by Staff Writers
Delft, Germany (SPX) Oct 13, 2011
Scientists at TU Delft have successfully matched a layer of sediment from the dunes near Heemskerk to a severe storm flood that occurred in either 1775 or 1776. This type of information helps us gain more insight into past storm floods and predict future surges more accurately. The scientists' findings have been published in the online edition of the scientific magazine Geology, and will be on the cover of the paper edition of November.
This is unfortunate, because the limited historical archive makes it difficult to formulate statistical conclusions and predictions about future storm floods. It is also harder for us to establish whether storm floods are becoming more severe over the years.
The method was applied to a layer of sediment in the dunes near Heemskerk, created during a storm flood centuries ago and exposed by a storm in 2007. The level to which the storms and waves pushed the water can be deduced from the height of this layer. During the storm-surge in question, the water was higher than the catastrophic flood of 1953.
In order to put these data on a historical timeline, however, it is essential to know when the storm occurred. The scientists have now been able to show that in all probability the layer of sediment was deposited in 1775 or 1776. Historical sources indicate that severe storm floods took place in both years.
Grains of sand
The strength of the luminescence signal grows stronger over time as a result of natural radioactivity (background radiation) from the surroundings. However, the signal is reset to zero when the grains of sand are exposed to sunlight.
The strength of the luminescence signal (and the local strength of the background radiation) indicates the length of time since the grains were last exposed to light; in other words, the moment when they were 'buried'. Using luminescence dating, a precision of 5% is achievable.
'Extracting storm-surge data from coastal dunes for improved assessment of flood risk', Alastair Cunningham, Marcel Bakker, Sytze van Heteren, Bert van der Valk, Ad van der Spek, Dennis Schaart and Jakob Wallinga. doi: 10.1130/G32244.1
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One-third of Thailand 'disaster' area: govt
Bangkok (AFP) Oct 12, 2011
Thailand on Wednesday declared a third of its provinces to be disaster zones, as auto giant Toyota called a halt to work after production was affected by the country's worst flooding in decades. The government's move aims to speed up relief operations, as the floods have left at least 281 people dead and damaged millions of homes and livelihoods in more than two months. "The government h ... read more
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