Home

CV

Publications

Principles

Software

Links

Contacts

 

en   ru

 
Topographic index

Topographic index (TI)* takes into account both a local slope geometry and site location in the landscape combining data on slope gradient and catchment area:

,

where CA and G are catchment area and slope gradient, respectively.

Topographic index is a measure of the extent of flow accumulation at the given point of the topographic surface. As catchment area increases and slope gradient decreases, topographic index increases.

Like other combined morphometric variables, topographic index can be derived from a digital elevation model (DEM) by the sequential application of methods for local and nonlocal morphometric characteristics, followed by an arithmetic combination of the results of these calculations.

Example**. A model of topographic index was derived from a DEM of Mount Ararat. CA was calculated by the Martzde Jong method adapted to spheroidal equal angular grids; G was calculated by the universal spectral analytical method. The model includes 779,401 points (the matrix 1081 x 721); the grid spacing is 1". The vertical exaggeration of the 3D model is 2x. The data processing and modelling were carried out using the software Matlab R2008b and LandLord 4.0.

 

References

* Beven, K.J., and Kirkby, M.J., 1979. A physically-based variable contributing area model of basin hydrology. Hydrological Science, 24, 43-69.

** Florinsky, I.V., 2016. An illustrated introduction to geomorphometry. Almamac Space and Time, 11 (1): 20 p. (in Russian, with English abstract).  Article at the journal website

 

For details and other examples, see:

DIGITAL TERRAIN ANALYSIS

IN SOIL SCIENCE AND GEOLOGY

 

2nd revised edition

 

 

I.V. Florinsky

 

Elsevier / Academic Press, 2016

Amsterdam, 486 p.

 

ISBN 978-0-12-804632-6

 

 

 

Contents    Summary

 

Elsevier    Amazon