A Pilot Study for Regionally Consistent Hazard Susceptibility Mapping of Submarine Mudslides

摘要

As part of our pilot project to delineate mudflow failures, sediments susceptible to future slope failure, and areas of relative stability in the Mississippi Delta, we have developed and tested a geomorphology-based approach to map mudflow susceptibility on the sea floor bottom. Our research is designed to provide regionally-consistent hazard information for the siting and design of pipelines and structures using readily available datasets. Based on interpretation of available datasets for the Mississippi Delta region, and our results for a test area using post-Hurricane Ivan (pre-Hurricane Katrina) bathymetric data, mudflow transport within the Delta generally occurs within well-defined submarine channels or gullies, spreading out onto the seafloor in deeper water to form overlapping lobes of thick, viscous silty clay. We have used available bathymetric data to delineate areas of relative sea floor stability over the past century, areas of active mudflow transport, and areas of active mudlobe deposition. Our mapping delineates the region of mudflow gullies, as mapped by Coleman et al, as the mudflow transport zone. Local accumulation of sediment coupled with scour during mudflow transport results in highly variable and unstable conditions within the gullies. Semi-stable areas between the mudflow channels locally provide the least hazardous locations for siting of future production facilities and pipeline routing. The zone of overlapping mudlobes located downslope of the gullies is an area of recent deposition vulnerable to mudflow overruns from upslope mudflows.