that apart from density, lot size, lot shape, location and dispersion of developments, street pattern or configuration relates to and has influence on infrastructure costs, particularly network infrastructure. In isolating the effect of street patterns on urban forms, the total capital costs of three infrastructure (roads, water and electricity distribution networks) revealed the tributary pattern as the most economical pattern in terms of the capital costs of linear infrastructure while the grid pattern is the least economical. The tributary pattern showed a 27% costs savings per dwelling over the costs of the grid pattern. The radial and hybrid patterns also indicated 9% and 3% savings per dwelling, respectively, in comparison with the grid pattern. Clearly, the savings in capital costs of linear infrastructure by the tributary, radial and hybrid patterns in comparison with the grid pattern, largely, resulted from savings in water distribution and road networks. The study showed that – it appears – other factors such as demand, density and type of distribution system other than the configuration of the street pattern influence the costs of electricity distribution network significantly. The capital costs per dwelling showed a gradual rise in infrastructure cost as one moved from the pure tributary pattern towards the pure grid pattern. Besides, in isolating the effect of density on linear infrastructure costs, it was revealed that the capital costs per dwelling of linear infrastructure reduce sharply, initially, with increasing density and later reduce, marginally, with further increments in density. Again, a density from 13 DPH to 53 DPH means approximately a 300% increment in density. However, the corresponding decrease in capital costs per dwelling for linear infrastructure was about 68% across the alternative hypothetical residential patterns. The general street pattern in Ghana is the cellular or grid type which is expensive in terms of linear infrastructure. Thus, since most developing countries (including Ghana) have fiscal challenges, urban configurations which reduce infrastructure costs and enhance revenues would be more appropriate. Thus, as shown by this study, the tributary pattern appears to fulfil this goal. However, the shortfall in accessibility – a key planning goal – could be augmented by a carefully designed network of footpaths. This measure fits well into Ghana or developing countries’ scheme of transportation – slow mode or walking. Again, geometry seems to provide a tool to optimise the values of infrastructure costs minimisation and accessibility enhancement. The fused grid, a new residential neighbourhood layout, is a good example. See Grammenos et al. (2008) for more discussions on the fused grid model. Besides, the price of infrastructure comprises costs and profits. Hence, an approach like urban configuration which seeks to reduce the costs is not enough. Other factors or areas which also influence the price of infrastructure to the user should also be considered and their effects – preferably – minimised. Such areas are developer or client’s costs, risks and contingencies related to the infrastructure development and profit margin of the construction contractor or developer.