Morphometric Signatures of Urban Blocks in Sana’a Old City: A Multivariate Taxonomy for Evidence-Based Conservation

The Old City of Sana’a, a UNESCO World Heritage Site, remains morphologically unclassified at the urban block scale, with understanding still grounded in descriptive narrative rather than quantitative data—leaving conservation decisions without a measurable, reproducible spatial evidence base. This study introduces a numerical taxonomy of 115 historic urban blocks built from four standardized morphometric indicators—area, compactness, elongation, and rectangularity—together with axially encoded orientation, reduced through Principal Component Analysis (74.7% variance, three components) and partitioned by K-means into five morphologically distinct block types (n=36,29,19,16,15). Kruskal–Wallis tests confirmed significant differentiation across all types for every rankable indicator (all p<0.001; Dunn’s post-hoc: 28 of 50 pairwise contrasts significant). Qibla deviation—a culturally specific measure of angular proximity to Mecca, deliberately withheld from clustering—emerged as the strongest discriminator between types (ηH2=0.714), showing that shape and orientation alone recover a coherent pattern in which one type’s mean orientation axis falls within 4.5∘ of the Qibla axis. However, this statistical discriminator reflects the distinctiveness of a single type rather than a universal cultural organizing principle across the fabric. Types are distributed across all three historic zones rather than clustering spatially, and shape regularity shows no association with distance from the Great Mosque. Building on these signatures, a percentile-based screening instrument offers a reproducible, block-level morphometric baseline to help prioritize this UNESCO-listed site’s conservation under active conflict-related threat.