LANDSLIDE RESEARCH AND MITIGATION A MUST, SAY EXPERTS
Tutuila is a geologically dynamic island, and one where landslide research and mitigation is vitally important. This, according to professional engineer Tim Bodell, who spoke to Samoa News following the rockfall which slowed traffic to a crawl last week on Tutuila’s only shoreline road between town and the Tafuna plains.
The landslide which occurred near Fatu ma Futi on Tuesday left a brutal scar on the mountainside; with its twisted tree trunks, tangled and exposed underbrush and broken boulders, it was reminiscent of a scene from a bad dream.
Thankfully, no one was injured and no buildings were destroyed, but that may not be the case next time, as the mountainside continues to be subject to weather, gravity and other natural forces says Bodell, who is here on contract with the American Samoa Environmental Protection Agency. providing technical support to the agency.
Natural events can lead to chaos and destruction, as island residents are well aware, having witnessed the aftermath of hurricanes, tsunami and great storms. Even small landslides can wreak havoc, if only in stalled traffic along the territory’s two-lane seaside road.
According to Bodell, whose background studies are in hydrology (the study of water science and resources) the landslide which occurred on Tuesday should be noted as part of a larger phenomena which occurs as humans take over more space on this volcanic rock we call home.
“Tuesdays landslide that blocked the road near Fatu ma Futi is the result of natural mechanisms reshaping the Tutuila landscape. Weather and gravity continuously act to pull down our island’s massive building blocks — usually in gentle, manageable pieces and occasionally — throughout geologic history — in enormous portions through a process called ‘mass wasting’.”
If not managed appropriately, urban growth accelerates the natural erosional cycle into more unpredictable and often catastrophic movement, especially damaging to steep coastal slopes, the kind of slopes that make up over 70 % of Tutuila's shoreline, says Bodell.
He explained Tutuila was much larger eons ago. “These dynamic processes are responsible for the whittling down of a much bigger Tutuila that emerged and dissolved over the last 1.3 million years. As illustrated in the topo-bathy-graphical image attached (Courtesy NOAA 2012 imagery) our current island is just a stub of its former size.”
The most catastrophic mass wasting will occur next to steep submarine ledges that aren't protected by coral reefs, such as those near Fogagogo and Larson's Cove — illustrated on the Southern Exposure of Tutuila.
Up until recently very little was known regarding how these natural processes work, which are sinking and shifting Tutuila at a rate of inches per year, he noted.
"Inches per year we can handle" says Robert Koch, American Samoa’s Dept. of Commerce Geographic Information Manager. “It's the big ones like those which occurred in the last century on Ta'u that submerged whole flanks of the island in a matter of days, resulting in tsunamis throughout the world that need to be monitored and planned for.”
According to Bodell, last week’s landslide was indica_tive of erosion which can and must be managed. Sediment, rockslides, landslides and mass wasting are the forms of erosion which we are seeing now, and are going to continue to see, says Bodell, who added, “We live on a dynamic rock that is slipping and sliding back into the ocean. Understanding how it is slipping and sliding — and planning for it — will save lives and property.”
USGS and the Army Corps of Engineers are agencies which can be called on for aid in this planning and mitigation, he noted.
Bodell ended his discussion with Samoa News by quoting AS-EPA Director, Ameko Pato, who said, “These are some of the reasons why environmental science makes great economic sense for places like American Samoa — that offer so many active natural processes to study and has so much sacred land and culture to protect."