Transformation Of Flood Waves Research Articles

IMPACT OF POLDER FLOOD PLAIN OF THE CISOWSKA STRUGA ON THE TRANSFORMATION OF FLOOD WAVES BETWEEN GDYNIA AND RUMIA

The paper presents the results of hydraulic calculations (numerical simulations), which were made to investigate the role of floodplain (polder) adjacent to the left bank of Cisowska Struga in Gdynia downstream Hutnicza St. in the process of retention and transformation of flood waves occurring in this river due to torrential rainfall. The paper also addressed the issue of the impact of potential changes in the development of the retention area under consideration for the flood risk in Rumia.

Численное моделирование трансформации паводковых волн в сложных речных руслах

Численное моделирование трансформации паводковых волн в сложных речных руслах

Experimental determination of the flood wave transformation and the sediment resuspension in a small regulated stream in an agricultural catchment

Abstract. This paper presents the methodology used for artificial flood experiments conducted in a small artificial, trained (regulated) channel on the Nučice experimental agricultural catchment (0.5 km2), central Czech Republic, and the results of the experiments. The aim was to monitor the transformation of the flood wave and the sediment transport within the channel. Two series of experiments were carried out in contrasting initial conditions: (a) in September, when the stream banks were dry, the baseflow was negligible, and the channel was fully overgrown with vegetation; and (b) in March, when the stream banks were almost water saturated, the baseflow was above the annual average, and there was no vegetation present. Within each campaign, three successive flood waves, each with an approximate volume of 17 m3 and peak flow of ca. 40 L s−1, were pumped into the upper part of the catchment drainage channel. The transformation of the flood wave and the sediment transport regime within an approximately 400 m long channel section were monitored by measuring the discharge, the turbidity, and the electrical conductivity in three profiles along the stream. On the basis of the results, it was concluded that there is a considerable amount of deposited sediment, even in the well-trained and straight channel that can be re-mobilized by small floods. Part of the recorded sediment therefore originates from the particles deposited during previous soil erosion events. The flood waves initiated in dissimilar instream conditions progressed differently – we show that the saturation of the channel banks, the stream vegetation and the actual baseflow had a strong influence on the flood transformation and the sediment regime in the channel. The sediment moves quickly in winter and early spring, but in the later part of the year the channel serves as a sediment trap and the resuspension is slower, if dense vegetation is present.

Floodplain retention capacity assessment for Lužnice river

One of main topics of interdisciplinary project NIVA – Water Retention in Floodplains and Possibilities of Retention Capacity Increase is the assessment of flood wave transformation in the floodplain. The project focuses on broad field of floodplain ecosystem services and flood mitigation is a phenomenon which is researched by the team from Czech Technical University from different points of view and using different methods. Despite the fact that the main influence on flood wave transformation is flow retardation due to the flow velocity decrease, the retention in surface depressions within floodplain has been analyzed to get better overview of whole transformation process. Detailed digital relief model (DRM) has been used for given purposes to be able to analyze terrain depressions volumes. First, the methodology of analysis was prepared and tested on artificial surface. This surface was created using random raster generation, filtration and resampling with final resolution of 1,000 × 1,000 units and height of maximum 10 units above datum. The methodology itself is based on analysis of areas inundated by water at different elevation levels. Volume is then calculated for each depression using extraction of terrain elevations under corresponding water level. The method was then applied on the area of Lužnice River floodplain section to assess the retention capacity of real floodplain with natural character which usually means higher surface retention capacity in comparison to trained rivers. Results obtained from above mentioned analysis applied on Lužnice river are presented in this paper. The importance of floodplain retention capacity for flood transformation is low as results from obtained values. <b>Stanovení retenční kapacity niv řeky Lužnice</b> Předmětem článku je odvození a popis metody pro stanovení retenční kapacity niv založené na aplikaci prostředků GIS. Metoda vychází z analýzy digitálního modelu terénu. Prezentována je aplikace na úsek toku řeky Lužnice mezi Suchdolem nad Lužnicí a dopravníkem mezi pískovnou SV od Nové Vsi nad Lužnicí a silnicí č. 103. Délka tohoto úseku činí cca 9 km nivy. Na základě zjištěných výsledků se prokázal prvotní předpoklad, že retenční kapacita nivy nemá u toků takovéto velikosti příliš velký význam, jelikož celkový potenciální retenční objem je velmi malý ve srovnání s objemy povodňových vln pro doby opakování 20 a 100 let, které byly pro posouzení získány od Českého ústavu.

Recent Extreme Floods and Their Transformation Along the Danube River

The article discusses the considerable changes in meteorological conditions and hydrological regime in the Danube River basin over the period from the late 20th century to the early 21st century. Particular attention is given to the recent extreme hydrological events in the Danube River basin: the disastrous rainfall flood that occurred in August 2002, and the extremely high spring–summer floods in 2006 and 2010. Specific features in the development and transformation of flood waves along the Danube River are discussed in detail, including the impact of the Iron Gate I Reservoir on these processes. In addition, the influence of the backwater effect of the Black Sea was evaluated, and probabilities of extreme floods were approximately estimated.DOI: http://dx.doi.org/10.5755/j01.erem.73.1.17988

Результаты и перспективы использования гидродинамической модели распространения паводочных волн в бассейне реки Амур

A 2013 disastrous inundation occurred on the Amur River indicated the necessity of reaching new solutions for floods prevention and their negative consequences minimization. One of the possible ways is development of a method for setting the discharge hydrograph of the Bureya, Nizhne-Bureya and Zeya reservoirs, nonsynchronous with the forecasted hydrograph of the flood wave passage for flood-risky ranges of the Middle and Lower Amur on the basis of the flood wave transformation calculations. Results of the digital experiments on simulating the Amur runoff transformation with a hydrodynamic model developed by RosNIIVKh Far Eastern Branch on the basis of DHI-MIKE11 for the Middle and Lower Amur for information/analytical support of the Amur BWA activities on determination of the high-water passage regime for the reservoirs. As a result of the hydrodynamic model verification over the 2016–2017 period as a whole we obtained satisfactory estimations of the simulation quality criteria. On the basis of the simulation results analysis requirements to the boundary conditions have been formulated in addition to the determination of a range of practical tasks to be solved to adopt successfully the hydrodynamic simulation methods to the operative practice of the flood regulation in the Amur River basin including provision of the beds’ and floodplains’ morphometric and hydraulic characteristics relevance; the use of the runoff formation modern forecast hydrological models calculation data; and automation of the scenario calculations on the basis of integration with the Far Eastern Department of Hydro/meteorological Service state hydrological monitoring information system.

Hydrological simulation of flood transformations in the upper Danube River: Case study of large flood events

Abstract The problem of understand natural processes as factors that restrict, limit or even jeopardize the interests of human society is currently of great concern. The natural transformation of flood waves is increasingly affected and disturbed by artificial interventions in river basins. The Danube River basin is an area of high economic and water management importance. Channel training can result in changes in the transformation of flood waves and different hydrographic shapes of flood waves compared with the past. The estimation and evolution of the transformation of historical flood waves under recent river conditions is only possible by model simulations. For this purpose a nonlinear reservoir cascade model was constructed. The NLN-Danube nonlinear reservoir river model was used to simulate the transformation of flood waves in four sections of the Danube River from Kienstock (Austria) to Štúrovo (Slovakia) under relatively recent river reach conditions. The model was individually calibrated for two extreme events in August 2002 and June 2013. Some floods that occurred on the Danube during the period of 1991–2002 were used for the validation of the model. The model was used to identify changes in the transformational properties of the Danube channel in the selected river reach for some historical summer floods (1899, 1954 1965 and 1975). Finally, a simulation of flood wave propagation of the most destructive Danube flood of the last millennium (August 1501) is discussed.

Causes and systematics of inundations of the Krasnodar territory on the Russian Black Sea coast

Abstract. The inundation situations on the Black Sea coast of the Krasnodar territory for the period from 1945 until 2013 were analysed and the main types of inundations at the coast are described. Synoptic factors of the formation of extreme precipitation and rainfall floods, features and regularities of the downstream flood wave transformation in the rivers are also studied. Therefore, assessments of seasonal and maximum flow of the Black Sea coast rivers for the period of hydrometric measurements were done. Regularities of change of the occurrence of inundations and their characteristics on the coastal terrain were analysed, for a year and on a perennial timescale. Most catastrophic and exceptional inundations arise in the summer and in early autumn. Small inundations during the remaining year reflect the seasonal distribution of river flow and floods in the Black Sea rivers. Extensive and sometimes extreme precipitation dominates the river flow regimes. The seasonal distribution of small and moderately dangerous inundations reflects, on average, a water regime of two groups of rivers of the coast – to the north and to the south of the Tuapse River. To the north of the Tuapse River, floods prevail from November until March (up to 70 % of observed floods took place in this period) as a result of precipitation and winter snowmelt during frequent thaw periods. In winter, high waters often overlap to form a multi-peak high water of 2–3 weeks' duration. In the summer and in early autumn we observe a steady low flow. The total amount of runoff increases both in a southeast direction, and with the altitude of the river basins. Interannual variability of mean annual runoff, as well as maximum runoff, on the contrary decreases in the southern direction and with an increasing area of the river basins. The coastal high waters of the rivers of the Sochi part of the coast are typical at any time of the year, but more often floods in the cold season result from incessant rain, and thawing snow. Annually up to 25 floods have been observed. The principal reason of such distribution is the increase of extreme rainfall in the warm season. Orographic features of the coast and detailed features of rainfall only cover a small number of local river basins and a limited area. The geographical correlation of individual rainfall and subsequent floods ceases to be statistically significant for distances over 40–60 km. The annual flow cycle is mainly determined by two seasons, winter/spring and summer, with strong and weak flows, respectively; almost 71 % of all catastrophic and exceptional inundations took place in July–August (71 %) and in October–November (29 %). The characteristic features of dangerous floods are their rapid formation and propagation, a significant increase of water level (up to 5–7 m and more) and the multiple increase of water discharges in comparison with low flow period. Analysis of the interannual changes of the number of inundations at the Black Sea coast of the Krasnodar territory has shown some increase of the number of inundations in the period from the early 1970s until the early years of the twenty-first century. Quantitative assessments of risk, hazard and damage for the population and economic activities from accidental inundations in the valleys of the Black Sea coast rivers show that economic and social losses from inundations at the Black Sea coast of the Krasnodar territory are some of the highest in the Russian Federation. The basic conclusion from recent inundations is the need to consider not only the lower reaches and mouths of the Black Sea coast rivers where the main part of the social and economic development of the coast is concentrated, but also whole river basins and catchments. Further, an analysis of the efficiency of the measures applied at the coast to mitigate inundations and their after-effects is provided.

The impact of floodplain land use on flood wave propagation

Due to their retention capacity, extensive flat floodplains have a significant impact on the propagation and transformation of flood waves. The conveyance and retention capacity of an area is significantly influenced by land use. The paper presents results of a hydraulic analysis of the impact of land use on the run-off regime in a retention area and consequently on flood wave propagation. The land use of the retention area was simulated by hydraulic roughness. The simulations were performed for flood waves with different values of peak discharge and with two lengths of duration. A spectrum of flood waves in which the retention areas have significant impact on the propagation was considered. To isolate the impact of topographical characteristics of riparian and retention areas on the communication of water between the channel and retention area, as well as on the formation of parallel streams in the area, a theoretical modelling area with simplified geometry was used in the first phase. Conclusions based on the results of the first-phase simulations were tested on a practical case of the plain Krsko–Brežisko polje, where data from field measurements as well as data from the physical model were used in the numerical calibration of the model.

Обоснование возможности использования защитных дамб для регулирования паводкового стока.

Effect of the flood regulation with the river floodplains was discussed, and a mechanism of the flood wave transformation with the basin channel network in the natural regime and during the floodplain banking was characterized. The possibility of dikes’ capacity use for cutting off the flood peak in extreme situations was substantiated and the relevant Chinese experience was analyzed. Theoretical basis for the channel network capacity management with pre-planned flooding of the “protected” floodplain areas was presented. The appropriated methods were developed; they included plotting of the maximal runoff calculated hydrographs, concurrent simulation of the flood wave passage and dikes capacities filling, more precise definition of parameters of the water-passing facilities in the dike body. Proposals on the designing of floodplain volumes and dikes intended for the flood runoff regulation were formulated. The Ingoda River (Transbaikal Kray) was taken as a study case. It was characterized by the flood maximal flows passage in different reaches due to the regulating impact of the bed and floodplain. Comparison of the real flood passage with the simulation results with the use of floodplain regulating capacities for this river was presented. Tentative results were the evidence of the principal possibility of the dikes capacity use in extreme conditions.

Extreme hydrological events in the Danube River basin over the last decades

The article discusses the considerable changes in hydrometeorological conditions that occurred in the Danube River basin over the period from the late XX century to the early XXI century. Mention is made of the air and water temperature rise, softening of ice conditions, and, above all, the noticeable increase in the river water runoff. Particular attention is given to the recent extreme hydrological events in the Danube River basin: the disastrous rainfall flood that occurred in August 2002, the extremely high spring-summer floods in 2006 and 2010, and the extraordinary low-flow period in summer 2003. The meteorological reasons for these events have been analyzed. Specific features in the development and transformation of flood waves along the Danube River are discussed in detail, including the impact of the Iron Gate-1 Reservoir on these processes.

Assessing the retention capacity of a floodplain using a 2D numerical model

Assessing the retention capacity of a floodplain using a 2D numerical modelThis paper presents a method for assessing the retention capacity of a floodplain in the course of flooding and for estimating the significance of its water storage for transforming a flood wave. The method is based on two-dimensional numerical modeling of the flood flow in a river channel and in the adjacent floodplains, and is suitable for cases when the morphology of the flooding area is variable and complex, e.g. broad inundation areas with meandering channels. The approach adopted here enables us to quantify the retention capacity for inundation areas of various characters and with various land uses, and provides a tool for estimating the efficiency of possible measures for increasing the water storage capacity of a floodplain. The retention capacity is estimated using an evaluation of a series of detailed flood flow modeling results; the flood wave transformation effect is predicted with the aim of creating a non-linear reservoir model. A parametric study of the floodplain retention capacity for the upper branch of the Lužnice River is presented here, and the results for the current state and for various hypothetical scenarios of changes in geometry and land use are evaluated and compared.

Mathematical modeling of transformation of flood waves in stream channels with floodplains

Two mathematical models based on the Saint-Venant equations are considered for calculating unsteady flows in stream channels with floodplains. In model 1, the influence of floodplain on the release or flood wave travelling is taken into account through the total morphological and hydraulic characteristics of stream channel and floodplain. In model 2, based on singling out a fluvial flow, the floodplain plays a role of an accumulation capacity. To study the field of a practical applicability of the proposed models, comparative calculations have been carried out with a two-dimensional (plan) model. The analysis of results demonstrated a sufficient efficiency of models 1 and 2 with allowance for floodplains in meandering stream channels. Due to a less laborious preparation of initial data, model 2 is more preferable.

Analysis of flood propagation changes in the Kienstock—Bratislava reach of the Danube River/Analyse des changements de propagation des crues dans le tronçon Kienstock—Bratislava du Fleuve Danube

In the first part of this study, a flood wave transformation analysis for the largest historical floods in the Danube River reach Kienstock–Bratislava was carried out. For the simulation of the historical (1899 and 1954) flood propagation, the nonlinear river model NLN-Danube (calibrated on the recent river reach conditions) was used. It was shown that the simulated peak discharges were not changed significantly when compared to their historical counterparts. However, the simulated hydrographs exhibit a significant acceleration of the flood wave movement at discharges of between 5000 and 9000 m3 s-1. In the second part, the travel time-water level relationships between Kienstock and Bratislava were analysed on a dataset of the flood peak water levels for the period 1991–2002. An empirical regression routing scheme for the Danube short-term water level forecast at Bratislava station was derived. This is based on the measured water level at Kienstock gauging station.

CHANGES IN THE MAGNITUDE AND TRANSFORMATION OF FLOOD WAVES SUBSEQUENT TO THE CHANNELIZATION OF THE RABA RIVER, POLISH CARPATHIANS

Alterations in flood flows of the Raba River are examined to determine the influence exerted on flood waves by changing morphological conditions. With stable vertical channel position, the river increased its sinuosity during the 1920s to 1940s, and the change was accompanied by a growing tendency to flood-wave attenuation. The temporal change in flood-wave transformation is typical of a developing low-flow system. Subsequently, streambed degradation has been induced due to channnelization works which straightened and narrowed the river. Flood waves became progressively more flashy as channel incision progressed. The increase in magnitude of flood waves passing the deepened reach was greatest for bankfull flows and diminished for lower in-bank flows and higher overbank flows. The tendency to magnification of peak discharges has been also found in other Carpathian rivers which were considerably degraded in the 20th century in response to channelization. Introducing an empirically found correcting factor into the analysis of the ratio of outflow to inflow peak discharges shows how the conditions of peak-flow transformation in a reach have changed since the beginning of the study period. A marked coincidence between changes in vertical channel location and variations in the ‘corrected’ peak-discharge ratio proves channel changes to be a very important reason for the growing flood hazard in southern Poland. Gradient oversteepening and channel narrowing, caused by channelization, lead to formation of a river system having a steep, straight, narrow and deep channel. Such a morphology distinguishes the system from natural low-flow and high-flow systems. Reduced floodplain water storage and self-acceleration of flow concentrated in a channel zone make flood waves progressively more flashy on their way down the channelization-formed system.

Analog Simulator of Flood Wave Transformation in Upper Vistula River System

The concept of a flood wave analog simulator interfaced to digital minicomputer is given this device can provide very fast and convenient tool for computing flood wave transformation. The particular design as developed in the Institute of Automatic Control, together with specialized software, is presented. The results of analog simulation (which takes about 0.8 SEC. when compared to 90 sec. digital simulation) show this concept valuable.