Mass Movement And Landslides Ch. 16-17

Front 1

landslide-potential map

Back 1

a map on which regions are ranked according to the likelihood that a mass movement will occur

Front 2

riprap

Back 2

loose boulders or concrete piled together along a beach to absorb wave energy before it strikes a cliff face

Front 3

abrasion

Back 3

the process in which one material (such as sand-laden water) grinds away at another (such as stream channel's floor and walls)

Front 4

alluvial fan

Back 4

a gently sloping apron of sediment dropped by an ephemeral stream at the base of a mountain in arid or semi-arid regions

Front 5

alluvium

Back 5

sorted sediment deposited by a stream

Front 6

bars

Back 6

a sheet or elongate lens or mound of alluvium

Front 7

base level

Back 7

the lowest elevation a stream channel's floor can reach at a given locality

Front 8

bed load

Back 8

large particles, such as sand, pebbles, or cobbles, that bounce or roll along a stream bed

Front 9

braided stream

Back 9

a sediment-choked stream consisting of entwined subchannels

Front 10

capacity

Back 10

the total quantity of sediment a stream can carry

Front 11

channel

Back 11

a trough dug into the ground surface by flowing water

Front 12

competence

Back 12

the maximum particle size a stream can carry

Front 13

delta

Back 13

a wedge of sediment formed at a river mouth when the running water of the stream enters standing water, the current slows, the stream loses competence, and sediment settles out

Front 14

discharge

Back 14

the volume of water in a conduit or channel passing a point in one second

Front 15

dissolved load

Back 15

ions dissolved in a stream's water

Front 16

distributaries

Back 16

the fan of small streams formed where a river spreads out over its delta

Front 17

downcutting

Back 17

the process in which water flowing through a channel cuts into the substrate and deepens the channel relative to its surroundings

Front 18

drainage divide

Back 18

a highland or ridge that separates one watershed from another

Front 19

drainage network or basin

Back 19

an array of interconnecting streams that together drain an area

Front 20

ephemeral (intermittent) stream

Back 20

a stream whose bed lies above the water table, so that the stream flows only when the rate at which water enters the stream from rainfall or meltwater exceeds the rate at which water infiltrates the ground below

Front 21

flood

Back 21

an event during which the volume of water in a stream becomes so great that it covers areas outside the stream's normal channel

Front 22

floodplain

Back 22

the flat land on either side of a stream that becomes covered with water during a flood

Front 23

headward erosion

Back 23

the process by which a stream channel lengthens up its slope as the flow of water increases

Front 24

longitudinal profile

Back 24

a cross-sectional image showing the variation in elevation along the length of a river

Front 25

meander

Back 25

a snake-like curve along a stream's course

Front 26

natural levees

Back 26

a pair of low ridges that appear on either side of a stream and develop as a result of the accumulation of sediment deposited naturally during flooding

Front 27

oxbow lake

Back 27

a meander that has been cut off yet remains filled with water

Front 28

permanent stream

Back 28

a stream that flows year-round because its bed lies below the water table, or because more water is supplied from upstream than can infiltrate the ground

Front 29

pothole

Back 29

a bowl-shaped depression carved into the floor of a stream by a long-lived whirlpool carrying sand or gravel

Front 30

rapids

Back 30

a reach of a stream in which water becomes particularly turbulent; as a consequence, waves develop on the surface of the stream

Front 31

running water

Back 31

water that flows down the surface of sloping land in response to the pull of gravity

Front 32

runoff

Back 32

the portion of meteoric water that eventually ends up in streams

Front 33

saltation

Back 33

the movement of a sediment in which grains bounce along their substrate, knocking other grains into the water column (or air) in the process

Front 34

scouring

Back 34

a process by which running water removes loose fragments of sediment from a stream bed

Front 35

sheetwash

Back 35

a film of water less than a few mm thick that covers the ground surface during heavy rains

Front 36

stream gradient

Back 36

the slope of a stream's channel in the downstream direction

Front 37

stream terrace

Back 37

borders of a floodplain

Front 38

stream

Back 38

a ribbon of water that flow in a channel

Front 39

suspended load

Back 39

tiny solid grains carried along by a stream without settling to the floor of a channel

Front 40

thalweg

Back 40

the deepest part of a stream's channel

Front 41

tributary

Back 41

a smaller stream that flows into a larger stream

Front 42

trunk stream

Back 42

the single larger stream into which an array of tributaries flow

Front 43

turbulence

Back 43

the chaotic twisting, swirling motion in flowing fluid

Front 44

V-shaped valley

Back 44

a valley whose cross-sectional shape resembles the shape of a V; the valley probably has a river running down the point of the V

Front 45

waterfall

Back 45

a place where water drops over an escarpment

Front 46

watershed

Back 46

the region that collects water that feeds into a given drainage network