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The Drainage Basin

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ANALYSIS GOOD FOR 1.5x length of data set Introduction --two general relationships realized concerning drainage basins Introduction --two general relationships ... – PowerPoint PPT presentation

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Title: The Drainage Basin


1
The Drainage Basin your friend, and all of
its secrets
2
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3
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4
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5
  • Introduction
  • --two general relationships realized concerning
    drainage basins

6
  • Introduction
  • --two general relationships realized concerning
    drainage basins
  • streams form their valleys in which they flow

7
  • Introduction
  • --two general relationships realized concerning
    drainage basins
  • streams form their valleys in which they flow
  • every river consists of a major stream that is
    fed by a
  • number of mutually adjusted branches that
    diminish in
  • size away from the main stem.

8
  • Introduction
  • II. Slope Hydrology and Runoff Generation

9
  • Introduction
  • II. Slope Hydrology and Runoff Generation
  • A. Basin Hydro. Cycle and Budget

Input Output change in storage
10
  • Introduction
  • II. Slope Hydrology and Runoff Generation
  • A. Basin Hydro. Cycle and Budget

Overland flow Interflow Baseflow
Input Output change in storage
11
  • Introduction
  • II. Slope Hydrology and Runoff Generation
  • Basin Hydro. Cycle and Budget
  • The Storm Hydrograph

12
B. The Storm Hydrograph
Unit hydrograph where the runoff volume is
adjusted to the same unit value (e.g., one inch
of rainfall spread evenly over a basin in one
day
13
Overland flow
Baseflow
Direct ppt
Interflow
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15
Discharge
Basin Area
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III. Initiation of Channels and the Drainage
Network A. The concept
18
  • III. Initiation of Channels and the Drainage
    Network
  • The concept
  • Shear stress.

19
  • III. Initiation of Channels and the Drainage
    Network
  • The concept
  • Shear stress.

t ?gds
Effects of Vegetation.
20
  • III. Initiation of Channels and the Drainage
    Network
  • The concept
  • Rills develop, and they begin to bifurcate
  • repeated divisions of single channel segments

21
Rills develop, and they begin to
bifurcate repeated divisions of single
channel segments
22
Rills develop, and they begin to
bifurcate repeated divisions of single
channel segments
23
III. Initiation of Channels and the Drainage
Network B. Basin Morphometry refers to the
geometry of the basin
24
B. Basin Morphometry refers to the geometry of
the basin Drainage Composition refers to the
distinct fabric of the drainage basin
25
  • Drainage Composition
  • refers to the distinct fabric of the
  • drainage basin

Strahler (1952) Shreve (1967)
26
2. Linear Morphometric Relationships Certain
linear parameters of a basin are
proportionally related to stream order.
  • Bifurcation ratio (Rb)
  • streams of one order
  • streams of the next highest order

27
2. Linear Morphometric Relationships Certain
linear parameters of a basin are
proportionally related to stream order.
  • Bifurcation ratio (Rb)
  • streams of one order
  • streams of the next highest order
  • Ex 1 6th order stream
  • 3 5th order
  • 9 4th order 27 3
  • 27 3rd order 9
  • 81 2nd order
  • Ratio value is nearly constant between adjacent
    orders
  • AND.where geology is homogeneous, Rb 3.0 5.0

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2. Linear Morphometric Relationships Certain
linear parameters of a basin are
proportionally related to stream order.
b. Length ratio ave length of streams of one
order ave length streams of the next
highest order Can be used to determine the
average length of streams in an unmeasured order.
30
3. Aerial Morphometric Relationships
  • Drainage density (Dd)
  • total length of streams in basin
  • basin area
  • Reflects the interaction between geology and
    climate
  • In general.

31
4. Relief Morphometric Relationships
  • Relief Highest elevation lowest elevation
  • Reflects the vertical dimensions of drainage
    basin
  • Includes factors of gradient and elevation

32
IV. Basin Morphology and Flood Hydrograph
33
IV. Basin Morphology and Flood Hydrograph
34
V. Basin Evolution and Denudation
35
V. Basin Evolution and Denudation A. Factors
affecting sediment yield climate
36
V. Basin Evolution and Denudation A. Factors
affecting sediment yield climate
37
V. Basin Evolution and Denudation A. Factors
affecting sediment yield basin size
38
V. Basin Evolution and Denudation A. Factors
affecting sediment yield elevation and relief
39
V. Basin Evolution and Denudation A. Factors
affecting sediment yield rock type
40
V. Basin Evolution and Denudation A. Factors
affecting sediment yield Human Factor
41
V. Basin Evolution and Denudation A. Factors
affecting sediment yield Human Factor
42
V. Basin Evolution and Denudation A. Factors
affecting sediment yield B. How do basins erode
(denute?)        
43
Sediment Transport and Denudation
44
0.398 km2
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Before
After
?
?
?
47
0.398 km2
13, 364 m3
48
Volume 13, 364 m3
0.034 m
Area 0.398 km2 or 398,000 m2
3.4 cm
49
Summary of Basin Denudation of Blue Ridge Systems
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Hurricane Camille
Rapidan Storm
52
B. How do basins erode (denute?)
High Magnitude Low Frequency
Low Magnitude High Frequency
53
VI. Basin Hydrology A. Subsurface Water
Hydrogeology (GEOL 460) M W 1010-11, Friday Lab
54
Hydrogeology (GEOL 460) M W 1010-11, Th lab
VI. Basin Hydrology A. Subsurface Water
55
VI. Basin Hydrology B. Surface Water 1.
Terms Discharge Q V A
56
VI. Basin Hydrology B. Surface Water 1.
Terms Discharge Q V A Velocity is highly
variable depends where measured.
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Velocity is highly variable depends where
measured.
58
VI. Basin Hydrology B. Surface Water 2. Reporting
discharge Daily vs annual discharge mean vs
median discharge
59
3. Flood Frequency
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What does this mean???  
61
What does this mean??? the curve estimates the
magnitude of a flood that can be expected within
a specified period of time  
62
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.
63
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. EX a 50
year flood has a 1/50, or a 2 percent chance of
occurring in any given year
64
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

65
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

EX a 50 year flood has an 86 chance of
occurring over 100 years
CAUTION!!! ANALYSIS GOOD FOR 1.5x length of data
set
66
The Mechanics of Determining RI Flood
recurrence interval (R.I.) use Weibull Method -
calculates the R.I. by taking the average time
between 2 floods of equal or greater
magnitude. RI (n 1) / m
where n is number of years on
record, m is magnitude
of given flood
67
VI. Basin Hydrology C. Paleoflood Hydrology
Slackwater deposits
68
VI. Basin Hydrology C. Paleoflood Hydrology
Which one is right????
carbon is your friend
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