Landslide Susceptibility Mapping

Definition

Landslide susceptibility mapping estimates the relative likelihood of landslide initiation based on terrain, geology, hydrology, and land use. Unlike runout models, it focuses on where slides may start, not how far they will go. Methods range from expert heuristic overlays to statistical and machine-learning models (logistic regression, random forests, gradient boosting) trained on inventories of past slides and non-slide controls. Predictor variables commonly include slope, aspect, curvature, lithology, soil depth, fault proximity, precipitation, NDVI, and road or river proximity. Because training data can be biased toward accessible areas, balanced sampling and spatial cross-validation are essential. The output is often a susceptibility index categorized into classes for planning. Uncertainty and temporal dynamics (e.g., post-fire periods) should be explicit.

Application

Planners restrict development or require engineering studies in high-susceptibility zones. Infrastructure managers prioritize slope stabilization and drainage maintenance. Emergency services monitor hotspots during extreme rainfall. Insurers and lenders use maps to understand portfolio risks. After wildfires, heightened susceptibility guides debris flow warnings.

FAQ

How do we deal with inventory bias?

Use spatially balanced background samples, correct for reporting bias, and validate in areas not used for training. Crowdsourcing with quality control can expand coverage.

Do models transfer between regions?

Caution is needed. Lithology, climate, and land use differ. Models often require retraining or at least recalibration with local data.

What temporal factors matter most?

Antecedent rainfall, snowmelt, and vegetation loss after fires. Include dynamic predictors or develop separate seasonal models where data allow.

How should susceptibility be expressed?

Use ordinal classes with descriptions (low–very high) and include maps of model confidence. Avoid implying precise probabilities without calibration.