More than 3,500 km of buried valleys have presently been mapped in Denmark. The highest valley density is found in areas where TEM data have been collected in dense grids and where the conditions for this specific method are ideal. Although many buried valleys have been mapped in these areas, even more valleys are expected to exist because all valleys cannot be mapped with the used methods, and all of the onshore area is not yet entirely covered with data.

Despite the high degree of mapping activity in Denmark only a minor part of the country has been surveyed by the TEM method. Therefore only a part of all buried valleys in Denmark is represented in the collected data, and the buried valley map can at best be considered to show the minimum occurrence. Therefore the map does not show the true distribution and density of buried valleys in Denmark. However, the mapped valleys show signs of a preferred geographical distribution. The valley density seems to be lower in areas dominated by hydraulically conductive sediments compared to areas dominated by impermeable sediments. The hydraulic conditions of the subsurface sediments are therefore expected to influence the valley formation.
 

Valley characteristics
 

The buried valleys can be divided into different generations that were formed under glaciers during successive glaciations. The valleys often cross-cut each other and sometimes they have different preferred orientations. A complicated pattern with three to five generations of valleys can often be distinguished in areas with high data resolution. If the ice flows were parallel or near-parallel to pre-existing valleys, these valleys would be liable to repeated erosion and re-filling producing a complicated cut-and-fill setting within the valleys. Multiple generations of valley erosion are therefore often found within the buried valleys themselves. The valley architecture is normally complex due to this cut–and–fill history, but also due to glaciotectonic disturbances. This complexity can be observed in both seismic data and TEM data. The complex fill is also often indicated by borehole data that show strong lithological variations over short distances.

The valley fill is deposited in sub-glacial and pro-glacial environments. Statistical analyses of borehole data in all the mapped valleys show that by far the most common infill sediment types are tills and meltwater deposits. In this group, 52% are coarse meltwater deposits (sand and gravel), 30% are clay-rich till and 18% are fine-grained meltwater deposits (silt and clay).

The mapped buried valleys vary in depth with the deepest features exceeding 350 m. The width is generally between 0.5 and 1.5 km, but widths of up to 4 km occur. The lengths of the valleys are difficult to evaluate, because many of the so far surveyed areas are small. However, the length of some valleys in larger survey areas exceed 25–30 km. Striking features of the valleys are that they often terminate abruptly and that they are highly irregular with depressions and thresholds along the valley floors.