Why do our rivers wind lazily back and forth instead of a flowing in a straight line.?

Answer 1

The winding nature of many river channels is called meandering, also referred to as sinuosity. The sinuosity of a river is not just the result of water taking the easiest path. There are many internal and external factors that determine the overall channel pattern. To some extent there is still debate within the science about what factors are most important. There are mathematical formulas that can be used to compare different rivers, but they are not quite good enough to actually explain all the variables yet.

If you look at a map you will see that the sinuosity of a river has a predictable wavelength (length of a full turn) and amplitude (width of a meander across the river flood plain), so it is clearly not a random process. One useful formula that relates the bankfull discharge of a river to its meander wavelength is the following:

Length of meander=L
Bankfull discharge (volume of the river)= Qb

L=54.3 (square root of Qb)

The factors that affect the size of meanders that are external to the river are things like the type and density of vegetation along the river bank, the type of material in the river bed and bank, the overall volume and variability of the river volume, and the overall gradient of the river. The higher the gradient the less likely a river will meander. Rivers that meander widely are typically flowing across a river-deposited flood plain of sand, silt and clay materials, but because these materials are not always deposited evenly the inconsistency will affect the river channel migration. Along many meandering rivers there are forests growing, and as trees fall into the rivers they can have major effects on the current flow.

The internal factors probably have much more to do with the strong tendency of rivers to meander (at least that is my opinion) and create the regularity of meanders. Small oscillations within flowing water creates alternating bed profiles along the length of most rivers. These alternating bed profiles correspond to higher and lower gradients resulting in faster and slower speeds of flow. These two bed profiles are known as riffles and pools. The riffles are typically spaced about 5-7 times the width of the river apart, along the length of the river and usually have bottom sediments of the largest size found in the river (more gravel, cobbles, etc). Turbulence in the river created by these variations in the bottom of the river creates cyclone-like spirals of water that will both erode the bottoms of pools and when they diverge they will build bars and riffles in the middle of the channel.

This internal turbulence also causes bank erosion, and once it begins it is self-perpetuating. As the meander begins to form, the water moving along the outside of the meander actually piles up, causing more bank erosion, and the higher speed of the water along the outside of the meander also allows the water to erode and carry more material. Meanwhile, the inside of the meander is the slowest moving water and will deposit material, building a sand bar, also called a point bar.

The meanders eventually reach a limit of size (amplitude) either when they encounter the edge of the flood plain and bedrock, or when they get so wide they begin to intersect each other. As this happens the river will cut them off forming an oxbow. Other times at flood stage a river will scour away the point bars and abandon its own meanders until flow returns to normal and the process of building meanders starts anew.

Here is a good resource with some illustrations of the process:
http://www.ucpress.edu/books/pages/6664/6664.ch04.html

Answer 2

Water will always take a path of least resistance.

It flows around objects or areas that it can not flow through.

For instance, it will not go uphill due to the force of gravity. Rather, it will take the path around a hill instead.

When a river winds "lazily" back & forth, this is referred to as a meander.

River paths are not constant but move according to changes in elevation, the amount of sediment deposited in its bed & its velocity.

Sometimes a meander is cut off and an oxbow lake is created. The name comes from the shape being something like a "U".

This cutoff is the direct result of water taking the 'path of least resistance'. When the meander can no longer take the amount of water surging through the river (for whatever reason) it will begin to cut off the meander and take a more direct 'straight line' path.

Answer 3

Not an easy one to do in 1 paragragh. You're describing MEANDERING which is done by mature rivers on flat ground. Young water ways have narrower channels & faster flows and generally go straighter given simular topo and other conditions. One of the easiest answers is erosion over time since a river curve will erode faster on the inside of the curve due to flow differences or ground/rock deposits. Where the flow is slower sediment is deposited and so the water course wanders around very slowly. High to low flows like mountain courses don't meander as much.

Answer 4

Its the most efficient form of energy use in flatlands. The outside curve gets eroded and the lee of the inside curve gets deposition so the entire thing moves downstream over a period of time. I forgot the math but its a modified sine wave

Answer 5

It is becoz water has a property that makes it flow from a higher region to a lower region. if in its path there is any block, then it is going to select a route to go round the block or if the region to any side of the block is a low region then it flows in it and forms a path.

Answer 6

Tosh is not gay, though he likes to do weird stuff on his show, most likely to keep people guessing in order to stay relevant. The comedy business can be short-lived unless you can find creative way to keep people interested. I seen perform at the Improv about 7 years ago before he has famous, and even then, there was nothing about him to set off a gaydar.

Answer 7

Its nature designed to slow the flow of water.

Answer 8

because they are older wider with less force newer younger rivers flow more straight

Answer 9

That's a good question, I was wondering the same thing myself

Answer 10

They meander because they are guided by the topography.