formerlyanonymous_

formerlyanonymous_ OP t1_jdi7ge8 wrote

Reply to comment by zorokash in Santa must have been really unreliable at deliveries prior to cartoons. Almost every cartoon character has had to help him at least once over the last 70 years. by formerlyanonymous_

No this has everything to do with kids cartoons having at least one dedicated christmas episode where the main character has to help Santa because some sort of catastrophe. His rates of catastrophe since the start of childrens' cartoons is extremely high. How on earth could he ever have succeeded when he's clearly relying on great logisticians such as Sponge Bob Squarepants or the Flintstones?

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formerlyanonymous_ t1_jbg8bfs wrote

Reply to comment by Friedumb in When a river floods after a rainstorm, does it flow slower or faster? by Chiraqiian

You're correct for the most part. Turbulence mixing can create localized areas of high velocity, but the free surface (more specifically, just below the free surface) is the highest average flow due to lack of friction.

Normally if you're seeing large current, the top will be reflective of that, with chops, waves, or dune/anti-dune shape.

And stream characterization does play a role, however very difficult to define accurately. My comment above was more related to sediment characteristics, but very much a braided gravel bed is going to be different than a braided river delta than a singular sand bed.

As far as braided being lower, that depends a lot on topography. You may see those with lower depth but higher velocity. Those braids exist partially from the large tractive forces cutting paths through the floodplain. They typically have larger sediment (gravel, cobble, boulders) that may also add friction. Sand braided rivers typically have fewer paths because the braids can cut deeper more easily, creating a greater cross sectional area to balance the increase in flow.

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formerlyanonymous_ t1_jairoz8 wrote

Reply to comment by coffeeeedrinker in When a river floods after a rainstorm, does it flow slower or faster? by Chiraqiian

There is increases in sediment load with increased water depth and hydraulic gradient (2 of the 3 major components to shear stress at the channel bottom), but that suspended sediment is marginally going to affect water velocity, and in ways that are terribly difficult to quantify. Larger waterborne debris could have a larger effect as trees or boulders deposit temporarily causing local scour or eddy currents.

Bed characteristics such as sediment type can be an identifier of what roughness (ie friction) the water will face at the boundary. The scoured bottom, a function of grain size, may also have localized effects to velocity, similar to the debris mentioned above. Small pockets form holes or preferred paths along the bed.

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formerlyanonymous_ t1_jaibldu wrote

Reply to When a river floods after a rainstorm, does it flow slower or faster? by Chiraqiian

Depends how you're measuring and where in the cross section. Assuming no tailwater downstream, you'll see an increase in velocity in the main channel/floodway. As water levels increase upstream, your hydraulic gradient increases, and per Mannings equation, increases your velocity.

In the wider floodplain, water will typically be mostly stagnant as more trees, vegetation, and buildings increase the Mannings roughness.

Therefore, average velocity of the entire cross section could be significantly slower if the floodplain is significantly wide.

Tailwater effects also play a significant role. If your downstream water is high, say due to flooding downstream or a reservoir, the main channel may not actually increase much at all until the downstream levels recede. You see this often near deltas where storm surge or tides provide resistance to flow coming off fairly flat topography.

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