Geomorphodiversity index: Quantifying the diversity of landforms and physical landscape

The physical landscape is the mosaic resulting from a wide spectrum of environmental components. The landforms define the variety, or diversity, of the geomorphological component: the geomorphodiversity. Landforms are usually represented in thematic maps where the scale and the graphic solutions are widely heterogeneous. Since geomorphological maps are not always easy to obtain and standardize, topography might be used as a proxy to infer the morphological signature. To recognize, evaluate, and in some cases promote the geomorphodiversity of an area, a numerical assessment is preferable. Through the use of quantitative approaches, indexes can be defined which quantitatively characterize the physical landscape in a discretized space consisting of continuous and regular cells. In this approach each cell is labelled with an algebraic value, which increases with the diversity degree. In this paper a quantitative index for geomorphodiversity is estimated stressing the topographic variables derived from Digital Elevation Models in a GIS environment. The resulting index is the sum of the variety of each terrain parameter taken into account. The areas characterized by the highest value of geomorphodiversity index show a good correspondence with well-known situations in the region where not always the geological heritage is properly acknowledged. The areas characterized by the lowest value of geodiversity correspond to the center of some intermountain basins of the region. Being the index strictly related to the topographic variety, this result is quite obvious but not easily predictable since in some flat areas the index is higher. Comparing the results with the geomorphological map of the area performs a validation procedure for the method. A positive correlation is found between the index calculated and the presence/absence of landforms. The paper shows that the index is a useful and simple tool for the identification, analysis and promotion of the geological heritage.