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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…….
