Geohazards, such as volcanoes, earthquakes and landslides, are the natural geological processes that present a direct risk to people or an indirect risk by impacting development. They can be subdivided between earth hazards , such as earthquakes, volcanoes and tsunamis, and shallow geohazards.
Shallow geohazards occur in the near-surface, typically including landslides, sinkholes and discontinuities that result from cambering or fault reactivation, as well as a range of hazards that occur as a consequence of karst and Quaternary processes. The term ‘shallow geohazard’ has also been extended by engineering geologists to embrace properties of geological materials that are a potential risk to infrastructure and include:
- clay shrink-swell
- collapsible soils
- compressible soils
- soluble rocks
- ground gases
- soil piping
- soil geochemistry
- running sand
The properties associated with each of these geohazards are sensitive to changes in moisture content and therefore to the consequences of climate change and hydrohazards, including the various types of flooding: pluvial, fluvial and groundwater.
Collaborative shallow-geohazard research is important to society for planning and development and for infrastructure management. In the international context, this research contributes to resilience through the United Nations’ Sustainable Development Goals.
The focus of BGS shallow geohazards research is on developing and communicating better understanding of distribution, characterisation, susceptibility and triggering and potential impacts of shallow geohazards.
The BGS is home to the National Landslide Database, the National Karst Database and a National Sinkhole Database. Data is collected using methods that range from Earth observation to literature searches, social media and crowd science. We draw from our researchers’ skills to respond to geohazard events, e.g. landslides induced by the Nepal earthquake of 2015 and sinkholes (e,g, Solotvyno, Ukraine), and we can assess data quality and representation in terms of size frequency distributions.
Conceptual classifications of shallow geohazards underpin geohazard communication, e.g. landslide, sinkhole and shrink–swell potential, which is based on the Atterberg limits of the soil and its position on the Casagrande plasticity chart.
Modelling commonly requires more specific, field-based information, e.g. dimensions, soil types and details of the triggering process. A number of techniques are used to collect this information, including Earth observation, ground based geomatics, geological and geomorphological mapping and ground investigation techniques such as probing, drilling and shallow geophysics. Examples of this activity include responsive visit case studies and specific research projects, e.g. Aldbrough and Barton on Sea.
Algorithms, based on process understanding, are developed to identify areas where the ground conditions are more susceptible to geohazards, e.g. BGS GeoSure products. By adopting a domains approach, we are recognising that regions of common geology and geomorphology give rise to similar styles of geohazard. Perturbations (triggers) that initiate geohazards may be meteorological, tectonic (e.g. earthquakes) or anthropogenic.
Our shallow geohazard trigger threshold value research takes a number of approaches to identify hazard tipping points. Input data includes the monitoring data from geohazard observatories. By combining the concepts of susceptibility with MetOffice weather forecasting, we contribute to the Natural Hazards Partnership daily hazard assessment. This is being advanced by domain-scale, real-time modelling.
By integrating susceptibility with hazard characterisation, we can better understand the potential impact of geohazards. Our research on this topic relies on both the development of impact libraries and modelling, which enable risk assessment and the provision of information for early warning systems to protect vulnerable communities and modelling for multi-hazard research.