Quaternary geology as a basis for landslide susceptibility assessment in fine-grained, marine deposits, onshore Norway

Abstract

For decades, mapping of Quaternary geology in Norway has been an important basis for hazard and risk assessment for landslides in highly sensitive clay (quick clay). One aspect of particular significance is information on the occurrence of fine-grained, marine deposits including clays. The marine limit (ML) defines a natural upper limit to these deposits, so issues concerning marine clays can be disregarded above ML. Below ML, a filtering of the Quaternary map information is needed to identify areas where clays are potentially present. Fine-grained, marine deposits are more frequently encountered below some deposit types than others, and the possibility of encountering marine clays within an area is defined as clay-deposit susceptibility. Stratigraphic information is needed for verification. Further landslide susceptibility assessment requires additional information on topography and ground conditions. Other geological information is also important such as on the distribution of landslide debris and landslide scars. Here, it is beneficial to use high-resolution, digital elevation models for detailed analysis of the terrain also below sea level in near-shore areas. Maps with filtered geological information can work as a supplement to maps produced during the ongoing quick-clay mapping program and as a help prioritize areas requiring further investigation.