dc.description.abstract |
Unplanned urban growth is one of the major challenges in developing countries. The literature on
urban growth has focused more on horizontal growth, without a corresponding emphasis on
vertical growth. Even within the urban horizontal growth analysis, greater attention has been on
the dynamic patterns rather than processes of growth. This study was, therefore, designed to
analyse the spatiotemporal dynamics, patterns, and processes of horizontal and vertical urban
growth in Lagos Island Local Government Area (LGA), Nigeria.
Urban Morphology and Complexity theories provided the framework, while a survey research
design was adopted. Lagos Island LGA was purposively selected given the concentration of high rise buildings. A total of 1,200, out of 47,447 households were systematically selected using
Neumann (2014) probability method. Socio-economic and building related data were collected
through questionnaire survey. Landsat (1984, 2000, and 2015) and IKONOS (2013) images
provided information on growth patterns and processes. Spatiotemporal dynamics of urban
growth were analysed using change detection and ANOVA. Moran’s Index (I), spatial metrics
(Clumpiness index) and spatial regression were used to analyse horizontal growth patterns and
processes. Three-Dimensional Spatial Index (3DSI), Nearest Neighbour Index (𝑅𝑛), vertical
entropy (𝐻𝑛) and standard regression were used to analyse patterns and processes of vertical
growth. Cellular Automata Markov model (CA-Markov) and binary logistic regression were used
to predict future urban growth. Analyses were conducted at p≤0.05.
Age of household heads was 39.92±12.48 years, while 65.5% were male. Household size was
4.92±2.38 and income was N66,468.43±N33,798.96 per month. Urban land area increased from
4.20km² in 1984 to 5.40km² in 2015. Net and gross changes in the built-up area were ±0.77km²
and 1.45km² respectively. There were significant spatial variations in urban horizontal growth in
1984 (F(1;18)=3.79), 2000 (F(1;18)=5.71) and 2015 (F(1;18)=11.75), but no significant temporal
variation. Horizontal temporal growth patterns were significantly clustered (I=0.28(1984),
0.53(2000) and 0.29(2015)). Fragmentation and aggregation were the major processes of urban
horizontal growth (Clumpiness index=0.87(1984), 0.84(2000) and 0.87(2015)). Population
growth (β=0.98), building lot size (β=0.04), demand for space (β=0.22) and housing stock
(β=0.0003) were major drivers of urban horizontal growth. Vertical growth increased between
2000 and 2015 (3DSI=6914.45) more than between 1984 and 2000 (3DSI=6601.82). Vertical
growth pattern was significantly clustered (𝑅𝑛=0.52), while aggregation (𝐻𝑛=0.1) was the major
temporal process of vertical growth. Number of financial institutions (β=0.68), rental value
(β=0.46) and proximity to water bodies (β=0.63) were the major drivers of vertical growth. By
2031, about 71.5% of Lagos Island would have been built-up. Proximity to water bodies through
land reclamation (β=4.11, Exp(β)=60.74) would be the most significant predictor of future urban
growth.
Lagos Island Local Government Area, Nigeria has witnessed both horizontal and vertical urban
growth due to fragmentation and aggregation of urban patches between 1984 and 2015. Urban
horizontal growth will decrease with the increasing vertical expansion, hence the need for
effective urban planning. |
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