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Proceedings, Volume 7, ECWS-3

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Research

Open AccessProceedings Response of Siberian River Discharge to Disturbances of Forests Caused by Wildfires
Proceedings 2019, 7(1), 1; https://doi.org/10.3390/ECWS-3-05801
Published: 15 November 2018
Viewed by 42 | PDF Full-text (816 KB)
Abstract
The objective of this work was to perform a quantitative analysis of the correlation between the forest burning index and abnormal decrease in river discharge under conditions of the cryolithozone of Siberia. We analyzed the long-term and seasonal variation of river discharge in [...] Read more.
The objective of this work was to perform a quantitative analysis of the correlation between the forest burning index and abnormal decrease in river discharge under conditions of the cryolithozone of Siberia. We analyzed the long-term and seasonal variation of river discharge in Central Siberia (Nizhnyaya Tunguska and Podkamennaya Tunguska rivers) and in Eastern Siberia (Aldan, Viluy rivers) together with the forest burning dynamics within the river basins. The data on river discharge were obtained from the archive of The Global Runoff Data Centre for 1939–2015. The relative burned area (RBA) index was calculated from wildfire databases collected using satellite technique for 1996–2017. RBA was evaluated as the ratio of the annual burned area within the river basin to the total area of the river basin. RBA values of 2.5–6.1% per year were considered as extremely high. The analysis of available chronologies of extreme fire events in Central and Eastern Siberia showed high correlation (r > −0.55) with long-term data on the runoff minima. Abnormally low levels of discharge were 68–78% of the averaged annual rate. The most significant response of river discharge to the wildfire effect was shown for the summer–autumn period of the season after extreme burning in mid-summer. Full article
Open AccessProceedings Assessment and Impact of Soil Moisture Index in Agricultural Drought Estimation Using Remote Sensing and GIS Techniques
Proceedings 2019, 7(1), 2; https://doi.org/10.3390/ECWS-3-05802
Published: 15 November 2018
Viewed by 103 | PDF Full-text (2798 KB) | Supplementary Files
Abstract
Soil moisture takes an important part involving climate, vegetation and drought. This paper explains how to calculate the soil moisture index and the role of soil moisture. The objective of this study is to assess the moisture content in soil and soil moisture [...] Read more.
Soil moisture takes an important part involving climate, vegetation and drought. This paper explains how to calculate the soil moisture index and the role of soil moisture. The objective of this study is to assess the moisture content in soil and soil moisture mapping by using remote sensing data in the selected study area. We applied the remote sensing technique which relies on the use of the soil moisture index (SMI) which uses the data obtained from satellite sensors in its algorithm. The relationship between land surface temperature (LST) and the normalized difference vegetation index (NDVI) are based on experimental parameterization for the soil moisture index. Multispectral satellite data (visible, red and near-infrared (NIR) and thermal infrared sensor (TIRS) bands) were utilized for assessment of LST and to make vegetation indices map. Geographic Information System (GIS) and image processing software were utilized to determine the LST and NDVI. NDVI and LST are considered as essential data to obtain SMI calculation. The statistical regression analysis of NDVI and LST were shown in standardized regression coefficient. NDVI values are within range −1 to 1 where negative values present loss of vegetation or contaminated vegetation, whereas positive values explain healthy and dense vegetation. LST values are the surface temperature in °C. SMI is categorized into classes from no drought to extreme drought to quantitatively assess drought. The final result is obtainable with the values range from 0 to 1, where values near 1 are the regions with a low amount of vegetation and surface temperature and present a higher level of soil moisture. The values near 0 are the areas with a high amount of vegetation and surface temperature and present the low level of soil moisture. The results indicate that this method can be efficiently applied to estimate soil moisture from multi-temporal Landsat images, which is valuable for monitoring agricultural drought and flood disaster assessment. Full article
Open AccessProceedings Evaluation of Extreme Dry and Wet Conditions Using Climate and Hydrological Indices in the Upper Part of the Gallikos River Basin
Proceedings 2019, 7(1), 3; https://doi.org/10.3390/ECWS-3-05823
Published: 15 November 2018
Viewed by 32 | PDF Full-text (1802 KB)
Abstract
Climate changes in the Mediterranean region, especially those related to changes in rainfall distribution and occurrence of extreme events, affect local economies. Agriculture is a sector strongly affected by climate conditions and concerns the majority of the Greek territory. The Gallikos river basin [...] Read more.
Climate changes in the Mediterranean region, especially those related to changes in rainfall distribution and occurrence of extreme events, affect local economies. Agriculture is a sector strongly affected by climate conditions and concerns the majority of the Greek territory. The Gallikos river basin is an area of great interest regarding climate change impacts since it is an agricultural area depended on surface water resources and an area in which extreme events relatively often take place (e.g., floods). Long time series precipitation (27 years) and temperature data derived from measurement stations along with reanalysis data (ERA INTERIM) were used for the estimation of water availability and climate type over time in the area. The Standardized Precipitation Index and De Martonne aridity index was employed. The water flow measurements were correlated in order to investigate the interrelation between the different river branches and the extent of the meteorological changes effect in the basin. Descriptive statistics and cumulative curves were applied to check homogeneity of data. The results revealed that the climate type varies from semi arid to very wet, and water availability ranges from moderately dry to extremely wet years. Reanalysis data overestimate precipitation. The meteorological changes affect, at the same time, the entire basin since the flow rate peaks occur simultaneously in the hydrographic network at different areas. Full article
Open AccessProceedings Copula Bias Correction for Extreme Precipitation in Reanalysis Data over a Greek Catchment
Proceedings 2019, 7(1), 4; https://doi.org/10.3390/ECWS-3-05817
Published: 15 November 2018
Viewed by 45 | PDF Full-text (536 KB)
Abstract
The projection of extreme precipitation events with higher accuracy and reliability that engender severe socioeconomic impacts more frequently is considered a priority research topic in the scientific community. Although large-scale initiatives for monitoring meteorological and hydrological variables exist, the lack of data is [...] Read more.
The projection of extreme precipitation events with higher accuracy and reliability that engender severe socioeconomic impacts more frequently is considered a priority research topic in the scientific community. Although large-scale initiatives for monitoring meteorological and hydrological variables exist, the lack of data is still evident particularly in regions with complex topographic characteristics. The latter results in the use of reanalysis data or data derived from regional climate models, however both datasets are biased to the observations resulting in nonaccurate results in hydrological studies. The current research presents a newly developed statistical method for the bias correction of the maximum rainfall amount at watershed scale. In particular, the proposed approach necessitates the coupling of a spatial distribution method, namely Thiessen polygons, with a multivariate probabilistic distribution method, namely copulas, for the bias correction of the maximum precipitation. The case study area is the Nestos River basin where the several extreme episodes that have been recorded have direct impacts to the regional agricultural economy. Thus, using daily data by three monitoring stations and daily reanalysis precipitation values from the grids closest to these stations, the results demonstrated that the bias corrected maximum precipitation totals (greater than 90%) is much closer to the real max precipitation totals, while the respective reanalysis value underestimates the real precipitation totals. The overall improvement of the output shows that the proposed Thiessen-copula method could constitute a significant asset to hydrologic simulations. Full article
Open AccessProceedings Energy Dissipation Structures: Influence of Aeration in Supercritical Flows
Proceedings 2019, 7(1), 5; https://doi.org/10.3390/ECWS-3-05812
Published: 15 November 2018
Viewed by 30 | PDF Full-text (1060 KB)
Abstract
Adequate design of energy dissipation structures is essential for effective flood control. The effect of aeration on water flow has been one of most analyzed phenomena during the last decades due to its influence on hydraulic structures. The purpose of this study is [...] Read more.
Adequate design of energy dissipation structures is essential for effective flood control. The effect of aeration on water flow has been one of most analyzed phenomena during the last decades due to its influence on hydraulic structures. The purpose of this study is to characterize the influence of aeration on the boundary friction in supercritical and fully turbulent flows. Our analysis is based on a physical model to reproduce these phenomena and consists of a spillway chute 6.5 m high, followed by a 10 m length and 2 m high still basin. Water and air are supplied by a pump and compressors, and is controlled at the entrance by several valves and flowmeters, while the channel is monitored to measure the velocity profile and air concentration in the intake flow to the still basin. Velocity results included in this paper show the relation between air concentration and energy dissipation by friction. To determine this relation, Manning roughness numbers have been obtained for all scenarios. It has been found that greater air entrainment implies acceleration of the flow, since friction is the main energy dissipation mechanism in open channels flow. Full article
Open AccessProceedings Effort and Performance of the Management of Water for Agriculture under Climate Change in Southern Europe
Proceedings 2019, 7(1), 6; https://doi.org/10.3390/ECWS-3-05813
Published: 15 November 2018
Viewed by 29 | PDF Full-text (2948 KB)
Abstract
We evaluate alternatives for the management of water for agriculture under climate change in six representative basins of Southern Europe: Duero-Douro, Ebro, Guadalquivir, Po, Maritsa-Evros, and Struma. Management objective is the maximization of water availability, understood as the maximum demand that can be [...] Read more.
We evaluate alternatives for the management of water for agriculture under climate change in six representative basins of Southern Europe: Duero-Douro, Ebro, Guadalquivir, Po, Maritsa-Evros, and Struma. Management objective is the maximization of water availability, understood as the maximum demand that can be satisfied with a given reliability. We focus on water availability for agriculture. For the sake of simplicity, we assume only two types of demands: urban and irrigation. Water is first allocated to urban demands following an established priority; the remaining resources are allocated to agriculture. If water availability does not satisfy all irrigation demands, management measures are applied with the goal of achieving a balance between resources and demands. We present an analysis of three possible management measures to face water scarcity in a long-term scenario: increasing reservoir storage, improving efficiency of urban water use and modifying water allocation to environmental flows. These management measures are globally evaluated for the selected basins in three representative climate scenarios, comparing their possible range and effectiveness. Although such measures can significantly increase water availability and counterbalance a portion of water scarcity due to climate change in some basins like Ebro or Struma, in other basins, such as Guadalquivir, water availability cannot be enhanced with management measures and irrigation water use must be reduced. Full article
Open AccessProceedings Preliminary Design of Nutrient Removal Basins in the Fisheating Creek Watershed in Florida, USA Subject to Drought Conditions and Low Water Availability
Proceedings 2019, 7(1), 7; https://doi.org/10.3390/ECWS-3-05803
Published: 15 November 2018
Viewed by 30 | PDF Full-text (4608 KB)
Abstract
The Fisheating Creek watershed located in Florida, United States of America (USA) is the focus of intense efforts to reduce nutrient transport into Lake Okeechobee which is located downstream. Public agencies and private land owners proposed constructing large nutrient removal basins in the [...] Read more.
The Fisheating Creek watershed located in Florida, United States of America (USA) is the focus of intense efforts to reduce nutrient transport into Lake Okeechobee which is located downstream. Public agencies and private land owners proposed constructing large nutrient removal basins in the watershed to reduce the overall nutrient load into Lake Okeechobee. This is challenging given the nature of the watershed with its low water availability and sensitivity to drought. This study evaluates the feasibility of implementing nutrient removal systems in such a watershed, including the overall risk and uncertainty of system performance. The study uses statistical evaluations of available water resources data and model simulations using Hydrologic Engineering Center Hydrologic Modeling System (HEC-HMS) to evaluate watershed flow conditions. Then, the study outlines alternatives for nutrient removal system implementation. The study revealed that considerable nutrient reduction is feasible but not optimal due to low overall water availability. The primary conclusion is that, while nutrient removal projects as large as 294 hectares can be constructed, the overall system operation will have to be very flexible to account for widely ranging inflows, including very low flows during drought situations. Full article
Open AccessArticle An Integrated Geoinformatics and Hydrological Modelling-Based Approach for Effective Flood Management in the Jhelum Basin, NW Himalaya
Proceedings 2019, 7(1), 8; https://doi.org/10.3390/ECWS-3-05804
Published: 15 November 2018
Viewed by 54 | PDF Full-text (1336 KB)
Abstract
In the present study, using static land system parameters, such as geomorphology, land cover, and relief, we calculated the water yield potential (RP) of all the watersheds of the Jhelum basin (Kashmir Valley) using the analytical hierarchy process (AHP) based watershed evaluation model [...] Read more.
In the present study, using static land system parameters, such as geomorphology, land cover, and relief, we calculated the water yield potential (RP) of all the watersheds of the Jhelum basin (Kashmir Valley) using the analytical hierarchy process (AHP) based watershed evaluation model (AHP-WEM). The results revealed that among the 24 watersheds of the Jhelum basin, the Vishav watershed, with the highest RP, is the fastest water yielding catchment of the Jhelum basin followed by Bringi, Lidder, Kuthar, Sind, Madhumati, Rembiara, Sukhnag, Dal, Wular-II, Romshi, Sandran, Ferozpur, Viji-Dhakil, Ningal, Lower Jhelum, Pohru, Arin, Doodganga, Arapal, Anchar, Wular-I, Gundar, and Garzan in the case of a same intensity storm event. The results were validated with the mean annual peak discharge values of the watersheds and a strong positive correlation of 0.71 was found. Further, for the forecasting of the floods in the watersheds that had a small lag time, such as in the case of Vishaw, Bringi, and Lidder, we evaluated the performance of the HEC-GeoHMS hydrological model to simulate stream discharge during storm events. It was observed that the model performs well for August-September period with a strong positive correlation (0.94) between the observed and simulated discharge and hence could be used as a flood forecasting model for this period in the region. Full article
Open AccessProceedings A Regional Sensitivity Analysis of a Multi-Variable Hydrological Model: A Case Study of a Greek Catchment
Proceedings 2019, 7(1), 9; https://doi.org/10.3390/ECWS-3-05816
Published: 15 November 2018
Viewed by 130 | PDF Full-text (1026 KB)
Abstract
The importance of climate data in hydrological process simulation is widely recognized. Evaluation of the hydrological budget response to climate variability is required, especially in water resource management. The present paper illustrates a case study of a sensitivity analysis for the hydrological model [...] Read more.
The importance of climate data in hydrological process simulation is widely recognized. Evaluation of the hydrological budget response to climate variability is required, especially in water resource management. The present paper illustrates a case study of a sensitivity analysis for the hydrological model SWAT (Soil and Water Assessment Tool) using climate data from the Havrias river basin in northern Greece. The ERA-Interim reanalysis daily climate data were used as input data to drive the SWAT model. The SWAT model was calibrated for the period from 1981 to 2000. The sensitivity of the hydrological parameters to the alteration of the climate data was analyzed by using eleven hypothetical scenarios. These scenarios regard different combinations of temperature, wind speed, precipitation, and relative humidity. The results show that the changes of precipitation temperature and relative humidity have a significant influence in evapotranspiration and percolation (and consequently recharge) in the study region. On the contrary, the wind speed negligibly affects the hydrological components. Overall, the Havrias river basin hydrological budget is sensitive to shifts in climate data and the utilization of reliable and accurate climate models outputs is necessary in order for water managers to be able to build scenarios providing sustainability against potential future climate change impacts. Full article
Open AccessProceedings Temporal and Elevation Trend Detection of Rainfall Erosivity Density in Greece
Proceedings 2019, 7(1), 10; https://doi.org/10.3390/ECWS-3-05814
Published: 15 November 2018
Viewed by 115 | PDF Full-text (836 KB)
Abstract
This paper presents certain characteristics of trends in rainfall erosivity density (ED), that have not been so far investigated in depth in the current literature. Raw pluviograph data were acquired from the Greek National Bank of Hydrological and Meteorological Information for 108 stations. [...] Read more.
This paper presents certain characteristics of trends in rainfall erosivity density (ED), that have not been so far investigated in depth in the current literature. Raw pluviograph data were acquired from the Greek National Bank of Hydrological and Meteorological Information for 108 stations. Precipitation time series values were cleared from noise and errors, and the ratio of missing values was computed. Erosive rainfalls were identified, their return period was determined using intensity–duration–frequency (IDF) curves and erosivity values were computed. A Monte Carlo method was utilized to assess the impact of missing values ratio to the computation of annual erosivity (R) and ED values. It was found that the R values are underestimated in a linear way, while ED is more robust against the presence of missing precipitation values. Indicatively, the R values are underestimated by 49%, when only 50% of the erosive rainfall events are used, while at the same time the estimation error of ED is 20%. Using predefined quality criteria for coverage and time length, a subset of stations was selected. Their annual ED values, as well as the samples' autocorrelation and partial autocorrelation functions were computed, in order to investigate the presence of stochastic trends. Subsequently, Kendall's Tau was used in order to yield a measure of the monotonic relationship between annual ED values and time. Finally, the hypothesis that ED values are affected by elevation was tested. In conclusion: (a) It is suggested to compute ED for the assessment of erosivity in Greece instead of the direct computation of R; (b) stationarity of ED was found for the majority of the selected stations, in contrast to reported precipitation trends for the same time period; and (c) the hypothesis that ED values are not correlated to elevation could not be rejected. Full article
Open AccessProceedings Comparison of Hydrologic Model Performance Statistics Using Rain Gauge and NEXRAD Precipitation Input at Different Watershed Spatial Scales and Rainfall Return Frequencies for the Upper St. Johns River, Florida USA
Proceedings 2019, 7(1), 11; https://doi.org/10.3390/ECWS-3-05806
Published: 11 November 2018
Viewed by 35 | PDF Full-text (546 KB)
Abstract
Water resources numerical models are dependent upon various input hydrologic field data. As models become increasingly complex and model simulation times expand, it is critical to understand the inherent value in using different input datasets available. One important category of model input is [...] Read more.
Water resources numerical models are dependent upon various input hydrologic field data. As models become increasingly complex and model simulation times expand, it is critical to understand the inherent value in using different input datasets available. One important category of model input is precipitation data. For hydrologic models, the precipitation data inputs are perhaps the most critical. Common precipitation model input includes either rain gauge or remotely-sensed data such next-generation radar-based (NEXRAD) data. NEXRAD data provides a higher level of spatial resolution than point rain gauge coverage, but is subject to more extensive data pre and post processing along with additional computational requirements. This study first documents the development and initial calibration of a HEC-HMS model of a subtropical watershed in the Upper St. Johns River Basin in Florida, USA. Then, the study compares calibration performance of the same HEC-HMS model using either rain gauge or NEXRAD precipitation inputs. The results are further discretized by comparing key calibration statistics such as Nash–Sutcliffe Efficiency for different spatial scale and at different rainfall return frequencies. The study revealed that at larger spatial scale, the calibration performance of the model was about the same for the two different precipitation datasets while the study showed some benefit of NEXRAD for smaller watersheds. Similarly, the study showed that for smaller return frequency precipitation events, NEXRAD data was superior. Full article
Open AccessProceedings Stochastic Assessment of the Influence of Reservoir Operation in Hydrological Dam Safety through Risk Indexes
Proceedings 2019, 7(1), 12; https://doi.org/10.3390/ECWS-3-05811
Published: 15 November 2018
Viewed by 30 | PDF Full-text (358 KB)
Abstract
Hydrological dam safety assessment methods traditionally assume that the reservoir is full while it receives the design flood. In practice, reservoir management strategy determines the probability distribution of reservoir levels at the beginning of flood episodes. In this study, we present a method [...] Read more.
Hydrological dam safety assessment methods traditionally assume that the reservoir is full while it receives the design flood. In practice, reservoir management strategy determines the probability distribution of reservoir levels at the beginning of flood episodes. In this study, we present a method to economically assess the influence of reservoir management strategy on hydrological dam safety and downstream flood risk. The method was applied to a gated spillway dam located in the Tagus River basin. A set of 100,000 inflow hydrographs was generated through a Monte Carlo procedure, reproducing the observed statistics of main hydrograph characteristics: peak flow, volume, and duration. The set of 100,000 hydrographs was routed through the reservoir applying the volumetric evaluation method as a flood control strategy. Three different scenarios were studied: Initial reservoir level equal to maximum normal level, equal to a maximum conservation level, and following the probability distribution of initial reservoir levels. In order to evaluate economically the influence of initial variable reservoir level and compare the three scenarios, a global risk index was applied. The index combines the hydrological risk for the dam, linked to the maximum water level experienced in the reservoir while the flood is routed, and the flood risk in the downstream river reach, linked to the discharge releases from the dam. The results highlighted the importance of considering the fluctuation of initial reservoir level for assessing the risk related to hydrological dam safety. Full article
Open AccessProceedings United States Bureau of Reclamation Type IX Baffled Chute Spillways: A New Examination of Accepted Design Methodology Using CFD and Monte Carlo Simulations, Part I
Proceedings 2019, 7(1), 13; https://doi.org/10.3390/ECWS-3-05805
Published: 15 November 2018
Viewed by 39 | PDF Full-text (1407 KB)
Abstract
So-called “Type IX” chute spillways with impact baffle blocks have been used successfully around the globe for over 50 years. A key advantage of the chute spillway is the elimination of a costly stilling basin allowing for a more simplistic outlet works design. [...] Read more.
So-called “Type IX” chute spillways with impact baffle blocks have been used successfully around the globe for over 50 years. A key advantage of the chute spillway is the elimination of a costly stilling basin allowing for a more simplistic outlet works design. The current design process is based upon physical models developed in the 1950s and observation of completed projects over the last 50 years. The design procedure is empirical and provides the designer with a range of workable layouts, baffle heights, and baffle spacing. Unfortunately, this approach may not be optimal. This first study of a longer research effort focus uses Monte Carlo simulations and computational fluid dynamics (CFD) to examine the design methodology and physical model basis for the current design procedure. Initially, the study examined the design procedure with a Monte Carlo simulation to explore the range of acceptable designs that can be realized. Then, using CFD, full-scale prototype (located in Gila, Arizona USA) physical model results that were a key basis for the current design procedure were recreated. The study revealed that a wide range of acceptable chute designs can result from following the current design procedure but that some of these may be better than others. The study also outlines future research efforts needed to revise the current design methodology. Full article
Open AccessProceedings Selection of Bias Correction Methods to Assess the Impact of Climate Change on Flood Frequency Curves
Proceedings 2019, 7(1), 14; https://doi.org/10.3390/ECWS-3-05809
Published: 15 November 2018
Viewed by 162 | PDF Full-text (1814 KB)
Abstract
Annual maximum daily rainfalls will change in the future because of climate change, according to climate projections provided by EURO-CORDEX. This study aims at understanding how the expected changes in precipitation extremes will affect the flood behavior in the future. Hydrological modeling is [...] Read more.
Annual maximum daily rainfalls will change in the future because of climate change, according to climate projections provided by EURO-CORDEX. This study aims at understanding how the expected changes in precipitation extremes will affect the flood behavior in the future. Hydrological modeling is required to characterize the rainfall-runoff process adequately in a changing climate to estimate flood changes. Precipitation and temperature projections given by climate models in the control period usually do not fit the observations in the same period exactly from a statistical point of view. To correct such errors, bias correction methods are used. This paper aims at finding the most adequate bias correction method for both temperature and precipitation projections, minimizing the errors between observed and simulated precipitation and flood frequency curves. Four catchments located in central western Spain have been selected as case studies. The HBV hydrological model has been calibrated, using the observed precipitation, temperature, and streamflow data available at a daily scale. Expected changes in precipitation extremes are usually smoothed by the reduction of soil moisture content due to expected increases in temperatures and decreases in mean annual precipitation. Consequently, rainfall is the most significant input to the model and polynomial quantile mapping is the best bias correction method. Full article
Open AccessProceedings Identification of Flood-Rich and Flood-Poor Periods by Using Annual Maximum Series of Floods in Spain
Proceedings 2019, 7(1), 15; https://doi.org/10.3390/ECWS-3-05829
Published: 15 November 2018
Viewed by 120 | PDF Full-text (344 KB)
Abstract
Currently, there is general concern about the non-stationary behaviour of flood series. Consequently, several studies have been conducted to identify large-scale patterns of change in such flood series. In Spain, a general decreasing trend was found in the period 1959–2009. However, a multi-temporal [...] Read more.
Currently, there is general concern about the non-stationary behaviour of flood series. Consequently, several studies have been conducted to identify large-scale patterns of change in such flood series. In Spain, a general decreasing trend was found in the period 1959–2009. However, a multi-temporal trend analysis, with varying starting and ending years, showed that trend signs depended on the period considered. Flood oscillations could influence the results, especially when flood-rich and flood-poor periods are located at the beginning or end of the series. In Spain, a flood- rich period in 1950–1970 seemed to lead to the generalised decreasing trend, as it was located at the beginning of the flood series. Nevertheless, the multi-temporal test can only find potential flood- rich and flood-poor periods qualitatively. A methodology has been developed to identify statistically significant flood-rich and flood-poor periods. The expected variability of floods under the stationarity assumption is compared with the variability of floods in observed flood series. The methodology is applied to the longest streamflow series available in Spain. Seven gauging stations located in near-natural catchments, with continuous observations in the period 1942–2014, are selected. Both annual maximum and peak-over-threshold series are considered. Flood-rich and flood-poor periods in terms of flood magnitudes and the annual count of exceedances over a given threshold are identified. A flood-rich period in the beginning of the series and a flood-poor period at its end are identified in most of the selected sites. Accordingly, a flood-rich period placed at the beginning of the series, followed by a flood-poor period, influence the generalised decreasing trend in the flood series previously found in Spain. Full article
Open AccessProceedings Continuous Simulation of Catchment Runoff in Flood Frequency Analysis: A Case Study from Slovakia
Proceedings 2019, 7(1), 16; https://doi.org/10.3390/ECWS-3-05828
Published: 15 November 2018
Viewed by 71 | PDF Full-text (1026 KB)
Abstract
Research questions relating to a reliable estimate of flood discharge have always interested both hydrologists and civil engineers. Over the decades, numerous methods have been proposed and used more or less successfully, all of them with known limitations restricting their use in a [...] Read more.
Research questions relating to a reliable estimate of flood discharge have always interested both hydrologists and civil engineers. Over the decades, numerous methods have been proposed and used more or less successfully, all of them with known limitations restricting their use in a wide range of conditions and problems. In the past, the characteristics of hydrological extremes were mostly estimated by the methods of statistical analyses. As this type of method is not suitable to estimate design discharges of high return periods, and by default does not account for uncertainty, a new family of methods is slowly taking the place of the traditional approaches. Many of these methods are based on a combination of stochastic rainfall models (weather generators) and rainfall-runoff models, which enables generation of an arbitrary number of synthetic floods, even in places with short or no record of river discharges available. In addition, as this type of method produces flood hydrographs, they can also be used in a multivariate flood frequency analysis to estimate joint probabilities of two or more flood characteristics. This study presents a methodology for flood frequency analysis that combines stochastic models of both rainfall amounts and air temperatures with a lumped rainfall-runoff model to transfer the outputs of the stochastic models into a series of corresponding river discharges. Both of the stochastic models are single-site weather generators that produce continuous time series of mean areal daily rainfall amounts and air temperatures. In this study, the method was used to generate a time series of 10,000 years of mean daily discharges, which was used to build a flood frequency curve and to estimate extreme flood discharges of given return periods. The method was applied to a mountainous catchment of the River Váh in Slovakia. Full article
Open AccessProceedings Effects of Key Properties of Rainfall Series on Hydrologic Design of Sustainable Urban Drainage Systems (SUDS)
Proceedings 2019, 7(1), 17; https://doi.org/10.3390/ECWS-3-05827
Published: 15 November 2018
Viewed by 39 | PDF Full-text (2503 KB)
Abstract
The aims of this study are to quantify the effects of key properties of rainfall time series on the hydrologic design of sustainable urban drainage systems (SUDS) to test a method for their estimation from daily time series and to quantify their uncertainty. [...] Read more.
The aims of this study are to quantify the effects of key properties of rainfall time series on the hydrologic design of sustainable urban drainage systems (SUDS) to test a method for their estimation from daily time series and to quantify their uncertainty. Several typologies of SUDS infrastructures are designed to achieve a target treatment capacity. This target capacity is usually defined according to two methods: treating a percentage of the total volume of rainfall (50, 80, 90, 95, 99%) or treating a percentage of the total number of rainfall events (50, 80, 90, 95, 99%). We considered the city of Madrid as the case study, compiling 58 years of observed data (10-minutetime step) and aggregating to daily time series. We obtained the design parameters from the full resolution dataset and for different storm thresholds (0, 1 and 2 mm). Second, we determined the design parameters from the aggregated daily time series by applying a temporal stochastic rainfall generator model (RainSimV3). Finally, we estimated the model parameters from daily data and generated 100 series of 58 years at 10-minute time step, then compared the results. Results showed a good agreement compared to the 10-minute time step rainfall series. The different thresholds selected do not affect in a relevant way the calculation by percentage of the total volume; in the case of calculation by events, the threshold can vary the design volume for up to 30%. Further research includes the analysis of different climate locations. Full article
Open AccessProceedings Analyses of Monthly Discharges in Slovakia Using Hydrological Exploratory Methods
Proceedings 2019, 7(1), 18; https://doi.org/10.3390/ECWS-3-05824
Published: 15 November 2018
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Abstract
Detailed analyses of hydrological data are necessary in order to prove changes in their character. This article focuses on an analysis of the average monthly discharges of 14 stage-discharge gauging stations in Slovakia. The measured period is from 1931 to 2016. The approaches [...] Read more.
Detailed analyses of hydrological data are necessary in order to prove changes in their character. This article focuses on an analysis of the average monthly discharges of 14 stage-discharge gauging stations in Slovakia. The measured period is from 1931 to 2016. The approaches used are hydrological exploration methods, which were created by hydrologists to describe the behavior of hydrological time series. The methods are used to identify a change-point using an analysis of any residuals, the Pettitt test, and an analysis of the relationship between the mean annual discharge deviations from the long-term annual discharge and the deviations of the average monthly discharge from the long-term average monthly discharge. A considerable number of change-points were identified in the 1970s and 1980s. The results of the analyses show changes in the hydrological regimes, but to confirm the accuracy of the outcomes, it is also necessary to examine other hydrological and meteorological elements such as, e.g., precipitation and the air temperature. Full article
Open AccessProceedings The Effect of Sample Size on Bivariate Rainfall Frequency Analysis of Extreme Precipitation
Proceedings 2019, 7(1), 19; https://doi.org/10.3390/ECWS-3-05815
Published: 15 November 2018
Viewed by 34 | PDF Full-text (1360 KB)
Abstract
The objective of this study is to compare univariate and joint bivariate return periods of extreme precipitation that all rely on different probability concepts in selected meteorological stations in Cyprus. Pairs of maximum rainfall depths with corresponding durations are estimated and compared using [...] Read more.
The objective of this study is to compare univariate and joint bivariate return periods of extreme precipitation that all rely on different probability concepts in selected meteorological stations in Cyprus. Pairs of maximum rainfall depths with corresponding durations are estimated and compared using annual maximum series (AMS) for the complete period of the analysis and 30-year subsets for selected data periods. Marginal distributions of extreme precipitation are examined and used for the estimation of typical design periods. The dependence between extreme rainfall and duration is then assessed by an exploratory data analysis using K-plots and Chi-plots and the consistency of their relationship is quantified by Kendall’s correlation coefficient. Copulas from Archimedean, Elliptical, and Extreme Value families are fitted using a pseudo-likelihood estimation method, evaluated according to the corrected Akaike Information Criterion and verified using both graphical approaches and a goodness-of-fit test based on the Cramér-von Mises statistic. The selected copula functions and the corresponding conditional and joint return periods are calculated and the results are compared with the marginal univariate estimations of each variable. Results highlight the effect of sample size on univariate and bivariate rainfall frequency analysis for hydraulic engineering design practices. Full article
Open AccessProceedings Multi-Index Drought Assessment in Europe
Proceedings 2019, 7(1), 20; https://doi.org/10.3390/ECWS-3-05822
Published: 15 November 2018
Cited by 2 | Viewed by 41 | PDF Full-text (1683 KB)
Abstract
Any attempt for the application of integrated drought management requires identifying and characterizing the event, per se. The questions of scale, boundary, and of geographic areal extent are of central concern for any efforts of drought assessment, impact identification, and thus, of drought [...] Read more.
Any attempt for the application of integrated drought management requires identifying and characterizing the event, per se. The questions of scale, boundary, and of geographic areal extent are of central concern for any efforts of drought assessment, impact identification, and thus, of drought mitigation implementation mechanisms. The use of drought indices, such as Standardized Precipitation Index (SPI) and the Standardized Precipitation Evapotranspiration Index (SPEI), has often led to pragmatic realization of drought duration, magnitude, and spatial extension. The current effort presents the implementation of SPI and SPEI on a Pan-European scale and it is evaluated using existing precipitation and temperature data. The ENSEMBLES Observations gridded dataset (E-OBS) for precipitation, minimum temperature, and maximum temperature used covered the period 1969–2018. The two indices estimated for time steps of 6 and 12 months. The results for the application period of recurrent droughts indicate the potential that both indices offer for an improvement on drought critical areas of identification, threshold definitions and comparability, and towards contingency planning, leading to better mitigation efforts. Full article
Open AccessProceedings Flood Risk Management Methodology for Lakes and Adjacent Areas: The Lake Pamvotida Paradigm
Proceedings 2019, 7(1), 21; https://doi.org/10.3390/ECWS-3-05825
Published: 15 November 2018
Viewed by 159 | PDF Full-text (2528 KB)
Abstract
In recent decades, natural hazards have caused major disasters in natural and man-made environments. Floods are one of the most devasting natural hazards, with high levels of mortality, destruction of infrastructure, and large financial losses. This study presents a methodological approach for flood [...] Read more.
In recent decades, natural hazards have caused major disasters in natural and man-made environments. Floods are one of the most devasting natural hazards, with high levels of mortality, destruction of infrastructure, and large financial losses. This study presents a methodological approach for flood risk management at lakes and adjacent areas that is based on the implementation of the EU Floods Directive (2007/60/EC) in Greece. Contemporary engineering approaches have been used for the estimation of the inflow hydrographs. The hydraulic–hydrodynamic simulations were implemented in the following order: (a) hydrologic modeling of lake tributaries and estimation flood flow inflow to the lake, (b) flood inundation modeling of lake tributaries, (c) simulation of the lake as a closed system, (d) simulation of the lake outflows to the adjacent areas, and (e) simulation of flood inundation of rural and urban areas adjacent to the lake. The hydrologic modeling was performed using the HEC-HMS model, and the hydraulic-hydrodynamic simulations were implemented with the use of the two-dimensional HEC-RAS model. The simulations were applied to three soil moisture conditions (dry, medium and wet) and three return periods (T = 50, T = 100 and T = 1000 years) and a methodology was followed for the flood inundation modeling in urban areas. Upper and lower estimates on water depths, flow velocities and inundation areas are estimated for all inflow hydrographs and for varying roughness coefficient values. The proposed methodology presents the necessary steps and the results for the assessment of flood risk management and mapping for lake and adjacent urban and rural areas. The methodology was applied to Lake Pamvotida in Epirus, Greece, Ioannina. Full article
Open AccessProceedings Hydrometeorological Extremes in a Warmer Climate: A Local Scale Assessment for the Island of Crete
Proceedings 2019, 7(1), 22; https://doi.org/10.3390/ECWS-3-05818
Published: 15 November 2018
Viewed by 22 | PDF Full-text (1193 KB)
Abstract
A future warmer atmosphere indicates that precipitation will increase as a consequence of the higher humidity concentrations. According to the Clausius–Clapeyron relationship, precipitation increases by a factor of 7% per degree of warming. However, recent studies have shown that increase in precipitation extremes [...] Read more.
A future warmer atmosphere indicates that precipitation will increase as a consequence of the higher humidity concentrations. According to the Clausius–Clapeyron relationship, precipitation increases by a factor of 7% per degree of warming. However, recent studies have shown that increase in precipitation extremes can exceed this scaling rate. In this regard, we focus on the flash flood prone area of Crete by analyzing high resolution precipitation records form a dense network of meteorological stations to see if the relationship of precipitation and dew point temperature lies within the Clausius–Clapeyron theory. We then use simulation outputs of a “present day event” from a set of very high resolution (about 2 km grid spacing) convective permitting regional climate models (CPRCM) to investigate if the models are able to capture intense convection and thus accurately simulate extreme precipitation events over Crete. A second set of simulations for the present day event, but with a perturbation of +2 °C, is used to examine intensity changes and to see what similar events might look like in a future weather. We finally focus on a high impact flash flood event that occurred on 17 October 2006, and we study changes in hydrological impacts. Information developed in this study can advance local scale knowledge in the context of climate change adaptation and appropriate risk management. Full article
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