Policy-oriented framework for multi-tiered urban development boundaries in the Tibetan-Qiang-Yi corridor

Urban development boundaries are essential instruments for regulating urban land expansion and structuring territorial spatial patterns. However, the influence of primary functional zoning on their delineation remains underexplored. This study integrates results from the dual evaluation system and township-level functional zoning to identify areas suitable and unsuitable for urban construction. Using the PLUS model, it simulates land use changes in the Panxi Dry Valley by 2035 and incorporates convex hull model validation to construct a multi-tiered urban development boundary system—comprising baseline, elastic, and priority boundaries. The results indicate that: (1) the western subregion emphasizes ecological protection, whereas the central subregion prioritizes both agricultural production and urban development; (2) under the Natural Development Scenario, construction land expands substantially by 2035, while the Policy-Driven Scenario effectively limits expansion, highlighting the regulatory role of policy constraints; and (3) the areas delineated for the baseline, elastic, and priority boundaries are 313.37 km², 5882.12 km², and 25,023.94 km², respectively. This approach integrates spatial planning with policy-oriented constraints, providing a systematic framework for hierarchical boundary delineation. It helps reconcile competing demands for urban development, cropland protection, and ecological conservation, offering practical insights for promoting coordinated regional development.