Authors: Hill, Alexandra
Lindner, Christian
Title: Modelling informal urban growth under rapid urbanisation
Other Titles: a CA-based land-use simulation model for the city of Dar es Salaam, Tanzania
Language (ISO): en
Abstract: Dar es Salaam in Tanzania is one of the fastest growing urban agglomerations in Africa and projected to become a megacity (i.e., a city with more than 5 mio. inhabitants) by 2025. Rapid urban growth under poverty has outstripped the capacities of planning authorities to cope with the enormous pace of urban expansion. As a consequence informal settlements absorb almost all urban settlers leading to rapid urban sprawl into the unplanned periphery. But still only little is known about the drivers and mechanisms of ongoing urbanisation processes and the means of intervention. The need for well balanced and informed decisions becomes evident and calls inter alia for support of urban planning by geo-information technology and so-called decision support systems. This thesis approaches these needs by designing a land-use simulation model for the city of Dar es Salaam. Particularly in developing countries urban modelling inevitably comprises the challenge of setting up an appropriate database. Public authorities in Dar es Salaam lack precise and up-to-date information and were unable to contribute to the database needed for the modelling work particularly since multi-temporal information was required. Basic datasets which have been provided by another research institution were extended and updated to serve as the database required by the analysis and modelling work. The model presented is based on standard GIS software and designed along the principles of Cellular Automata (CA) which are particularly suitable to capture neighbourhood dynamics and likewise do not demand for a highly sophisticated database. Population projections by the UN Population Division have been used to determine future demand for informal residential land. The model simulates its allocation based on variables which represent major drivers of informal urban growth: natural conditions, accessibility and local-scale dynamics, i.e., so-called neighbourhood effects. These drivers have been proven to be adequate to explain and project urban growth during the process of model calibration and validation based on regression analyses. The model has been employed to project land-use patterns until 2022 as a baseline scenario. In accordance with recent local urban planning and development discourse the impact of transport infrastructure projects on the distribution of future urban growth has been simulated in four scenario settings. The results have been analysed with reference to the baseline scenario to compare the characteristics of likely urban futures. The application of the model demonstrates the considerable potential of urban growth modelling for the situation in Dar es Salaam and its transferability to cities facing similar conditions. It provides a valuable laboratory to test the drivers and mechanisms of urban growth and the associated means of intervention. During field work interim results have proven that the model is able to establish and maintain a discourse among planners and other stakeholders thus mitigating one of the major weaknesses of urban development planning - the lack of cooperation and coordination. This is an essential first step for strategic intervention into informal urban development processes given the limited resources at hand and to support planning authorities in Dar es Salaam to cope with future urban development in a pro-active manner.
Subject Headings: Africa
cellular automata
Dar es Salaam
informal urban dynamics
urban modelling and simulation
Subject Headings (RSWK): Daressalam
Stadt / Wachstum
Issue Date: 2010-06-30
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