Scouring of a sand bed in front of a vertical breakwater

The scouring profile of a bottom consisting of movable material as this is formed in front of a vertical wall under influence of the standing wave against this wall is discussed. The form of this profile is different for coarse and fine material. In the case of fine material this material is moved in suspension by the mass transport currents...

Concentration and flow velocity measurements in a local scour hole

Flume experiments with small Froude numbers have been carried out to study the concentration field in a local scour hole without supply of sediment load. The measuring results will be used to check the validity of the two dimensional scour model DUCT-SUSTRA. The objective of the experiments was to measure the concentrations at various locations...

Users manual: DUCT-SUSTRA

Some information is given how to use the scour model DUCT-SUSTRA (Hoffmans, 1991). The scour model predicts the morphological process in scour holes or trenches and consists of two separated sub-models: a flow model DUCT and a morphological model SUSTRA. The flow model is based on the equation of continuity and the momentum equations for...

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...

Ontgrondingen rond pijpleidingen op slibhoudend zand

Het transport en de erosie van mengsels van zand met 10 tot 30% slib is onderzocht. Zowel het transport in de algemene zin als de erosie rond pijpleidingen is in beschouwing genomen. De transport karakteristieken van zand waar zich slib in bevindt verschillen van die van zuiver zand. De critische bodemschuifspanning neemt toe voor een toenemend...

Migrating Pools in Yangtze River

The severity and location of bank erosion and bed scour changes with the variation of water level. At low flows, the main flow thread tends to follow the concave bank. As the discharge increases, the flow tends to cut across the convex bar, to concentrate against concave bank only downstream the bend apex. This change of flow pattern is...

Bowthruster-induced damage

The stability of stones in propeller-induced jet wash is still difficult to predict. Especially the trend of bowthrusters increasing in size and power in sea going ships (especially ferries) over the last years may be a reason for concern when dealing with the protection of slopes and beds. But also ships used in inland navigation are using...

The design and application of scour anticipated designs in river related and coastal structures in various countries and their effectiveness

Keynote lecture at the ICSE2006. Various types of scour can confront the engineer, who has to design and construct a hydraulic structure in a marine environment. The engineer is interested in the magnitude of the scour to be expected and its development in time. He hopes that such information, if at all available, is accurate and that he can...

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...

Uncertainties in the design of bed protections near quay walls

Design formulas for bed protections in the port of Rotterdam were investigated. Using depthsoundings, the actual level of stability of a quay wall can be compared with the design formulas. The loads on a bottom protection differ, because of diversity in shipping and tidal motion. Therefore a better comparison can be made by resembling the...

Scour around an offshore windturbine

During the construction of the first Dutch offshore wind farm prototype measurements were performed. These measurements were aimed to monitor the behaviour of the granular filter layer of the scour protection around the mono-piles upon which the wind turbines are founded. These measurements were compared to scale model test results and...

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...

Falling aprons at circular piers under currents

Traditional guidelines on rock protection at circular piers predominantly focus on preventing shear failure (by choosing a sufficiently large rock size), winnowing failure (by designing an appropriate filter) and edge failure (by selecting a sufficient extent). In particular areas (e.g. in an eroding river channel or in an area with large-scale...

Modelling Scour in Front of Dune Revetments in a Surf-beat Model

This paper presents adaptations to the XBeach model aimed at including the relevant processes for the generation of scour holes at the toe of a revetment. Dutch assessment rules for the safety of sea defenses need to be adjusted to cope with a combination of sandy dunes and hard elements. To that end, the XBeach model is prepared to be...