Advancing River Health Assessment: An Integrated ISC Methodology Applied to Taiwan’s River Restoration Case Study

River health assessment frameworks play a critical role in guiding restoration planning and watershed management, yet conventional index-based approaches often rely on fixed weighting schemes that limit diagnostic sensitivity and interpretability. This study proposes an integrated assessment framework that enhances the traditional Index of Stream Condition (ISC) by incorporating data-driven structural information while preserving transparency and regulatory relevance. Rather than replacing existing indices, the framework recalibrates sub-index contributions based on intrinsic data patterns derived from nonlinear embedding and density-based clustering. The proposed methodology is applied to the Zhuoshui River basin in Taiwan to demonstrate its capability to improve internal consistency, reduce metric redundancy, and clarify dominant environmental drivers. Results indicate that the recalibrated index provides clearer differentiation among ecological conditions and improves explanatory consistency compared with the original ISC formulation. By balancing methodological innovation with interpretability, the proposed framework offers a practical pathway for strengthening river health assessment and supporting restoration-oriented decision-making.