TH scores update: LANDSLIDE

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Hazard Processing Method

• Data Source: Single landslide index raster (classes 1-5)
• Unit: Index
• Default Value Threshold: 0 (not used)
• Default Area Threshold: 2%

Workflow:

1. Count percentage of pixels for each index class (1-5)
2. Find highest index class where area ≥ area threshold %
3. Check from highest to lowest: 5 → 4 → 3 → 2 (skip 1 = no hazard)
4. Remap index to hazard score using:
   • Index 1 → Score 0 (no hazard)
   • Index 2 → Score 0
   • Index 3 → Score 1
   • Index 4 → Score 2
   • Index 5 → Score 3

Scoring Logic:

• Highest index class meeting area threshold determines score
• Value threshold parameter is disabled (area-based only)

Output Columns:

• LS_Index_max: Highest qualifying index class
• LS_Index1_area_pct through LS_Index5_area_pct: Area coverage per class
• Hazard_score: Final remapped score

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Comparison

Comment: the new source and method returns scores that are overall quite close to the original, but also introduces the "not affected" class.

New score distribution: ADM2

New score distribution: URBAN

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Original (2019) vs. 2025 Update

Data Overview

• Original Dataset: 38,229 administrative regions (ADM2 level)
• 2025 Dataset: 39,370 administrative regions (ADM2 level)
• High-Quality Matches: 33,207 regions (90%+ matching confidence)
• Unmatched Original: 5,022 regions
• Unmatched 2025: 6,268 regions

Technical Notes

• Hazard ranks: -1 = N/A, 0 = Very Low, 1 = Low, 2 = Medium, 3 = High
• Original data used text codes (VLO, LOW, MED, HIG), converted to numeric for easier comparison (delta)
• Matching threshold: 90% similarity required for inclusion in analysis
• Medium-quality matches (70-90%) available in separate sheet for manual review

Matching Method

Fuzzy string matching using hierarchical location names (Country | Admin1 | Admin2).
Only high-quality matches (≥90% similarity) were used for hazard comparison.

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• Regions Compared: 21,919
• Agreement: 47.7% (10,459 unchanged)
• Net Trend: Downgrades (9,141 downgrades vs 2,319 upgrades)
• Average Change: -0.73 ranks
• Notable Shifts:
  • High → Medium: 2,831 regions
  • Low → Very Low: 2,125 regions
  • Many high-risk regions were downgraded

Comment

New approach introduces many more N/A areas (large american and asian planes), new high resolution dataset allows for better details and, consequentely, relatively smaller high-hazard areas, i.e. the peak areas of a mountain instead of the whole mountain range. Hotspots regions are mostly unchanged.