A Dutch-Texan team uncovered that many Houston-area drowned deaths indigenous Hurricane Harvey occurred outside the area designated by government as gift at higher risk that flooding: the 100- and also 500-year floodplains. Harvey, one of the costliest storms in united state history, fight southeast Texas top top 25 august 2017 leading to unprecedented flooding and killing dozens. Researcher at Delft university of modern technology in the Netherlands and also Rice university in Texas released their outcomes today in the european Geosciences Union newspaper Natural Hazards and also Earth mechanism Sciences.
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"It was surprising to me the so many fatalities developed outside the flood zones," states Sebastiaan Jonkman, a professor in ~ Delft"s Hydraulic engineering Department that led the brand-new study.
Drowning caused 80% of Harvey deaths, and also the research showed that only 22% the fatalities in Houston"s 4,600-square-kilometre district, Harris County, arisen within the 100-year floodplain, a mapped area the is offered as the key indicator that flood risk in the US.
Flood zones, or floodplains, are low-lying areas surrounding rivers and also streams that room subject to flooding. To evaluate flood threat for insurance allowance purposes and to set development standards, united state authorities synopsis floodplains for 100- and also 500-year floods. These occasions have a 1% probability (100-year flood) and also a 0.2% probability (500-year) of emerging in any given year.
"Hurricane Harvey to be much bigger than a 100- or 500-year flood, so flooding exterior of these boundaries was expected," states Jonkman. Rainfall totals in the mainly after the hurricane make landfall were amongst the highest possible recorded in us history, with over 1000 mm the rain fallout’s in just three work in big parts of both Harris and surrounding counties. Together a result, a report by Delft University uncovered that "unprecedented flooding developed over one area the dimension of the Netherlands."
Nonetheless, it to be surprising for the researchers to find that so countless of Harvey"s fatalities happened exterior the designated floodplains offered that this zones room expected to it is in "reasonable predictors that high-risk areas," according to Jonkman.
The research started within work of the storm: "We want to identify lessons that might be learned, for both Texas and the Netherlands, indigenous Harvey"s affect and the local and also government an answer to the flooding," says study co-author Antonia Sebastian, a postdoctoral research associate at Rice University"s serious Storm Prediction, Education and Evacuation from tragedies (SSPEED) Center, who was based in ~ Delft University when Harvey struck.
The team compiled a database that fatalities, making use of official federal government records and also media sources, which they analysed in the Natural Hazards and also Earth system Sciences study published today. Lock concluded the at the very least 70 deaths developed as a consequence of Hurricane Harvey, consisting of 37 in Harris County. The the Harris ar deaths, eight to be in the 100-year floodplain, 10 an ext fell within the larger 500-year floodplain, and also 19 to be recovered external the 100- and 500-year zones. "The number of fatalities exterior of the floodplains highlights just how widespread flooding from Harvey really was," claims Sebastian.
The new study likewise shows that many fatalities -- over 80% -- were drownings, many developing either in vehicles or when civilization were brushed up away when trying to obtain out of their cars. Six human being died once their boat capsized during a rescue. The 2nd largest causes of death were electrocution and lack of medical treatment, responsible because that 6% the fatalities each.
About 70% that those eliminated by Harvey were men. The team think the factor behind the high portion of male fatalities can be that men tend come show more risk-taking behaviour, such together driving with flooded crossings or taking component in rescues.
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The researchers hope your findings encourage authorities to recognize high risk locations outside of the designated floodplains and also to take it preventive steps to alleviate the variety of victims in future floods, including closing short water crossings and underpasses during extreme flood events.
Jonkman says that the present flood maps will should be improved, yet that floodplains must not it is in abandoned as an indicator the high-risk areas. "Better interaction of your purpose and also limitations would aid reduce risk."