Sinuosity

"Sinuous" redirects here. For the fictional snake from the animated children's television series The Animals of Farthing Wood, see Sinuous (Farthing Wood).

Calculation of sinuosity for an oscillating curve.

Sinuosity or sinuosity index is a measure of deviation of a path between two points from the shortest possible path (the geodesic, in planar geometries a straight line between the two points). It is given by the ratio of:

$\frac{{\text{actual path length}}}{{\text{shortest path length}}}$

This sinuosity index is 1 in the case in which the actual path length is equal to the shortest path length, and can increase to infinity for a closed loop (where the shortest path length is zero) or for an infinitely-long actual path.^[1]

Rivers

The meandering Rio Cauto at Guamo Embarcadero, Cuba, is not taking the shortest path downslope. Therefore, its sinuosity, or sinuosity index, is > 1.

In studies of rivers, the sinuosity index is similar but not identical to the general form given above, being given by:

$\text{SI} = \frac{{\text{channel length}}}{{\text{downvalley length}}}$

The difference from the general form happens because the downvalley path is not perfectly straight. The sinuosity index can be explained, then, as the deviations from a path defined by the direction of maximum downslope. For this reason, bedrock streams that flow directly downslope have a sinuosity index of 1, and meandering streams have a sinuosity index that is greater than 1.^[2]

References

1. ^ Leopold, Luna B., Wolman, M.G., and Miller, J.P., 1964, Fluvial Processes in Geomorphology, San Francisco, W.H. Freeman and Co., 522p.
2. ^ Mueller, Jerry (1968). "An Introduction to the Hydraulic and Topographic Sinuosity Indexes1". Annals of the Association of American Geographers 58 (2): 371. doi:10.1111/j.1467-8306.1968.tb00650.x.