Thursday, July 30, 2015

You're Looking Mighty FINE with a "mudstache".

Hjustrom Diagram:

Hi, Brooke here!

While we are snorkeling in the rivers we often grow a “mudstache” throughout the search. These fashionable features are due to the sediment flowing through the river. The interaction between the velocity of water and the sediment flowing in it is an important one! The energy (determined by the velocity) of the river, determines how much sediment is entrained and suspended - with more sediment suspended, the greater the “mudstaches” we get.

There are two important diagrams that show the relationship between sediment size and energy of the river system.

One is The Hjulström Diagram below shows the relationship of sediment diameter versus water velocity - showing what speed a particle is in transport, being eroded and deposited.   

Another is Shield's diagram. Put simply, this diagram shows at what shear stress is particle is likely to be entrained (or move along the bed or in suspension).


There are three categories of sediment transport; the wash load, suspended load and bedload.

The wash load of a river is the sediment/debris in the river that is carried by the water near the surface. Usually it will not ever deposit.

The suspended load is the sediment that settles very slow, so slow that it also may never touch the bed of the river. It is upheld by turbulence - and is what causes us to get our great five o’clock shadows.

The bedload of a river is the sediment that is transported along the bed. This transport occurs through the saltation, rolling and sliding of the sediment. Saltation is jumping along of a particle along the bed - rolling and sliding are pretty intuitive.


Unfortunately we do not have any images of us with our fancy-staches, but instead is here a picture of Maya as a burrito! We call this a burrito because we wrap ourselves up in a tarp to keep the car somewhat dry when driving from site to site!


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