Winter bed card — (Water key)

The purpose of the winter bed map is to identify the areas where land use changes may give rise to a change in the drainage behaviour in the event of flooding the area. Certain forms of land use or vegetation are characterised by a high ‘rawness’, which has a higher flow resistance compared to other forms of land use. For example, a wooded valley area that occasionally floods will give rise to the occurrence of higher water levels in the same flood, compared to an unforeseen area. As such changes in polling and flow rates are only relevant for relatively large flood areas, the winter bed map was limited to areas subject to flooding from the navigable watercourses. The term winter bed is also used in Flanders only for the areas that occupy navigable watercourses at very high water drains.