Rock-fall runout simulation using a QGIS plugin along north–west coast of Malta (Mediterranean Sea)

Abstract

Coastal instability in the form of rock fall is widespread along the northern coasts of Malta and is strictly connected to structural controls, such as lithology and tectonics. The local geological and geomorphological setting combined with extreme weather events, whose spatial and temporal occurrence is enhanced by ongoing climate and land use change, determines rock-fall hazard along the north–west coast of Malta, a hotspot for Mediterranean tourism. The present research portrays the results of a pilot study aimed at analyzing rock-fall runout probability along this stretch of coast. Cliffs and downslope terrains were the object of detailed field surveys. This included the detection of persistent joints in the source areas and the identification of slope-forming materials like debris and boulders present along the downslope terrains. The outcomes of the field surveys and GIS-based processing of topographic information were used for identification of the input parameters for rock-fall runout simulation. The latter was performed using a QGIS based plugin (QPROTO) that allows to determine expected runout extents and assess the rock-fall susceptibility. The result is the characterization and mapping of rock-fall runout probability zones along six investigated sites. The outputs of the research and the replicability of the method can be of interest for authorities aiming at defining risk management actions and undertaking mitigation measures compliant with sustainable development of coastal areas.