Chapter 9 Study Guide

How important is water for sculpting the land surface?

Extremely Important

Aside from artificial levees, how does human activity increase the frequency and severity of floods?

Human activities that degrade the environment often increase flooding. An example of an activity that will increase frequency and severity of floods is deforestation.

The circulation of the Earth's water supply is called

Hydraulic Cycle

Most water evaporates from the (oceans, land). Most precipitation falls on the (oceans, land).

Land

Evaporation

The change of state from a liquid to a gas

Where in a stream channel is velocity the highest? The lowest?

The middle of the stream. Lowest all along the banks and at the bottom

How does discharge usually change down the length of a stream? Explain. What happens to the velocity, width and depth as a result? Name one river that violates this trend and tell why.

The shape of the channel is important because of the reduction in velocity due to friction along the channel margins. In a natural situation, an increase in discharge will result in all three parameters.

Explain/describe how streams evolve over time from having narrow valleys to having wide floodplains.

The young stage rivers cut V shaped valleys. Downcutting and headward erosion are the major processes of river erosion. Meandering however makes the water shift from side to side rather than downward which creates a wide floodplain

What are artificial levees? Why are they built? What are the consequences?

They prevent rivers from flooding cities in a storm surge.

Land areas evaporate (more, less) water than falls as precipitation. Return of water to the atmosphere from land is actually a combination of two processes:

Transpiration and Evaporation

oxbow lake

a curved lake that is created when a stream cuts off a meander

meander

a loop like bend in the course of a stream

competence

a measure of the largest particle a stream can transport; a factor dependent on velocity

tribituary

a river or stream flowing into a larger river or lake.

Distributary

a section of a stream that leaves the main flow

delta

an accumulation of sediment formed where a stream enters a lake or an ocean

levee

an embankment built to prevent the overflow of a river

Divide

an imaginary line that separates the drainage of two streams, often found along a ridge

bar

common term for sand and gravel deposits in a stream channel

turbulent flow

erratic movement of water often characterized by swirling, whirlpool-like eddies

bed load

sediment moved along the bottom of a stream by moving water, or particles moved along the ground surface by wind

cut bank

the area of active erosion on the outside of a meander

sorting

the degree if similarity in particle size in sediment or sedimentary rocks

suspended load

the fine sediment carried within the body of flowing water

Floodplain

the flat, low-lying portion of a stream valley subject to periodic inundation

drainage basin

the land area that contributes water to a stream

base level

the level below which a stream cannot erode

Infiltration

the movement of surface water into rock or soil through cracks and pore spaces

laminar flow

the movement of water particles in straight-line paths that are parallel to the channel

dissolved load

the portion of a stream's load that is carried in solution

discharge

the quantity of water in a stream that passes a given point in a period of time

Transpiration

the release of water vapor to the atmosphere by plants

Gradient

the slope of a stream, generally expressed as the vertical drop over a fixed distance

capacity

the total amount of sediment that a stream is able to transport

hydrologic cycle

the unending circulation of earth's water supply.

Alluvium

unconsolidated sediment deposited by a stream

runoff

water that flows over land rather than infiltrating into the ground

downcutting

when a river erodes downward through its bed

Approximately what percentage of water is in the oceans?

97%

point bar

A crescent-shaped deposit of sediment on the inside bank of a meander

alluvial fan

A fan-shaped deposit of sediment formed when a stream's slope is abruptly reduced

Name five of the top ten rivers in the world as far as discharge goes.

Amazon River, Congo River, Orinoco River, Yangtze River, Rio Negro River

What river has by far the highest discharge in the world? Where is it?

Amazon River, South America

How does "roughness" of the channel influence velocity?

An increase in roughness will decrease the channel velocity

What does meandering refer to in a stream? What is an oxbow lake? How does one form? Is this a feature of a young, mature or old system?

Meandering refers to bends or curves in the river. An oxbow lake is a curved lake that is created when a stream cuts off a meander. The shape of the meander may grow more exaggerated until it loops back on itself. This is a feature of a mature system

What river in the USA has the highest discharge?

Mississippi River

What channel shape promotes the highest velocity? The lowest velocity?

Narrow, deep, smooth, and semicircular channel. A shallow channel will have lower velocity cause there is more friction.

What is the longest river in the world?

Nile River

When a stream bends, where is velocity highest? Lowest?

Outside of the channel. Lowest on the inside of the channel

What three factors contribute to determining stream velocity?

Shape of the channel, volume of water, and slope of the river