Sediment gravity flows are the world’s largest sediment movements, consisting of mixtures of sand, mud, and water that episodically travel down subaqueous slopes. They are reported to damage or destroy critical seabed infrastructure along the world’s continental margins, such as internet cables, pipelines, or windfarm anchors. However, due to their large-scale and inaccessible environments, little is known about their triggering mechanisms, behaviour, and interactions with engineered objects. This makes the design and maintenance of offshore structures extremely challenging.

Using repeat bathymetric surveys spanning over a decade, we reveal patterns of erosion and deposition in a submarine channel where turbidity currents have impacted and continue to impact critical seafloor infrastructure. We compare the erosion patterns through time to external triggers like typhoons and earthquakes and conclude that episodic increased sediment supply during typhoons is an important priming condition but far from a universal predictor of catastrophic events. By analysing yearly to weekly seafloor change, we are able to constrain the extent of erosion, predict future patterns, and propose effective mitigation strategies. We demonstrate that erosion and deposition along the submarine channel is driven by knickpoint migration, with areas of localised catastrophic erosion while in other parts of the channel net deposition occurs. This highlights the need for large-area surveying and an integral sedimentary system approach in order to design effectively, tailoring to these dynamic and catastrophic environments.