The Force of Moving WaterChapter 8 Section 3

Work and EnergyEnergy- the ability to do work or cause changePotential energy- energy that is stored and waiting to

be used laterKinetic energy- the energy an object has due to its

motionAs gravity pulls water down a slope, the water’s

potential energy changes to kinetic energy that can do work

Energy is transferred from one object to another (water to mills; kinetic to mechanical)

Kinetic energy of a river also moves sediment and erodes banks and valleys

How Water Erodes and Carries SedimentDuring water erosion, water moves sediment

including soil, rock, clay, and sandMost sediment washes into rivers as a result of

mass movement and runoffOther sediment erodes from the bottom or sides of

the riverAbrasion- the wearing away of rock by a grinding

action that occurs when particles of sediment in flowing water bump into the stream bed repeatedly

Abrasion grinds sediment into smaller and smaller particles

Sediments also chip away rock of the stream bed, making the stream’s channel wider and deeper

Load- the amount of sediment that a river carriesLarge sediment falls to the bottom and moves by

rolling and slidingWater carries some sedimentOther sediment dissolves completely

Erosion and Sediment Load A river’s slope, volume of flow, and the shape of its stream bed all

affect how fast the river flows and how much sediment it can erode

Slope- the steeper the slope of a river, the faster the speed of the river

As speed of a river increases, its load and power to erode increases

The more water flow through a river, its speed increases and its power to erode

Stream bed shape affects the amount of friction between the water and the stream bed

The deeper the river, the less friction, and the faster the flow of the river

Shallow rivers have more friction due to more contact of the water with the streambed

Rough streambeds create more friction and reduce a river’s speed Turbulence- type of movement in which water moves every which

way Friction and turbulence slow a river’s speed Water flows faster near the center of the river than along its sides Deposition occurs along the sides of a river, where water moves

slower Water moves fastest along the outside of a river’s curve; there the

river erodes the banks Water moves slowest along the inside curves of a river; depositing

sediment

Section ReviewHow can moving water on Earth’s surface do work?

As gravity pulls water down a slope, the water’s potential energy changes to kinetic energy that can do work

How does a river collect sediment?Most sediment washes or falls into a river as a result of mass movement and runoff. Other sediment erodes from the bottom or sides of a river.

What are 3 factors that affect a river’s sediment load?Slope, volume of flow, and streambed shape

Describe three ways that sediment moves in a river.Large sediment moves by rolling or sliding along the streambed. Smaller sediment moves when water lifts it up and carries it downstream. Some sediment is also carried as dissolved sediment in solution.

What effect does increased slope have on a river’s speed and sediment load?As slope increases, so does a river’s speed. And as a river’s speed increases, so does its sediment load