Nonstationarities in the occurrence rates of flood events in Portuguese watersheds
An exploratory analysis on the variability of flood occurrence rates in 10 Portuguese watersheds is made, to ascertain if that variability is concurrent with the principle of stationarity. A peaks-over-threshold (POT) sampling technique is applied to 10 long series of mean daily streamflows and to 4...
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ftdoajarticles:oai:doaj.org/article:112843e8650b4749bcfed65007f04ab3 2023-05-15T17:35:41+02:00 Nonstationarities in the occurrence rates of flood events in Portuguese watersheds A. T. Silva M. M. Portela M. Naghettini 2012-01-01T00:00:00Z https://doi.org/10.5194/hess-16-241-2012 https://doaj.org/article/112843e8650b4749bcfed65007f04ab3 EN eng Copernicus Publications http://www.hydrol-earth-syst-sci.net/16/241/2012/hess-16-241-2012.pdf https://doaj.org/toc/1027-5606 https://doaj.org/toc/1607-7938 doi:10.5194/hess-16-241-2012 1027-5606 1607-7938 https://doaj.org/article/112843e8650b4749bcfed65007f04ab3 Hydrology and Earth System Sciences, Vol 16, Iss 1, Pp 241-254 (2012) Technology T Environmental technology. Sanitary engineering TD1-1066 Geography. Anthropology. Recreation G Environmental sciences GE1-350 article 2012 ftdoajarticles https://doi.org/10.5194/hess-16-241-2012 2022-12-31T00:53:25Z An exploratory analysis on the variability of flood occurrence rates in 10 Portuguese watersheds is made, to ascertain if that variability is concurrent with the principle of stationarity. A peaks-over-threshold (POT) sampling technique is applied to 10 long series of mean daily streamflows and to 4 long series of daily rainfall in order to sample the times of occurrence (POT time data) of the peak values of those series. The kernel occurrence rate estimator, coupled with a bootstrap approach, was applied to the POT time data to obtain the time dependent estimated occurrence rate curves, λ ˆ ( t ), of floods and extreme rainfall events. The results of the analysis show that the occurrence of those events constitutes an inhomogeneous Poisson process, hence the occurrence rates are nonstationary. An attempt was made to assess whether the North Atlantic Oscillation (NAO) casted any influence on the occurrence rate of floods in the study area. Although further research is warranted, it was found that years with a less-than-average occurrence of floods tend to occur when the winter NAO is in the positive phase, and years with a higher occurrence of floods (more than twice the average) tend to occur when the winter NAO is in the negative phase. Although the number of analyzed watersheds and their uneven spatial distribution hinders the generalization of the findings to the country scale, the authors conclude that the mathematical formulation of the flood frequency models relying on stationarity commonly employed in Portugal should be revised in order to account for possible nonstationarities in the occurrence rates of such events. Article in Journal/Newspaper North Atlantic North Atlantic oscillation Directory of Open Access Journals: DOAJ Articles Hydrology and Earth System Sciences 16 1 241 254 |
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Open Polar |
collection |
Directory of Open Access Journals: DOAJ Articles |
op_collection_id |
ftdoajarticles |
language |
English |
topic |
Technology T Environmental technology. Sanitary engineering TD1-1066 Geography. Anthropology. Recreation G Environmental sciences GE1-350 |
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Technology T Environmental technology. Sanitary engineering TD1-1066 Geography. Anthropology. Recreation G Environmental sciences GE1-350 A. T. Silva M. M. Portela M. Naghettini Nonstationarities in the occurrence rates of flood events in Portuguese watersheds |
topic_facet |
Technology T Environmental technology. Sanitary engineering TD1-1066 Geography. Anthropology. Recreation G Environmental sciences GE1-350 |
description |
An exploratory analysis on the variability of flood occurrence rates in 10 Portuguese watersheds is made, to ascertain if that variability is concurrent with the principle of stationarity. A peaks-over-threshold (POT) sampling technique is applied to 10 long series of mean daily streamflows and to 4 long series of daily rainfall in order to sample the times of occurrence (POT time data) of the peak values of those series. The kernel occurrence rate estimator, coupled with a bootstrap approach, was applied to the POT time data to obtain the time dependent estimated occurrence rate curves, λ ˆ ( t ), of floods and extreme rainfall events. The results of the analysis show that the occurrence of those events constitutes an inhomogeneous Poisson process, hence the occurrence rates are nonstationary. An attempt was made to assess whether the North Atlantic Oscillation (NAO) casted any influence on the occurrence rate of floods in the study area. Although further research is warranted, it was found that years with a less-than-average occurrence of floods tend to occur when the winter NAO is in the positive phase, and years with a higher occurrence of floods (more than twice the average) tend to occur when the winter NAO is in the negative phase. Although the number of analyzed watersheds and their uneven spatial distribution hinders the generalization of the findings to the country scale, the authors conclude that the mathematical formulation of the flood frequency models relying on stationarity commonly employed in Portugal should be revised in order to account for possible nonstationarities in the occurrence rates of such events. |
format |
Article in Journal/Newspaper |
author |
A. T. Silva M. M. Portela M. Naghettini |
author_facet |
A. T. Silva M. M. Portela M. Naghettini |
author_sort |
A. T. Silva |
title |
Nonstationarities in the occurrence rates of flood events in Portuguese watersheds |
title_short |
Nonstationarities in the occurrence rates of flood events in Portuguese watersheds |
title_full |
Nonstationarities in the occurrence rates of flood events in Portuguese watersheds |
title_fullStr |
Nonstationarities in the occurrence rates of flood events in Portuguese watersheds |
title_full_unstemmed |
Nonstationarities in the occurrence rates of flood events in Portuguese watersheds |
title_sort |
nonstationarities in the occurrence rates of flood events in portuguese watersheds |
publisher |
Copernicus Publications |
publishDate |
2012 |
url |
https://doi.org/10.5194/hess-16-241-2012 https://doaj.org/article/112843e8650b4749bcfed65007f04ab3 |
genre |
North Atlantic North Atlantic oscillation |
genre_facet |
North Atlantic North Atlantic oscillation |
op_source |
Hydrology and Earth System Sciences, Vol 16, Iss 1, Pp 241-254 (2012) |
op_relation |
http://www.hydrol-earth-syst-sci.net/16/241/2012/hess-16-241-2012.pdf https://doaj.org/toc/1027-5606 https://doaj.org/toc/1607-7938 doi:10.5194/hess-16-241-2012 1027-5606 1607-7938 https://doaj.org/article/112843e8650b4749bcfed65007f04ab3 |
op_doi |
https://doi.org/10.5194/hess-16-241-2012 |
container_title |
Hydrology and Earth System Sciences |
container_volume |
16 |
container_issue |
1 |
container_start_page |
241 |
op_container_end_page |
254 |
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1766134916095934464 |