Physical modelling of san-filled geosystems for coastal protection

Unidirectional irregular waves of varying significant wave-height and peak period but with a constant spectral shape (JONSWAP spectrum, ?=3.3) were generated over a sandy 3:20 sloped plane beach to investigate scour fronting a dune erosion control system constructed from geotextiles, slope inclined at 45º. Both passive (i.e., three dune erosion...

Jet scour

This paper discusses scour without bed protection, such as propeller scour, two-dimensional horizontal, three-dimensional horizontal scour generated by free jets downstream of gates and outlets, two-dimensional vertical and three-dimensional vertical scour. The flow velocities in two- and three-dimensional propeller and free jets are briefly...

Breach growth in clay-dikes

Numerous flood disasters occur every year worldwide, mostly resulting from failure of dikes, some with catastrophic outcomes. Examples are the dike failures along the Yangtze River in China in 1931 due to heavy rainstorms and those in the Netherlands in 1953 due to a storm surge at the North Sea. Both floods induced many deaths and enormous...

Ontgrondingen rondom brugpijlers en aan de kop van kribben

Het doel van het handboek ontgrondingen is een antwoord te geven op ontgrondingsvraagstukken zoals een ontwerper van waterbouwkundige constructies die tegenkomt. Verschillende deelstudies worden voor het afronden van dit handboek uitgevoerd. Het verifiëren van ontgrondingsformuies staat centraal in deze studies. Hier is de voorspellingskracht...

A hydraulic and morphologic criterion for upstram slopes in local-scour holes

Scour is a natural phenomenon caused by the flow of water in rivers and streams. Scour occurs naturally as part of the morphological changes of rivers and as result of structures man-made. Several types of scour can be distinghuished. Experience has shown that due to sand or flow slides or micro instabilities at the end of the bed protection,...

A study concerning the influence of the relative local turbulence on local-scour holes

Scour is the lowering of the sea or river-bed as a result of non-equilibrium sediment transport conditions and can be divided into several categories (Breusers and Raudkivi, 1991). Local scour, which may occur at the base of a structure because of the affected flow pattern, can severely endanger the stability of this structure. Many varieties of...

The influence of upstram turbulence on local-scour holes

Excessive local scour can progressively undermine the foundation of a structure. Because complete protection against scour is too expensive generally, the maximum scour-depth and the upstream slope of the scour hole have to be predicted to minimize the risk of failure. In 1961 a systematical research 'tY'ith respect to scour holes started in the...

Seabed scour by currents near platforms

The gravity platforms in the North Sea, sitting directly on granular seabeds, may be undercut by scour and need scour protection. Conventional methods of protections are developed for structures 1or 2 orders of magnitude smaller and seem unnecessarily conservative when scaled to these larger sizes. The reason is that some of the flow details...

Systematisch onderzoek naar twee en drie dimensionale ontgrondingen

Samenvattend rapport van alle twee- en drie dimensionale ontgrondingsonderzoeken uit de periode 1960-1970 bij het Waterloopkundig Laboratorium in opdracht van Rijkswaterstaat. De informatie uit de onderzoeken M648 en M863 zijn in deze rapporten samengevat, evenals de resultaten uit M847. (3 delen).

Time scale of two dimensional local scour

The time scale of local scour is of importance in many model studies of practical problems. The use of a time scale is justified by the similarity in experimental scouring holes under different conditions. A time scale is derived from experiments with a wide range of length scales, velocity scales and material scales. The influence of velocity...