Geohazard Unit

The Durable Solutions Geo-Hazard Technical Unit oversees the geological assessments of geo-hazard and relocation sites, and provides an overall geo-hazard technical support within the Secretariat. In addition, the Geo-Hazard Unit supports the NRA in identifying and verifying the safety of land selected for purchase by eligible program participants.

The Unit also supports the NRA in promoting national design standards for geo-hazard mitigation works necessary for the safe mitigation of Category 2 geo-hazards.

Relative Risk Scoring Methodology

The purpose of scoring process is to identify those communities located in the most hazardous environments to assist with planning of communication strategies, prioritization of intervention and monsoon preparedness. The risk ratings undertaken relate specifically to landslide risk (as opposed to flooding and seismic amplification, for example).

Risk rating has only been undertaken for communities classified by the NRA geo-hazard assessment as Category 2 (with geo-hazards that can be managed without the requirement for household relocations) and Category 3 (requiring household relocations to safer areas).

Scoring scales of 1 to 5 were developed for each of four components:

  • High Risk of (or, hazard magnitude)
  • Probability of Risk Occurring
  • Direct Risk for (or, significance of the elements at risk)
  • Potential Impact (or, vulnerability)

Each component is then multiplied to provide a Risk Score where the higher the score, the higher the relative risk.

Risk Score High Risk Of Risk Probability Direct Risk For Potential Impact
1 Small failure or erosion Unlikely (event expected  to occur every 1,000 to 10,000 years) Agricultural land Little or no effect
2 Moderate failure – small falling blocks or small shallow failures. All plan dimensions ≤ 100 m, depth  ≤ 3 m) Possible (event expected  to occur every 100 to 1,000 years) Infrastructure (roads, footpaths, water supply) Minor damage (easily recovered)
3 Substantial failure – large falling blocks or large  shallow failure. At least    one plan dimension > 100 m, depth ≤ 3 m) Likely (event expected to occur every 10 to 100 years) Residential, 1 to 5 households Significant damage (hard to recover)
4 Substantial deep seated failure. Any failure with depth > 3 m Very Likely (event expected to occur every 2 to 10 years) Residential, 6 to 10 households Major damage (cannot be recovered)
5 Major failure (e.g. Jura landslide scale) Almost Certain (event expected to occur at least once per year) Residential, > 10 households Fatalities


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