fourth, fifth and higher order. The stream networks vary from first to seventh order
(Fig. 16.4), and further study area has been
divided into three river basins: Spiti, Parechu and
Tsarap Chu. Stream order in Spiti basin indicated
3265 of first order, 1442 of second, 802 of third,
490 of fourth, 284 of fifth, 140 of sixth order and
74 of seventh-order streams. The order of stream
network in Parechu basin indicated 439 of first
order, 196 of second, 106 of third, 77 of fourth
and 53 of fifth-order streams. Stream network in
Tsarap Chu basin indicated 651 of first order, 226
of second, 215 of third, 102 of fourth and 83 of
fifth-order streams (Fig. 16.5).
Table 16.1 Formulae incorporated for computation of morphometric parameters
S. no
Morphometric parameters
Formula
References
1
Stream order
Hierarchical rank
Strahler (1964)
2
Stream length (Lu)
Length of the stream
Horton (1945)
3
Mean stream length (Lsm)
Lsm = Lu/Nu, where Lsm = Mean stream length
Lu = Total stream length of order “u”
Nu = Total no. of stream segments of order “u”
Strahler (1964)
4
Stream length ratio (RL)
RL = Lu/Lu-1, where RL = Stream length ratio
Lu = The total stream length of the order “u”
Lu-1 = The total stream length of its next lower order
Horton (1945)
5
Bifurcation ratio (Rb)
Rb = Nu/Nu + 1, where Rb = Bifurcation ratio
Nu = Total no. of stream segments of order “u
Nu + 1 = No. of segments of the next higher order
Schumm
(1956)
6
Mean bifurcation ratio
(Rbm)
Rbm = Average of bifurcation ratios of all orders
Strahler (1957)
7
Relief ratio (Rh)
Rh = H/Lb, where Rh = Relief ratio
H = Total relief (Relative relief) of the basin (Km)
Lb = Basin length
Schumm
(1956)
8
Drainage density (D)
D = Lu/A, where D = Drainage density
Lu = Total stream length of all orders
A = Area of the basin (km
2
)
Horton (1932)
9
Stream frequency (Fs)
Fs = Nu/A, where Fs = Stream frequency
Nu = Total no. of streams of all orders
A = Area of the basin (km
2
)
Horton (1932)
10
Drainage texture (Rt)
Rt = Nu/P, where Rt = Drainage texture
Nu = Total no. of streams of all orders
P = Perimeter (km)
Horton (1945)
11
Form factor (Rf)
Rf = A/Lb 2, where Rf = Form factor
A = Area of the basin (km
2
)
Lb 2 = Square of basin length
Horton (1932)
12
Circulatory ratio (Rc)
Rc = 4*Pi*A/P2, where Rc = Circulatory ratio
Pi = “Pi” value, i.e., 3.14
A = Area of the basin (km
2
)
P2 = Square of the perimeter (km
2
)
Miller (1953)
13
Elongation ratio (Re)
Re = 2√(A/Pi)/Lb, where Re = Elongation ratio
A = Area of the basin (km
2
)
Pi = “Pi” value, i.e., 3.14
Lb = Basin length
Schumm
(1956)
14
Length of overland flow (Lg)
Lg = 1/D*2, where Lg = Length of overland flow
D = Drainage density
Horton (1945)
216
A. Husain and P. Kumar
(Fig. 16.4), and further study area has been
divided into three river basins: Spiti, Parechu and
Tsarap Chu. Stream order in Spiti basin indicated
3265 of first order, 1442 of second, 802 of third,
490 of fourth, 284 of fifth, 140 of sixth order and
74 of seventh-order streams. The order of stream
network in Parechu basin indicated 439 of first
order, 196 of second, 106 of third, 77 of fourth
and 53 of fifth-order streams. Stream network in
Tsarap Chu basin indicated 651 of first order, 226
of second, 215 of third, 102 of fourth and 83 of
fifth-order streams (Fig. 16.5).
Table 16.1 Formulae incorporated for computation of morphometric parameters
S. no
Morphometric parameters
Formula
References
1
Stream order
Hierarchical rank
Strahler (1964)
2
Stream length (Lu)
Length of the stream
Horton (1945)
3
Mean stream length (Lsm)
Lsm = Lu/Nu, where Lsm = Mean stream length
Lu = Total stream length of order “u”
Nu = Total no. of stream segments of order “u”
Strahler (1964)
4
Stream length ratio (RL)
RL = Lu/Lu-1, where RL = Stream length ratio
Lu = The total stream length of the order “u”
Lu-1 = The total stream length of its next lower order
Horton (1945)
5
Bifurcation ratio (Rb)
Rb = Nu/Nu + 1, where Rb = Bifurcation ratio
Nu = Total no. of stream segments of order “u
Nu + 1 = No. of segments of the next higher order
Schumm
(1956)
6
Mean bifurcation ratio
(Rbm)
Rbm = Average of bifurcation ratios of all orders
Strahler (1957)
7
Relief ratio (Rh)
Rh = H/Lb, where Rh = Relief ratio
H = Total relief (Relative relief) of the basin (Km)
Lb = Basin length
Schumm
(1956)
8
Drainage density (D)
D = Lu/A, where D = Drainage density
Lu = Total stream length of all orders
A = Area of the basin (km
2
)
Horton (1932)
9
Stream frequency (Fs)
Fs = Nu/A, where Fs = Stream frequency
Nu = Total no. of streams of all orders
A = Area of the basin (km
2
)
Horton (1932)
10
Drainage texture (Rt)
Rt = Nu/P, where Rt = Drainage texture
Nu = Total no. of streams of all orders
P = Perimeter (km)
Horton (1945)
11
Form factor (Rf)
Rf = A/Lb 2, where Rf = Form factor
A = Area of the basin (km
2
)
Lb 2 = Square of basin length
Horton (1932)
12
Circulatory ratio (Rc)
Rc = 4*Pi*A/P2, where Rc = Circulatory ratio
Pi = “Pi” value, i.e., 3.14
A = Area of the basin (km
2
)
P2 = Square of the perimeter (km
2
)
Miller (1953)
13
Elongation ratio (Re)
Re = 2√(A/Pi)/Lb, where Re = Elongation ratio
A = Area of the basin (km
2
)
Pi = “Pi” value, i.e., 3.14
Lb = Basin length
Schumm
(1956)
14
Length of overland flow (Lg)
Lg = 1/D*2, where Lg = Length of overland flow
D = Drainage density
Horton (1945)
216
A. Husain and P. Kumar