Seasonal Trafficability of Forest Soils and Gravel Roads

Finland has one of the densest forest road networks in Europe, with approximately 160,000 km of forest roads (6-16.5 m/ha) built to meet the transport needs of the forest industry, forest management and others such as recreational users and emergency services. Forest management and harvesting activities are heavily influenced by changing weather conditions outside the road network. Reliable quality information is currently not available for most of these areas and roads. The terrain trafficability in Scandinavia is highly affected by seasonal changes and conditions which can vary greatly from year to year, creating difficulties for forestry operations. Mechanized wood harvesting requires adequate trafficability conditions for forest tractors. Operations are avoided on soils with a high moisture content, i.e. peatlands and fine-textured soils during low bearing capacity periods due to the high risk of serious rutting, soil compaction and root damage. Consequently, harvesting is often postponed to the winter season, when soil is typically frozen. Moreover, within the existing forest network there is a limited number of roads that are suitable for year-round use by heavy-duty vehicles. The additional yearly costs caused by challenging trafficability conditions could be reduced by obtaining additional information on soil and road conditions, especially their bearing capacity.

The aim of the project is to develop a concept to collect the necessary information regarding the load bearing capacity of selected forest sites, forest road sections and their associated characteristics. These sites and road sections represent critical bottlenecks within the transportation system. Specifically, the project seeks to identify those forest sites and sections of forest roads where the characteristics (ditch depth and quality, road width, road level in relation to the surrounding terrain) are not at a sufficient level and are therefore likely to represent bottleneck in terms of trafficability. In this project, bottlenecks will be identified using both existing and new field data. In addition, the project will utilize various airborne data including Airborne Laser Scanning (ALS) data, drone-based gamma-ray maps, the Topographic Wetness Index (TWI) layer and the Harvest Season Map Service Data. The integration of these data sources will support the development of predictive models. We expect, that trafficability of terrain soils and roads can be effectively characterized and dynamic models can be created to support decision making in forestry operations.

Academy of Finland has awarded a total of 419 379 € for this project (2025-2029), and it is implemented jointly with Luke