Geological overview map of Lower Saxony 1: 500 000 — Early History Flood Events (WFS Service)

The "Geological Overview Map of Lower Saxony 1: 500,000 — Early-historical flood events" is a digital dataset of the Geological Survey Map of Lower Saxony 1: 500,000 derived analysis map. Taking into account the age, nature and origin of geological strata, this map identifies areas that were affected by floods in recent geological past, i.e. in the last 11,500 years ago, which was summarised here as an early history. From a geological point of view, these areas are also potentially at risk of flooding in the future, as the natural water balance (e.g. precipitation, above-ground drain) has not changed significantly. Since the early-historical flood events took place mainly in times before human intervention into the landscape (e.g. hydrological protection measures such as dikes and dams, processes of land extraction), such protective measures that exist today are not taken into account in the mapwork. The early-historical flood deposits therefore give an impression of how deep flooding events can penetrate the hinterland in the event of failure of protective measures (e.g. dyke breakage). The map distinguishes between widespread deposits of early-historical flood events (hazard level 1) and “deposits of early-historical flood events in sub-areas, e.g. deposits of early-historical flood events” (hazard level 2)”. In areas with risk level 1, there are widespread deposits that have been disposed of in early-historical flood events (e.g. floodplain deposits in river valleys or marine and brackish water deposits in the coastal area). Failure of any existing protective measures in these areas is highly likely to be flooded. The areas of hazard level 2 are generally higher than those at risk level 1. In some areas, however, early-historical flood deposits can also be found here, sometimes in small areas. Therefore, a flood risk cannot be ruled out in principle for the future. In individual cases, the local geological situation must be assessed.