Drainage

1. Basin Morphometry
Measures, control and Geographic Significance
Presented By: Kamal Shahi Presented To: Proff.
Motilal Ghimire
Roll no: 30
Central Department of Geography Central Department of Geography
MA in Geography, Ist year / Ist Semester

2. Drainage Basin
• Drainage basin is simply the area that gathers water from
precipitation and deliver it to large stream or lakes.
• Comprises of different segments
Maps are not in scale

3. Catchment
The area from
which water drains
into a particular
drainage basin.
Tributary
A river which joins a larger river.
Confluence
The point at which two rivers join.
Watershed
The boundary
dividing one
drainage basin
from another- a
ridge of high
land.
Source
The upland area
where the river
begins.
Mouth
Where the river
flows into the sea,
or sometimes a
lake.

4. • In general ‘Drainage Basin’ is
an area of land drained by a
river and its tributaries,
bounded by a watershed
(boundary).
• It is sometimes called the
‘catchment area’ of a river
because it is the bowl which
catches the rain
Drainage Basin

5. • Morphometry is the science that deals with quantitative
measurement of the Shape or Geometry of any natural forms
• Basin morphometry denotes the measurement of three dimensional
geometrical properties of the land surface of a fluvial erosion system.
• This modern approach of quantitative analysis of drainage basin
morphology was given inputs by Horton (1945) the first pioneer in this
field
• Horton’s laws were subsequently modified and developed by several
geomorphologist, most notably by Strahler (1952, 1957, 1958, and
1964), Schumm (1956), Morisawa (1957, 1958), Scheidegger (1965),
Shreve (1967), Gregory (1966, 1968), Gregory and Walling (1973
Drainage Basin Morphometry

6. • Morphometric features are classified into three categories
– Linear properties (one dimension)
– Aerial properties (Two dimension)
– Relief properties (Three dimension)
• It incorporates quantitative study of the various components such
as, stream segments, basin length, basin parameters, basin area,
altitude, volume, slope, profiles of the land which indicates the
nature of development of the basin.
Drainage Basin Morphometry

7. Linear Aspect
• Stream order(U)
• There are four different system of ordering streams that are available Gravelius
(1914), Horton (1945), Strahler (1952) and Schideggar (1970).
• Order :The drainage network transport water and the sediments of a basin through a
single outlet, which is marked as the maximum order of the basin and conventionally
the highest order stream available in the basin considered as the order of the basin.
• The size of rivers and basins varies greatly with the order of the basin.

8. Scheme Description
Horton Subjective, integer order only
Strahler Objective, convenient for sampling, integer order
Shreve Objective, integer order, no violation of distributive law,
each junction should change order
Gregory & Walling Use in process investigation (count of each segment)
By NRK sir Note

9. Linear Aspect
• Stream Number (Nu)
• The total number of stream segments present in each order
is the stream number (Nu).
• Nu is number of streams of order u.
• Stream Length (Lu)
• The length of the stream channel is a dimensional property,
which reveals the size component of drainage lines.
• Total length of stream in a particular order.
• Most significant hydrological feature of the basin as it
reveals surface runoff characteristics.
• Stream of relatively smaller length are characteristics of
areas with larger slopes and finer texture. Generally, the
total length of the stream segment is maximum in first order
streams and decreases as the stream order increases

10. Linear Aspect
• Length Ratio(RI)
• Ratio of the mean length of the one order to the next lower order of the stream
segment (Horton 1945)
• The Rl between streams of different orders in the study area reveals that there is a
variation of Rl in each sub-basin and this may be due to change in slope and
topography.
• Bifurcation Ratio
• The bifurcation ratio is the ratio between the number of streams in one order and in
the next
Rb= Nu/Nu+1
Nu= Rb (k-u)
Where Nu= number of streams;
u = stream order segment
k = order of main stream
∑Nu = Rb k – 1/Rb-1
Rl = L
̄ u/ L
̅ u-1
Ra = Āu / Ā u-1
Where Rl = river length ratio and Ra = basin area ratio
L
̄ u = mean length and Ā = mean basin area

11. Aerial Aspect
• Drainage Area (Au)
• The entire area drained by a stream or system of streams such that all streams flow
originating in the area is discharged through a single outlet is termed as the
Drainage Area.
• Drainage Density(Dd)
• Expresses the closeness of spacing of channels, thus providing a quantitative
measure of the average length of stream channel for the whole basin

12. Number of squares
fully covered = 42
Stream order at X = 4
Number of squares covered
by more
than half = 13
Total number of
Squares = 55
Area of 1 square
= L X B
1 cm
1 cm
= 1cm X 1cm
= ,5 km X ,5 km
= ,25 square km
Area of 55 squares
= 55 x ,25 sq. km
= 14 sq. km

13. • Stream frequency (Fs)
• The number of stream segments per unit area is termed Stream Frequency or
Channel Frequency or Drainage Frequency (Fs) Horton (1945). Tab
• Circularity and Elongation ratio
• The values of circularity ratio and elongation ratio indicate that the
basin is moderately circular and somewhat elongated
Aerial Aspect

14. • Basin Relief
• Basin relief is the elevation difference of the highest and lowest point of the valley
floor.
• Relief ratio
• Relief ratio is defined as the ratio between the total relief of a basin i.e. elevation
difference of lowest and highest points of a basin, and the longest dimension of the
basin parallel to the principal drainage line (Schumn 1956).
This is a dimensionless height-length ratio and allows comparison of the relative relief of any basin regardless
of difference in scale or topography
Relief Aspect

15. • Many more factors
– Drainage Texture (Rt)
– Form Factor (Rf)
– Infiltration Number (If)
– Length of Overland Flow (Lg)
– Channel gradient
– Ruggedness Number (HD)
– Hypsometric Curve
– Longitudinal Profile

16. Significances
• Quantitative measurements of morphometry used as a reconnaissance tools to make
inferences about particular characteristic of an area viz., tectonic activity. Some
geomorphic indices like hypsometric integral, drainage basin asymmetry, stream
length gradient index, mountain front sinuosity etch are used a measure of active
tectonics (Keller and Pinter, 1996; Sinha-Roy, 2002)
• The basin geomorphic characteristics have long been believed to be important indices
of surface processes.
• These parameters have been used in various studies of geomorphology and surface-
water hydrology, such as flood characteristics, sediment yield, and evolution of basin
morphology (Jolly, 1982; Ogunkoya et al., 1984; Aryadike and Phil-Eze, 1989;
Breinlinger et al., 1993; Jensen, 1991).

17. • By including basin characteristics such as elevation and main
channel gradient, predictions of stream discharge were substantially
improved in comparison to using only drainage area and
precipitation (McArthur and Hope, 1993).
• More recently, terrain characterization became an important part in
modelling surface processes (Nogami, 1995).