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Address : Geological Survey of Finland, Finland
Celebration date : 23 Tuesday September 2008
Author name : Lehtinen, Kristina

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  • Article title : Geological factors affecting erosion rate in nature trails, northern Finland
    Article type : Geomorphology
    Location : International Geological Congress,oslo 2008

    Fulltext :

    Increasing tourism, round-year use and new activities cause erosion on nature trails around tourist centers. To predict and prevent erosion damages it is necessary to study factors affecting erosion. Research for the geological factors is important, because geology forms a basement for the trails and other activities, and defines the vulnerability of the ground to erosion. The purpose of this study is to find equipment to estimate erosion problems on nature trails and to create a classification of erosion resistance for different type of geo-environments in northern Finland.
    The study area and methods
    Geological factors affecting erosion rate is studied at 10 study areas (tourist destinations) in northern Finland. Target area selection was done so that different types of bedrock and surficial deposits typical for northern Finland are represented. Hypothesis was that the soil erosion has correlation with the quality of bedrock and soil, geomorphology, topography, grain size distribution, moisture conditions, climate, vegetation, and amount of visitors. Also, the way how, and the seasons when the trails are used are affecting. Three to six sites at nature trails from all of the targets were chosen. Width and depth of the trail were measured and the thickness of soil layer was estimated. Erosion rate was estimated visually. Soil and stone samples were taken at every site on the trail and beside it. Soil samples were sieved and the grain size distribution determined. Rock type of the stone samples was specified and roundness measured. Geophysical measurements were carried out during 2006 and 2007 at early and late summer to find out seasonal variation on soil conditions.
    Preliminary results
    Preliminary results show that surficial deposits composed of till are complex base for the nature trails. Some till types could bare erosion quite well when other are sensitive to it. Grain size distribution seems to have great influence on trails’ physical characteristics; especially on water content. Even big changes in water content both on the trail and beside it do not affect much on erosion resistance in some till areas. Stone samples show that stones are usually more rounded beside the trail than on the trail. Hard, durable stones like quartzite are more abundant on trail than beside. Stones that are sensible to erosion like schists are in minority or absent on trail. Angular rocks on trail seem to compound erosion. Bedrock quality affects erosion rate especially on hill slopes. Nature trails on till ground in which stones are composed of coarse granites and quertzites are often more eroded. At slopes melt water erosion usually causes biggest erosion damages. Trail is acting as drainage channel for melt water, washing away loose material. Especially, the till-covered slopes with shallow soil and stones composed of coarse granites are vulnerable.