Spatiotemporal dynamics of informal settlement thermal environments and their driving factors in Nairobi, Kenya
Year: 2026
Type: article
Abstract: Rapid urbanization in sub-Saharan Africa (SSA) has expanded informal settlements where residents face extreme heat, yet informal settlement thermal dynamics remain understudied. Nowhere is this more evident than in Nairobi, one of SSA’s most rapidly growing metropolises, which faces critical challenges from unregulated informal settlement expansion, characterized by high population density and threats to urban sustainability and resident well-being. Using Landsat 8/9 imagery from three February scenes (2015, 2020, 2025), remotely sensed indices, and geospatial data, this study investigated land surface temperature (LST) evolution across Nairobi’s 17 subdivisions and 13 mapped informal settlements, of which 12 were retained for formal analysis. Informal settlements consistently exhibited elevated LSTs, with Kibera approximately 2.6 °C warmer than its parent administrative subdivision in 2015 (34.28 °C vs. 31.67 °C), a pattern that persisted with variations of 1.5–2.9 °C. The urban heat island followed a persistent east–west gradient: industrial and informal settlements were > 95% heat-dominated, while western highlands remained cool. The anomalously wet February of 2020 temporarily reduced area-weighted mean LST from 33.1 °C (2015) to 29.9 °C (2020), with partial rebound to 30.7 °C by 2025, without resetting the spatial pattern. Because this wet anomaly confounds interpretation as a continuous trend, the 2015–2025 comparison was treated as an interannual snapshot comparison rather than a linear trend analysis. Standard deviation ellipse (SDE) analysis revealed a net southeastward shift of the heat island centroid (~ 0.72 km). NDBBI showed the strongest positive correlation with LST ( r = 0.86) and FVC the strongest negative correlation ( r = − 0.77). Spatial principal component analysis (SPCA) extracted three composite drivers explaining 77.2% of variance. A tentative comparison of summed regression coefficients suggested a larger aggregate association for human-related factors than natural factors, though these are associations, not causal estimates. These findings highlight the need for targeted interventions for Nairobi’s approximately 2.5 million informal settlement residents.
Source: Discover Cities
Authors: Godfrey Nkugwa, Doreen Loyo
Institution: Wuhan University of Technology
Language: English
Topic: Urban Heat Island Mitigation
Subfield: Environmental Engineering
Field: Environmental Science
Domain: Physical Sciences
Open Access status: diamond
Funder: U.S. Geological Survey
OpenAlex ID: W7225383712