HR: 0800h
AN: NS51C-03    [Abstracts]
TI: Cliff stability assessment using electrical resistivity tomography at the historic WWII D-Day invasion site, Pointe du Hoc, France
AU: * Everett, M E
EM: everett@geo.tamu.edu
AF: Texas A&M University, Dept. of Geology and Geophysics, College Station, TX 77845, United States
AU: Udphuay, S
EM: suwimon@geo.tamu.edu
AF: Texas A&M University, Dept. of Architecture, College Station, TX 77845, United States
AU: Warden, R
EM: r-warden@tamu.edu
AF: Texas A&M University, Dept. of Architecture, College Station, TX 77845, United States
AB: The 1944 D-Day invasion site at Pointe du Hoc, Normandy, France is an important WWII battlefield and cultural resource but is at risk from chalk cliff collapse. The American Battle Monuments Commission tasked us to evaluate the geohazard to the observation post and other cliff-side buildings of historical significance. Geophysical multi-electrode resistivity profiling is used to study cliff stability and the condition of the observation- post foundations. Preliminary 2-D geological interpretations are provided of individual profiles. The copious steel, concrete and void spaces at the site renders hydrogeological interpretation challenging but tractable. The cliff face appears to be relatively intact and well-drained. Several routes taken by groundwater into fractures within the chalk were identified mainly on the western side of the site. The eastern side is drier and somewhat sheltered from the Atlantic storms but may contain large void spaces that could efficiently transmit groundwater flow during heavy precipitation events, thereby imperiling the major antiaircraft gun emplacement occupied by Col. Rudder in the early days of the Allied invasion. The forward German observation post perched close to the sea stack, which now hosts the U.S. Ranger memorial, may be moving with the soil and not securely anchored to bedrock. A complex failure mechanism is identified as a combination of groundwater dissolution of the fractured chalk and sea wave attack at the cliff base.
DE: 0925 Magnetic and electrical methods (5109)
DE: 1834 Human impacts
DE: 5104 Fracture and flow
SC: Near-Surface Geophysics [NS]
MN: 2007 Joint Assembly