Stream Succession State Shift

The consequence of increased sediment size, supply (load), aggradation, degradation, vertical and/or lateral stability and channel enlargement can lead to long-term significant channel adjustments, changing stream type and related beneficial uses. The various evolutionary scenarios are depicted in Figure 42 and rated in Worksheet 14 (PDF version, 43 kb, 1 p. or Excel spreadsheet). For example a potential shift from a C to G (as indicated by bank-height ratio and width/depth ratio ratings (Figure 108 (PDF, 29 kb, 1 p.), Figure 109 (PDF, 16 kb, 1 p.), Figure 110 (PDF, 20 kb, 1 p.), and Figure 111 (PDF, 57 kb, 1 p.)) would create long-term serious adverse effects on sediment supply and beneficial uses. The user is advised to review the discussion in Introduction to Sediment & River Stability addressing channel evolution shifts indicating the physical and biological consequence of changing stream type. Certain ratings, however, could indicate a positive response or an evolutionary direction toward natural recovery or stabilization. This consequence is a result of evaluation of Step 24 through Step 26. Worksheet 29b (PDF, 29 kb, 1 p.) is used to describe the stability consequences of the existing successional stages of the assessed stream segments.

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