July 18, 2017

The science before (and during) the storm – Part 2

Posted by larryohanlon

Caught in the Storm

By Robert Emberson

Sampling landslides in the field varies in difficulty; some are high up on hillslopes or in the headwaters of steep catchments, while others tumble into easily accessed river valleys. When planning for such sampling, we had mainly anticipated that the weather would not be the biggest obstacle, but that’s what transpired for a major portion of our fieldwork in central Taiwan. The typical spring monsoon combined with the remnants of a tropical storm over the Indian Ocean to dump around 1.2 metres of rainfall onto the catchment in which we were working over only about 48 hours. That rate of rainfall meant the rivers rapidly went from relatively normal flow conditions to some of the highest flows in 20 years in very short order. Below is the river right at the beginning of the storm:

Chenyoulan River, at Tongfu village. Image courtesy Dr Aaron Bufe (GFZ Potsdam)

Compare that to this clip of the river from the same point after over a metre of rain had fallen:

Such intense rainfall is a trigger for mass-wasting on hillslopes, and this led to many of the roads in the catchment getting blocked by sediment, accessible only to the most all-terrain of vehicles (our hire car definitely didn’t qualify).

The loss of electricity and road access made this quite an adventure; Taiwan is a small island, and is also very highly populated (23.5 million people living in an area approximately the same size as the US state of Indiana), but it’s clear that in the mountains it can still be pretty isolated at times.

Any chance of safely reaching landslides basically evaporated in the high waters; in many cases we had been wading up small streams to reach some sites, but these were now so swollen as to be impassable. Instead, we focused on sampling the larger rivers where we could, to assess how the water chemistry changed over the course of such a large flood.

The author attempting to take measurements in the river at near-peak flood. Image courtesy Dr.
Aaron Bufe (GFZ Potsdam)

Fieldwork campaigns can sometimes be somewhat of a bubble; you have specific sampling goals and limited time, so tourism and taking in the local culture can often pass you by. But getting caught in what nearly amounted to a disaster zone was a shift in perspectives; we were somewhat at a loss, but the local residents could not have been more friendly and welcoming, and it was hugely impressive to see how quickly they bounced back from the storm, even as houses, roads and bridges had been washed away:

Left: bridge washed out by the river. Right: parts of a house, similarly washed into the river. Images
both courtesy of Dr Aaron Bufe (GFZ Potsdam).


Above all, it emphasised the importance of preparing for even the most unexpected events, and being flexible in the face of adverse conditions. And hopefully some interesting results will come of it!

Robert Emberson was working with Dr Aaron Bufe in Taiwan on research funded by the GFZ in Potsdam, Germany, where Dr Bufe currently works. Robert completed his PhD work also at the GFZ in December 2016, and is currently working as a freelance science writer in British Columbia, Canada. Questions or comments can be directed to @RobertEmberson or via www.robertemberson.com