Abstract

Coastal erosion is widespread and around 28% of the English and Welsh coastline experiences erosion rates of at least 10 cm/year. Environmental change due to a changing climate will almost certainly lead to a significant increase in these erosion rates. For cliff coasts, much existing protection is expected to be abandoned. The stretch of coastline on the North Norfolk Coast has some of the highest rates of retreat in Europe. Local authorities are trying to address this challenge. However, it is currently difficult to forecast where and when hazardous collapses will occur, rendering management and mitigation of the risk extremely challenging. Traditional methods of subsurface monitoring are restricted in either time or space. Distributed Sensing is a new technology that utilises optical fibre. The interrogator sends a series of pulses into the fibre at up to 100 kHz and records the return of the naturally occurring scattered signal. In doing this, the distributed sensor measures at all points along the fibre, with samples as closely spaced as 25 cm. In summer of 2023, we deployed 2 km of fibre optic cable on the North Norfolk Coast to monitor coastal processes. Using machine learning techniques, we are constructing a database of micro-earthquakes associated with subsurface cracking and rockfalls and creating a local magnitude scale related to the volume of rock affected along with a real-time map to show regions that are more seismically active and therefore more likely to see movement. We are also using ambient noise from the nearby crashing waves to monitor the geomechanical properties of the subsurface as they evolve using seismic tomography.