Validation of the OpCost logging cost model using contractor surveys

Abstract

ABSTRACTOpCost is a harvest and fuel treatment operations cost model developed to function as both a standalone tool and an integrated component of the Bioregional Inventory Originated Simulation Under Management (BioSum) analytical framework for landscape-level analysis of forest management alternatives. OpCost is an updated implementation of the Fuel Reduction Cost Simulator (FRCS). However, neither FRCS nor OpCost have been formally validated. Validation of simulation models using data that are independent of those used for model development is important for building user confidence in model predictions. This is particularly true when models are embedded in decision support systems and deployed regionally to inform policy. To evaluate the quality of OpCost predictions in fuel reduction treatments, a mixed method survey was conducted in Oregon, Washington, and Idaho. Professional logging contractors were asked to estimate the production rates and costs of common logging systems using timber sale prospectus data generated using GIS and the FVS model. Comparing survey results to production and cost estimates generated by OpCost for the same stand and site conditions facilitated evaluation of prediction error for both entire harvest systems and their individual equipment components. Model predictions were not different from expert estimates of total costs for harvest systems, but there were differences between predicted and expert estimates of production rates for individual pieces of equipment.