Rockfall risk analysis in Valle Gran Rey, La Gomera (Spain) (2021-04-30)

<br/> Activation date: 2021-04-30 <br/> Event type: Mass movement <br/> <br/> Activation reason: <br/> EMSN093 was activated&nbsp;&nbsp; to demonstrate that satellite-derived data can be used to study small-medium sized rockfalls, as the one occurred in Valle Gran Rey of the La Gomera island (Canary Islands, Spain) on the 14th of November 2021. Moreover, the results will support local authorities by offering information on the potential hazard of the area, to carry out the adequate management plans.The products resulting from this activation are:Product 2Pre-event DEM extracted using photogrammetric methodologies on the stereo VHR images acquired the 21/05/2020.&nbsp;&nbsp;&nbsp;Product 3Post-event DEM extracted using photogrammetric methodologies on the stereo VHR images acquired the 29/05/2021.&nbsp;&nbsp;&nbsp;Product 4: Delineation of rockfall extentThe delineation of the rockfall extent, obtained using multi-source data approach. The rockfall area was divided into three zones the source area of the rocks, the the runout area where the rocks were deposited and the submerge area.&nbsp;&nbsp;&nbsp;Product 5The estimated rockfall generated mass volume difference generated from the substruction of the VHR pre-event DEM and post-event DEM.&nbsp;&nbsp;&nbsp;Product 6Map the rockfall / rockslide hazard in the whole area of interest using ISVS susceptibility index. The index considers geological, geomorphological and geomechanical characteristics of rock mas lithotypes.&nbsp;&nbsp;&nbsp;&nbsp;Product 7The product summarizes assets and population exposed to rockfall hazard by delineation of their uphill hazard zones and zonal aggregation of the hazard susceptibility levels.&nbsp;&nbsp;&nbsp;&nbsp;Product 8The map provides rockfall risk by extending the ISVS index using the rockfall risk index for volcanic slopes (IRVS) following the methodology of de Vallejo et al. (2020). Assets and population at risk are summarized. Tourists are accounted considering two scenarios: overnight stays in high (December) and low (July) touristic season.&nbsp;&nbsp;&nbsp;&nbsp;Product 9The time series of PS/DS located in the rockfall area, obtained through the Multi-Temporal Interferometry analysis, exhibits an acceleration started several months before the rockfall event (14 November 2020). After the rockfall, the time series is noisy since the associated PS has lost its coherence (temporary PS). This confirms the potential of MTI as an operative displacement monitoring tool.&nbsp;&nbsp; <br/> <br/>