California Rapid Assessment Method for Wetlands - State Water ...
California Rapid Assessment Method for Wetlands - State Water ...
California Rapid Assessment Method for Wetlands - State Water ...
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<strong>Cali<strong>for</strong>nia</strong> <strong>Rapid</strong> <strong>Assessment</strong> <strong>Method</strong> <strong>for</strong> <strong>Wetlands</strong> v. 5.0.2 – Chapter 4<br />
Riverine: For riverine wetlands, Hydrologic Connectivity is assessed based on the<br />
degree of channel entrenchment (Leopold et al. 1964, Rosgen 1996, Montgomery and<br />
MacDonald 2002). Entrenchment calculated as the flood-prone width divided by the<br />
bankfull width. The flood-prone width is measured at the elevation equal to twice the<br />
maximum bankfull depth; maximum bankfull depth is the height of bankfull flow<br />
above the thalweg. The process <strong>for</strong> estimating entrenchment is outlined below.<br />
Worksheet 4.5: Riverine Wetland Entrenchment Ratio Calculation<br />
The following 5 steps should be conducted <strong>for</strong> each of 3 cross-sections located in the AA at the<br />
approximate mid-points along straight riffles or glides, away from deep pools or meander bends.<br />
Steps Replicate Cross-sections 1 2 3<br />
1 Estimate<br />
bankfull width.<br />
2: Estimate max.<br />
bankfull depth.<br />
3: Estimate flood<br />
prone depth.<br />
4: Estimate flood<br />
prone width.<br />
5: Calculate<br />
entrenchment.<br />
6: Calculate average<br />
entrenchment.<br />
This is a critical step requiring familiarity with field<br />
indicators of the bankfull contour. Estimate or<br />
measure the distance between the right and left<br />
bankfull contours.<br />
Imagine a level line between the right and left bankfull<br />
contours; estimate or measure the height of the line<br />
above the thalweg (the deepest part of the channel).<br />
Double the estimate of maximum bankfull depth<br />
from Step 2.<br />
Imagine a level line having a height equal to the flood<br />
prone depth from Step 3; note where the line<br />
intercepts the right and left banks; estimate or<br />
measure the length of this line.<br />
Divide the flood prone width (Step 4) by the bankfull<br />
width (Step 1).<br />
Calculate the average results <strong>for</strong> Step 5 <strong>for</strong> all 3 replicate cross-sections.<br />
Enter the average result here and use it in Tables 4.15 a, b.<br />
Flood Prone Width<br />
Bankfull Width<br />
Flood Prone Depth<br />
Bankfull Depth<br />
Figure 4.5: Parameters of Channel entrenchment. Flood prone depth is twice maximum<br />
bankfull depth. Entrenchment equals flood prone width divided by bankfull width.<br />
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