Geological Map of Lower Saxony 1: 50 000 — Early History Flood Events (WMS Service)

The "Geological Map of Lower Saxony 1: 50 000 — Early-historical flood events" is a digital dataset of the Geological Map of Lower Saxony 1: 50,000 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.《下萨克森州1:50000地质图——早期历史洪水事件》是一套基于下萨克森州1:50000地质图衍生的数字化分析数据集。该数据集结合地质地层的年代、性质与成因，识别出近地质历史时期（即距今11500年以来）受洪水影响的区域，此处将该时期概括为早期历史阶段。从地质学视角来看，由于自然水平衡（如降水、地表径流）未发生显著变化，这些区域未来仍存在潜在洪水风险。由于早期历史洪水事件主要发生在人类干预自然景观之前（如修建堤坝、开展土地开发等水文保护措施实施前），因此本次制图未考虑当前已存在的各类防护工程。 因此，早期历史洪水沉积可反映出，当防护工程失效（如堤坝溃决）时，洪水可渗透至内陆腹地的范围与强度。 该地图将早期历史洪水沉积分为两类：广泛分布的早期历史洪水沉积（风险等级1），以及分区内早期历史洪水沉积（例如局部区域的早期历史洪水沉积）（风险等级2）。 风险等级1区域内分布有早期历史洪水沉积（如河谷河漫滩沉积或沿海区域的海相、咸淡水混合相沉积）。此类区域若现有防护工程失效，发生洪水的概率极高。 风险等级2区域的整体地势通常高于风险等级1区域。但部分区域内仍可发现小规模的早期历史洪水沉积。因此，原则上无法完全排除未来的洪水风险，具体需结合局部地质情况进行个案评估。