scholarly journals DESTRUCTIVE WAVE OVERTOPPING AND WAVE RUN-UP TESTS ON GRASS COVERED SLOPES OF REAL DIKES

2012 ◽  
Vol 1 (33) ◽  
pp. 64
Author(s):  
Gosse Jan Steendam ◽  
Yvo Provoost ◽  
Jentsje Van der Meer
Keyword(s):  
The Netherlands ◽  
Pilot Test ◽  
Grass Cover ◽  
New Wave ◽  
Wave Overtopping ◽  
Erosion Stability ◽  
Sand Core ◽  
Run Up ◽  
First Time ◽  
Upper Slope

In March 2011 new wave overtopping tests have been performed in the Netherlands. In contrast to previous tests the grass cover of this dike was not maintained well, which had significant effect on erosion stability. Additionally, for the first time a pilot test has been made on wave run-up from an asphalt berm onto the grass covered upper slope of the dike. The tested dike sections had a sand core covered by a layer of clay and a grass cover. The objective was to test the erosion stability of seaward and landward slopes for wave overtopping as well as wave run-up. For the wave overtopping also the influence on erodibility of the grass cover caused by obstacles or other elements, which may be present at dikes (stairs, fences), was investigated.

scholarly journals DESTRUCTIVE WAVE OVERTOPPING TESTS ON GRASS COVERED LANDWARD SLOPES OF DIKES AND TRANSITIONS TO BERMS

2011 ◽  
Vol 1 (32) ◽  
pp. 8 ◽  
Author(s):  
Gosse Jan Steendam ◽  
Jentsje W. Van der Meer ◽  
Bianca Hardeman ◽  
André Van Hoven
Keyword(s):  
The Netherlands ◽  
Grass Cover ◽  
Wave Overtopping ◽  
Sand Core ◽  
Boulder Clay ◽  
River Dike

In 2009 tests have been performed at the Afsluitdijk, the closure dike of Lake IJssel in the Netherlands. This dike has a sand core covered by layers of clay and boulder clay, and a grass cover. In 2010 succeeding tests were performed at a river dike near Zwolle. This dike was a sand dike with a grass cover. In all of these tests research was performed on the behaviour of the grass cover on the landward slope of the dikes. Furthermore, the influence on erodibility of the grass cover caused by damage of the grass cover by mice, moles or other influences like tractor tracks were investigated. Also the influence of obstacles or other elements, which may be present at dikes, was part of the investigations (tree, stairs, fence, maintenance road). It was observed that all of these influences are to some extent contributing to a decrease of the resistance against failure.

scholarly journals WAVE RUN-UP SIMULATIONS ON REAL DIKES

2017 ◽  
pp. 42
Author(s):  
Gosse Jan Steendam ◽  
Jentsje Wouter Van der Meer ◽  
Andre Van Hoven ◽  
Astrid Labrujere
Keyword(s):  
Critical Velocity ◽  
New Technique ◽  
Grass Cover ◽  
Clay Layer ◽  
New Wave ◽  
Wave Overtopping ◽  
New Device ◽  
Hydraulic Load ◽  
A New Technique ◽  
Run Up

A new Wave Run-up Simulator has been designed, constructed, calibrated and used for testing of the seaward face of dikes. The upper part of dikes or levees often have a clay layer with a grass cover. The new device is able to test the strength of the grass cover under simulation of up-rushing waves for pre-defined storm conditions. The cumulative overload method has been developed to describe the strength of grass covers on the crest and landward side of dikes, for overtopping wave volumes. In essence there is not a lot of difference between the hydraulic load from an overtopping wave volume or from an up-rushing wave. Therefore the hypothesis has been evaluated that the cumulative overload method should also be applicable for up-rushing waves. Tests on a real dike have been used to validate this hypothesis. The main conclusions are that the new Wave Overtopping Simulator works really well, but that the results on testing till so far has not yet been sufficient for a full validation of the method. More research is required. Furthermore, a new technique has been developed to measure the strength of a grass sod on a dike: the grass pulling device. Tests with this device showed that it is possible to measure the critical velocity (= strength) of a grass cover, which is much easier than performing tests with a Wave Run-up or Overtopping Simulator.

scholarly journals THE WAVE RUN-UP SIMULATOR, THEORY AND FIRST PILOT TEST

2012 ◽  
Vol 1 (33) ◽  
pp. 65 ◽  
Author(s):  
Jentsje Van der Meer ◽  
Yvo Provoost ◽  
Gosse Jan Steendam
Keyword(s):  
Prediction Method ◽  
Pilot Test ◽  
Wave Overtopping ◽  
Run Up

The idea of the Wave Run-up Simulator is based on the experiences with the Wave Overtopping Simulator. It is possible to simulate wave tongues overtopping a dike crest in reality. It must also be possible to simulate waves in the run-up and run-down zone of the seaward slope. This is the zone after waves have broken and when they rush-up the slope. The present paper describes this new idea of the Wave Run-up Simulator, why it is useful to develop the machine, to perform research with it and to develop a prediction method for slope strength. In fact, a prediction method can already be developed from the Cumulative Overload Method, which was developed on the basis of results with the Wave Overtopping Simulator, see Van der Meer et al. (2010). It also means that tests on the seaward slope will be done for validation purposes only. The paper describes in detail what is known about the movement of waves in this run-up zone and what actually the Wave Run-up Simulator has to simulate. Not a lot of research has been performed to describe the wave run-up process in detail, physically nor statistically. Finally, the pilot test has been described including hydraulic measurements on the slope.

DEVELOPMENT OF NEW WAVE OVERTOPPING MODELS FOR SEAWALLS WITH WAVE ABSORBING BLOCKS AND SLOPED SEAWALLS

2019 ◽  
Vol 75 (2) ◽  
pp. I_721-I_726
Author(s):  
Naoto HIGUCHI ◽  
Yoji TANAKA ◽  
Katsuyuki SUZUYAMA ◽  
Hidenori SHIBAKI
Keyword(s):  
New Wave ◽  
Wave Overtopping

scholarly journals A Meningo-Leucoencephalomyelitis Resembling Visna in Dutch Zwoeger Sheep

1966 ◽  
Vol 3 (5) ◽  
pp. 401-411 ◽  
Author(s):  
A. A. Ressang ◽  
F. C. Stam ◽  
G. F. De Boer
Keyword(s):  
White Matter ◽  
The Netherlands ◽  
Final Stage ◽  
Chronic Condition ◽  
Cerebral Lesions ◽  
Terminal Stage ◽  
Icelandic Sheep ◽  
Close Relationship ◽  
Secondary Demyelination ◽  
First Time

Zwoegerziekte is a disease in Dutch sheep which morphologically closely resembles an Icelandic sheep disease, Maedi2. Chronic lung affection and emaciation are the principal symptoms of both diseases. Visna is another chronic condition in Icelandic sheep affecting mainly the C.N.S. A virus has been isolated from sheep affected with Maedi or Visna and a close relationship in properties has been found between both viruses. In two Dutch sheep autopsied in the final stage of Zwoegerziekte, lesions were present in the C.N.S., which histologically resembled those in Visna. Another sheep slaughtered at the municipal abattoir, with lung lesions characteristic for the terminal stage of Zwoegerziekte, exhibited early cerebral lesions resembling Visna. The lesions in the C.N.S. of these three sheep were meningitis and severe encephalomyelitis of the glial type affecting the white matter. Secondary demyelination was striking. Though Zwoegerziekte has been known for several decades in the Netherlands, the accompanying C.N.S. lesions are described for the first time.

De windmolen

2020 ◽  
Vol 5 (1) ◽  
pp. 17-32
Author(s):  
JOS BAZELMANS
Keyword(s):  
The Netherlands ◽  
19Th Century ◽  
Turn Of The Century ◽  
The 19Th Century ◽  
First Time ◽  
At Home

The windmill. The origins of a Dutch icon The windmill is an icon of the Netherlands. But when did this instrument acquire this symbolic role at home and abroad? After all, mills are also common outside of the Netherlands. In this essay, it is argued that during the second half of the 19th century, foreigners systematically identified the Netherlands and the windmill for the first time. More than in other countries, there was a varied use of mills in the Netherlands, large and robust mills and clusters of industrial mills. Within the Netherlands itself, development towards an iconic position is only visible around the turn of the century when the mill turned out to be a plus in tourist recruitment abroad and when mills were slowly disappearing from the landscape.

scholarly journals PHYSICAL MODEL TESTS ON WAVE OVERTOPPING AND FLOW PROCESSES ON DIKE CRESTS INFLUENCED BY WAVE-CURRENT INTERACTION

2012 ◽  
Vol 1 (33) ◽  
pp. 34 ◽  
Author(s):  
Stefanie Lorke ◽  
Babette Scheres ◽  
Holger Schüttrumpf ◽  
Antje Bornschein ◽  
Reinhard Pohl
Keyword(s):  
Physical Model ◽  
Model Tests ◽  
Longshore Current ◽  
Wind Fields ◽  
Incoming Wave ◽  
Wave Overtopping ◽  
Improve Design ◽  
Physical Model Tests ◽  
Flow Processes ◽  
Run Up

Flow processes like flow depths and flow velocities give important information about erosion and infiltration processes, which can lead to an unstable dike structure and consequently to dike failure. Up to now several physical model tests on wave run-up and wave overtopping are available to adjust and improve design formula for different dike structures. This kind of physical model tests have been performed in the here presented project FlowDike. Its main purpose is to consider two new aspects that could influence the assessment of wave run-up and wave overtopping as well as the flow processes on dikes which have not been investigated yet: longshore current and wind. Especially in estuaries and along coasts, the effect of tidal and storm induced currents combined with local wind fields can influence the incoming wave parameters at the dike toe as well as the wave run-up height, the wave overtopping rate and the flow processes on dikes. This paper will focus on these flow processes on dike slopes and dike crests on an 1:6 sloped dike influenced by oblique wave attack and longshore current.

Taxonomic notes on Dutch desmids VI (Streptophyta, Desmidiales): new species, newly described zygospores

Phytotaxa ◽  
2014 ◽  
Vol 166 (4) ◽  
pp. 285 ◽  
Author(s):  
MARIEN VAN WESTEN ◽  
PETER COESEL
Keyword(s):  
New Species ◽  
The Netherlands ◽  
Rare Species ◽  
First Time

From the Netherlands, three desmid species are newly described to science: Actinotaenium spinosporum (with zygospores), Staurastrum brachiatoides (with zygospores) and Staurastrum quadriradiatum. In addition to that, zygospores of the rather rare species Staurastrum echinatum are described for the first time. Differences with similar-looking species are discussed.

scholarly journals Changes in cannabis potency and first-time admissions to drug treatment: a 16-year study in the Netherlands

2018 ◽  
Vol 48 (14) ◽  
pp. 2346-2352 ◽  
Author(s):  
Tom P. Freeman ◽  
Peggy van der Pol ◽  
Wil Kuijpers ◽  
Jeroen Wisselink ◽  
Ravi K. Das ◽  
...  
Keyword(s):  
The Netherlands ◽  
Drug Treatment ◽  
Time Dependent ◽  
Time Lags ◽  
Linear Regression Models ◽  
Treatment Data ◽  
Treatment Entry ◽  
Positive Time ◽  
First Time ◽  
Ongoing Monitoring

AbstractBackgroundThe number of people entering specialist drug treatment for cannabis problems has increased considerably in recent years. The reasons for this are unclear, but rising cannabis potency could be a contributing factor.MethodsCannabis potency data were obtained from an ongoing monitoring programme in the Netherlands. We analysed concentrations of δ-9-tetrahydrocannabinol (THC) from the most popular variety of domestic herbal cannabis sold in each retail outlet (2000–2015). Mixed effects linear regression models examined time-dependent associations between THC and first-time cannabis admissions to specialist drug treatment. Candidate time lags were 0–10 years, based on normative European drug treatment data.ResultsTHC increased from a mean (95% CI) of 8.62 (7.97–9.27) to 20.38 (19.09–21.67) from 2000 to 2004 and then decreased to 15.31 (14.24–16.38) in 2015. First-time cannabis admissions (per 100 000 inhabitants) rose from 7.08 to 26.36 from 2000 to 2010, and then decreased to 19.82 in 2015. THC was positively associated with treatment entry at lags of 0–9 years, with the strongest association at 5 years, b = 0.370 (0.317–0.424), p < 0.0001. After adjusting for age, sex and non-cannabis drug treatment admissions, these positive associations were attenuated but remained statistically significant at lags of 5–7 years and were again strongest at 5 years, b = 0.082 (0.052–0.111), p < 0.0001.ConclusionsIn this 16-year observational study, we found positive time-dependent associations between changes in cannabis potency and first-time cannabis admissions to drug treatment. These associations are biologically plausible, but their strength after adjustment suggests that other factors are also important.

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