383 research outputs found
A comparative analysis of the relationship between flood experience and private flood mitigation behaviour in the regions of England
There has been a move towards a more integrated approach to flood risk management, which includes a stronger focus on property level measures. However, in England the uptake of these measures remains low. Flood experience has been found to influence preparedness (i.e. the uptake of measures), but even experience does not always result in an increase in preparedness. We investigate the variations in the relationship between experience and preparedness for the regions of England as defined by the Environment Agency. Analysis of survey data collected by the Environment Agency among the at risk population between 1997 to 2004 was undertaken to determine the differences between the seven regions. We find that in the South West, Southern and Anglian regions increases in preparedness with increasing experience are higher compared to other regions. In the Thames, Midlands and North West regions the preparedness increases less with increasing experience. We explore the influence of other factors influencing flood mitigation behaviour that have been previously found in the literature and find that the differences between regions are correlated with the severity of experienced flooding and whether English is the first language of the respondents
Lagrangian pathways of upwelling in the Southern Ocean
The spatial and temporal variability of upwelling into the mixed layer in the Southern Ocean is studied using a 1/10° ocean general circulation model. Virtual drifters are released in a regularly-spaced pattern across the Southern Ocean at depths of 250, 500, and 1000 m during both summer and winter months. The drifters are advected along isopycnals for a period of four years, unless they outcrop into the mixed layer, where lateral advection and a parameterization of vertical mixing is applied. The focus of this study is on the discrete exchange between the model mixed layer and the interior. Localization of interior-mixed layer exchange occurs downstream of major topographic features across the Indian and Pacific basins, creating “hotspots” of outcropping. Minimal outcropping occurs in the Atlantic basin, while 59% of drifters outcrop in the Pacific sector and in Drake Passage (the region from 140° W to 40° W), a disproportionately large amount even when considering the relative basin sizes. Due to spatial and temporal variations in mixed layer depth, the Lagrangian trajectories provide a statistical measure of mixed layer residence times. For each exchange into the mixed layer, the residence time has a Rayleigh distribution with a mean of 30 days; the cumulative residence time of the drifters is 261 ± 194 days, over a period of four years. These results suggest that certain oceanic gas concentrations, such as CO_2 and ^(14)C, will likely not reach equilibrium with the atmosphere before being re-subducted
Temporal Scaling of Streamflow Elasticity to Precipitation: A Global Analysis
Streamflow elasticity to precipitation, defined as the percent change of streamflow resulting from a 1% change in precipitation, is sometimes used as an alternative to rainfall-runoff models in climate impact analyses. Elasticity is usually estimated from long streamflow and precipitation series aggregated at annual time steps while the climate impact analyses are usually geared toward changes at decadal scales. The purpose of this paper is therefore to understand how the elasticity depends on the aggregation time scale and the process controls of such a dependence. We analyze streamflow records of 7,053 catchments around the world over the period 1950–2016, and select 5,327 with reliable elasticity estimates for aggregation time ranging from 13 to 60 months. We find a significant scaling of streamflow elasticity to precipitation with aggregation time in 66% of the catchments which is much larger than expected by chance. Positive scaling occurs much more frequently than negative scaling. More arid/less rainy catchments, less forested catchments and catchments with a large base flow contribution to streamflow are more frequently characterized by a positive scaling. A random forest classification model identifies aridity index, latitude, mean annual precipitation, the potential evapotranspiration seasonality, the base flow index and the precipitation seasonality as relevant explanatory variables of the scaling. We interpret the sign of the scaling by non-linear runoff generation in arid regions, by the effect of climate modes and snow processes, and by the regulation capacity of vegetation to transpire more water if the past years were wet. It is suggested to use decadal elasticities instead of annual elasticities in climate impact analyses in order to account for their scaling behavior
The role of flood wave superposition in the severity of large floods
Abstract. The severity of floods is shaped not only by event- and catchment-specific characteristics but also depends on the river network
configuration. At the confluence of relevant tributaries with the main
river, flood event characteristics may change depending on the magnitude
and temporal match of flood waves. This superposition of flood
waves may potentially increase the flood severity downstream in the main
river. However, this aspect has not been analysed for a large set
of river confluences to date. To fill this gap, the role of flood wave superposition in the flood
severity at downstream gauges is investigated in four large
river basins in Germany and Austria (the Elbe, the Danube, the Rhine and
the Weser). A novel methodological approach to analyse flood wave
superposition is presented and applied to mean daily discharge data from
37 triple points. A triple point consists of three gauges: one in the
tributary as well as one upstream and downstream of the confluence with the
main river respectively. At the triple points, differences and similarities in
flood wave characteristics between the main river and the tributary are
analysed in terms of the temporal match and the magnitudes of flood peaks. At many of the confluences analysed, the tributary peaks consistently arrive
earlier than the main river peaks, although high variability in the
time lag is generally detected. No large differences in temporal matching are
detected for floods of different magnitudes. In the majority of
cases, the largest floods at the downstream gauge do not occur due to
perfect temporal match between the tributary and the main river. In terms of
spatial variability, the impact of flood wave superposition is
site-specific. Characteristic patterns of flood wave superposition are
detected for flood peaks in the Danube River, where peak discharges
largely increase due to inflow from alpine tributaries. Overall, we
conclude that the superposition of flood waves is not the driving
factor behind flood peak severity at the major confluences in Germany; however,
a few confluences show the potential for strong flood magnifications if a temporal shift in flood waves was to occur
Citalopram amplifies the influence of living conditions on mood in depressed patients enrolled in the STAR*D study
Selective serotonin reuptake inhibitors (SSRIs), the most commonly prescribed antidepressant drugs, have a variable and incomplete efficacy. In order to better understand SSRI action, we explored the hypothesis that SSRIs do not affect mood per se but amplify the influence of the living conditions on mood. To this aim, we exploited the Sequenced Treatment Alternatives to Relieve Depression (STAR*D) data set, selected a subpopulation of 591 patients with an overlapping clinical history and analyzed treatment outcome according to dosage −20 or 40 mg per day of citalopram. We found that sociodemographic characteristics affected treatment response in the same direction in the two dose groups, but these effects reached statistical significance only in the 40 mg per day dose group. In the latter, higher improvement rate was associated with having a working employment status (P=0.0219), longer education (P=0.0053), high income (P=0.01) or a private insurance (P=0.0031), and the higher remission rate was associated with having a working employment status (P=0.0326) or longer education (P=0.0484). Moreover, the magnitude of the effect of the sociodemographic characteristics on mood, measured as the percent of patients showing a positive outcome when exposed to favorable living conditions, was much greater—up to 37-fold—in the 40 compared to the 20 mg per day dose group. Overall, our results indicate that citalopram amplifies the influence of the living conditions on mood in a dose-dependent manner. These findings provide a potential explanation for the variable efficacy of SSRIs and might lead to the development of personalized strategies aimed at enhancing their efficacy
A comparative analysis of the relationship between flood experience and private flood mitigation behaviour in the regions of England
There has been a move towards a more integrated approach to flood risk management, which includes a stronger focus on property level measures. However, in England the uptake of these measures remains low. Flood experience has been found to influence preparedness (i.e., the uptake of measures), but even experience does not always result in an increase in preparedness. We investigate the variations in the relationship between experience and preparedness for the regions of England as defined by the Environment Agency. Analysis of survey data collected by the Environment Agency among the at risk population between 1997 and 2004 was undertaken to determine the differences between the seven regions. We find that in the South West, Southern and Anglian regions increases in preparedness with increasing experience are higher compared to other regions. In the Thames, Midlands and North West regions the preparedness increases less with increasing experience. We explore the influence of other factors influencing flood mitigation behaviour that have been previously found in the literature and find that the differences between regions are correlated with the severity of experienced flooding and whether English is the first language of the respondents
An Inventory of Problems–29 Study on Random Responding Using Experimental Feigners, Honest Controls, and Computer-Generated Data
Flood trends in Europe: are changes in small and big floods different?
Abstract. Recent studies have revealed evidence of trends in the median or mean flood discharge in Europe over the last 5 decades, with clear and coherent
regional patterns. The aim of this study is to assess whether trends in flood discharges also occurred for larger return periods, accounting for
the effect of catchment scale. We analyse 2370 flood discharge records, selected from a newly available pan-European flood database, with record
length of at least 40 years over the period 1960–2010 and with contributing catchment area ranging from 5 to 100 000 km2. To estimate
regional flood trends, we use a non-stationary regional flood frequency approach consisting of a regional Gumbel distribution, whose median and
growth factor can vary in time with different strengths for different catchment sizes. A Bayesian Markov chain Monte Carlo (MCMC) approach is used
for parameter estimation. We quantify regional trends (and the related sample uncertainties), for floods of selected return periods and for
selected catchment areas, across Europe and for three regions where coherent flood trends have been identified in previous studies. Results show
that in northwestern Europe the trends in flood magnitude are generally positive. In small catchments (up to 100 km2), the 100-year flood
increases more than the median flood, while the opposite is observed in medium and large catchments, where even some negative trends appear,
especially in northwestern France. In southern Europe flood trends are generally negative. The 100-year flood decreases less than the median flood,
and, in the small catchments, the median flood decreases less compared to the large catchments. In eastern Europe the regional trends are negative
and do not depend on the return period, but catchment area plays a substantial role: the larger the catchment, the more negative the trend
Estimating the flood frequency distribution at seasonal and annual time scales
Abstract. We propose an original approach to infer the flood frequency distribution at seasonal and annual time scale. Our purpose is to estimate the peak flow that is expected for an assigned return period T, independently of the season in which it occurs (i.e. annual flood frequency regime), as well as in different selected sub-yearly periods (i.e. seasonal flood frequency regime). While a huge literature exists on annual flood frequency analysis, few studies have focused on the estimation of seasonal flood frequencies despite the relevance of the issue, for instance when scheduling along the months of the year the construction phases of river engineering works directly interacting with the active river bed, like for instance dams. An approximate method for joint frequency analysis is presented here that guarantees consistency between fitted annual and seasonal distributions, i.e. the annual cumulative distribution is the product of the seasonal cumulative distribution functions, under the assumption of independence among floods in different seasons. In our method the parameters of the seasonal frequency distributions are fitted by maximising an objective function that accounts for the likelihoods of both seasonal and annual peaks. In contrast to previous studies, our procedure is conceived to allow the users to introduce subjective weights to the components of the objective function in order to emphasize the fitting of specific seasons or of the annual peak flow distribution. An application to the time series of the Blue Nile daily flows at the Sudan–Ethiopia border is presented
- …