Detecting slope deformation at Coniale (FI) by a detailed InSAR survey (“Consorzio di Bonifica della Romagna Occidentale”)

Coniale is a small town that is located in the province of Florence, Northern Apennines of Italy (see figure 1 a). Here, the well-stratified sandstones of the Marnosa Arenacea formation form the bedrock. This formation is prone to a particular type of landslides that occurs where the stratification dips downslope. If this is the case, sliding occurs frequently along the pelitic, mechanically weaker bedding planes.

The slope of Coniale hosts several old landslide bodies, and their deformation is responsible for moderate to severe damages on houses and infrastructure in the lower areas of the slope. In particular, a bridge that crosses the Santerno river (figure 1 b), as well as a house next to the bridge (figure 1 c) are displaying a damage-picture that is common to the interaction between man-made structures and slope deformation. There are also different signs on the central part of the slope that indicate recent displacements, like a retaining wall that detached from its original position along a trench (figure 1 d), as well as crevices on the road. Due to these damages, the regional authorities installed a monitoring system on the bridge, as well as three inclinometers in the lower part of the slope. One of the regional authorities (“Consorzio di Bonifica della Romagna Occidentale”) asked Fragile srl for a detailed InSAR analysis. The survey includes data from an ascending and a descending orbit of Sentinel 1 (figure 1 a) and was designed to better understand the spatial and temporal distribution of the deformation between 2014 and 2018.

Figure 1 a) The slope of Coniale is located in the Northern Apennines in province of Florence (Tuscany). The area is covered by one ascending and one descending orbit. b) A bridge that crosses the Santerno river and c) the house next to the bridge are affected by moderate to intense damages. d) Trench-like morphological feature with detached retaining wall in the central part of the slope.