Abstract:

A coastal management study at areas with steep anaglyph requires detailed knowledge of the onshore surface and subsurface regime regarding the erosional procedures. Active faults produce dynamic and continuously evolving geomorphological structures, which require investigation and continuous monitoring. Detailed mapping on and adjacent to these surfaces is required in order to study the complexity of various tectonic discontinuities, which contribute significantly to erosion and rock-falls resulting rapid and significant changes on the landscape. The technology of ground-based Light Detection and Range (LiDAR) capturing devices is a powerful and valuable tool, providing detailed mapping and surface change detection of inapproachable and nearly vertical surfaces. In this paper we introduce the diachronic monitoring and detection of alterations on the surface of the shore-side active fault of Psatha (Greece), with terrestrial LiDAR scanning, for a state of the art mapping of the almost vertical limestone fault surface. The monitoring procedure includes high-detailed topographic survey at the adjacent area using Real Time Kinematics Global Positioning System equipment (RTK-GPS), which is consisted of a large pile of brittle debris, laying on top the fault surface, by the sea. The described methodology involved the production of a high resolution DEM based on historic topographic maps (scale 1:5,000) of the regional area and comparing it with the higher resolution DEM representing the contemporary morphology, produced by the combination of the fault wall LiDaR “point cloud” and the dense grid of the RTK-GPS measurement points. The comparison between these datasets and recently acquired high resolution IKONOS satellite images revealed impressive surface changes caused mainly by the human intervention as well as the erosional processes which were accelerated due to the absence of safety measures along the coastal zone. Furthermore, the regional subsurface of the hanging wall zone area was also investigated, especially underneath the brittle debris formation, applying the highresolution near surface geophysical technique of Electrical Resistivity Tomography (ERT). Several sections were conducted aiming to represent the subsurface extension of the visible structures in three dimensions and combine it with the aforementioned datasets. The successful combination of different techniques revealed and quantified the landscape evolution involving the surface alternations at the fault adjacent coastal zone, the sea intrusion and even the coastline displacement, during the last four decades. Most of these yielded to the anthropogenic interference on the brittle debris formation and even the construction of the coastal road.