Detection of slope deformation at the Tröllaskagi peninsula, N-Iceland, using Sentinel-1 D-InSAR time series (2016-2022)

Following last deglaciation, glacially eroded hillslopes of the Tröllaskagi peninsula in N-Iceland experienced intensive rockslide activity. In the Almenningar site, located on the outermost part of the peninsula, several rockslide features show active surface displacement, which have repeatedly caused major damages and hazardous conditions to a road crossing the area. Since 1977 the Icelandic Road and Coastal Administration (IRCA) has maintained regular measurements and in 2022, GNSS stations were installed for real time monitoring. These measurements indicate deformation rates up to 70 cm per year. Monitoring results further suggest a relationship between deformation and hydroclimatological factors. Furthermore, the front of the deformation area reaches the coast forming up to 60 m high cliffs where clear indications of extensive coastal erosion can be found. Whereas traditional landslide monitoring and field measurements can be expensive and time consuming, remote sensing methods such as Differential satellite Interferometric Synthetic Aperture Radar (D-InSAR) time series analysis has proven to be a valuable tool for large-scale slope deformation detection. In our study, we implement multitemporal D-InSAR methods, which decrease limiting factors like atmospheric delay, orbital errors and decorrelation. We use the Copernicus Sentinel-1 SAR satellite constellation with its 6 day (since 2022: 12 day) revisit time over Iceland. Besides the monitored Almenningar site, two additional sites in Tröllaskagi, Stífla and Siglufjarðarfjall, were selected for slope deformation detection due to their landform similarity and possible threat to infrastructure. The displacement time series was generated for the summers of 2016 through 2022 to (i) detect the spatio-temporal slope deformation patterns in Almenningar, Stífla and Siglufjarðarfjall, (ii) analyse if these landforms have similar deformation response to hydroclimatological conditions and/or seismic episodes and (iii) if there is noticeable difference in deformation rates at the coast or inland. The results of this research will be presented here. In conclusion, D-DInSAR provides useful information to analyse other rockslide features in Tröllaskagi and correlate detected deformation to hydroclimatological conditions and seismic episodes. Results will serve as an important support for hazard and risk assessment and contribute to further research on triggering factors.