Speaker
Description
Forest roads are a critical component of forest management infrastructure. They ensure access to timber resources but may also support recreation, conservation and access to rural areas. In Norway, extreme precipitation events have lately caused widespread road failures and erosion and have highlighted limitations in existing drainage design standards. This study presents final results from an integrated assessment of forest road drainage performance under extreme rainfall conditions with respect to culvert design, density and placement.
We chose two case study areas heavily affected by extreme precipitation events in recent years to study the efficiency of current design standards under present and future climate conditions. We combined detailed field surveys with digital terrain data to model flow paths, estimate surface runoff and evaluate the hydraulic performance of existing drainage structures for different return periods and under climate-adjusted precipitation scenarios. These analyses were complemented by cost–benefit assessments to quantify the relationship between drainage capacity, infrastructure damage, and investment costs.
The results indicate that minimum design standards based on 25–50-year return periods are often insufficient under current and projected climate conditions, particularly in steep terrain. Culvert capacity, inlet and outlet configuration, road alignment, and longitudinal slope were identified as key factors influencing failure risk. The study further demonstrates that targeted upgrades of critical drainage elements, including increased culvert dimensions and improved inlet protection, can substantially reduce damage while remaining economically viable.
Based on the empirical findings and model simulations, the project delivers updated, evidence-based recommendations for forest road drainage design, upgrading, and maintenance. A practical risk assessment framework and a spreadsheet-based decision-support tool for culvert dimensioning were developed and validated in the study areas. These tools enable forest road planners and managers to identify vulnerable sections, prioritize interventions, and balance technical performance with economic constraints.
By integrating field observations, hydrological modelling, and economic analysis, this research provides concrete guidance for improving the resilience of forest road networks under increasing climate variability. The outcomes support adaptive infrastructure planning and contribute to strengthening sustainable and resilient forest value chains.
| Keywords | Forestroads; Precipitation; Culverts; Resilience |
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