Ch. 18

Front 1

Abrasion

Back 1

the erosive action that occurs when suspended and saltating sediment particles move along the bottom and sides of a stream channel

Front 2

Alluvial fan

Back 2

a cone- or fan-shaped accumulation of sediment deposited where a stream widens abruptly as it leaves a mountain front and enters a broad, relatively flat valley

Front 3

Antecedent stream

Back 3

a stream that existed before the present topography was created and so maintained its original course despite changes in the structure of the underlying rocks and in the topography

Front 4

Base level

Back 4

The elevation at which a stream ends by entering a large standing body of water

Front 5

Bed load

Back 5

the material a stream carries along its bed by sliding and rolling

Front 6

Bottomset bed

Back 6

a thin, horizontal bed of mud deposited seaward of a delta and then buried by continued delta growth

Front 7

braided stream

Back 7

a stream whose channel divides into an interlacing network of channels, which then rejoin in a pattern resembling braids of hair

Front 8

capacity

Back 8

the total sediment load carried by a current

Front 9

channel

Back 9

a well-defined trough thru which the water in a stream flows

Front 10

competence

Back 10

the ability of a current to carry material of a given size

Front 11

delta

Back 11

a large, flat-topped deposit of sediments formed where a river enters an ocean or lake and its current slows

Front 12

dendritic damage

Back 12

an irregular drainage network that resembles the limbs of a branching tree

Front 13

discharge

Back 13

the volume of groundwater leaving an aquifer in a given time OR the volume of water that passes a given point in a given time as it flows thru a channel of a certain width and depth

Front 14

distributary

Back 14

a smaller stream that receives water and sediment from the main channel of a river, branches off downstream, and thus distributes the water and sediment into many channels, typically found on a delta

Front 15

divide

Back 15

a ridge of high ground along which all rainfall runs off down one side or the other

Front 16

drainage basin

Back 16

an area of land, bounded by divides, that funnels all its water into the network of streams draining the area

Front 17

drainage network

Back 17

the pattern of connections of all the large and small streams in a drainage basin

Front 18

dune

Back 18

an elongated mound or ridge of sand formed by a current of wind or water

Front 19

flood

Back 19

inundation that occurs when increased discharge, resulting from a short-term imbalance between inflow and outflow, causes a stream to overflow its banks

Front 20

floodplain

Back 20

a flat area about level with the top of a channel that lies on either side of the channel; the part of a valley that is flooded when a stream overflows its banks

Front 21

foreset bed

Back 21

a gently inclined deposit of fine-grained sand and silt, resembling large-scale cross-beds, on the outer front of a delta

Front 22

graded stream

Back 22

a stream in which the slope, velocity, and discharge combine to transport its sediment load, with neither net sedimentation nor net erosion in the stream or its floodplain

Front 23

laminar flow

Back 23

fluid movement in which straight or gently curved streamlines run parallel to one another w/out mixing or crossing between layers

Front 24

longitudinal profile

Back 24

the smooth, concave-upward curve that represents a cross-sectional view of a stream, from notably steep near its head to almost level near its mouth

Front 25

meander

Back 25

a curve or bend in a stream that develops as the stream erodes the outer bank of a bend and deposits sediment against the inner bank

Front 26

natural levee

Back 26

a ridge of coarse material built up by successive floods that confines a stream within its banks between floods, even when water levels are high

Front 27

oxbow lake

Back 27

a crescent-shaped, water-filled loop created in the former path of a stream when it bypasses a meander and takes a new, shorter course

Front 28

point bar

Back 28

a curved sandbar deposited along the inside bank of a stream, where the current is weakest

Front 29

pothole

Back 29

a hemispherical hole in the bedrock of a streamed, formed by abrasion by small pebbles and cobbles rotating in a swirling eddy

Front 30

ripple

Back 30

a very small ridge of sand or silt whose long dimension is at right angles to the current that formed it

Front 31

river

Back 31

a major branch of a stream system

Front 32

saltation

Back 32

the transportation of sand or smaller sediment particles by a current in such a manner that the particles move along in a series of short intermittent jumps

Front 33

settling velocity

Back 33

the speed at which particles of various weights suspended in a current settle to the bed

Front 34

stream

Back 34

any body of water, large or small, that flows over the land surface

Front 35

superposed stream

Back 35

a stream that erodes a gorge in a resistant formation because its course was established at a higher level on uniform rock before downcutting began

Front 36

suspended load

Back 36

all the material temporarily or permanently suspended in the flow of a current

Front 37

terrace

Back 37

a flat, steplike surface in a stream valley that parallels a stream above its floodplain, often paired one one each side of the stream, marking a former floodplain that existed at a higher level before regional uplift or an increase in discharge caused the stream to erode into the former floodplain

Front 38

topset bed

Back 38

a horizontal bed of sediment - typically sand - deposited on top of a delta

Front 39

tributary

Back 39

a stream that discharges water into a larger stream

Front 40

turbulent flow

Back 40

fluid movement in which streamlines mix, cross, and form swirls and eddies

Front 41

valley

Back 41

the entire area between the tops of the slopes on both sides of a stream