Integrated Geomechanical and Digital Photogrammetric Survey in the Study of Slope Instability Processes of a Flysch Sea Cliff (Debeli Rtič Promontory, Slovenia)

This work presents an integrated study approach that combines the results of a geomechanical survey with data obtained using digital photogrammetry (DP), to assess slope instability processes affecting a sea cliff at the Debeli Rtič promontory (Slovenia). The investigated cliff is 4–18 m-high and is made up of an alternation of sandstones and marlstones belonging to the Flysch Formation of Trieste, which is Eocene in age. The studied cliff was subjected to localized slope failures that occurred in the past and is currently subject to frequent rock collapses, thus resulting in its partial and episodic retreat. Field evidence acquired through a traditional survey was integrated with outputs of the DP technique based on 1399 images that were collected using both a commercial unmanned aerial vehicle (UAV) and a mobile phone (MP). UAV-derived images were useful for performing rock mass structure analysis in the upper part of the investigated cliff, where the traditional survey was not possible due to hazardous operating conditions. In addition, the use of a MP was observed to be a useful tool for the rapid collection of images at the toe of unsafe marine cliff environments. This study highlights that UAV-DP and MP-DP techniques can only be effective if the outcomes obtained from the 3D model reconstruction are validated by direct measurements acquired by means of the traditional field survey, thus avoiding improper or even erroneous results while enlarging the amount of data and the area of investigation. The study approach presented herein allowed for the assessment of slope instabilities affecting the Flysch Sea cliff, whose retreat is caused by the combined action of marine erosion and slope gravitational processes

Integrated Geomechanical and Digital Photogrammetric Survey in the Study of Slope Instability Processes of a Flysch Sea Cliff (Debeli Rtic Promontory, Slovenia)

This work presents an integrated study approach that combines the results of a geomechanical survey with data obtained using digital photogrammetry (DP), to assess slope instability processes affecting a sea cliff at the Debeli Rtic promontory (Slovenia). The investigated cliff is 4-18 m-high and is made up of an alternation of sandstones and marlstones belonging to the Flysch Formation of Trieste, which is Eocene in age. The studied cliff was subjected to localized slope failures that occurred in the past and is currently subject to frequent rock collapses, thus resulting in its partial and episodic retreat. Field evidence acquired through a traditional survey was integrated with outputs of the DP technique based on 1399 images that were collected using both a commercial unmanned aerial vehicle (UAV) and a mobile phone (MP). UAV-derived images were useful for performing rock mass structure analysis in the upper part of the investigated cliff, where the traditional survey was not possible due to hazardous operating conditions. In addition, the use of a MP was observed to be a useful tool for the rapid collection of images at the toe of unsafe marine cliff environments. This study highlights that UAV-DP and MP-DP techniques can only be effective if the outcomes obtained from the 3D model reconstruction are validated by direct measurements acquired by means of the traditional field survey, thus avoiding improper or even erroneous results while enlarging the amount of data and the area of investigation. The study approach presented herein allowed for the assessment of slope instabilities affecting the Flysch Sea cliff, whose retreat is caused by the combined action of marine erosion and slope gravitational processes

Dataset of gravity-induced landforms and sinkholes of the northeast coast of malta (Central mediterranean sea)

This study investigates gravity-induced landforms that populate the North-Eastern coast of Malta. Attention is focused on tens of persistent joints and thousands of boulders associated with deep-seated gravitational slope deformations (DGSDs), such as lateral spreads and block slides. Lateral spreads produce deep and long joints, which partially isolate limestone boulders along the edge of wide plateaus. These lateral spreads evolve into large block slides that detach thousands of limestone boulders from the cliffs and transport them towards the sea. These boulders are grouped in large slope-failure deposits surrounding limestone plateaus and cover downslope terrains. Gravity-induced joints (n = 124) and downslope boulders (n = 39,861) were identified and categorized using Google Earth (GE) images and later validated by field surveys. The datasets were digitized in QGIS and stored using ESRI shapefiles, which are common digital formats for storing vector GIS data. These types of landslides are characterized by slow-moving mechanisms, which evolve into destructive failures and present an elevated level of risk to coastal populations and infrastructure. Hundreds of blocks identified along the shore also provide evidence of sinkholes; for this reason, the paper also provides a catalogue of sinkholes. The outputs from this research can provide coastal managers with important information regarding the occurrence of coastal geohazards and represent a key resource for future landslide hazard assessment