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Channel Evolution/Successional Stages

Many stream channels change over time due to geologic influences, climatic changes, and anthropogenic influences. The tendency of rivers is to seek their own flow-related and sediment-related stability within a certain climatic regime. Following disturbance, streams will try to reestablish the dimension, pattern, and profile of a pre-disturbance morphology. Reference reaches that represent the stable stream type for a specific valley type are used to verify morphological relations of the stable stream. The existing stream type must be compared to the potential stable form, thus, this assessment involves determining where the stream type is in comparison to its stable endpoint. The information required to complete this RRISSC step includes:

  1. Example of nine scenarios of various stream channel successional stages (Figure 42, PDF, 94 kb, 1 p.)
  2. Stream type

The various successional stage departures are shown in Figure 42, and their corresponding risk ratings are shown in Table 13, below. The results of this step are recorded into Worksheets 5a & 5b for individual reaches, and the data for multiple locations are summarized in Worksheet 6.

Worksheet 5a: Printable PDF (10 kb, 1 p.) | Excel Spreadsheet (27 kb)
Worksheet 5b: Printable PDF (9 kb, 1 p.) | Excel Spreadsheet (35 kb)
Worksheet 6: Printable PDF (8 kb, 1 p.) | Excel Spreadsheet (21 kb)

Table 13. Risk rating for various stream channel successional state scenarios.

Channel Successional States Risk Rating
E to C Moderate
C to D High
B or C or E or D to G Very High
G to F High
G to B Low
F to B Very Low
F to C Low
F to D Moderate
All others (eg, C to E) Low
* See Figure 42: Stream type succession scenarios.

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