What is a river strainer?

Answer 1

Strainers are formed when an object blocks the passage of larger objects but allows the flow of water to continue - like a big food strainer or colander. These objects can be very dangerous, because the force of the water will pin an object or body against the strainer and then pile up, pushing it down under water. Strainers are formed by many different objects, like storm grates over tunnels, trees that have fallen into a river ("log jam"), bushes by the side of the river that are flooded during high water, or rebar from broken concrete structures in the water. In an emergency it is often best to try and climb on top of a strainer so as not to be pinned against the object under the water. If you are in a river, swimming aggressively away from the strainer and into the main channel is your best bet. If you cannot avoid the strainer, you should swim hard towards it and try to get as much of your body up and over it as possible.

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Answer 2

Mechanical or electrical?

By imposing electrical signals (short high impulse energy peaks), barriers can be constructed to keep fish and other vertebrates from passing the barrier. These are common to prevent non-native species from moving upstream into sensitive native habitat.

Mechanical strainers are things like log booms or oil booms, device that float of the water to prevent material from moving downstream with the flow of water. And, if we think back to a few years ago, strainers - more like seines - were used to catch fish.

Answer 3

an ocean, because it sorta empties it out.