earth science

Rainbowing

Rainbowing is a earth science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Rainbowing rather than just read about it. In short: Rainbowing is the process in which a dredging ship propels sand that has been claimed from the ocean floor in a high arc to a particular location. This is used for multiple purposes, ranging from building up a beach to prevent erosion to constructing new islands.

Key takeaways

Rainbowing belongs to earth science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Rainbowing to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Rainbowing from memory before moving on to harder problems.

Reference excerpt

Rainbowing is the process in which a dredging ship propels sand that has been claimed from the ocean floor in a high arc to a particular location. This is used for multiple purposes, ranging from building up a beach to prevent erosion to constructing new islands. The name is derived from the appearance of the arc, which closely resembles a brown-colored rainbow. This technique was used extensively in the construction of the Palm Islands and The World, Dubai.

Process The process of rainbowing begins with the excavation of sediment, typically sand, from the seabed by a dredger. Dredgers excavate the sediment using mechanical or hydraulic methods or a combination of both. During the excavation process, large quantities of water are collected along with sediment creating a mixture called slurry. The slurry can then be utilised on-site or transported to where it will be deposited. The liquid characteristics of the slurry allow the dredger to transfer the slurry by ejecting it through the air in arcs.

Rainbowing nozzles The projection of slurry for beach nourishment and other dredging uses is achieved through the use of nozzles which affect the output and trajectory of the slurry. The diameter of the nozzle affects the output of the dredger and the distance that the slurry is projected. Smaller diameters, for instance, have less flow leading to lower hourly output, but are able to project the slurry over a further distance due to a higher exit velocity. Jumbo dredgers today can easily achieve distances in excess of 150 metres, but at the cost of 30% extra discharge time. Nozzles that are angled 30° from the horizontal are standard. Although 45° nozzle angles achieve longer distances from a ballistics perspective, 45° nozzles have been observed to create large craters. In addition, a high amount of sand flows back towards the dredger. 30° nozzles instead project the sand with a flatter trajectory, minimizing back flow while achieving a final distance comparable to that reached by a 45° nozzle. Other methods of disposing and transferring the slurry include pumping the slurry through pipelines or using natural forces such as wave currents.

Advantages Since rainbowing transfers material by ejecting it through the air, the technique is useful for reclaiming areas that are too shallow for direct placement. In addition, rainbowing allows the dredger to dispose excavated sediment on-site. This is useful for dredging operations such as creating trenches since the dredger can simply cast the excavated sediment to the side as opposed to spending time dumping or transporting the collected sediment. This allows for a continuous trenching operation.

Environmental impact Rainbowing, along with other dredging and reclamation methods, has various effects on the environment apart from vastly changing its geographical structure. Throughout the dredging and nourishment process, plumes of fine sediment, which can take longer to settle, can remain suspended in the water for long periods of time. These clouds of fine sediment can have adverse effects on the ecosystem, asphyxiating fish and other fauna as well as blocking sunlight. As organisms die, the water becomes toxic as decomposed organic materials raise hydrogen sulfide levels. In such cases, it is often impossible for an ecosystem to revive. It often takes a couple years for the ecosystem to recover, when recovery does occur. In addition, coral can be removed or become buried by the sediment.

References

External links https://web.archive.org/web/20061117204621/http://channel.nationalgeographic.com/channel/totalmegastructures/photogallery_rainbowing_island.html http://www.accessmylibrary.com/premium/0286/0286-11654915.html

Illustrations

Worked examples

Example 1 — a first encounter with Rainbowing

Start with the simplest possible case. Write down what Rainbowing claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In earth science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Rainbowing before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Rainbowing ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Rainbowing

In research: Rainbowing appears in earth science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Rainbowing in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Rainbowing is common in secondary-school and first-year university syllabi. It links to neighbouring topics Coastal construction, Ocean pollution, so understanding it makes those chapters shorter.
In everyday life: Look for Rainbowing outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Rainbowing in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Rainbowing means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Rainbowing out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Rainbowing in simple terms?

Why does Rainbowing matter?

Because it connects several earth science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Rainbowing?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Rainbowing.