Calculating stream sinuosity (in esri products)

A river’s sinuosity is its tendency to meander back and forth across its floodplain, in an S-shaped pattern, over time. As the stream moves across the landscape, it may leave behind evidence of where the river channel once was (these can take the form of meander scars or oxbow lakes). These patterns usually appear in stream channels found in softer sediments. If a river’s course is bedrock-controlled, other factors—primarily rock strength and structure—control the river’s flow. Few stream courses are completely straight, and most exhibit meanders.

If you ever work with hydrologic data in GIS, you may wish to determine the sinuosity for an entire river or a particular ‘reach‘ of a river of interest. A stream that doesn’t meander at all has a sinuosity of 1. The more meanders in a stream, the closer the sinuosity value will get to 0. Fortunately, it’s simple to determine the sinuosity of a line using either the field calculator or Python. Depending on the version of GIS software you are using, the method differs. See this post for details for ArcView 3 (old!) and ArcMap 8.x-10.2.

Using GIS to determine stream sinuosity

Sinuosity is a measure of how much a river (or other linear feature) deviates from being straight. A truly straight river or road has a sinuosity of 1; as the number of meanders increases, sinuosity approaches 0.

I wrote a document describing how to determine the sinuosity of linear features years ago. I will update it for ArcGIS 10 as time permits, but the original document, written for ArcView 3.x and ArcGIS 8x/9x is available here.