A New Method for Measuring River Sinuosity across Varying Length Scales

Abstract:

Sinuosity is an emergent characteristic of meandering rivers. In bedrock rivers, climate (Stark 2009) and bedrock lithology (Johnson and Finnegan 2015) likely influence sinuosity. Comparing trends in sinuosity between and along rivers with different climates, lithology, and tectonics has the potential to shed light on what controls sinuosity. However, measuring sinuosity in a meaningful way is challenging.

The length scale over which sinuosity is calculated affects the measurement. For example, a river with many tight curves generates greater sinuosities with a shorter length scale, and a river with a curved valley might generate greater sinuosities with a longer length scale. Therefore, to find the distribution of sinuosity across length scales, a method is needed that can compare sinuosities at a variety of length scales.

To achieve this goal, we made a tool that calculates sinuosities across many length scales along a river and derives both the maximum sinuosity and the length scale at which these maximums occur for each point on the river.

Using digital elevation models (DEMs) of a number of landscapes with varying climate, lithology and uplift rate, we extracted river networks using a flow accumulation method. From this, our code works within the ArcGIS Python window. It applies a moving window to calculate sinuosity at each point along the river for a wide range of length scales. All the points’ maximum sinuosities can be displayed, even if they are derived from different length scales. Because the code is run within ArcGIS, it is easy to display these sinuosity data as attributes of the original river networks.

This tool opens new possibilities for tracking patterns in sinuosity along and between rivers. Our preliminary data suggests that this method will be useful for interpreting trends in sinuosity and learning about what factors influence them.