Suggested Enhancements to the Geologic Model Complexity Rating System

Abstract

The suggested Geologic Model Complexity Rating System, introduced in 2014, was developed considering the 1993 Oregon rockfall hazard rating system with four rating levels. Five of the nine Geologic Model Complexity Rating System components pertained to geologic complexity: four regional components (genetic, structural/deformation, alteration/dissolution, and weathering/erosion) and one site-scale component. The other Geologic Model Complexity Rating System components were: terrain features, information quality, geologist competency, and level of effort. A pairwise comparison of components for a landslide hazard study, using a multi-factor decision analysis procedure called Analytic Hierarchy Process (AHP), weighted geologist competency highest (20%), followed by genetic complexity and deformation (each 18%) and site-scale complexity and level of effort (each ~11%). The other four components had weights from 8 to 3%. The 1–9 scoring for AHP, with 1 indicating that components are equal and 9 indicating one is extremely more important, appeared to be useful for objective comparisons. The AHP matrix configuration lists components in the same order in rows and columns. Regional complexity is now being considered as a single four-element component that depends not only on the basic geology of the site area, but also on the purpose of the geologic evaluation. Thus, the suggested enhancements streamline the Geologic Model Complexity Rating System, reducing it from nine components to six, but also complicates it by considering basic geology and purpose of evaluation as fundamentally important to the geologic model. These enhancements bring the suggested Geologic Model Complexity Rating System into alignment with the Oregon rockfall hazard rating system, which included facility components (i.e., what is at risk) for which the hazard was being rated.