Spatial Morphology of Historic Built Environments in Valley Settings: A Comparative GIS and Space Syntax Analysis for Sustainable Conservation Planning

The sustainable development of valley-type historic towns is increasingly challenged by tourism growth, infrastructure modernization, and community change. Effective responses require a systematic understanding of how spatial morphology mediates the trade-offs between heritage conservation and socio-economic vitality. However, existing studies rarely connect configurational analysis with actionable sustainability strategies in topographically constrained settings. This study addresses this gap by developing a multi-level comparative framework that integrates GIS-based environmental assessment, space syntax configurational modelling, and building-fabric fieldwork. The framework is applied to three historic towns in the upper Yellow River Basin—Qingcheng, Hekou, and Hongcheng—which share similar valley constraints but diverged in historical functions (commercial, defensive, and mixed). Four dimensions are examined, mountain–water patterns, street networks, building fabric, and public-space systems, using indicators including elevation, slope, distance to water, axial integration, intelligibility, shop-front proportion, street aspect ratio, and public-node service radius. The results reveal two complementary layers of spatial logic. At the environmental level, all three towns exhibit shared valley-adaptive traits—near-water locations on relatively gentle terrain, low-slope terrace occupation, axial elongation, and concentrated public spaces. Flood risk was not directly assessed in this study. At the functional level, marked differentiation emerges. Hekou shows the highest network intelligibility (R2 = 0.900) and commercial frontage (35% shop-front proportion), which may be interpreted in relation to its commercial and transportation history; however, socio-economic vitality was not directly measured. Hongcheng displays lower intelligibility (R2 = 0.556) and thicker defensive walls (0.6–0.8 m), which may be interpreted in relation to its defensive history; however, cultural resilience and economic adaptability were not directly measured. Qingcheng presents a mixed pattern with a single high-integration axis and diverse public nodes, which may be interpreted as functional layering; this interpretation is theoretical and was not directly tested. Rather than offering a universal model, this study provides an evidence-based framework for diagnosing the sustainability implications of spatial form in valley-type historic towns. The findings translate morphological indicators into differentiated management strategies—prioritising commercial corridor continuity in Hekou, preserving defensive spatial sequences in Hongcheng, and balancing functional layering along the historic axis in Qingcheng. This framework contributes to sustainable heritage management by demonstrating how spatial analysis can inform context-sensitive planning that reconciles conservation with development in environmentally constrained settings.