From Fragmented Plans to a Public Regulatory Knowledge Infrastructure: Harmonizing Flood and Landslide Risk Planning in the Central Apennine River Basin District, Italy

Italy’s transition to river basin district governance within the framework of Directive 2000/60/EC unified institutional responsibilities while leaving existing flood and landslide plans in force. District authorities therefore had to integrate instruments with different knowledge bases, classifications and land-use rules. This article examines the integration of nine Hydrogeological Setting Plans (PAIs) into two coordinated plans for the Central Apennine district (42,275 km2), adopted in final form in May 2026. Document analysis compared classifications, intervention conditions and assessment responsibilities, examining 175 public submissions and 118 first-round regional determinations. Geographic information system analysis quantified current classification correspondences and coverage: approximately 1860 km2 within the fluvial planning framework, including safeguard proposals, and 107,045 landslide phenomena occupying approximately 4970 km2. Initial flood transposition retained inherited boundaries, while landslide classification followed a common type–activity matrix. Regulatory comparisons identified conditional extensions of admissibility alongside more selective urban restructuring rules; the plans also established formal updating procedures. Institutional review connected technical choices with regulatory decisions, producing amendments while leaving some precautionary disagreements unresolved. The framework coordinated inherited knowledge without eliminating differences in detail or completeness. The article offers a procedural and regulatory reference for other authorities facing fragmented planning systems; implementation and risk-reduction outcomes require subsequent evaluation.