Suchergebnisse

Abstract. The Karakoram Highway (KKH) is an important route,
which connects northern Pakistan with Western China. Presence of steep
slopes, active faults and seismic zones, sheared rock mass, and torrential
rainfall make the study area a unique geohazards laboratory. Since its
construction, landslides constitute an appreciable threat, having blocked the
KKH several times. Therefore, landslide susceptibility mapping was carried
out in this study to support highway authorities in maintaining smooth and
hazard-free travelling. Geological and geomorphological data were collected
and processed using a geographic information system (GIS) environment.
Different conditioning and triggering factors for landslide occurrences were
considered for preparation of the susceptibility map. These factors include
lithology, seismicity, rainfall intensity, faults, elevation, slope angle,
aspect, curvature, land cover and hydrology. According to spatial and
statistical analyses, active faults, seismicity and slope angle mainly
control the spatial distribution of landslides. Each controlling parameter
was assigned a numerical weight by utilizing the analytic hierarchy process
(AHP) method. Additionally, the weighted overlay method (WOL) was employed to
determine landslide susceptibility indices. As a result, the landslide
susceptibility map was produced. In the map, the KKH was subdivided into four
different susceptibility zones. Some sections of the highway fall into high
to very high susceptibility zones. According to results, active faults, slope
gradient, seismicity and lithology have a strong influence on landslide
events. Credibility of the map was validated by landslide density analysis
(LDA) and receiver operator characteristics (ROC), yielding a predictive
accuracy of 72 %, which is rated as satisfactory by previous researchers.

Abstract
Background
In July 2021, destructive floods in Western Europe were triggered by enormous precipitation rates related to a low-pressure system named "Bernd." These catastrophic events led not only to major damage to infrastructure, severe economic losses, and the loss of lives but also to significant landscape changes and modifications. Here, we focus, as a case study, on the flood aftermath of the Ahr Valley in Rhineland-Palatinate state in western Germany, as it was one of the most affected and destroyed regions by the flood. We utilize high-resolution Digital Terrain Models (DTMs) based on airborne Light Detection and Ranging (LiDAR) that were taken shortly before and after the flood to investigate insights into geomorphic changes.

Results
By calculating Digital Terrain Models of Difference (DoD), we are able to quantify volumetric and areal changes caused by erosional and depositional processes for different sites in the Ahr Valley. Due to the morphology of the narrow Ahr Valley, most of the erosion and deposition is located within the deeply incised canyon of the Ahr River. The comprehensive analysis reveals notable morphological modifications throughout the study area, with a calculated erosion/deposition areal ratio of 0.46 and an erosion/deposition volumetric ratio of 0.63. Our findings indicate massive deposition regarding both areal and volumetric. We selected six different locations along the Ahr Valley that showcase distinct aspects of flood-induced fluvial morpho-dynamics. Deposition occurred mainly in point bars and downstream of destroyed artificial levees, in a braided river style.

Conclusion
Our investigations contribute to an overview and assessment of the morphological response to the destructive flood in the Ahr Valley. The results emphasize the necessity for implementing effective flood management strategies, as most of the urban areas in the Ahr Valley were flooded. Moreover, our results provide valuable insights into the impacted areas, highlighting vulnerable locations for flood-related erosion and deposition. This information could contribute to future mitigation and protection efforts, aiding in the development of comprehensive strategies to minimize the impact of similar events in the future.