Stream power index (SI)* takes into account both a local slope geometry and site location in the landscape combining data on slope gradient and catchment area:
Stream power index can be used to describe potential flow erosion at the given point of the topographic surface. As catchment area and slope gradient increase, the amount of water contributed by upslope areas and the velocity of water flow increase, hence stream power index and erosion risk increase.
Like other combined morphometric variables, stream power 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 stream power index was derived from a DEM of Mount Ararat. CA was calculated by the Martz–de 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.
* Moore, I.D., Grayson, R.B., and Ladson, A.R., 1991. Digital terrain modelling: A review of hydrological, geomorphological and biological applications. Hydrological Processes, 5, 3-30.
** 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: