An Internal Validation Assessment of Scale Across Composite Index Model Structures

Area of Science:

• Environmental Science
• Public Health
• Geospatial Analysis

Background:

• Natural hazard planning is crucial for mitigating destruction and socioeconomic impacts.
• Composite indices, such as the Social Vulnerability Index (SVI), help identify populations at risk for equitable planning.
• Existing research on SVI construction has not fully explored the spatial elements, particularly scale selection, and their influence on index outcomes.

Purpose of the Study:

• To evaluate the impact of scalar properties (areal units, geographic boundaries) and indicator selection on Social Vulnerability Index (SVI) ranks.
• To compare the robustness of different SVI model structures (hierarchical and inductive) under varying spatial and indicator selections.
• To address the underexplored spatial elements in SVI models and their contribution to uncertainty in hazard preparedness.

Main Methods:

• Assessed two established SVIs (CDC SVI, HVRI SVI) across three model structures: hierarchical with z-score standardization, hierarchical with percentile ranking normalization, and inductive with z-score standardization.
• Employed uncertainty and sensitivity analysis to quantify the impact of changes in scalar properties and indicator selection.
• Examined the influence of scale selection and indicator choice on SVI ranks and model robustness.

Main Results:

• The inductive model structure was found to be less robust compared to hierarchical models when altering scalar and indicator properties.
• Indicator selection emerged as the primary factor driving variability in SVI ranks across all tested model structures.
• Scale selection demonstrated significant, albeit mixed, effects on SVI rank variability, with notable interaction effects observed.

Conclusions:

• Scale selection plays a critical role in shaping Social Vulnerability Index (SVI) outcomes, influencing hazard management and preparedness.
• Indicator selection is a major source of variability in SVI results, necessitating careful consideration during index construction.
• Critical evaluation of SVI creation processes, including scale and indicator choices, is essential for advancing equitable natural hazard management.