scholarly journals Flood type classification and assessment of their past changes across Europe

2017 ◽  
Author(s):  
Yeshewatesfa Hundecha ◽  
Juraj Parajka ◽  
Alberto Viglione
Keyword(s):  
Eastern Europe ◽  
State Variables ◽  
Flood Events ◽  
Rainfall Events ◽  
Short Rain ◽  
Investigation Period ◽  
The Alps ◽  
Flood Generation ◽  
Rain Events ◽  
Summer Rain

Abstract. This study was carried out to establish the characteristics of observed flood events across Europe in the past in terms of their spatial extent and the processes leading up to the events. Daily discharge data from more than 745 stations of the Global Runoff Data Centre were used to identify peak flows at each station for the period 1961-2010. The identified events at the different stations were further analysed to determine whether they form the same flood event, thereby delineating the spatial extent of the flood events. A pan-European hydrological model was employed to estimate a set of catchment hydrological and hydro-meteorological state variables that are relevant in the flood generation process for each of the identified spatially delineated flood events. A subsequent clustering of the events based on the simulated state variables was used to identify the flood generation mechanism of each flood event. Four general flood generation mechanisms were identified: long-rain flood, short-rain flood, snowmelt flood, and rain-on-snow flood. A trend analysis was performed to investigate how the frequency of each of the flood types has changed in time over the investigation period. In order to investigate whether there is a regional and seasonal pattern in the dominant flood generating mechanisms, this analysis was performed separately for winter and summer seasons and five different regions of Europe: Northern, Western, Eastern, Southern Europe, and the Alps. Continentally, the total number of flood events didn’t show a significant change. However, the frequency of winter long rain events increased significantly while that of summer rain-on-snow events decreased significantly over the investigation period. Regional differences were detected in the dominant flood generating mechanism and the corresponding trends. In Western Europe, the frequency of both winter and summer rainfall events increased significantly. In Northern and Eastern Europe, the frequency of summer rain-on-snow events decreased significantly. In addition, winter short rainfall events increased significantly in Eastern Europe. In the Alps, the frequency of summer short rain events increased significantly.

scholarly journals Extreme Floods in the Eastern Part of Europe: Large-Scale Drivers and Associated Impacts

Water ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1122
Author(s):  
Monica Ionita ◽  
Viorica Nagavciuc
Keyword(s):  
Water Vapor ◽  
Heavy Rainfall ◽  
Large Scale ◽  
Vapor Transport ◽  
Water Vapor Transport ◽  
Flood Events ◽  
Rainfall Events ◽  
Catchment Areas ◽  
Large Scale Atmospheric Circulation ◽  
Heavy Rainfall Events

The role of the large-scale atmospheric circulation in producing heavy rainfall events and floods in the eastern part of Europe, with a special focus on the Siret and Prut catchment areas (Romania), is analyzed in this study. Moreover, a detailed analysis of the socio-economic impacts of the most extreme flood events (e.g., July 2008, June–July 2010, and June 2020) is given. Analysis of the largest flood events indicates that the flood peaks have been preceded up to 6 days in advance by intrusions of high Potential Vorticity (PV) anomalies toward the southeastern part of Europe, persistent cut-off lows over the analyzed region, and increased water vapor transport over the catchment areas of Siret and Prut Rivers. The vertically integrated water vapor transport prior to the flood peak exceeds 300 kg m−1 s−1, leading to heavy rainfall events. We also show that the implementation of the Flood Management Plan in Romania had positive results during the 2020 flood event compared with the other flood events, when the authorities took several precaution measurements that mitigated in a better way the socio-economic impact and risks of the flood event. The results presented in this study offer new insights regarding the importance of large-scale atmospheric circulation and water vapor transport as drivers of extreme flooding in the eastern part of Europe and could lead to a better flood forecast and flood risk management.

scholarly journals Spatial structures and directionalities in Monsoonal precipitation over South Asia

2010 ◽  
Vol 17 (5) ◽  
pp. 371-381 ◽  
Author(s):  
N. Malik ◽  
N. Marwan ◽  
J. Kurths
Keyword(s):  
Indian Subcontinent ◽  
Monsoon Season ◽  
Daily Rainfall ◽  
Heavy Rain ◽  
Data Sets ◽  
Spatial Structures ◽  
Break Phase ◽  
Rainfall Events ◽  
Monsoonal Precipitation ◽  
Rain Events

Abstract. Precipitation during the monsoon season over the Indian subcontinent occurs in form of enormously complex spatiotemporal patterns due to the underlying dynamics of atmospheric circulation and varying topography. Employing methods from nonlinear time series analysis, we study spatial structures of the rainfall field during the summer monsoon and identify principle regions where the dynamics of monsoonal rainfall is more coherent or homogenous. Moreover, we estimate the time delay patterns of rain events. Here we present an analysis of two separate high resolution gridded data sets of daily rainfall covering the Indian subcontinent. Using the method of event synchronization (ES), we estimate regions where heavy rain events during monsoon happen in some lag synchronised form. Further using the delay behaviour of rainfall events, we estimate the directionalities related to the progress of such type of rainfall events. The Active (break) phase of a monsoon is characterised by an increase(decrease) of rainfall over certain regions of the Indian subcontinent. We show that our method is able to identify regions of such coherent rainfall activity.

scholarly journals Conceptual model of sedimentgraph from flood events in a small agricultural watershed

2008 ◽  
Vol 39 (1) ◽  
pp. 49-57 ◽  
Author(s):  
Kazimierz Banasik ◽  
J. Mitchell
Keyword(s):  
Conceptual Model ◽  
Suspended Sediment ◽  
Sediment Concentration ◽  
Agricultural Watershed ◽  
Sediment Flux ◽  
Flood Events ◽  
Rainfall Events ◽  
Sediment Routing ◽  
Suspended Sediment Flux ◽  
Lag Times

Conceptual model of sedimentgraph from flood events in a small agricultural watershed A procedure for predicting the sediment graph (i.e. the suspended sediment flux), from a small river catchment by heavy rainfall, has been developed using the concept of an instantaneous unit hydrograph (IUH) and dimensionless sediment concentration distribution (DSCD). A formula for instantaneous unit sedimentgraph (IUSG) is presented, and a procedure for estimating the sediment routing coefficient, which is a key parameter of the IUSG, based on measured data of rainfall-runoff-suspended sediment is applied. Field data from a small, field sized agricultural basin, lacated in center of Illinois has been used for analizing lag times for runoff (LAG) and sediment yield (LAGs). Assumptions about sediment generated during rainfall events are discussed.

scholarly journals The role of precipitation for high-magnitude flood generation in a large mountainous catchment (upper Rhône River, NW European Alps)

2019 ◽  
Author(s):  
Florian Raymond ◽  
Bruno Wilhelm ◽  
Sandrine Anquetin
Keyword(s):  
Heavy Precipitation ◽  
European Alps ◽  
Flood Events ◽  
Rhône River ◽  
High Magnitude ◽  
Extreme Flood ◽  
Rhone River ◽  
Flood Generation ◽  
Rain Floods

Abstract. High-impact climate events such as floods are highly destructive natural hazards causing widespread impacts on socio-ecosystems. However, processes leading to such events are still poorly understood, which limiting reliable prediction. This study takes advantage of centennial-long discharge series (1923–2010) and meteorological reanalysis (ERA-20C) to study processes generating the high-magnitude flood events (i.e. above the percentile 99.9) of the upper Rhône River (NW European Alps). A particular focus is paid to the role of precipitation on the flood generation to explore in what extent such events could be explained by only atmospheric variables. A flood typology is thus established using a hierarchical clustering analysis and three variables: long (8-day) and short (2-day) precipitation accumulations as well as an index characterizing the amplitude of the discharge increase during the 7 days prior to the flood day. The typology result in four classes, of which two are directly linked to precipitation. One results from heavy precipitation over two days (similar to short-rain floods in the literature) and the other one from a combination of short and long intense precipitation sequences (similar to long-rain floods). The two other types of floods cannot be explained by precipitation only, most probably involving ice and snow melting. The four events of highest magnitude (> 20 year return period) are of various types but are all triggered by heavy precipitation during the days preceding the floods. The role of the precipitation accumulations progressively decreases when considering floods of weaker magnitude, suggesting a higher diversity of processes involved in the generation of e.g. annual flooding. Our results highlight the needs to better understand the atmospheric processes leading to heavy precipitation accumulation since this would allow a better understanding of past and future trends of extreme flood events.

Budgets of major ionic species and nutrients on a dam reservoir in forested watershed

2007 ◽  
Vol 56 (1) ◽  
pp. 287-293 ◽  
Author(s):  
Y. Komai ◽  
S. Umemoto ◽  
Y. Takeda ◽  
T. Inoue ◽  
A. Imai
Keyword(s):  
Water Surface ◽  
Stream Water ◽  
Ionic Species ◽  
Forested Watershed ◽  
Bulk Precipitation ◽  
Dam Reservoir ◽  
Average Precipitation ◽  
Investigation Period ◽  
Rain Events

To evaluate the role of a dam reservoir in the runoff of pollutant loadings from a forested watershed, the input–output budgets in the Ikuno dam reservoir had been investigated for eight years since 1996. The T-N, T-P, TOC and major ionic species in the bulk precipitation, stream water, and outflow were measured. The residence time calculated by using the data of the inflow and outflow was 0.3 year. The average precipitation was 1,772 mm during the investigation period (1996–2004). The direct deposition to water surface was less than one percentage to total loadings of nutrients and major ionic species. The ratios of output to input of TOC, TN, and TP were 1.04 to 1.42, and those of major ionic species were from 0.83 to 0.99 except for NO3−, which was 1.12. However, the ratios of output to input of major ionic species except for NO3− at the Ikuno dam reservoir will be larger, and those of NO3−, TOC, TN, and TP will be smaller, if we also include rain events. These results suggested that the dam reservoir played a role as a sink for pollutants in forested watershed, and that the pollutant loadings to downstream may decrease.

scholarly journals Assessment of Regional Site-Specific Sorghum Ergot Severity Potential Using Radar-Rainfall Measurement

Plant Disease ◽  
2006 ◽  
Vol 90 (6) ◽  
pp. 704-707 ◽  
Author(s):  
F. Workneh ◽  
B. Narasimhan ◽  
R. Srinivasan ◽  
C. M. Rush
Keyword(s):  
Assessment System ◽  
Radar Rainfall ◽  
Web Based ◽  
Site Specific ◽  
Rainfall Events ◽  
Management Actions ◽  
Texas Panhandle ◽  
Claviceps Africana ◽  
Weather Stations ◽  
Rain Events

Sorghum ergot, caused by Claviceps africana, generally requires cool weather and humid conditions for optimum infection. Rainfall reportedly is not required for infection as long as relative humidity is high. However, occurrence of high humidity in the Texas Panhandle during the summer is usually associated with rain showers, and ergot incidence in the region has been observed to be associated with rain events. These events are often irregular and can vary within a small area both in incidence and intensity. Existing ground weather stations are too far apart to provide accurate representation of localized rainfall events. Radar-based precipitation measurements have a resolution of 4 × 4 km out to 230 km from the radar location. In the present study, radar rainfall measurements were used to assess regional site-specific sorghum ergot potential in the Texas Panhandle. The results have a potential for development of a web-based ergot risk assessment system in which growers can enter the GPS locations of their fields and determine whether management actions are necessary.

scholarly journals Predictability of prototype flash flood events in the Western Mediterranean under uncertainties of the precursor upper-level disturbance: the HYDROPTIMET case studies

2005 ◽  
Vol 5 (4) ◽  
pp. 505-525 ◽  
Author(s):  
R. Romero ◽  
A. Martín ◽  
V. Homar ◽  
S. Alonso ◽  
C. Ramis
Keyword(s):  
Case Studies ◽  
Large Scale ◽  
Flash Flood ◽  
Heavy Rain ◽  
Western Mediterranean ◽  
Flood Events ◽  
Southern France ◽  
The Alps ◽  
Upper Level ◽  
Level Disturbance

Abstract. The HYDROPTIMET case studies (9–10 June 2000 Catalogne, 8–9 September 2002 Cévennes and 24–26 November 2002 Piémont) appear to encompass a sort of prototype flash-flood situations in the western Mediterranean attending to the relevant synoptic and mesoscale signatures identified on the meteorological charts. In Catalogne, the convective event was driven by a low-pressure system of relatively small dimensions developed over the mediterranean coast of Spain that moved into southern France. For Cévennes, the main circulation pattern was a synoptic-scale Atlantic low which induced a persistent southerly low-level jet (LLJ) over the western Mediterranean, strengthened by the Alps along its western flank, which guaranteed continuous moisture supply towards southern France where the long-lived, quasistationary convective system developed. The long Piémont episode, very representative of the most severe alpine flash flood events, shares some similarities with the Cévennes situation during its first stage in that it was controlled by a southerly moist LLJ associated with a large-scale disturbance located to the west. However, these circulation features were transient aspects and during the second half of the episode the situation was dominated by a cyclogenesis process over the Mediterranean which gave place to a mesoscale-size depression at surface that acted to force new heavy rain over the slopes of the Alps and maritime areas. That is, the Piémont episode can be catalogued as of mixed type with regard to the responsible surface disturbance, evolving from a large-scale pattern with remote action (like Cévennes) to a mesoscale pattern with local action (like Catalogne). A prominent mid-tropospheric trough or cut-off low can be identified in all events prior and during the period of heavy rain, which clearly served as the precursor agent for the onset of the flash-flood conditions and the cyclogenesis at low-levels. Being aware of the uncertainty in the representation of the upper-level disturbance and the necessity to cope with it within the operational context when attempting to issue short to mid-range numerical weather predictions of these high impact weather events, a systematic exploration of the predictability of the three selected case studies subject to uncertainties in the representation of the upper-level precursor disturbance is carried out in this paper. The study is based on an ensemble of mesoscale numerical simulations of each event with the MM5 non-hydrostatic model after perturbing in a systematic way the upper-level disturbance, in the sense of displacing slightly this disturbance upstream/downstream along the zonal direction and intensifying/weakening its amplitude. These perturbations are guided by a previous application of the MM5-adjoint model, which consistently shows high sensitivities of the dynamical control of the heavy rain to the flow configuration about the upper-level disturbance on the day before, thus confirming the precursor characteristics of this agent. The perturbations are introduced to the initial conditions by applying a potential vorticity (PV) inversion procedure to the positive PV anomaly associated with the upper-level disturbance, and then using the inverted fields (wind, temperature and geopotential) to modify under a physically consistent balance the model initial fields. The results generally show that the events dominated by mesoscale low-level disturbances (Catalogne and last stage of the Piémont episode) are very sensitive to the initial uncertainties, such that the heavy rain location and magnitude are in some of the experiments strongly changed in response to the "forecast errors" of the cyclone trajectory, intensity, shape and translational speed. In contrast, the other situations (Cévennes and initial stage of the Piémont episode), dominated by a larger scale system wich basically acts to guarantee the establishment and persistence of the southerly LLJ towards the southern France-north Italy orography, exhibit much higher predictability. That is, the slight modifications in the LLJ direction and intensity encompassed by the ensemble of perturbed forecasts are less critical with respect to the heavy precipitation potential and affected area.

Daily and seasonal spore dispersal by Mycosphaerella pinodes and development of mycosphaerella blight of field pea

2005 ◽  
Vol 83 (3) ◽  
pp. 302-310 ◽  
Author(s):  
Jin Xiu Zhang ◽  
W G Dilantha Fernando ◽  
Allen G Xue
Keyword(s):  
Disease Severity ◽  
Field Pea ◽  
Mycosphaerella Pinodes ◽  
Rain Event ◽  
Spore Dispersal ◽  
Rainfall Events ◽  
Inoculum Source ◽  
Practical Applications ◽  
Spore Release ◽  
Rain Events

Daily and seasonal spore dispersal of Mycosphaerella pinodes (Berk & Bloxam) Vestergren and the relationship of spore dispersal to distance and disease severity were investigated in a pea field in western Canada during two consecutive years. Most ascospores were released in response to rain events, during the first 23–27 d after the inoculum source area was infested with naturally diseased pea residue, whereas most pycnidiospores were trapped during the first 20 d. For both ascospores and pycnidiospores, the highest peaks of spore release occurred during the first 14–20 d after infestation. Few spores were trapped after day 27 after infestation. Daily peaks of ascospore and pycnidiospore release occurred between 1700 and 0400 hours. Most ascospores were released 1–2 d after a rain event and the largest peak appeared the first day after rain. In contrast, most pycnidiospores were released on the same day as rain occurred or the following day. The release of both spore types was associated with rainfall events ≥2 mm during the first 27 d after infestation but not with rainfall events after 27 d. Ascospore density was negatively correlated with distance from the inoculum source (r ≤ –0.92) and positively related to the disease severity (r ≥ 0.92). Disease severity decreased with increasing distance from the inoculum source. The patterns of spore dispersal associated with rain events have practical applications in the disease forecasting and spraying of chemicals to control the disease.Key words: field pea, mycosphaerella blight, rainfall, spore release.

scholarly journals Detailed procedure for outdoor measurement of raindrop size distribution using photogrammetry

2021 ◽  
Vol 69 (2) ◽  
pp. 171-179
Author(s):  
Zahra Abdollahi ◽  
Seyed Hamidreza Sadeghi ◽  
Abdulvahed Khaledi Darvishan
Keyword(s):  
Digital Imaging ◽  
Rainfall Intensity ◽  
Size Variation ◽  
Short Exposure ◽  
Northern Iran ◽  
Short Exposure Time ◽  
Rainfall Events ◽  
Raindrop Size Distribution ◽  
Raindrop Size ◽  
Rain Events

Abstract Kinetic energy and corresponding erosive force of rainfall are strongly influenced by raindrop. The present paper aims to explore the raindrop size variation during rainfall events with different intensities in northern Iran by applying the processes of camera-taken photographs. Five rainfall intensities of 1 to 10 mm h–1 that occur frequently in the study area were analyzed. A camera with a very short exposure time was used to record the distribution of raindrops size. The raindrops diameters of the rain events ranged from <0.2 to 5.1 mm while the majority of them were between 1 and 2 mm. The results also showed that the variation of rainfall intensity significantly influenced (P< 0.05) raindrops size. Image processing was proven as an accurate technique of translation between the human visual system and digital imaging devices. The findings of the study can be practically utilized by researchers who work in the field of soil erosion and meteorology.

scholarly journals Impact of Atmospheric Circulation on Flooding Occurrence and Type in Luxembourg (Central Western Europe)

2020 ◽  
Author(s):  
Judith Meyer ◽  
Audrey Douinot ◽  
Erwin Zehe ◽  
Carol Tamez-Meléndez ◽  
Olivier Francis ◽  
...  
Keyword(s):  
Atmospheric Circulation ◽  
Large Scale ◽  
Western Europe ◽  
Flash Flood ◽  
Flood Events ◽  
Intense Rainfall ◽  
European Continent ◽  
Rainfall Events ◽  
Area Of Interest ◽  
Winter Flood

&lt;p&gt;In the second half of the 20&lt;sup&gt;th&lt;/sup&gt; century, hydrological regimes in central Western Europe were largely characterised by large-scale winter floods. This type of event was predominantly triggered by westerly atmospheric fluxes, bringing moist and mild air masses from the Atlantic Ocean to the European continent. Since the late 1990&amp;#8217;s, major flooding events seem to have shifted in time and magnitude. Flash flood events, while being a well-known phenomenon in Mediterranean catchments, are increasingly also reported at higher latitudes. Unlike the large-scale winter flood events, flash floods are of very narrow spatial extension and triggered by rather short, but highly intense rainfall events.&lt;/p&gt;&lt;p&gt;Here, we focus on the specific case of rivers in Luxembourg that have experienced several flash flood events in recent years, while only small to moderate winter flood events have been reported since the late 1990&amp;#8217;s. National hydro-meteorological monitoring and flood forecasting systems have been designed for large-scale floods and are not suited for simulating local flash flood events. Therefore, there is a need to increase our understanding of the hydro-meteorological processes underlying flash flood occurrences in our area of interest.&lt;/p&gt;&lt;p&gt;While increasing air temperature is known to allow a higher air moisture content that can lead to more intense rainfall events and possible flooding, we moreover hypothesize that the recent increase in flash flood occurrences in Luxembourg is reinforced by a change in atmospheric circulation patterns. To test this hypothesis, we analyse the prevailing atmospheric patterns on rainy days during summer and winter months over the period 1954 - 2019, with a particular focus on rainfall events that lead to moderate and extreme floods. In a next step, we intend to extend our findings for Luxembourg in a larger European context. This analysis should allow to better assess the current situation of hydrological extreme events in central Western Europe in order to take precaution measures and prepare for a diversifying hazard.&lt;/p&gt;

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