There’s a watery theme to this week’s article, with all three sections looking at the sea. As a bonus, each piece of research covered shows how the particular area of study is linked to another part of the Earth system, illustrating the complicated and interrelated nature of our planet.
Hurricane Harvey: Where Did the Fatalities Occur?
Hurricane Harvey was just one of of the four serious hurricanes of the 2017 season — so severe that its name, along with Irma and Maria, has been officially retired from the World Meteorological Organisation’s hurricane list. Striking Texas in August 2017 with winds reaching 130 mph, Harvey caused an estimated $125 million damage and cost 88 lives.
While we know a lot about the physical properties of hurricanes, it’s the human impacts that make the news and from which we can learn, so as to reduce future death and damage. This week a new study into the hurricane, published in the journal Geophysical Research Letters, looks at the deaths that were caused.
Hazard management relies on predicting what damage will occur and where. You may have heard terms such a “100-year flood” (or storm or whatever) and that essentially means that planning is made on the basis of an event that might occur once in every hundred years. “To assess flood risk for insurance purposes and to set development standards,” notes the study’s press release, “US authorities outline floodplains for 100- and 500-year floods. These events have a 1% probability (100-year flood) and a 0.2% probability (500-year) of occurring in any given year.”
The analysis of 70 of the 88 deaths provides a number of interesting points. Not all of them are surprising — it’s hardly unexpected that the majority of deaths were from drowning, or that older people were more likely to die than younger. But perhaps the most significant result of the analysis relates to where people died. Of the 57 deaths associated with Hurricane Harvey in one area, Harris County, just over half occurred outside the 500-year flood plan and over three-quarters outside the 100 year flood plain.
Of course, there are many factors influencing the death toll of any natural hazard, and the study goes on to list some of them, but the obvious implication is that using the 100 and 500 year flood plains is probably too general to be helpful. The study concludes that: “The events during Harvey can … be utilized to evaluate and improve the performance of the evacuation strategy and emergency management for the region, also addressing the need for timely evacuation from specific high- risk areas”.
When the Winter Storms Begin…
Last week I mentioned, as a footnote, the chances of a slightly above-average hurricane season. This week, research published by the journal European Geophysical Union looks at storms on the other side of the Atlantic, and concludes that “average winter wave heights along the Atlantic coast of Western Europe have been rising for almost seven decades”.
I don’t want to get into the causes of this, which are so complicated as to be way beyond either my meteorological knowledge or the scope of this article. (For interest, the study itself notes that: the “North Atlantic Oscillation (NAO) and West Europe Pressure Anomaly (WEPA) affect atmospheric circulation in the North Atlantic. NAO and WEPA primarily explain the increase in winter‐mean wave height and periodicity, respectively, while both WEPA and NAO explain the increase in interannual variability”.
At a simpler level, such research does raise the ever-present issue of whether such change is natural or anthropogenic. As the study notes: “It will therefore be critical to address the evolution of the winter wave height over the next years and decades to explore if the recent increase in the mean, variability, and periodicity is related to a natural anomaly or if it is the expression of climate change.”
Whatever the cause, it’s the effects that are significant. If it’s the case that more severe winter storms are both occurring and likely to continue to occur, then steps need to be taken to mitigate against increased storm damage and coastal erosion rates.
I hope you’ll forgive me if I go off down an apparently irrelevant alley and talk about a piece of research into a landslide that occurred probably around 60 million years ago.
You probably won’t have heard of the Halibut Slide, described as “the world’s largest epicontinental submarine landslide”. (It was 190km long, and occurred in the North Sea off eastern Scotland.) Geologists have drilled into the compacted sediments from this landslide and concluded that it resulted from the tectonic uplift of the North Atlantic.
This is all very interesting for people like me, but is it really relevant? I would say yes. Submarine landslides are capable of generating huge tsunamis and while that caused by the Halibut Slide obviously had no direct impact on humans, others in the past have done so. The Storegga Slide, for example, generated a tsunami that wiped out settlements on North Sea coasts over 7000 years ago.
In itself the Halibut Slide probably isn’t important, but like so many other historic events, it has a lot to contribute to our understanding of potential future events.