Morphotectonic parameter

Mathematical expression

Classes

References

Stream Length Gradient Index (SL)

$\text{SL}=\left(\Delta \text{H}/\Delta \text{Lr}\right)\text{Lt}$

where, ΔH is change in altitude, ΔLr is the length of a reach, and Lt is the horizontal distance from the watershed divide to the centre of the reach

Class 1

(>500)

Hack (1973)

Class 2

(500 - 300)

Class 3

(<300)

Valley floor width-to-height ratio (Vf)

$\text{Vf}=\text{2}\left\{{\text{V}}_{\text{fw}}/\left({\text{E}}_{\text{ld}}+{\text{E}}_{\text{rd}}-{\text{2E}}_{\text{sc}}\right)\right\}$

where, V_fw is the width of the valley floor, E_ld and E_rd are elevations of the left and right valley divides (facing downstream) respectively, and E_sc is the elevation of the valley floor.

Class 1

(<0.5)

Bull and McFadden, 1977

Class 2 (0.5 - 1.0)

Class 3

(≥1)

Drainage basin asymmetry factor (Af)

$\text{Af}=100\left({\text{A}}_{\text{r}}/{\text{A}}_{\text{t}}\right)$

where A_r is the area of the basin to the right (downstream) of the trunk rivulet, A_t is the total area of the drainage basin

Class 1

(>15)

Hare and Gardner, 1985; Keller and Pinter, 2002

Class 2

(5 - 15)

Class 3 (<5)

Hypsometric integral (HI)

$\text{HI}=\left({\text{E}}_{\text{L}}\text{avg}-{\text{E}}_{\text{L}}\text{min}\right)/\left({\text{E}}_{\text{L}}\text{max}-{\text{E}}_{\text{L}}\text{min}\right)$

where, E_L avg = average elevation, E_L min = minimum elevation, E_L max = maximum elevation.

Class 1

(> 0.47)

Strahler, 1952; Keller and Pinter, 2002

Class 2 (0.46 - 0.47)

Class 3 (<0.46)

Basin shape index (Bs)

${\text{B}}_{\text{S}}={\text{B}}_{\text{L}}/{\text{B}}_{\text{W}}$

where B_L is the length of a basin and it is measured from the head point to the mouth, and B_W is the width of a basin and is measured at widest point of the basin.

Class 1

(>1.76)

Bull and McFadden, 1977; Ramirez- Herrera, 1998

Class 2 (1.11 - 1.76)

Class 3

(<1.11)