The document discusses morphometric analysis of drainage basins. It describes how drainage basins can be analyzed based on their linear, aerial, and relief aspects. Linear aspects include stream order, length, and bifurcation ratio. Aerial aspects include basin area, shape, and drainage density. Relief aspects examine the relationship between area, altitude, and slope. Morphometric analysis of drainage basin parameters provides insight into the physical characteristics and evolution of the landforms.

1. MORPHOMETRIC
ANALYSIS OF DRAINAGE
BASIN
SOJA S
GEL8012
I SEM MSc APPLIED GEOLOGY
UNIVERSITY OF CALICUT

2. INTRODUCTION
Geomorphometry is the measurement and mathematical analysis
of the earth’s surface and its dimensions of the landform.
Drainage basin is simply the area that gathers water from
precipitation and deliver it to large stream or lakes.
It comprises of different segments.
There are three important aspects used for analyzing the drainage
basin characteristics.
They are ;
 Linear aspects (one dimension)
 Aerial aspects (two dimension)
 Relief aspects (three dimension)

3. DRAINAGE BASIN : A GEOMORPHIC
UNIT
Drainage basin is taken to be an open system.
It has been important for determining territorial boundaries.
The drainage basin receives energy from two sources.They
are;
 From the atmosphere in the form of precipitation
 From within the earth where the endogenic forces causing
upliftment, warping, faulting, tilting etc.
On the other hand, the drainage basin loses energy through ;
 Evaporation , transpiration
 Outflow of water and sediments through its mouth.

4. DRAINAGE BASIN STUDY; HISTORICAL
PERSPECTIVE
The drainage basin has recently been acclaimed as the basic
unit in geomorphological study of fluvially eroded
landscapes.
In 1674, P. Perrault, is considered as the first investigator. He
visualized the significance of drainage basin and also he
attempted to measure rainfall for three year period to estimate
drainage area and run off.
After the investigation he postulated that “only one sixth of
the rainfall over the basin was necessary to sustain river flow
for a year ”

5. In 1802, John Playfair appreciated the significance of
drainage basin.
In 1851, T.J.Taylor stressed the principle that the discharge
of a river depend upon the area of drainage basin.
In 1899, W.M.Davis visualized the significance of rivers an
dpresented the concept of span of drainage basin.
In 1932, R.E.Horton who first said about the drainage
characteristics and in 1945 he acknowledged the drainage
basin as a ‘morphometric system’

6. BASIN MORPHOMETRY
Simplest of drainage basin parameters are those that
summarize spatial characteristics.
It includes the analyses of characteristics of linear , areal and
relief aspects of fluvially originated drainage basins.
LINEAR ASPECTS
The linear aspect includes the discussion and analysis of stream
order (u), stream number (N), bifurcation ratio (Rb), stream
lengths (Lu) length ratio (RL), length of overland flow (Lg).
sinuosity indices etc.

7. 1) Stream order (U)
A system of classifying river and streams based on their
relationship or position in the drainage network.
It can be used to describe a stream and to conveniently divide a
stream network into component parts.
 Two principal stream order schemes
are in use today. They are;
A. The Strahler Order system
B. The Shreve Magnitude system

8. A. The Strahler Order system
 So that stream order only increases
when two streams of the same order
join. Therefore, where a 2nd order
stream joins a 3rd stream there is no
change in stream order; the 3rd order
stream remains 3rd order.
 It designates 1st order streams as those that lack a tributary.
Second order streams are formed at the junction of 1st order
streams. Third order streams are formed at the junction of 2nd
order streams, fourth at the junction of 3rd order streams, and so
forth.

9. B. The Shreve Magnitude system
 Streams lacking a tributary are 1st magnitude.
 Where streams join, their magnitudes are added together.
 For instance, where a magnitude 2 stream joins a magnitude 3
stream, the magnitudes are added to form a magnitude 5 stream.

10. 2) Stream number (Nu)
The total number of stream segments present in each order.
 Nu is the number of streams of order u
 Example;
• Order 1 - 7 streams
• Order 2 - 5 streams
• Order 3 - 1 stream

11. 3) Bifurcation ratio (Rb)
It is is defined as a ratio of the number of streams of a given order
(Nu) to the number of streams of the next higher order (Nu+1).
Where Nu = number of streams of a given order
Nu+1 = number of streams of the next higher order
The higher bifurcation ratio leads to less chances of risk of
flooding.
Rb = Nu / Nu+1

12. 4) Mean stream length
Calculated by dividing the total stream length of order ‘u’ and
a number of stream segments of order ‘u’.
Lsm=Σ Lu/Nu
• Lsm = Mean Stream Length
• Σ Lu = Total stream length of order u
• Nu = Total number of stream segments of order u

13. 5) Length ratio (RL)
The proportion of increase of mean lengths of stream segments of two
successive basin orders is defined as length ratio (RL) .
It is calculated according to the following equation;
 Lu is the mean length of all stream
segments of a given order (u).
 ∑ Lu is the sum o f lengths of all
stream segments of a given order.
 Nu is the number of stream segments of
a given order.

14. AERALASPECTS
Basin area is important morphometric attribute
It is related to the spatial distribution of a number of significant
attributes such as drainage density, stream frequency, drainage
texture, slopes, absolute and relative reliefs, dissection index etc.
1) Geometry of the basin shape
 The geometry of basin shape is of paramount significance.
 It helps in the description and comparison of different forms of the
drainage basin.

15. On an average 3 sub categories of basin shape has been recognized.
They are;
Circular
Elongated
Indented
2) Law of Basin Perimeter, Basin Length and Basin Area
Basin area, basin perimeter, and channel length are significant
morphometric variables which determine the shape, size and
genetic aspect of drainage basins.
Basin perimeter can be directly correlated with the square roots of
the basin area.

16. 3) Area ratio (Ra)
Area ratio denotes proportion of increase of mean basin areas
between two successive orders.
It can be calculated by the equation;
Ra =
𝑨𝒖
𝑨𝒖−1
 Where 𝐴𝑢is the mean area of the given order of the basin.
 When 𝐴𝑢 = ∑ Au / Nu
 Where Nu = number of all segments of a given order
 ∑ Au= total area of al streams segments of the same order

17. 4) Stream frequency
• The stream frequency (Fs) of a basin may be defined as the total
number of stream segments within the basin per unit area.
• The general categories of stream frequencies are very poor, poor,
moderate, high and very high.
• Climatic character, vegetation coverage, rock and soil types, rainfall
intensity, infiltration capacity, relief, run-off intensity, permeability
terrain, slope has played vital role in controlling the drainage
frequency and density.

18. 5) Drainage density
It is the ratio of total channel segment length cumulated for all orders
within a basin to the basin area.
It is expressed in terms of Km/Km².
Low drainage density indicates the basin is a highly permeable subsoil
and thick vegetative cover.
High drainage density is the result of weak or impermeable subsurface
material, sparse vegetation, and mountainous relief.
Low drainage density leads to coarse drainage texture while high
drainage density leads to fine drainage texture.

19. 6) Drainage texture
Drainage texture is the relative spacing of drainage lines.
Horton defined drainage texture on the basis of stream frequency
as number of streams per unit area.
Drainage texture has been classified into five categories.They are;
 Very coarse drainage texture (above 0.8)
 Coarse drainage texture(0.8 - 0.6)
 Moderate drainage texture (0.6 - 0.4)
 Fine drainage texture (0.4 - 0.2)
 Very fine drainage texture (0.2 - 0.001)

20. Spatial patterns of stream frequency (A), drainage density(B), and
drainage texture (C), Ranchi,Bihar

21. RELIEF ASPECTS
The relief aspects of the drainage basins arc related to the study
of three dimensional features of the basins involving area, volume
and altitude of vertical dimension of landforms.
It includes the analysis of the relationships between area and altitude
(hyposometric analysis), altitude and slope angle (clinographic
analysis), average ground slope, relative reliefs, relief ratio, dissection
index, profiles of terrains and the rivers etc.

22. 1) Hypsometric analysis
It includes the analysis of the relationships between area and
altitude.
The area may be measured with the help of Planimeter.
The height is obtained from the contour maps.
2) Clinographic analysis
Clinographic curves represent average slopes between successive
contours and thus present panoramic view of the terrain.
The construction of clinographic curves require data of slope
angles between successive contours, contour lengths, heights and
areas between successive contours.

23. 3) Profile analysis
Profiles are basically of two types viz. (1) river profiles and (2)
terrain profiles.
River profiles are further divided into (i) longitudinal and (ii)
transverse profiles.
Terrain profiles are classified into (i) serial profiles,(ii)
superimposed profiles, (iii) projected profiles, and (iv) composite
profiles.

24. CONCLUSION
 The measurement of linear, areal and relief aspects
generated from contour and spot height are really useful to
identify physical and meteorological characteristics of the
particular basin area.
GIS has proved to be an effective and efficient tool for
computation and analysis of various morphometric parameters of
the basin.

25. THANK YOU