Fluvial Processes

I. The Hydrologic Cycle

1) Precipitation

The Hydrologic Cycle

2) Evaporation-Transpiration

The Hydrologic Cycle

3) Infiltration

The Hydrologic Cycle

4) Runoff

II. Water DistributionA. In Virginia

* annual rainfall: 43”

II. Water Distribution

A. In Virginia

* annual rainfall: 43”

* Appalachian Plateau: 51”

II. Water Distribution

A. In Virginia

* annual rainfall: 43”

* Appalachian Plateau: 51”

* Coastal Plain: 55”

II. Water Distribution

A. In Virginia

* annual rainfall: 43”

* Appalachian Plateau: 51”

* Coastal Plain: 55”

* Shenandoah Valley: 34-37”

II. Water Distribution

A. In Virginia

yearly variation…….

II. Water Distribution

A. In Virginia

yearly variation…….

YEAR Total Runoff ET Infilt.

II. Water Distribution

A. In Virginia

yearly variation…….

YEAR Total Runoff ET Infilt.

1956 43” 15” 25” 3”

II. Water Distribution

A. In Virginia

yearly variation…….

YEAR Total Runoff ET Infilt.

1956 43” 15” 25” 3”

1949 57” 26” 25” 6”

II. Water Distribution

A. In Virginia

yearly variation…….

YEAR Total Runoff ET Infilt.

1956 43” 15” 25” 3”

1949 57” 26” 25” 6”

1930 30” 5” 28” -3”

II. Water Distribution

A. In Virginia

yearly variation…….

YEAR Total Runoff ET Infilt.

1956 43” 15” 25” 3”

1949 57” 26” 25” 6”

1930 30” 5” 28” -3”

ET remains ~ constant

II. Water Distribution

1.36 billion cubic km of water

97.2% oceans

2.15% glacial ice

0.65% lakes, streams, ground water

III. Stream Flow

A. Terms

III. Stream Flow

A. Terms1. Laminar vs. Turbulent

III. Stream Flow

A. Terms1. Laminar vs. Turbulent

III. Stream Flow

A. Terms2. Velocity, Area, Discharge

Water Velocity

Area

Discharge

Discharge

Discharge = Velocity x Area

Discharge

Discharge = Velocity x AreaQ = V x A

III. Stream Flow

A. Terms3. Gradient

III. Stream Flow

A. Terms3. Gradient

Rise = Vertical drop of the stream

Run Horizontal Distance

Rise = Vertical drop of the stream

Run Horizontal Distance

III. Stream Flow

B. Downstream Trends1. gradient

2. width and depth

3. discharge

4. velocity

III. Stream Flow

B. Downstream Trends a. gradient

b. width and depth

c. discharge

d. velocity

III. Stream Flow

B. Downstream Trends a. gradient

b. width and depth c. discharge

d. velocity

III. Stream Flow

B. Downstream Trends a. gradient

b. width and depth c. discharge d. velocity

III. Stream Flow

B. Downstream Trendsa. gradient b. width and depth c. discharge d. velocity

C. Work of Running Water

1. Erosion* Sheet flow

C. Work of Running Water

1. Erosion

* Sheet flow* Rill flow

C. Work of Running Water

1. Erosion

* Sheet flow* Rill flow* Stream (gully) flow

C. Work of Running Water2. Transportation

a) dissolved load

2. Transportationa) dissolved loadb) suspended load

2. Transportationa) dissolved loadb) suspended loadc) bedload

c. Bed load – i. Rolling

ii. Sliding

iii. Saltation

Saltation

IV. Features of Streams

IV. Features of Streams

A) Waterfalls and Rapids

IV. Features of Streams

B) Meanders

Pointbars

Cutbanks

IV. Features of Streams

C) Pointbars

IV. Features of Streams

D) Cutbanks

IV. Features of Streams

E. Oxbow lakes

IV. Features of Streams

E) Oxbow lakes

IV. Features of Streams

• Oxbow lakes (Cont’d)

IV. Features of Streams

• Oxbow lakes (Cont’d)

IV. Features of StreamsF) Braided Streams

•

IV. Features of StreamsG) Natural Levees

IV. Features of StreamsH) Deltas

IV. Features of StreamsH) Deltas

IV. Features of StreamsI) Floodplains and Terraces

V. The Drainage BasinA. Overview….

B. Stream Ordering

Stream Ordering

Strahler (1952) (after Horton, 1945)

Shreve (1967)

Strahler (1952) (after Horton, 1945)

Shreve (1967)

Bifurcation ratio (Rb)streams of one orderstreams of the next highest order

Ex: 1 6th order stream3 5th order9 4th order 27 = 327 3rd order 981 2nd order

Ratio value is nearly constant between adjacent ordersAND….where geology is homogeneous, Rb = 3.0 – 5.0

C. The Hydrograph1. General

C. The Hydrograph1. General2. The Storm Hydrograph

C. The Hydrograph1. General2. The Storm Hydrograph

a. Shape and distribution of events

direct ppt., runoff, baseflow, interflow

Comparing the characteristics of flashy and sluggish hydrographs

VI. Flood Frequency

VI. Flood Frequency

y = 1708.5Ln(x) + 1705.1

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

1 10 100

RI (yrs)

Dis

char

ge

(cfs

)

What does this mean???

 

What does this mean???

the curve estimates the magnitude of a flood that can be expected within a specified period of time 

What does this mean???

the curve estimates the magnitude of a flood that can be expected within a specified period of time The probability that a flow of a given magnitude will occur during Any year is P = 1/RI.

What does this mean???

the curve estimates the magnitude of a flood that can be expected within a specified period of time The probability that a flow of a given magnitude will occur during anyyear is P = 1/RI. EX: a 50 year flood has a 1/50, or a 2 percent chance of occurring

in any given year

For multiple years: q = 1- ( 1-1/T)n

where q = probability of flood with RI of T with a specified number of years n

For multiple years: q = 1- ( 1-1/RI)n where q = probability of flood with RI with a

specified number of years n

EX: a 50 year flood has an 86% chance of occurring over 100 years

“Other Topics”Channelization

Channelization

Channelization

Channelization

Channelization

Channelization

Rise = vertical dropRun horizontal distance

Channelization

Channelization

Channelization

Channelization

Channelization

Tomorrow’s excursion to South River…….