Landslide inventory for the administrative area of Breaza, Curvature Subcarpathians, România

Abstract

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This paper presents a landslide inventory for the administrative area of Breaza, Prahova County, Romônia. The Breaza administrative area is located between 25°35′37.8″ and 25°42′12″ east longitude and 45°7′47″ and 45°13′45″ north latitude, covering an area of approximately 50 km^2. The landslide inventory contains 177 old and new landslides classified by type of movement, depth and activity. The landslides were mapped by combining image interpretation of old air-photos and recent orthophotos with detailed field surveys. By type of movement, most of the landslides are rotational slides (ca. 92%) and very few are translational slides (3%), complex landslides (3%) or earth flows (2%). The size of the landslides is diverse, ranging from very small (0.001 km) to big landslides extending over an entire hillslope (0.65 km2). An important contribution in mapping the landslides bodies was the use of oblique and vertical aerial photos. These photos were taken from a small aircraft (Cessna F172H) using a Canon 400D camera equipped with an 18–250 mm lens. The aerial photos provide, from different view points, a large scale perspective over natural landscape processes and helped us to classify the landslides by type of movement. Some of them were used to create anaglyph images, bringing a 3D perspective to the image interpretation process. The vertical photos were successfully georeferenced with a standard error of approximately 10 m and used in a GIS for mapping the location of the landslides units. The landslide inventory is presented as two maps: (1) landslides by type of movement overlain onto the landslide depth and (2) landslide activity. The scale of mapping ranges from 1:200 for field surveys up to 1:5,000 for landslide mapping from the orthophotos and topographical maps. For the final maps the features were adjusted to a scale of 1:5,000.