Map of geohazards in Lower Saxony — mass movements

The State Office for Mining Energy and Geology (LBEG) publishes in scale 1: 50 000 and 1: 25,000 Geohazards in Lower Saxony. These hazard information maps present the natural hazards of subrosion and mass movement by individual objects (earthfall, mass movement) or the demarcation of endangered areas (earth-risk area, salt stock elevation). Mass movements are geomorphological processes in which rock or loose stone, under the influence of gravity, move downhill in periods from seconds to years. Natural causes such as an unfavorable inclination of geological layers or weathering of rock sections favor the formation of mass movements. Ultimately, triggers of a mass movement can be both natural (downfall, etc.) as well as anthropogenic (construction measures, traffic, etc.) influences. Mass movements cause serious damage to buildings, roads, railways or waterways due to spilling with rock or loose rocks and deep terrain breaks. Sliding, fall and flow processes are distinguished as superordinate movement processes of mass movements. The motion mechanisms tilting and drifting are no longer differentiated and are assigned to one of the higher-level processes. • Sliding processes are downhill, sliding movements of fixed and/or loose rocks on discrete sliding surfaces. During movement, the slip compound on the sliding surface largely maintains contact with the solid surface. Slides are classified by the shape of the sliding surface, so that it is necessary to distinguish between translation and rotation slides or a combined sliding surface shape. • In a fall process such as a rockfall or a rock fall, the falling masses temporarily lose contact with the solid ground. Boulders or rock masses fall, jump or roll downhill following gravity. Fall processes are classified according to the volume of the collapsed rock material. • Flowing processes such as earth/shoe/block currents, murmuring and creep movements of all kinds have no defined sliding surfaces. In contrast to the slipping process, the water content of the flowing masses is usually significantly increased. The movement is comparable to a highly viscous liquid. Flow processes are classified according to their speed of movement. The basis of the map of geohazards in Lower Saxony — mass movements — with a representation of the individual objects — is an event cadastre based on information from topographic, geological and engineering geological maps, reports and literature. In one case, a high-resolution, digital terrain model from laser scan images (LIDAR) could be evaluated. The mass movements hazard statement map is geared to the needs of spatial planning, not parcel-sharp and does not replace object-related geotechnical examination. The map representation documents the current state of knowledge in the LBEG, but cannot guarantee the completeness of the phenomena. It serves ministries, specialised authorities, district and local governments as well as business enterprises and citizens as the first basis for risk assessment with the aim of preventing or minimising damage caused by predictive planning. Areas adjacent directly to the designated areas may also be affected. The intensity and probability of a possible event cannot be derived from the map. Local circumstances (e.g. protective measures, renovations, topographical features) must be taken into account in further investigations.下萨克森州采矿、能源与地质国家办公室（State Office for Mining Energy and Geology, LBEG）发布了比例尺为1:50000和1:25000的下萨克森州地质灾害图件。此类灾害信息图件通过单体地物（崩塌、块体运动）标识或受威胁区域划定（地面风险区、盐丘抬升区），展示了潜蚀（subrosion）与块体运动（mass movement）两类自然灾害。 块体运动是指岩土体在重力作用下，于数秒至数年的周期内沿坡向下运动的地貌过程。地质层倾角不利、岩体风化等自然因素会助长此类过程的发生，而其触发因素既包括降雨等自然诱因，也涵盖工程施工、交通活动等人为扰动。 块体运动会因岩土体堆积、地形剧烈塌陷，对建筑、道路、铁路及航道造成严重损毁。 作为块体运动的一级运动类型，可划分为滑动、崩塌与流动三类过程。倾斜、漂移等运动机制不再单独区分，均归属于上述三类一级过程中。 • 滑动过程：指固定岩体或松散岩土体沿离散滑动面向下滑移的运动。运动过程中，滑动体与基底固面基本保持接触。根据滑动面形态，可将滑动划分为平移滑动、旋转滑动或兼具二者特征的复合型滑动面滑动。 • 崩塌过程：以落石、岩崩为例，崩塌体在运动过程中会暂时脱离基底固面，岩块或岩体在重力作用下沿坡向下坠落、弹跳或滚动。崩塌过程可按崩塌岩土体的体积进行分类。 • 流动过程：包括土体/碎屑/块体流、蠕动等各类无明确滑动面的运动。与滑动过程不同，流动体的含水率通常显著升高，运动形态类似高黏度流体。流动过程可按运动速率进行分类。 本次下萨克森州地质灾害（块体运动类）图件及其单体地物标识的编制基础，是基于地形、地质与工程地质图件、报告及文献资料构建的事件登记册，部分场景还可利用激光扫描成像（LIDAR）生成的高分辨率数字地形模型进行分析验证。 该块体运动灾害图件服务于空间规划需求，并非宗地精准级别的图件，且不能替代针对单体地物的岩土工程勘察。图件所呈现的内容仅反映LBEG当前的认知水平，无法保证灾害现象记录的完整性。其可为各部委、专业主管部门、区县及地方政府、企业与公民提供风险评估的初步依据，旨在通过预判性规划预防或降低灾害损失。划定区域的毗邻区域同样可能受到影响，图件无法推导潜在灾害的强度与发生概率。后续调查需结合当地实际情况（如防护措施、修缮工程、地形特征等）开展。