BazTech - Yadda

1

Experimental investigation for the local scour around V-shaped spur-dikes

Alasadi Layth Abdul Rasool, Khlif Tagreed Hameed, Hassan Fadhel Abdulabbas

Przegląd Naukowy Inżynieria i Kształtowanie Środowiska

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2023

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Vol. 32, No. 1

68--86

EN

Spur-dikes are efficient hydraulic structures that are made for numerous purposes. They have one end on the stream bank and another extending into the current. As a result of the existing spur-dikes in the stream course, the local scour phenomena usually occur around them, leading to several predicaments which have been of great concern to the hydraulic engineers. For the present work, laboratory experiments were carried out to measure the scour depths around several spur-dikes located at different distances for the V-shaped one. The experiments were conducted using physical models installed in a non-curved flume with a bed with uniform cohesion-less sediment of a medium particle size (d50 = 0.7 mm). All the models were operated under the subcritical flow of clear-water conditions. The investigations include three spur-dikes (1, 2 and 3) and three distances between them (1, 1.5 and 2 of spur-dike length) as two countermeasures to minimize the local scour depths. The results showed that an increasing number of spur-dikes and the distances between them would decrease the scour depths within the limit of the present study. The experimental data were used to create a new formula of R = 0.954 that reflects a good agreement with the experimentally observed results.

2

Natural and anthropogenic influences on the development of mud depocenters in the southwestern Baltic Sea

Porz Lucas, Zhang Wenyan, Schrum Corinna

Oceanologia

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2023

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Vol. 65 (1)

182--193

EN

The morphological evolution of two mud depocenters in the southwestern Baltic Sea is investigated by comparison of numerical model results to geological and oceanographic data. The pathways of dense currents during episodic dense-water inflows from the North Sea are shown to correspond to current pathways inferred from contouritic depositional geometries in the flow-confining channels within the study area. A favorable comparison of model results to published current speed observations shows that the mesoscale dynamics of individual inflow events are reproduced by the model, indicating that external forcing and basin geometry rather than internal dynamics control the mesoscale dynamics of inflow events. The bottom current directions during inflows show high stability in the flow-confining channels and explain the contouritic depositional geometries. Asymmetric depositional features in the channels are qualitatively reproduced in the model. Bottom currents are less stable in areas without contouritic features, possibly resulting in an overall diffusive effect on sediment distribution in those areas. In a simulation of resuspension by bottom-contacting fishing gear, inter-basin sediment transport is increased by 4–30%, depending on the area, compared to the case of natural hydrodynamic resuspension. The model predicts an increased winnowing of the finest sediment fraction due to bottom trawling, leading to an overall coarsening-to-fining trend in the direction of net sediment transport. The results show that rather than hemi-pelagic background sedimentation, episodic events with high bottom current velocities as well as bottom-trawling induced resuspension are responsible for the present-day and future morphological configuration of the mud depocenters in the southwestern Baltic Sea.

3

Two-Dimensional Numerical Modeling of Morphodynamic Evolution in Bouregreg Estuary (Morocco)

El Assaoui Naïma, Sadok Abdelaziz, Bendaraa Anass, Charafi Moulay Mustapha

Ecological Engineering & Environmental Technology

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2023

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Vol. 24, iss. 5

217--230

EN

The Bouregreg valley, located on the Atlantic coast of Morocco, has been subject to several anthropogenic and natural impacts that disturb the proper functioning of the estuary’s ecosystem. Important dredging operations influenced by both tides and freshwater inflows have created a significant variation of estuary’s morphology characterized by a sand bar developed at the mouth. The main objective of this study is to investigate the Morphodynamic processes of the estuary and in particular the impact of dredging operations using a two-dimensional horizontal numerical (2DH) modeling approach based on the shallow water equations. Several numerical tests have been carried out to calibrate the model and to investigate the hydrodynamic and morphological aspects of the estuary. For this technical solution, the modelling simulations show that in addition to the quantities of sand that will be dredged initially, the maintenance of the channel will facilitate a better water circulation between the Bouregreg valley and the Atlantic Ocean and improve the stability of the civil engineering structures and the neighbouring monuments. In addition, this water circulation will guide the river flow in the ebb phase of the tide. The model results show a reduction of about 30% in the impact of erosion, observed before the digging of the canal.

4

Analysis and Mapping of Water Erosion Vulnerability Using GIS for the Mghila Watershed, Northwest of Algeria

Ratiat Abdelkader, Haddad Ali, Bouaichi Ilham, Matene Chahrazed Naziha

Archives of Hydro-Engineering and Environmental Mechanics

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2023

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Vol. 70, nr 1

71--87

EN

Intensification of extreme rainfall-runoff events in arid and semi-arid regions because of climate change induce the water erosion that contributes considerably to the loss of vegetal layers of soils and reduce the storage capacity of dams by silting of transported sediments from the watershed to the impoundment. This paper aims at proposing means for protecting the Mghila dam against silting by identification and delimitation of vulnerable areas to water erosion. This dam, built in the North-West of Algeria, ensures irrigated cultivation. Topographical, geological, and land use characteristics of the watershedwere analyzed using the geographic information system (GIS). Analysis of results has allowed the identification by area percentage four-vulnerability classes with sensitivity to the water erosion: low (18.89%), medium (13.08%), high (65.05%) and very high (8.38%). The spatial distribution of the lithological substratum friability, the vegetation cover and slope degrees have led to the development of an efficient strategy for the watershed management in order to reduce the effect of water erosion on soil degradation and silting of the Mghila dam.

5

A coupled model for sediment transport dynamics and prediction of seabed morphology with application to 1DH/2DH coastal engineering problems

Afentoulis Vasileios, Papadimitriou Andreas, Belibassakis Kostas, Tsoukala Vasiliki

Oceanologia

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2022

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No. 64 (3)

514--534

EN

Coastline retreat poses a threat to nearshore environment and the assessment of erosion phenomena is required to plan the coastal engineering works. The hydro-morphodynamic response of a beach to natural and artificial forcing factors differ considerably, as the nearshore processes are especially complex and depended on a multitude of parameters, including prevailing wave and hydrodynamic conditions, beach topography, sediment characteristics and the presence of coastal protection works. The present study serves the purpose of numerically evaluating nearshore morphological processes and ultimately assessing the capacity of coastal defence structures to control beach erosion. For this reason, a new sediment transport model including unsteady effects and swash zone morphodynamics, was coupled to the highly nonlinear Boussinesq wave model FUNWAVE-TVD, providing integrated predictions of bed level evolution, across various timescales of interest. The compound model was validated thoroughly against laboratory data and other numerical investigations. Overall, a good agreement between experimental and numerical results was achieved for a number of test cases, investigating the effects of different types of shore protection structures. The proposed integrated model can be a valuable tool for engineers and scientists desiring to obtain accurate bed level predictions, over complex mildly and steeply sloping sea bottoms composed of non-cohesive sediment particles.

6

Wpływ zbiornika retencyjnego Jeziorsko na układ dna i transport rumowiska na odcinku od zapory czołowej do Uniejowa

Hämmerling Mateusz, Kałuża Tomasz, Zawadzki Paweł, Zaborowski Stanisław

Gospodarka Wodna

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2022

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Nr 9

13--17

PL

Przegrodzenie rzeki ułatwia gospodarowanie wodą na danym odcinku cieku. Budowa zbiornika retencyjnego jest bardzo korzystna, ponieważ umożliwia zwiększenie retencji, przyczynia się do ochrony przeciwpowodziowej, umożliwia korzystanie ze zgromadzonych wód przez różnych użytkowników. Wpływ zbiornika retencyjnego na warunki przepływu wody oraz środowisko jest zagadnieniem wieloaspektowym. Dlatego w badaniach przedstawionych w niniejszym artykule skupiono się głównie na wpływie piętrzenia na warunki przepływu wody i transport rumowiska na dolnym stanowisku budowli. W artykule przedstawiono analizę zmian poziomów dna, zwierciadła wody oraz rumowiska poniżej zbiornika Jeziorsko na rzece Warcie. Ocenę skutków procesu erozji koryta rzeki Warty wykonano na podstawie sondowań dna, pomiarów zwierciadła wody oraz składu granulometrycznego pobranych próbek rumowiska wykonanych w latach 1975-2010.

EN

Building dams on rivers facilitates water management in a given section of the river. Building a retention reservoir brings a lot of benefits, as it increases retention, contributes to flood protection, gives different users the possibility to benefit from the accumulated water. Impact of a retention reservoir on the water flow conditions and the environment is a complex issue. Therefore, the study presented in this article focuses mainly on the effect of damming on the water flow conditions and sediment transport in the lower station of the construction. The article presents an analysis of the Warta River bottom, water table and sediment levels changes downstream of the reservoir. The assessment of the Warta riverbed erosion process impact was made based on the bottom probing, water table levels measurement and granulometric composition of sediment samples collected in the years 1975-2010.

7

Numerical Calculations with a Multi-layer Model of Mixed Sand Transport Against Measurements in Wave Motion and Steady Flow

Kaczmarek Leszek M., Radosz Iwona, Zawisza Jerzy

Rocznik Ochrona Środowiska

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2021

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Tom 23

629--641

EN

A multi-layer model is used to calculate time-dependent sediment velocity and concentration vertical profiles. This model, in which the differences in sediment transport at different distances from the bed are considered is intended both for the wave motion and steady flow. Numerical calculations were carried out for sediment transport during the wave crest and trough and total sediment transport as a sum of their absolute values. The model concept of variation in shear stress from the skin stress value above the bed to the stress value at the bed previously proposed for steady flow is extended here for the wave motion and verified by direct stress measurements. The calculations were carried out for mixed sand sediments with different grain size distributions including semi-uniform and poorly sorted grains. Comparison with the available small- and large-scale data from flumes and oscillating tunnels yields agreement typically within plus/minus a factor two of measurements.

8

The impact of Klaipėda Port entrance channel dredging on the dynamics of coastal zone, Lithuania

Žilinskas Gintautas, Janušaitė Rasa, Jarmalavičius Darius, Pupienis Donatas

Oceanologia

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2020

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No. 62 (4PA)

489--500

EN

Dredging entrance channels to ports on open littoral drift seashores often causes major morphological changes to the shoreline. This study aims to assess the impact of dredging the Port of Klaipėda's entrance channel and the construction of the jetties on the coastal zone. Based on an analysis of cartographic material collected between 1835 and 2017, and on field data (bathymetric surveys and cross-shore profile levelling), changes to the coastal zone in the area nearest to the port were evaluated. The dominant longshore sediment transport on the Lithuanian nearshore runs from south to north. Thus, based on established patterns, intensive accretion could have been expected to take place on the southern side of the port jetties and erosion on their northern side. However, in the case of the Port of Klaipėda, in the area nearest to the port on the updrift side of the port jetties, where accretion would have been expected to take place, the nearshore depth increased throughout the 20th century (when the length and configuration of the jetties did not change). The shoreline shifted landward instead of moving further out to sea. The present study shows that the intensive dredging of the entrance channel caused nearshore and shore erosion on the updrift side of the port jetties, even while a sufficient sediment load was being transported by the longshore drift.

9

Influence of the climatic variations in the wind waves parameters on the alongshore sediment transport

Divinsky Boris V., Kosyan Ruben D.

Oceanologia

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2020

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No. 62 (2)

190--199

EN

The purpose of this work was to analyze the influence of climatic variability of wind waves and swell parameters in the coastal zone on the sediment transport and to assess the contribution of the swell to the formation of alongshore fluxes. The object of research is the Anapa bay-bar (the Black Sea). Mathematical modeling has shown that in the Anapa bay-bar area the average annual wind waves and swell powers have significant interannual variability. For the period from 1979 to 2017, in the southern part of the bay-bar, there was a statistically significant decrease in the share of swell in the alongshore transport, directed from NW to SE, in the central part – an increase in the contribution of swell to the total sediment flow from SE to NW, in the northern part – probable increase in flows to NW and decrease – to SE. Such a dynamic is consistent, in general, with experimental observations of the processes of erosion and accumulation of beach-forming material along the Anapa bay-bar coastline. A separate description of the bottom sediment fluxes under the influence of wind waves and swell made it possible to explain the fluctuations of the coastline over a climatic period.

10

Grain-size characteristics and net transport patterns of surficial sediments in the Zhejiang nearshore area, East China Sea

Liang Juan, Liu Jian, Xu Gang, Chen Bin

Oceanologia

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2020

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No. 62 (1)

12--22

EN

Spatial variations in grain-size parameters can reflect sediment transport patterns and depositional dynamic environments. Therefore, 616 surficial sediment samples taken from the Zhejiang nearshore area in the East China Sea were analyzed to better understand the net sediment transport pattern in this region. The study area is generally dominated by clayey silt and has relatively coarse mud sediment in the southeast. The sorting coefficient of surface sediment is higher than 1.4, and sediment is poorly sorted throughout the study area. The skewness has a strong correlation with the mean grain-size diameter. The net sediment transport pathways obtained by the grain-size trend analysis indicate several distinct characteristics of the surficial sediment transport. The sediment is transported southward under the action of the stronger southward Zhejiang-Fujian Coastal Current (ZMCC) in winter in the upper part of the nearshore area. Influenced by the obstruction of the Taiwan Warm Current (TWC) and the tidal current, surficial sediment transport vectors display two areas of grain-size trend convergence and indicate the net deposition environment has a high sedimentation rate. However, the transport is mainly toward the north under the control of the prevailing northward ZMCC and the strong TWC in the summer. The sedimentary rate is closely related to the processes of the sediment transport. On the one hand, sediment transportation affects the depositional rate in a different environment. On the other hand, the modern sedimentary rate can reflect indirectly the sediment source and sediment transportation.

11

Features of the Sediment Runoff Regime Downstream the Ile River

Duskayev Kassym, Myrzakhmetov Akhan, Zhanabayeva Zhanar, Klein Igor

Journal of Ecological Engineering

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2020

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Vol. 21, nr 2

117--125

EN

This paper is devoted to study on the sediment runoff of the Ile River downstream. The article analyses the Kapshagai reservoir impact on the regime and characteristics of the sediment runoff in the Ile River downstream before and after construction of the reservoir in 1970. Along with the calculation of characteristics of sediment runoff, an assessment of the amount of the suspended sediment, which is in the bowl of the reservoir, was shown. Furthermore, the impact reservoir on the granulometric composition of the suspended and bed sediment of Ile River was calculated.

12

A new mathematical model to calculate the equilibrium scour depth around a pier

Gazi Ainal Hoque, Afzal Mohammad Saud

Acta Geophysica

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2020

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Vol. 68, no. 1

181--187

EN

This paper sheds light on the formulation of a new equilibrium local scour depth equation around a pier. The total bed materials removed from the scour hole due to the force exerted by the fowing fuid after colliding with the pier in the fow feld are estimated. At the equilibrium condition, the shape of the scour hole around the pier may take any form, viz. linear, circular, parabolic, triangular, or combination of diferent shapes. To consider that, two functions are assumed at the stoss and the lee sides of the pier. The total volume of bed materials removed from the scour hole of an arbitrary shape at the stoss and the lee sides of the pier is obtained by integrating the two functions. The equilibrium scour depth is formed by applying the energy balance theorem. An example problem is illustrated and the results are compared with the equations presented by Melville and Coleman (Bridge scour. Water Resources Publication, Colorado, 2000) and HEC-18 (Richardson and Davis in Evaluating scour at bridges, HEC-18. Technical report no. FHWA NHI, 2001).

13

Use of modelling for the renovation of drainage channels – The case of the Bouteldja plain in northeastern Algeria

Sennaoui Foued, Benabdesselam Tamara, Saihia Abdallah

Journal of Water and Land Development

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2019

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no. 43

1--8

EN

Agricultural drainage has become a priority in agriculture and the economic development of the state. Algeria has launched several agro-economic projects pertaining to natural resources and human potential for development in agricultural areas. Our aim is to model the morphological evolution of open drainage channels, under the influence of sedimentary transport processes. The application of the Hydrologic Engineering Center’s River Analysis System (HEC-RAS) software is to examine two-phase mathematical models. In our case it is the flow and the sedimentary charge along a trapezoidal earth channel of a wetland north east of Algeria. The results of these models were validated by actual data obtained during the observation period from 2017 to 2018, for various rainy events. The solid transport and sedimentation velocity equations of Engelund and Hansen and Van Rijn respectively used by this model, give Nash performance criteria equal to 0.95 and determination coefficient R2 equal to 0.91. On the other hand, the laying of a coarse gravel layer of median diameter of the grains d50% = 60 mm on the bottom of the channels reduces the rate of sedimentation by about 32% over an 11-year period. This satisfying objective study of the modelling allows to obtain an approach to the renovation and a plan for new design of drainage systems, that participates to the sustainable development in the agricultural field.

PL

Drenowanie stało się priorytetem w rolnictwie i gospodarczym rozwoju kraju. W Algierii uruchomiono kilka programów rolniczych odnoszących się do zasobów naturalnych i potencjału rozwojowego obszarów wiejskich. Naszym celem było modelowanie zmian morfologicznych w otwartych kanałach drenarskich pod wpływem procesów transportu zawiesiny. W dwufazowym modelu matematycznym wykorzystano program HEC-RAS (Hydrologic Engineering Center’s River Analysis System). Zmiennymi w modelu były przepływ i ładunek zawiesiny wzdłuż ziemnego kanału o trapezoidalnym przekroju w środowisku podmokłym północnowschodniej Algierii. Wyniki modelu porównano z rzeczywistymi danymi opadowymi pozyskanymi w różnych okresach w latach 2017 i 2018. Równania Engelunda i Hansena (transport zawiesiny) i Van Rijna (tempo sedymentacji) użyte w modelu dały w wyniku kryterium Nasha równe 0,95 i współczynnik determinacji R2 równy 0,91. Warstwa grubego żwiru o medianie średnic ziaren d50% = 60 mm na dnie kanału spowalniała tempo sedymentacji o ok. 32% w ciągu 11 lat. Przedstawione badania umożliwiają nowe podejście do renowacji istniejących i projektowania nowych systemów drenarskich, które przyczyniają się do zrównoważonego rozwoju rolnictwa.

14

Impact study of Beni-Haroun dam on the environmental and socio-economic elements in Kébir-Rhumel basin, Algeria

Marouf Nadir, Remini Boualem

Journal of Water and Land Development

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2019

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no. 43

120--132

EN

Surface water of Kébir Rhumel basin is indispensable for domestic and industrial needs of this region. Industrial development, with water excessive use and chemical products, in production and industrial treatment, and not sustainable fertilizers in agriculture, constitutes a serious threat to maintain our resources of good water quality. The majority of domestic and industrial wastewaters of the region, discharged to the stream water of Kébir Rhumel basin, promote the water enrichment in nutritious elements, phosphorus and nitrogen and particularly, the resulting increase in the aquatic primary production, mainly the planktonic or benthic algae. As a result, the physical and chemical properties of water deteriorate. This basin allows construction of the largest dam in Algeria “Beni-Haroun dam”. The infrastructure that was one of the greatest challenges of Algeria is now a reality. Hydraulic complex of Beni-Haroun remains a strategic and major achievement in the development program of water resources sector. This enormous building was constructed in the territory of the Wilaya (province) of Mila, used to meet water needs, with four million inhabitants, of eastern Algeria and other neighbouring regions that have suffered from lack of water consumption, especially in summer. In addition, it will irrigate over 42 000 ha, going thus to the several plains. Integration of sociological and environmental concerns into dams design is a recent phenomenon. It is considered at the impact study level, during which the dam study project is accompanied by a survey to assess project impact on natural environment and socioeconomic development.

PL

Wody powierzchniowe na terenie basenu Kébir-Rhumel są niezbędne do zaspokojenia domowych i przemysłowych potrzeb regionu. Rozwój przemysłowy z jego nadmiernym zużyciem wody i substancji chemicznych w procesie produkcji i przetwarzania oraz niezrównoważone stosowanie nawozów w rolnictwie stwarzają poważne zagrożenie dla jakości wody. Większość domowych i przemysłowych ścieków z regionu jest odprowadzana do wód płynących basenu Kébir-Rhumel, powodując ich wzbogacenie w pierwiastki biogenne (fosfor i azot), co skutkuje zwiększoną produkcją pierwotną głównie planktonowych i osiadłych glonów. W wyniku tego pogarsza się jakość wody. Układ basenu umożliwił zbudowanie największej zapory w Algierii – zapory Beni-Haroun. Ten obiekt infrastruktury wodnej, będący jednym z największych wyzwań Algierii, stał się rzeczywistością. Kompleks wodny Beni-Haroun jest strategiczym i głównym osiągnięciem programu rozwoju zasobów wodnych. Ta ogromna budowla umieszczona w prowincji Mila zaspokaja potrzeby 4 mln mieszkańców wschodniej Algierii i sąsiadujących regionów, które cierpiały na brak wody pitnej, szczególnie latem. Ponadto wodą ze zbiornika będzie się nawadniać 42 000 ha na kilku równinach. Zagadnieniem ostatnio branym pod uwagę podczas projektowania zapór jest integrowanie problemów społecznych i środowiskowych. Te problemy są rozważane na etapie oceny oddziaływania na środowisko, w którym projektowaniu zapory towarzyszy analiza wpływu projektu na środowisko naturalne i rozwój społeczno-gospodarczy.

15

Effect of Riffle Sequences on Discharge and Sediment Transport in a Mountain Stream

Korpak Joanna, Lenar-Matyas Anna, Łapuszek Marta, Mączałowski Andrzej

Journal of Ecological Engineering

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2019

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Vol. 20, nr 3

157--166

EN

Natural riffles are formed as a result of fluvial processes in the stream channel, water flow, and sediment movement. In recent years, artificial riffles have also been constructed in order to improve the water flow and sediment transport as well as to initiate the processes that lead to the restoration of natural riffle–pool sequences. In river engineering, the utilization of artificial riffles (rapid hydraulic structures) is still in its experimental stage. Artificial riffles are studied and described in the literature on a case study basis. However, the studies on riffle sequences and their effects on stream channel evolution need to be improved. A system of artificial riffles was created in the mouth section of Krzczonówka Stream in 2013. The new riffles made the stream channel more morphologically diverse and also reduced its longitudinal slope. The check dam on the stream, located upstream of the newly formed riffles, was renovated and lowered in 2014. At this time, a flood occurred and released a large mass of sediment downstream of the check dam. Then, the sediment settled in the sections between the artificial riffles, thus covering some of them. The aim of the study was to examine the effect of the system of riffles on the changes in sediment transport and water flow in the studied stream channel. Calculations indicate that the system of riffles established downstream of the check dam has limited the movement of sediment. The sediment transport is varied throughout the studied stream course and is mostly dependent on the sediment supply.

16

Transport odwodnionych osadów ściekowych na duże odległości

Tomczak Waldemar

Forum Eksploatatora

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2019

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Nr 3 (102)

48-50

PL

Stary, dobry system pneumatyczny mógł stać się prekursorem technologii przyszłości. Wraz ze Smart Air Injection (SAl) firma SEEPEX GmbH z Bot- trop wprowadza na rynek szyte na miarę rozwiązanie systemowe, która łączy w sobie zalety dwóch technologii pompowania, umożliwiając energetycznie wydajny transport osadów odwodnionych na duże odległości. Długość przewodów których skompresowane do postaci placków odwodnione osady ściekowe transportowane są do celu za pomocą sprężonego powietrza, może wynosić nawet 1000 metrów. To alternatywne rozwiązanie dla tradycyjnych procesów zostało już wypróbowane w wielu europejskich oczyszczalniach i stanowi inwestycję, która szybko może się zwrócić.

17

Quantification and study of monthly variation of suspended sediment loads in Tafna basin – Algeria

Belarbi F., Bouchelkia H., Remini B., Benmansour A.

Journal of Water and Land Development

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2018

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no. 37

29--38

EN

The magnitude of the phenomenon is disproportionate in semi-arid or in temperate climates. Thus Algeria is one of the most affected countries by this phenomenon and its consequences. To enable a rapid response to the request of engineers and managers to quantify sediment transport at the outlet of a watershed, a simple, easy tool to implement was developed. The principle adopted is based on hydrometric data sets from gauging stations with seasonal and annual time steps to define a suitable method for estimating sediment production. The sediment study was conducted by analysing the daily flows. Pierre du Chat station at the outlet of the Tafna basin served as an application. The obtained results are entirely satisfactory because the correlation coefficients of model Qs = f(Q) range between 72 and 95%. This method, once refined can be generalized to all watersheds in northern Algeria.

PL

Rozmiary sedymentacji są nieporównywalne w klimacie półpustynnym i umiarkowanym. Algieria jest jednym z państw dotkniętych tym procesem i jego skutkami. Aby zapewnić szybką reakcję na wymagania inżynierów i zarządców co do ilościowej oceny transportu osadu, na odpływie ze zlewni skonstruowano proste i łatwe w użyciu narzędzie nadające się do wdrożenia. Przyjęte zasady opierają się na zestawie danych hydrometrycznych z posterunków pomiarowych z użyciem sezonowych i rocznych kroków czasowych w celu zdefiniowania odpowiedniej metody do oceny produkcji osadu. Badania prowadzono, analizując dobowe przepływy. Przykładem był posterunek Pierre du Chat zamykający zlewnię Tafna. Uzyskane wyniki są w pełni satysfakcjonujące, ponieważ współczynnik korelacji modelu Qs = f(Q) wynosił od 72 do 95%. Przedstawiona metoda, po udoskonaleniu, może zostać uogólniona na wszystkie zlewnie w północnej Algierii.

18

The impact of processes of sediment transport on storage reservoir functions

Szlapa M., Hachaj P. S.

Technical Transactions

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2017

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Vol. 7(114)

113--126

EN

Maintaining the good condition of water reservoirs is always one of the main tasks of water management. This is especially vital when the reservoir serves as a water supply and/or a facility for recreational activities. No only what goes into the lake but also everything that is stored within the area needs to be considered. In a case of dam reservoirs, one of the important issues is the transport and storage of sediment. This paper focuses on the sediment which is characteristic of the Dobczyce Reservoir and considers situations which may potentially generate problems from the point of view of maintaining good condition of the water body.

PL

Utrzymanie dobrego stanu zbiorników wodnych jest zawsze jednym z najważniejszych zadań gospodarki wodnej. Jest tak zwłaszcza, gdy wśród funkcji rezerwuaru znajduje się zaopatrzenie w wodę i/lub rekreacja. Z jednej strony należy zwrócić uwagę na materię dostarczaną do zbiornika, z drugiej zaś na to, co w tej przestrzeni jest deponowane. Ta praca skupia się na charakterystyce osadów zbiornika Dobczyckiego i rozważeniu scenariuszy mogących generować sytuacje problemowe dla utrzymania dobrego stanu zbiornika wodnego.

19

The impact of tides and waves on near-surface suspended sediment concentrations in the English Channel

Guillou N., Rivier A., Chapalain G., Gohin F.

Oceanologia

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2017

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No. 59 (1)

28--36

EN

Numerous ecological problems of continental shelf ecosystems require a refined knowledge of the evolution of suspended sediment concentrations (SSC). The present investigation focuses on the spatial and temporal variabilities of near-surface SSC in coastal waters of the English Channel (western Europe) by exploiting numerical predictions from the Regional Ocean Modeling System ROMS. Extending previous investigations of ROMS performances in the Channel, this analysis refines, with increased spatial and temporal resolutions, the characterization of near-surface SSC patterns revealing areas where concentrations are highly correlated with evolutions of tides and waves. Significant tidal modulations of near-surface concentrations are thus found in the eastern English Channel and the French Dover Strait while a pronounced influence of waves is exhibited in the Channel Islands Gulf. Coastal waters present furthermore strong SSC temporal variations, particularly noticeable during storm events of autumn and winter, with maximum near-surface concentrations exceeding 40 mg l−1 and increase by a factor from 10 to 18 in comparison with time-averaged concentrations. This temporal variability strongly depends on the granulometric distribution of suspended sediments characterized by local bimodal contributions of silts and sands off coastal irregularities of the Isle of Wight, the Cotentin Peninsula and the southern Dover Strait.

20

Modelling nearshore hydrodynamics and circulation under the impact of high waves at the coast of Varkiza in Saronic-Athens Gulf

Belibassakis K. A., Karathanasi F. E.

Oceanologia

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2017

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No. 59 (3)

350--364

EN

A plethora of physical parameters, such as hydro-, litho- and morpho-dynamic characteristics, are essential for understanding the response of coastal systems to intense sea states in terms of sediment transport and shoreline evolution. Nowadays, numerical models are extensively applied to meet the above needs and support coastal planning and management. In the present work, a 2DH dynamic modelling system is used for simulating the hydrodynamic and meteorological/oceanographic characteristics of the Saronic Gulf, in order to examine circulation patterns and predict sediment transport phenomena under high wave conditions at the coast of Varkiza, a sandy beach in the southern Attica, Greece. Time series of wind and wave data were used as input at the open boundaries of the model domain while the model was calibrated and validated through (linear and directional) statistical measures with respect to in situ wave measurements, since there was lack of hydrodynamic data at the site of interest. The simulation period of the model was between January 3 and February 19, 2013, with consecutive high waves in-between. The good agreement of the numerical results from the wave and hydrodynamic model with in situ measurements confirmed the suitability of the model for the support of sediment transport rates at Varkiza coastal segment. Model results reveal that there is a counter-clockwise water circulation during high waves that contribute to the erosion of the examined beach, which is also confirmed by independent field measurements.