A New Symmetrical Unit for Breakwater Armour: First Tests

A new and symmetrical single layer armour unit, the crablock, has been designed in the UAE. One breakwater was reconstructed with crablock, but very limited testing had been performed. Just to become more acquainted with this new unit, pre-competitive research at a university has been performed, which is the subject of this paper. Being a new...

Wave overtopping simulator tests on Vietnamese sea dikes

Little is known about the strength of the land-side slopes of the Vietnamese sea dikes under overtopping attack. Some grass-covered slopes were tested by a wave overtopping simulator. The paper describes the simulator and presents the test results. The tested grass covers could withstand overtopping rates varying from 20 l/s to 100 l/s per meter...

Waardevolle lessen na overstromingen in Thailand

Een verkenningsmissie na de overstromingen in Thailand in 2011 heeft meer inzicht gegeven in het functioneren van het waterkeringssysteem tijdens de ramp. Dijken bleken kwetsbaar door overloop, evenals de aansluitingen tussen dijken en constructies.

Notional Permeability

Different layer design of a rock slope and under layers has a large effect on the strengths on the rock slope itself. In the stability formula developed of VAN DER MEER [1988] this effect is represented by the term Notional Permeability with symbol P. A more open, or permeable, structure underneath the armour layer has the ability to dissipate...

Strength of the landward slopes of sea dikes in Vietnam

The landware slopes of sea dikes in the north of Vietnam are steep and solely constructed by soil covered with grass due to the budget constraints and also the out-of-date design guidelines.The resistance against erosion due to wave overtopping of several grass covered slopes were tested with the Wave Overtopping Simulator to show if a slope...

Wave overtopping resistance of grassed slopes in Viet Nam

The Simulator was applied to test the resistance against wave overtopping of grass covered dike slopes in Viet Nam. Observation and measurement during destructive tests were performed to investigate the development process of damage induced by overtopping flow. Damages were likely to be initiated at transition of either geometry or materials, at...

Numerical simulations of upstream and downstream overdeepening

Local geometrical perturbations of alluvial channels can generate a pattern of non-migrating bars and pools. This phenomenon is known as “overdeepening”, because the pools locally enhance the scour in river bends. Overdeepening occurs only downstream of a perturbation if the channel is in the subresonant and subcritically damped regime, which...

Wave overtopping resistance of grassed dike slopes in Vietnam

The resistance of various grassed slopes against wave overtopping has been appraised by means of the Wave Overtopping Simulator in situ for a couple of years in Viet Nam. Destructive test results show that a dike slope covered with grass could suffer a certain overtopping discharge not smaller than 20 l/s per m. During testing it was difficult...

Flow depths and velocities at crest and landward slope of a dike, in theory and with the wave overtopping simulator

Wave overtopping discharges at coastal structures are well described in the EurOtop Manual (2007), including the distribution of overtopping wave volumes. Each volume that overtops a dike or levee will have a certain flow velocity and depth record in time, often given by the maximum velocity and flow depth. This paper describes some further...

Wave overtopping simulator tests in Vietnam

Sea dikes in Viet Nam have been built up during a long history. Every year, about 4 to 6 storms attack the coast and cause severe damages of the sea dikes. Till now, little is known about strength and stability of the inner slope covered with grass under impacts of wave overtopping during storm surges. Destructive tests have been performed with...

Individual overtopping events at dikes

Recently, formulae have been derived for maximum flow depths and velocities on the crest and inner slope of dikes or levees at wave overtopping. Two independent physical model test programs in different wave flumes showed, however, a large difference in the results. The present paper clarifies this discrepancy and shows that the empirical...

Wave transmission at low-crested structures using neural networks

The European Union funded project DELOS was focused on wave transmission and an extensive database on low-crested rubble mound structures was generated. During DELOS, new empirical wave transmission formulae were derived. These formulae still showed a considerable scatter due to a limited number of parameters included. Neural networks based on a...

Stabiliteitsfactor en kans op afschuiven van grondlichamen

In de ontwerppraktijk wordt de stabiliteit van grondlichamen onderzocht m.b.v. een glijvlakanalyse. Bij zo'n analyse wordt verondersteld, dat een deel van het grondlichaam over een bepaald vlak kan afglijden. Er worden zekere vooronderstellingen omtrent de vorm van dat vlak gemaakt, d.w.z. dat het een plat vlak is, of een cirkelcilinder, etc....

Het opkomen van den waterstaat als taak van het landsbestuur in de Republiek der Vereenigde Provincien

Beschrijving van de opkomst van de waterschappen, hoogheemraadscahppen, heemraadschappen en polderdistricten in de Nederlanden in de 16e en 17e eeuw. Beschrijving van de situatie in de afzonderlijke provincien. De regeling van de financien van de waterstaat. Aandacht voor interprovinciale belangen