Abstract The frequent sinkholes along the temporary water streams in Saffré basin can be compared with those occurring in Upper Normandy which are commonly referred to as ‘bétoires’. These collapses are not directly linked to karst cavities. They result from a draw-off effect of fine particles contained in the Plio-Quaternary alluvium lying above the carbonate Oligocene series. The draw-off phenomenon appears through fine cracks (1 to a few millimetres) open in soft palustrine limestones broadly comparable with chalk. Based on the knowledge of backfilling work design undertaken at some ‘bétoires’ in Upper Normandy, a new project was undertaken at four sinkhole funnels, which appeared near the surface in the Saffré basin at the end of the winter in 2017. The works consisted of digging the decompressed surface and filling up the excavation pit with materials of decreasing granulometry from bottom to top in order to ease the surface water infiltration through the identified fractured zones to the bottom of the excavation. This design was also complemented by the implementation of a filtering trench in between the watercourse and the filtering bed, laid above the fractured zones, which were enlarged by the dissolution process, on the one hand, and by the construction of a pipe network on top of the filtering bed to allow for pressurized air exhaust towards the surface, on the other hand. The pressurized air comes up from the aquifer as it recharges as soon as the surface water streamflow resumes and takes part in the mechanism, leading to sinkhole collapse, which should be prevented by this backfilling design.

Abstract Through Ireland's national seabed mapping programme, Integrated Mapping for the Sustainable Development of Ireland's Marine Resource (INFOMAR), the collaboration between Geological Survey Ireland and the Marine Institute continues to comprehensively map Ireland's marine territory in high resolution. Through its work, the programme builds on earlier Irish seabed mapping efforts, including the Irish National Seabed Survey project in producing seabed mapping products that support Ireland's blue economy, European marine policy and international efforts to understand our global oceans. INFOMAR uses a variety of marine technologies to deliver accurate bathymetric maps and useful data products to end users through a free and open source licensing agreement. To reflect the diversity of applications these data products serve, a series of four case studies are presented here focusing on marine geophysical and geological data from locations within Ireland's marine territories. The case studies illustrate how data generated through seabed mapping may be interpreted to directly impact the generation of blue knowledge across a variety of marine environments ranging from shallow coastal and shelf waters to the deep oceanic depths of the continental slope of Ireland's marine area. The impact of Ireland's seabed mapping efforts is further considered in the context of national, European and international initiatives where Ireland's marine knowledge resource is leveraged to deliver positive benefit to the programme's stakeholders.