URBAN GROWTH PATTERNS AND PROCESSES IN LAGOS ISLAND LOCAL GOVERNMENT AREA, NIGERIA

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.