Channel Disturbance

Step Wise Guide

Aquatic/Riparian Habitats

· Where are the channels located that have the greatest susceptibility to disturbances?

There are numerous types of natural disturbances including erosion, flooding, and sedimentation. Disturbances can create and also destroy habitats. Natural disturbances also can negatively effect in-stream restoration work and monitoring sites. Some areas of channels are more prone to disturbances than others. From a restoration and monitoring perspective, site selection may want to avoid areas with predicted high levels of disturbance. For example, certain tributary confluences may be more disturbance prone (floods and sedimentation) compared to other parts of a river network. Immediately upstream and downstream of canyons may be areas of increased sedimentation.

Step 1: Go to NetMap Aquatic Habitat Tools > Channel Disturbance Index. This tool has the same data and analysis structure as the “Create Aquatic Habitat Indices” tool for anadromous fish. From the drop down lists on the left hand side, choose the parameters of interest (up to 6) and then modify the data divisions and the preference curve weightings (0-1) on the right hand side. For example, you could weight low gradient streams, tributary confluence effects, and valley width transitions higher. You could also select in-stream erosion potential values (using GEP, shallow landslide or debris flow) higher.

The result is a map indicating where natural disturbances may occur at a higher frequency.