Extreme Hydrological Phenomena Research Articles

Determination of Hydrography Elements Using Image Interpretation and Processing Techniques

Abstract Determining the geometric elements required for the probabilistic calculation of flood bands for watercourses within a hydrographical basin can be achieved by extracting information from remote sensing digital recordings. Given the increasing frequency of extreme hydrological phenomena, the use of data obtained through aerial remote sensing offers the advantage of rapidly determining the geometric characteristics needed to generate profiles for the probabilistic calculation of flood bands for all watercourses within a hydrographical basin.

Demonstrating the Potential of Low-Cost GNSS Receiver for tidal monitoring, storms, and flood detecting: example of 2022 Noru Storm in Thua Thien Hue province, Vietnam

Extreme hydrological events such as tsunamis, high tides, or storm surges seriously threaten coastal communities. These events result in flooding, property damage, loss of life, and long-term economic and social impacts. Therefore, monitoring and detecting extreme hydrological events significantly affect coastal areas in disaster response efforts. However, the cost of installing and maintaining these stations can be a significant challenge for developing countries. The objective of this study is to use a low-cost GNSS receiver to monitor tides and detect extreme coastal hydrological phenomena by analyzing changes in water level, using analysis of the signal-to-noise ratio (SNR) data. Data used in this study were collected from a GNSS station located in the Tam Giang Lagoon area, Thua Thien Hue, Vietnam, from September to October 2022. The water level based on GNSS-R is compared with the sensor's measured water level, with the Pearson correlation coefficient reaching 0.96 and RMSE of 0.08m. Continuous Wavelet Transform analysis demonstrated the relationship between water levels and extreme hydrological events. The results show that distinct signatures in the data correspond to the Noru typhoon from September 27-29, 2022, and the inundation from October 14-19, 2022, in Thua Thien Hue. This information is the basis for forecasting and early warning of extreme events and informing disaster response and management efforts.

Simulation of the Hydraulic Model HEC-RAS Coupled with GIS and Remote Sensing to Study the Effect of River Cross-section Width in Detecting Flood-prone Areas

Abstract Flooding is one of the extreme hydrological phenomena. It is a recurring natural disaster that causes loss of life and property in many parts of the world, particularly during the monsoon season. It is important to address such issues for local government and policymakers to manage the flood properly. One such flood management activity is to develop a flood-prone area that depicts the spatial and temporal extent of flood accurately. The integration of the Hydrologic Engineering Centre - River Analysis System (HEC-RAS) model and geospatial tools have emerged as a crucial approach for identifying and mapping flood-prone areas. The successful application of the HEC-RAS model generally depends on the topographical data, which represents the channel and floodplain geometry. In floodplain geometry, discrete cross-sections play a vital role to develop the floodplain map, particularly in the flat topographical region. To extract these data it needs a high-quality digital elevation model (DEM), such as light detection and ranging (LiDAR). However, due to a lack of high-resolution topographical data, flood hazard mapping in developing countries is rare. In common practice, the centerline of the river is considered the flow path for the channel. The orientation of the cross-sections is perpendicular to this line and extends to reach the limits of the floodplain. But, it is difficult to define the limits and it may depend on the magnitude of the flood. Hence, in this study, the HEC RAS model coupled with ArcGIS has been applied to the Ganga River, which traverses through the Bihar state of India to study the effect of cross-sectional width to define the floodplain. The Bihar state is facing substantial hardships from annual flooding events with approximately 16.5% of India’s flood-prone area. The extreme flood values for 5, 10, and 25 years of return period have been determined and the influence of the three different cross-sectional widths to mapping the floodplain has been investigated. This novel perspective adds dimension to the understanding of flood dynamics and its implications for flood risk assessment. In this analysis, it has been observed that, with an increase in the width of the cross-section, the floodplain area also getting increased. In this topographical region, keeping a fixed flow path will underestimate the flood-prone area. The width of the flow path depends on the topography of the region and the river flow. The outcomes of this analysis provide valuable insights into the flood-inundated areas for the specified return periods, enabling the identification and prioritization of flood-prone zones.

Water retention and runoff quality of a wildflower meadow green roof with different drainage layers

Extreme meteorological and hydrological phenomena, including high air temperatures and rainstorms, are becoming increasingly dangerous, causing floods and inundations, as well as long periods without precipitation, which lead to droughts. Green roofs may be one of the possible measures providing solutions to these problems. Rainfall, runoff and water quality data from three different intensive green roof models covered with wildflower meadows (WFs) over 20 months have been analysed to establish the extent to which the type of drainage layer affects hydrological performance. The field experiment was conducted at the Warsaw University of Life Sciences Water Centre park from November 2019 to November 2021. The monitoring of the quality and quantity of runoff was carried out on three models of green roofs incorporating wildflower meadows with drainage layers of 2 cm (WF 1) and 4 cm (WF 2) of polypropylene mat, as well as 6 cm of chalcedony (WF 3), in an urbanized area under moderate climate conditions. The model with the 4 cm polypropylene mat drainage layer retained approx. 6 % more rainwater compared to the model with the one made of chalcedony, and 4 % more than the one with the 2 cm polypropylene mat. Phosphates were detected in most of the leachates from all the wildflower-covered green roof models at 0 ÷ 0.459 mg PO4-P/L, 0 ÷ 0.402 mg PO4-P/L, and 0÷0.360 mg PO4-P/L for WF 1, WF 2 and WF 3. This may suggest that the type of drainage layer was not an important source of phosphates in the leachates.

Current and future variability of water supply to a mountain reservoir (Polish Carpathians)

AbstractThis study presents the characteristics of the current course of the phenomenon of droughts and floods in the catchment area of a man-made mountainous reservoir and forecasts of water inflow changes to the reservoir over the next three decades. The catchment area of the Klimkówka reservoir on the Ropa River, a tributary of the Wisłoka River, located within the Polish Carpathians was selected for the study. The analysis carried out, using Soil and Water Assessment Tool (SWAT) modelling among other techniques, showed an increase in the importance of low-flow outflow from the upper Ropa catchment and a negative balance of inflow to the reservoir (Q < 2 m3 s−1), manifested by a prolonged duration of low flows and an increase in outflow deficit during the year. The duration of flood flows and the runoff excess during these periods show a constant or decreasing tendency, while the length and excess of runoff increase during large floods. Thus, in the upper Ropa catchment, an increase in the intensity of extreme hydrological phenomena is observed. The prepared forecasts indicate an increase in annual runoff from the catchment in the decades 2021–2030 and 2031–2040 and a marked decrease in the decade 2041–2050. In the annual cycle, the projected changes in the coming decades will take different directions. In December only, throughout the entire period 2021–2050, the outflow will increase, whereas in May it will systematically decrease.

Statistical Approach to Hydrological Analysis

Despite the extensive body of research on the topic, the physical processes leading to the formation of extreme hydrological phenomena are still not fully understood, and robust deterministic models that would reliably describe them are yet to be developed [...]

Analysis of hydrological extremes in the Guaíba hydrographic region: an application of extreme values theory

Knowing the behavior of extreme hydrological phenomena is essential so that the impacts resulting from these natural events are minimized. Rio Grande do Sul has frequently been hit by extreme events such as droughts and floods, and these events are associated with several consequences, such as energy or water rationing, urban flooding and damage to hydraulic structures. In this context, the analysis of historical series extremes of hydrometeorological data through the Extreme Values Theory (EVT) is one of the ways to determine the variability due to climate change, enabling the modeling of extreme events. EVT makes it possible to know the frequency with which extreme events occur, allowing extrapolation beyond the historical series, generating occurrence probabilities of such an event. Therefore, the purpose of this work was to apply the Extreme Values Theory in hydrological the data historical series of flow and precipitation in the Guaíba hydrographic region and to carry out occurrence probabilities of intense events return, helping in the planning of the hydrographic watersheds that are in this region, as well as to verify whether the EVT has return periods similar to the climate projections of CMIP5 models. The results demonstrate that the values of flow and precipitation, in the historical series used, have already presented changes regarding the volume and frequency of extreme events occurrence and, in the future, for some stations, values can be expected both above and below the extremes already observed in the historical series.

GIS MULTITEMPORAL ANALYSIS OF REMOTE SENSING IMAGES TO ASSESS THE SILTING OF ANTHROPOGENIC DAM LAKES IN THE OUTER SUBCARPATHIAN AREA. CASE STUDY: PUCIOASA ACCUMULATION LAKE, ROMANIA

On Romania's territory, after the major floods that took place during the 70s, the hydrotechnical setup of the large rivers that drain the peri-Carpathian areas was made. The purpose of building these anthropogenic dam lakes is complex, given that extreme hydrological phenomena occurred in late spring and early summer, caused by a significant rainwater supply (about 70%), the difference being made up by the underground supply. Such a hydrotechnical setup was made in the Subcarpathian areas, on large rivers, to mitigate flood waves, but also to create water resources to supply local communities. The main problem facing these lakes is the massive silting due on the one hand to the geological and geomorphological characteristics of the Subcarpathians and, on the other hand, to the high degree of anthropization. The Subcarpathians are, from a geological point of view, made up of friable deposits (marls, clays, marl-clays, gypsums, conglomerates), which trigger a series of geomorphological processes of slope erosion (areal streaming, ravine creation, runoffs, torrential rainfall, and landslides), all of which are involved in the hydrological drainage regime. The Subcarpathians also make up a geographical area with a high density of population and, implicitly, of anthropogenic activities, which under certain conditions favour the erosion and degradation of land. These factors ensure that the solid flow recorded on the Subcarpathian Rivers is between 5-25 million tons/ha per annum. All this leads to the intense silting of anthropogenic lakes, which causes the volume of water stored in the tank to sometimes decrease to 1/3 of its initial volume. Under these conditions, in the extremity of basins, lacustrine plains were formed, and within the dam area, the pelitic sedimentary deposits exceeded 7-10 m in thickness. The aim of this study is to perform a multitemporal analysis of lake silting in the Subcarpathian area by using GIS and integrating the suite of bathymetric elevations and the series of satellite images existing from the time of the lake's construction to present-day.

Preface to Drought Risk Management to Reflect Changing Meteorological Conditions

Drought is one of the main extreme meteorological and hydrological phenomena which influence both the functioning of ecosystems and many important sectors of human economic activity [...]

Specific species response of Cladocera to the trophic and hydrological environments of lakes: A case study of a typical shallow mesotrophic lake

At present, most lakes in the world are facing the threat of eutrophication, especially mesotrophic lakes, which are in a critical period of ecosystem transformation. However, how the internal biological composition and structure of these lakes change accordingly has not yet been explored extensively. Here, a paleolimnological evaluation of subfossil Cladocera was initiated to study ecological and hydrological environmental changes in Nanyi Lake, which is a large (203 km2) shallow freshwater lake in the lower reaches of the Yangtze River Basin, China. In this study, subfossil Cladocera data combined with several geochemical proxies from three well-dated sediment cores were obtained. Both the sedimentary subfossil Cladocera and the modern Cladocera in the water column indicated that Bosminidae was the dominant species in Nanyi Lake. We observed that the changes in the density of Bosminidae and Cladocera hadstrongtiesto changes in the cultivated land area, which could cause the obvious alteration of the sedimentation rate around the lake. In addition, the ratio of planktonic species to littoral species (P/L ratio) in Nanyi Lake responded to the occurrence of several extreme hydrological phenomena, such as flooding corresponding to a high P/L ratio and drought corresponding to a low P/L ratio, during the past 200 years. The analysis of Cladocera assemblages and the geochemical indices of the three cores in Nanyi Lake indicated increases in trophy and water levels, especially since the modern 1970s.

The Domaša Reservoir in the Spectrum of Climate Change

Abstract The importance of water reservoirs in the uneven distribution of discharges over time and space does not need to be explicitly justified. There is a more than 6,000-year history of convincing evidence. In Slovakia, the construction of reservoirs can be dated to two periods. The first period was the 18th century, when the construction of water reservoirs was stimulated by the need for water for the mining industry in the vicinity of the town of Bánska Štiavnica. The second period falls into the second half of the 20th century. The construction of reservoirs was initiated by the post-war period, including the need to increase society’s standard of living, the electrification of the region, the development of industry and agriculture, flood protection, etc. Reservoirs with multi-annual regulations have an essential position in the types of water reservoirs. While small water reservoirs and annual or seasonal regulation can regulate flows in a short period, reservoirs with multi-annual regulation can regulate flows over several years. This benefit is evident, especially during periods of extreme hydrological phenomena and short-term aquatic and long-term dry, so-called low water periods. We have illustrated our knowledge of and experience gained from their impact on the flows downstream of the Veľká Domaša dam. We analyzed two time periods, i.e., before and after the year 2000. The influence of extreme hydrological phenomena on the runoff conditions downstream of the dam is presented by statistical processing of the available flow series

Extreme flow variability analysis at the Bianouan hydrometric station on the Bia River watershed in Côte d'Ivoire

Abstract. Extreme hydrological phenomena recurrence in West Africa in recent decades is a problem in the anthropized watershed management. Link analysis between extreme hydrological phenomena and climate variability is necessary to guard against their consequences. However, qualitative data accessing difficulties and explanatory variable definition of extremes hydrological phenomena limit extreme flows rate studies. This study proposes the analysis the variability of the floods and the low flows at the Bianouan hydrometric station. Thus, five (5) floods characteristics variables (QCX5, QXJA, F90p, F95p and F99p) and three (3) for, the low flows (VCN10, QJNA and F10p) were extracted daily flows from the Bianouan hydrometric station from 1 January 1962 to 31 December 2005. The variability of these extremes has been studied by the trend analysis (linear regression) and of the stationarity (Pettitt and Hubert tests). The results show that for flood variables the negative trend is very significant and ruptures are observed in 1980. For low flow variables the negative trend is significant and the ruptures are observed in 1981. From this study, we can deduce that the ruptures observed in the rains and flows average in the end 1960s and early 1970s have affected later the extreme flows around the 1980s.

Extreme hydrological phenomena in the forest steppe and steppe zones of Ukraine under the climate change

Abstract. Nowadays, during the period of the global climate change, scientists around the world have noticed an increased incidence of extreme natural disasters. The authors of the study suggested methods of using climate change as a part of a genetic model of maximal floods runoff. This model makes possible the introducing of “climate changes” directly through the maximal stocks of snow and precipitation during the spring flood and runoff coefficients. The object of study is the basin of the Southern Bug – one of the largest rivers in Ukraine, which flows within two geographical zones – forest-steppe and steppe. Overall results using scenario RCP 4.5 showed a decrease of runoff by the end of 2050 from 20 % in the north part of the basin (the forest-steppe zone) to 50 % – in the south (the steppe part of basin). On the other hand, the characteristics of minimal river flow in the Southern Bug basin – winter and summer low waters had been analyzed. One option for low water flow simulation is to study the connection between the drought index (e.g. SPEI) and the minimal water. Studies show that such correlation exists, so knowing the forecast of drought index it is possible to project the value of minimal water discharge, which is the object of the research.

On the Uncertainty and Changeability of the Estimates of Seasonal Maximum Flows

A classical approach to flood frequency modeling is based on the choice of the probability distribution to best describe the analyzed series of annual or seasonal maximum flows. In the paper, we discuss the two main problems, the uncertainty and instability of the upper quantile estimates, which serve as the design values. Ways to mitigate the above-mentioned problems are proposed and illustrated by seasonal maximum flows at the Proszówki gauging station on the Raba River. The inverse Gaussian and generalized exponential distributions, which are not commonly used for flood frequency modeling, were found to be suitable for Polish data of seasonal peak flows. At the same time, the heavy tailed distributions, which are currently recommended for extreme hydrological phenomena modeling, were found to be inappropriate. Applying the classical approach of selecting the best fitted model to the peak flows data, significant shifts in the upper quantile estimates were often observed when a new observation was added to the data series. The method of aggregation, proposed by the authors, mitigates this problem. Elimination of distributions that are poorly fitted to the data series increases the stability of the upper quantile estimates over time.

Research possibilities of extreme hydrological phenomena in Serbia in the function of climate change adaptation

Many natural disasters are nowadays interpreted as consequences of climate changes. They represent a form of extreme occurrences, i.e. deviation of normal conditions. They are recognized as deviation in the intensity, frequency or spatial distribution of a phenomenon from normal conditions. Thus, they represent a threat to ecosystems, economic stability and can lead to social and political problems. So far, there is no generally accepted classification of the disasters. This paper starts from the fact that a special grouping represents disasters that are happening as result of interaction of atmosphere and hydrosphere, due to the mutual interconnections. It is considered that the genetic grouping of climatehydrological extremes represents the majority of natural disasters. In the near past, the Southeast Europe countries were exposed to hydrological extremes whose causes were atmospheric occurrences. Due to the region's compactness and similar geographical conditions, these countries were sensitive to similar phenomena. The paper discusses about the hydrological extremes in Serbia that represents the result of extreme climatic conditions in relation to the consequences they have in the geographical surrounding. A total of 19 extreme hydrological phenomena have been outlined in this paper. Based on the level of destructiveness, they are classified into five categories: exceptional, significant, dangerous, strong and catastrophic. Each of them can be identified using statistical thresholds as physical parameters. The type of distribution basically determines the way in which thresholds are calculated. Four methods for their detection are outlined: the normal distribution method, the peaks method, the deciles method and the recurrence interval method. Defining each unfavorable phenomenon, their classification and determination of methods for detection are conditions for recognition and announcement. This allows an adequate reaction from the social community and the risks of disasters are reduced.

Temporal trend of drought and aridity indices in semi-arid pernambucano to determine susceptibility to desertification

ABSTRACT In semi-arid regions, the use of drought and aridity indices in order to establish diagnoses and prognoses that help in water resources management is crucial, above all, for the evaluation of long-term water availability, and monitoring hydrological extreme events. Therefore, the aim of this study was to evaluate the trends of extreme events to determine susceptibility to desertification in the Brígida river basin, by Drought (RAI, SPI and PDSI) and Aridity (MIA, AI and AIASD) Indices. The results of these indices submitted to statistical analysis (Tukey Test) and to the evaluation of the climate trend (TREND software). The Tukey Test indicated that the PDSI and RAI method are the most suitable for drought analysis, while AI is most appropriate for aridity. The results indicated that regardless of the indices employed, the stations presented significant results in the trend analysis, suggesting intensification of these events over time. Therefore, concluded that drought and aridity indices could help water resources management by managing bodies, indicating the evolution of extreme hydrological phenomena, suggesting the adoption of preventive and mitigating actions regarding the use of water priority. In conclusion, these indices can be used as a tool for indicating areas susceptible to the desertification process.

Extreme Hydrological Phenomena in the Esil River Basin: Genesis, General Patterns of Manifestation

Extreme Hydrological Phenomena in the Esil River Basin: Genesis, General Patterns of Manifestation

IMPACTS OF EXTREME HYDROLOGICAL EVENTS ON SUSTAINABLE WATER RESOURCES MANAGEMENT AND HUMAN WELL-BEING

The aim of this research is to emphasize the impact of extreme hydrological phenomena on thesustainable management of water-related societal needs. Therefore, it provides a definition of extreme hydrological events, as well as a survey of extreme hydrological events in the Republic of Serbia. It also gives a brief overview of Agenda 2030 with particular respect to Sustainable Development Goal (SDG) No 6 and highlights the impacts of extreme hydrological phenomena on the water resources, both from the perspective of the ecosystem and the society. Root-cause analysis and synthesis of data related to extreme hydrological events that occurred in the Republic of Serbia for characteristic years have been used as primary methods. The conclusion highlights the necessity of ensuring sustainable management of water resources in order to achieve the desired state of human well-being, as well as a healthy ecosystem. Keywords: extreme hydrological events, ecosystem services, sustainability, water resources, management

Determination of input parameters necessary for the design of the polder in the Horná Topl’a basin, Slovakia

In the last decade, there have been many destructive floods in various parts of Slovakia. Despite the extensive investment in flood control works, there are only small changes and neither flood occurrences nor damages are decreasing. A possible consequence of climate change is an increased frequency of extreme meteorological events that may cause floods. The determination of the occurrence of these extreme hydrological phenomena in a particular catchment is directly subject to the input data in dependence on climatic and geomorphological processes. This article deals with the method of comparing the retention capacity of the polder by means of geographic information systems (GIS) compared to the results from map data and design of flood wave diagram for the river of Banský Stream. This proposal is part of the flood protection of the area of Čergov Mountain in eastern Slovakia where is designed the system of polders.

REHABILITATION OF HYDROTECHNICAL STRUCTURES IN THE ACTUAL CONDITIONS OF CLIMATE AND ANTHROPIC CHANGES

In the eastern part of Romania, there are a lot of reservoirs of water whose age exceeds 30-40 years. They were built taking into account the existing norms and the specific environmental conditions at that time. Over time, there have been numerous changes in the parameters that define how these water reservoirs are exploited, which have questioned their safety in operation. The deforestation that has taken place over the last 30 years in Romania and the climate change have led to the emergence of extreme weather and hydrological phenomena that have put hydrotechnical structures to a challenging test. Lately, securing the ability to transit the floods through medium and small hydrotechnical arrangements safely has become a stringent problem that requires finding solutions. The fact that the hydrotechnical structures are unique and the solutions adopted in a situation cannot be adopted altogether and in another work, leads to difficulties in the safety of these types of structures. The more the problem becomes worse when the initial use of the work needs to be changed.