Three topographical approaches to survey soil erosion on a mountain trail affected by a forest fire. Barranc de la Manesa, Llutxent, Eastern Iberian Peninsula

Soil erosion on mountain trails threaten the sustainability of soils and vegetation. There is a wide theoretical knowledge about the effects produced by mountain recreational activities, but particularly for soil erosion there is a shortage of field data. This is why it is necessary to properly survey the soil losses on mountain trails. The most widely applied method in scientific literature is the Cross-Section field survey as is easy-to-apply and low- cost. However, there is a doubt about its accuracy and the development of the new technologies may improve the quality and accuracy of the measurements. Aerial and terrestrial photogrammetric methods are difficult to apply when vegetation is present but, an opportunity arises to apply this method when fire takes place. This paper analyses the soil losses in a recently fire-affected land to check the accuracy of the three methodologies to assess soil loss on mountain trails. The results obtained show an average soil loss between 1287 and 1404 Mg ha-1 of trail erosion for the three methodologies applied, which implies that the Cross-Sectional-Area method, aerial photography and terrestrial photography provide very similar values. Therefore, the conventional Cross-Section field surveys method is useful and adequate to evaluate the impacts generated on mountain trails as it provides accurate measurement and can be repeated any time and below different vegetation covers. The terrestrial photogrammetric methods are accurate too, but they can only be used when there is very little vegetation cover such as in semiarid and arid landscapes or after forest fires. Moreover, they are more expensive and time consuming.