Depressions caused by localized subsidence in the Netherlands, Belgium and Germany: a link with coal mining?

In the coal mining districts of the Netherlands, Belgium and Germany, we identified 662 previously unidentified depressions at the land surface using LIDAR data. Their density decreases westwards along with deepening of the Carboniferous coal layers, while not changing in dimensions. The timing of their formation based on historical maps and landowner reports, suggest that they mostly formed during the period 1920-1970, the peak of mining activity. Based on their position, density and age, we link the formation of depressions to the coal-mining activities in South Limburg, Germany and Belgium. Our working hypothesis tentatively explains the origin, mechanism of formation and timing of these local subsidence features.