Modelling and simulating ‘informal urbanization’: An integrated agent-based and cellular automata model of urban residential growth in Ghana

The global urban population is expected to grow by 2.5 billion over the next three decades, and 90% of this growth will occur in African and Asian countries. Urban expansion in these regions is often characterised by ‘informal urbanization’ whereby households self-build without planning permission in contexts of ambiguous, insecure or disputed property rights. Despite the scale of informal urbanization, it has received little attention from scholars working in the domains of urban analytics and city science. Towards addressing this gap, we introduce TI-City, an urban growth model designed to predict the locations, legal status and socio-economic status of future residential developments in an African city. In a bottom-up approach, we use agent-based and cellular automata modelling techniques to predict the geospatial behaviour of key urban development actors, including households, real estate developers and government. We apply the model to the city-region of Accra, Ghana, drawing on local data collection, including a household survey, to parameterise the model. Using a multi-spatial-scale validation technique, we compare TI-City’s ability to simulate historically observed built-up patterns with SLEUTH, a highly popular urban growth model. Results show that TI-City outperforms SLEUTH at each scale, suggesting the model could offer a valuable decision support tool in similar city contexts.

Lack of vegetation exacerbates exposure to dangerous heat in dense settlements in a tropical African city

Both climate change and rapid urbanization accelerate exposure to heat in the city of Kampala, Uganda. From a network of low-cost temperature and humidity sensors, operational in 2018-2019, we derive the daily mean, minimum and maximum Humidex in order to quantify and explain intra-urban heat stress variation. This temperature-humidity index is shown to be heterogeneously distributed over the city, with a daily mean intra-urban Humidex Index deviation of 1.2°C on average. The largest difference between the coolest and the warmest station occurs between 16:00 and 17:00 local time. Averaged over the whole observation period, this daily maximum difference is 6.4°C between the warmest and coolest stations, and reaches 14.5°C on the most extreme day. This heat stress heterogeneity also translates to the occurrence of extreme heat, shown in other parts of the world to put local populations at risk of great discomfort or health danger. One station in a dense settlement reports a daily maximum Humidex Index of >40°C in 68% of the observation days, a level which was never reached at the nearby campus of the Makerere University, and only a few times at the city outskirts. Large intra-urban heat stress differences are explained by satellite earth observation products. Normalized Difference Vegetation Index (NDVI) has the highest (75%) power to predict the intra-urban variations in daily mean heat stress, but strong collinearity is found with other variables like impervious surface fraction and population density. Our results have implications for urban planning on the one hand, highlighting the importance of urban greening, and risk management on the other hand, recommending the use of a temperature-humidity index and accounting for large intra-urban heat stress variations and heat-prone districts in urban heat action plans for tropical humid cities.

Pediatric brain abscess – etiology, management challenges and outcome in Lagos Nigeria

Background: Brain abscess in children is a neurosurgical emergency with potentially catastrophic outcome despite the advances made in neuroimaging techniques and antibiotic therapy. Symptoms are nonspecific and may vary with the child’s age, location, size, numbers and stage of abscess, and the primary source of infection. Treatment is usually with broad-spectrum antibiotics in combination and surgical evacuation in most cases or antibiotics alone in selected cases with clear-cut indications. This study was to document clinical characteristics, etiological factors, and spectrum of bacteriologic agents responsible for pediatric brain abscess in an African city, the challenges and management outcome over the study period. Methods: This was a retrospective study over an 11-year period involving 89 children who presented with brain abscess. Information of interest was extracted from the medical records of each participant. The results from data analysis were presented in charts and tables. Results: Eighty-nine children aged 0.85–15.7 years (median age of 6.4 years) met the inclusion criteria. The male-to-female ratio was 1.8:1. Headache (80%), fever (78%), and hemiparesis (78%) were the most common symptoms. Brain imaging deployed was CT scan in 56 (63%), MRI in 9 (10%), and transfontanel ultrasound scan in 24 (27%) children. Seventy-one (80%) children had antibiotics with surgical evacuation while 18 (20%) children received only antibiotics. In 19 (27%) children, the culture of the abscess was negative. In 53 (75%) children, Gram-positive aerobic organisms were isolated. A total of 75 patients (84%) had a favorable outcome. Conclusion: Pediatric brain abscess still poses significant public health challenge, especially in resource-limited regions. Successful management of brain abscess requires high index of suspicion for early diagnosis, referral, and intervention.

Revitalising South African City Centres Through ICT

The majority of South African city centres are in a state of degeneration and need revitalising. The factors that contributed to the degeneration and how the integration of information and communications technology (ICT) can be used to revitalise them were examined in three South African city centres. The research was grounded in place theory. A survey method, including the Delphi technique, followed by factor analysis, and ordinal regression modelling was used to collect and analyse data. The findings indicated that enhancing accessibility and safety, social and community involvement, human experience, built-up environment, and vibrancy were the five major components which needed reinforcing to revitalise the city centres. However, ICT-linked strategies, including networking the areas with free Wi-Fi hotspots, creating places in which to congregate, providing digital screens, and installing cameras and remote monitoring, are expected to attract people and to facilitate accessing real-time information about different events, marketing, branding, and creating a unique image. Also, the use of ICT will assist in reducing criminal activities and dispel the fear of crime. The combined effect is likely to encourage people and businesses to return the city centres, making these areas vibrant and accessible.

Urban Growth, Fuel Service Station Disasters and Policy Compliance in Ghana

Disasters associated with Fuel service stations (FSS) in Ghana have been debated severally and attracted policy attention, yet their mitigation strategies seem too far off and unimaginably unrealistic. Knowing that such disasters can limit enjoyment of citizenship rights, Ghana has developed safety standards geared towards mitigating their effects. Framed around the compliance theory and drawing on data from 150 residential owners located within 15.4m buffer zone and five state institutions, this article examined the extent of compliance with safety policies guiding FSS in Kumasi, Ghana. The results showed that compliance with safety policies was sinking into its bare existential levels as none of the facilities selected for the study passed all the 11 safety standards. The facilities also negatively affected residents who never considered their place of abode as perilous and that they live in zones of vulnerabilities. This situation it is argued, fundamentally affects development trajectory of the contemporary African city. It obviously obscures the realities of interrelated processes shaping urban disaster management. Even though the spring-up of FSS have catapulted economic growth, inherently they are also hazard-ridden. We suggest that in the broad scheme of urban planning, FSS safety policies must not be discussed in the margins.

Tracking Airborne Pollution with Environmental Magnetism in A Medium-Sized African City

As in other parts of the world, air pollution over West and Central Africa has major health and meteorological impacts. Air quality assessment and its possible sanitary impact have become essential even in medium-sized towns, therefore amplifying the need for easy-to-implement monitoring methods with low environmental impact. We present here the potential of magnetic methods to monitor air quality at street level in the medium-sized city of Maroua (northern Cameroon) affected by dust-laden desert winds. More than five hundred (544) samples of bark and leaves taken from Neem trees in Maroua were analyzed. Magnetic susceptibility, saturation remanence, and S-ratio were found to determine the concentration and nature of magnetic particles. They are dominated by magnetite-like particle signals as a part of particulate emissions due to urban activities, including both traffic, composed of a substantial proportion of motorcycles, and wood burning for food preparation. We show that both bark and leaves from Neem trees are adequate passive bio-recorders. The use of both enables different times and heights to be sampled, allowing for the high-resolution monitoring, in terms of spatialization, of various urban environments. Particle emissions require assessment and screening that could be carried out rapidly and efficiently by magnetic methods on bio-recorders, even in cities impacted by dust-laden wind.