Geohazard Analysis
Definition
Geohazard analysis is the assessment of natural Earth processes that pose risks to people and assets, including earthquakes, landslides, sinkholes, volcanic activity, tsunamis, coastal erosion, and ground subsidence. The analysis blends geology, geodesy, geomorphology, hydrology, and remote sensing to quantify where hazards are likely, how severe they could be, and how frequently they may occur. In a GIS, geohazard studies combine terrain models, soils, geology maps, rainfall or seismic indices, and human exposure to produce susceptibility, hazard, and risk maps. The approach supports mitigation, land use planning, early warning, and emergency response.
Application
Governments use geohazard analysis to guide zoning and building codes. Transportation and energy companies use it to select alignments and harden infrastructure. Insurers rely on hazard and risk layers for underwriting and pricing. Humanitarian agencies overlay exposure and vulnerability to target preparedness. Researchers evaluate landslide triggers with rainfall thresholds and soil moisture from satellites. Mining and construction firms monitor slope stability and ground movement. The common goal is to reduce losses through informed planning and timely action.
FAQ
What is geohazard analysis in GIS and how do hazard, exposure, and risk differ?
Geohazard analysis estimates the likelihood and intensity of damaging Earth processes. Hazard is the probability and magnitude of the event itself, exposure is what is in harm's way such as people and buildings, and risk is the expected consequence that combines hazard with exposure and vulnerability. Mapping all three gives a complete picture for decision making.
How do you build a landslide susceptibility model in GIS that stakeholders can trust?
Compile an inventory of past landslides, then assemble predictors such as slope, aspect, lithology, land cover, curvature, distance to streams, and rainfall. Split the data into training and validation sets. Use logistic regression or machine learning, assess performance with ROC curves, and calibrate thresholds for alerts. Document data sources, dates, and limitations, and publish a simple guide for nontechnical users that explains interpretation.
What mistakes undermine geohazard studies and how can teams prevent them?
Mistakes include mixing incompatible elevation models, ignoring temporal change in land cover, and treating susceptibility as if it were risk. Another issue is failing to quantify uncertainty or to validate against independent events. Prevent these mistakes by versioning inputs, including exposure and vulnerability in risk assessments, and reporting confidence intervals and caveats with every map.
Where has geohazard analysis delivered practical benefits in policy and operations?
Coastal cities used erosion hazard maps to set setback lines that saved homes during storms. A highway agency prioritized slope stabilization where risk was highest rather than where complaints were loudest. An insurer combined liquefaction hazard with building age to refine premiums and incentives, improving portfolio resilience while keeping rates fair.