Lecture 12

Streams and Floods

Lecture Outline

I The Hydrologic CycleIIDefinitionsIII Drainage

A) Runoffi. Channel Flowii. Sheet Flow

B) Drainage Basinsi. Mississippi River Drainage Basinii. Chesapeake Bay Drainage Basin

C) Stream OrderD) Drainage Patterns

i. Dendriticii. Radialiii. Rectangulariv. Trellis

E) Stream Valley Developmenti. Base Level

Lecture 12i

Lecture Outline

III DrainageE) Stream Valley Development

ii. The Graded Streamiii. Lateral Erosioniv. Headward Erosion

IV Stream FunctionA) Controls on Stream Function

i. Velocityii. Channel Propertiesiii. Gradientiv. Discharge

B) ErosionC) TransportationD) Deposition

i. Barsii. Braided Streams

iii. Meandering Streams and Point Bars

Lecture 12ii

Lecture Outline

Lecture 12iii

IV Stream FunctionD) Deposition

iv. Flood Plainsv. Deltas

vi. Alluvial Fans

V Other Fluvial MorphologiesA) Stream TerracesB) Incised MeandersC) Superposed Streams

The Hydrologic Cycle

Lecture 12I

Definitions

Lecture 12II

stream - a body of water found on Earth's surface and confined to a narrow topographic depression, down which it flows and

transports rock particles, sediment, and dissolved particles.Rivers, creeks, brooks, and runs are all streams.

Runoff

Lecture 12III.A

Channel Flow

Sheet Flow

RunoffOverland (Sheet) Flow

Lecture 12III.A

Drainage Basin

Lecture 12III.B

drainage basin - the total land surface drained by a system of streams leading to the same outflow.

drainage system - the streams, tributaries, and other bodies of water by which a region is drained.

drainage divide - the boundary between adjacent drainage basins.

Drainage BasinMississippi River and Chesapeake Bay

Lecture 12III.B.i

Stream Order

Lecture 12III.C

stream order - a classification of relative position of streams in achannel network, assigning each link an integer ordernumber determined by thepattern of confluences in thetributary network headward ofthe given link.

Stream System Components

Lecture 12III.C

Drainage Patterns

Lecture 12III.D

Dendritic

Radial

Rectangular

Trellis

Deranged

Drainage PatternsDendritic

Lecture 12III.D.1

Drainage PatternsRadial

Lecture 12III.D.2

Drainage PatternsRectangular

Lecture 12III.D.3

Drainage PatternsTrellis

Lecture 12III.D.4

Drainage PatternsDeranged

Lecture 12III.D.4

The Stream Valley

Lecture 12III.D.4

Stream Valley DevelopmentEvolution

Lecture 12III.E.iii

Stream Valley DevelopmentStream Profile

Lecture 12III.E

Base Level/Grade

Lateral Erosion

Headward Erosion

Stream Valley DevelopmentBase Level

Lecture 12III.E.i

Stream Valley DevelopmentThe Graded Stream

Lecture 12III.E.ii

graded stream - a streammaintaining an equilibrium between the processes oferosion and deposition, and therefore betweenaggradation anddegradation.

Stream Valley DevelopmentLateral Erosion

Lecture 12III.E.iii

Stream Valley DevelopmentEvolution – Headward Erosion

Lecture 12III.E.iii

Stream Functions

Lecture 12IV

Erosion

Transportation

Deposition

Controls on Stream Function

Lecture 12IV.A

Velocity

Channel Properties

Gradient

Discharge

Controls on Stream FunctionVelocity

Lecture 12IV.A.i

Controls on Stream FunctionChannel Properties – Cross-Sectional Area

Lecture 12IV.A.ii.1

Controls on Stream FunctionChannel Properties – Longitudinal

Organization

Lecture 12IV.A.ii

Straight Channel

Meandering Channel

Braided Channel

Controls on Stream FunctionStraight Channel

Lecture 12IV.A.ii

Controls on Stream FunctionMeandering Channel

Lecture 12IV.A.ii

Controls on Stream FunctionBraided Channel

Lecture 12IV.A.ii

Controls on Stream FunctionGradient

Lecture 12IV.A.iii

Controls on Stream FunctionDischarge

Lecture 12IV.A.iv

discharge : volume of water flowing past a point in a given amount of time.

Erosion

Lecture 12IV.B

Sediment Transport

Lecture 12IV.C

capacity: the total volume of sediments a stream cancarry; a function of discharge

competence: the maximum size of sediment the stream can carry

Transport Modes

1Suspended load

2Bed load

3Dissolved load

Depositional and Other Fluvial Landforms

Lecture 12IV.D

Flood PlainsMeandering StreamPoint BarCutbankOxbow LakesNatural LeveesOverbank DepositsYazoo TributaryBackswamps

Bars

Braided Streams

Deltas

Alluvial Fans

Flood Plains

Lecture 12IV.D.iv

Meandering Streams and Point Bars

Lecture 12IV.D.iii

Meandering Streams and Point Bars

Lecture 12IV.D.iii

Meandering StreamsMigration

Lecture 12IV.D.iii

Lecture 12IV.D.iii

Meandering Streams and Oxbow Lakes

Flood PlainsNatural Levees

Lecture 12IV.D.iv

Natural levees

Bars

Lecture 12IV.D.i

Braided Streams

Lecture 12IV.D.ii

Deltas

Lecture 12IV.D.v

Deltas

Lecture 12IV.D.v

Alluvial Fans

Lecture 12IV.D.vi

Alluvial Fan (Death Valley, CA)

Other Fluvial Morphologies

Lecture 12V

Stream Terraces

Incised Meanders

Superposed Streams

Stream Terraces

Lecture 12V.A

Incised Meanders

Lecture 12V.B

Superposed Streams

Lecture 12V.C