Mapping geomorphic hazards in Romania: small, medium and large scale representations of land instability / Carte des aléas géomorphologiques en Roumanie : représentation à petite, moyenne et grande échelles

Abstract

Abstract Geomorphic hazard maps are based on the categorisation of ongoing dynamics and an understanding of future trends. Terrain classification in the map legends is based on an assessment of geomorphic agencies. The level of detail is scale-dependent. This paper presents a nested sequel of three geomorphic hazard maps, which reveal aspects of land instability in Romania from the national to the small catchment scale. When addressed at a synthetic and small-scale level of analysis, the geomorphic hazard map is essentially based on the frequency of geomorphic processes and the intensity of morphodynamic factors. The Map of Geomorphological Hazards in Romania (scale 1 : 3,000,000) thus classifies processes in terms of whether they are governed by structural, pétrographie or geomorphic factors. At such a low-resolution, only three levels of hazard are considered: small, moderate and high. Its practical value is fairly low. A second map on the larger scale of 1 : 400,000 is presented for the Hârtibaciu Tableland. The legend provides greater detail in classifying the diversity of geomorphic processes. Finally, a map on the scale of 1: 25,000 presenting a portion of this tableland shows still greater complexity. Its legend emphasizes five levels of hazard susceptibility: hazard-free, low, moderate, high and severe. The large-scale approach incorporates quantitative geomorphic indicators (drainage density, local relief, slope gradient) established at the resolution of 1 km2 cells.