A dataset and review of empirical estimation relationships for landslide runout distances

Estimating landslide runout distances is crucial for assessing their potential impacts on surrounding infrastructure and communities. By comparing estimated runout distances with the proximity of landslides to vulnerable sites, the likelihood of landslide impact can be assessed, and the volume of debris that may reach such locations can be indirectly quantified. This paper presents a comprehensive review of 28 empirical relationships developed to estimate landslide runout distances associated with various triggering factors, including earthquakes, rainfall, and other factors, while also accounting for different material types such as soil, rock, and soil-rock mixtures. The relationships are analyzed in terms of equation formats, adopted parameters, and the number of parameters involved, identifying volume and height as the most frequently used variables and mixed equation formats (e.g., logarithmic and linear combinations) as the most common. Existing definitions of runout distance are reviewed, and this study adopts the definition as the horizontal distance between the upper point of the landslide source and the lowest point of deposition, chosen for its clarity and ease of measurement from mapped landslide inventories. To validate the summarized relationships, a dataset comprising 22,456 landslides was established. The analysis revealed low R² values for many existing empirical relationships, highlighting the necessity for developing improved empirical relationships. This study develops new empirical estimation relationships tailored to different triggering factors and material types, enhancing estimation accuracy of landslide runout distances. The finalized empirical relationships are offered and aim to serve as practical tools for the rapid estimation of landslide runout distances, thereby supporting effective disaster response and mitigation strategies.