Urban morphology plays a decisive role in regulating microclimate and outdoor thermal comfort in arid cities, where extreme heat and intense solar radiation amplify thermal stress. This study examines the influence of four contrasting urban fabrics in Béchar (Algerian Sahara): the vernacular Ksar, the regular-grid colonial fabric, a modern large-scale residential estate, and low-density detached housing, on local microclimatic conditions. An integrated methodological framework is adopted, combining qualitative morphological analysis, quantitative indicators including density, porosity, height-to-width ratio, and sky view factor, in situ microclimatic measurements, and high-resolution ENVI-met simulations performed for the hottest summer day. Results show that compact urban forms, characterized by low sky view factor values, markedly reduce radiative exposure and improve thermal performance. The vernacular Ksar, exhibiting the lowest SVF, records the lowest mean radiant temperature (approximately 45 °C) and the most favorable average comfort conditions (PMV = 3.77; UTCI = 38.37 °C), representing a reduction of about 3 °C, while its high-thermal-inertia earthen materials ensure effective nocturnal thermal recovery (PMV ≈ 1.06; UTCI = 27.8 °C at 06:00). In contrast, more open modern fabrics, including the colonial grid, large-scale estates, and low-density housing, experience higher thermal stress, reflecting vulnerability to solar exposure and limited thermal inertia. Validation against field measurements confirms model reliability. These findings highlight the continued relevance of vernacular bioclimatic principles for sustainable urban design in arid climates.

Rapid urban expansion in arid intermediate cities often produces fragmented urban structures that exacerbate inequalities in public transport accessibility and hinder sustainable mobility. However, the relationships between urban fragmentation, transport accessibility, and travel behavior remain insufficiently explored in pre-Saharan cities. This study investigates these interactions through the case of El Bayadh, Algeria, using an integrated methodology combining urban morphological analysis, Geographic Information Systems (GIS), a household survey of 577 households, traffic counts, institutional interviews, and spatial equality assessment based on the Gini coefficient. Public transport accessibility was evaluated using a 300 m walking threshold, complemented by sensitivity analyses at 400 m and 500 m. The results indicate that approximately 65% of the population lives within 300 m of a bus stop, although coverage is strongly concentrated in central districts. A Gini coefficient of 0.41, provided by the El Bayadh Directorate of Transport and computed across 20 urban zones, indicates moderate-to-high spatial inequalities in accessibility that persist despite increasing the service threshold, suggesting that these disparities are more closely associated with urban fragmentation than with the specific walking-distance threshold used to define service coverage. The transport network comprises 11 bus routes, approximately 160 bus stops, and 90 km of routes; however, limited service quality and uneven spatial distribution contribute to a high dependence on private transport, with 45% of trips made by private car, 35% by taxi, and only 20% by bus. These findings are consistent with accessibility inequalities arising from the mismatch between fragmented urban morphology, centralized urban functions, and the configuration of the public transport network. The proposed framework provides transferable insights for planning more equitable and sustainable mobility systems in rapidly urbanizing arid intermediate cities.

Saharan ksour are undergoing a profound transformation as urbanization spreads, building practices change, and old functions give way to new ones. Their architecture and building materials have been studied extensively. What has not been documented is how these pressures reshape the spatial relations that bind a historic core’s parts together. This matters because it is morphological continuity, not architectural fabric alone, that keeps a historic settlement legible once it is absorbed into a modern city. This study addresses that gap through a diachronic morphological reading of the Ksar of Béchar, in southwestern Algeria. It traces seven structuring components, the perimeter wall (Essour), defensive towers (Bordjs), gates (Bâb), the alley network (droub), collective open spaces (Rahbas/Nouader), the El Masdjid El Atik mosque, and the housing stock, across more than a century of change. The analysis draws on a triangulated corpus of historical archives, redrawn historic plans, archival photographs, 1952 and 1962 aerial imagery, recent satellite imagery, field observations, and testimonies from long-standing residents. Rather than comparing historical and current states at the level of individual components alone, the relational reading combines two analytical levels: it traces the differentiated trajectories of the seven components while simultaneously examining the persistence, transformation, and recomposition of the spatial relations between them across documented temporal states. This relational analysis reveals two differentiated morphological trajectories and one cross-cutting process. The defensive envelope (Essour, Bordjs, Bâb) has fragmented and largely disappeared. The internal structures (droub, Nouader, the mosque, housing) show strong spatial permanence beneath their architectural and functional change. And across all seven components, spatial relations have been recomposed as a system, progressively opening the once-enclosed core to the surrounding city. The Ksar of Béchar’s evolution is therefore neither integral conservation nor outright erasure. It is a relational recomposition in which peripheral, boundary-defining elements erode while internal structuring relations persist. Beyond this case, the study offers a transferable, source-triangulated analytical framework for reading morphological recomposition in Saharan and other vernacular historic settlements, one directly usable in heritage conservation and historic urban landscape management strategies.