California Rapid Assessment Method for Wetlands - State Water ...

California Rapid Assessment Method for Wetlands v. 5.0.2 – Chapter 4
B. Rationale: Wetlands are often important components of local mosaics of multiple types of
habitat. The components of such mosaics tend to be inter-connected by the flow of water and
movements of wildlife, such that they have additive influences on the timing and extent of many
landscape-level processes, including flooding, filtration of pesticides and other contaminants,
and wildlife support. In turn, these processes can strongly influence the form and function of
wetlands. The functional capacity of a wetland is therefore determined not only by its intrinsic
properties, but by its relationship to other habitats across the landscape. For example, Frissell et
al. (1986) concluded that the structure and dynamics of stream habitats are determined by the
surrounding watershed. Several researchers have concluded that landscape-scale variables are
often better predictors of stream and wetland integrity than localized variables (Roth et al. 1996;
Scott et al. 2002). Wetlands that are close together without hydrological or ecological barriers
between them are better able to provide refuge and alternative habitat patches for metapopulations
of wildlife, to support transient or migratory wildlife species, and to function as
sources of colonists for primary or secondary succession of newly created or restored wetlands.
In general, good landscape connectivity exists only where neighboring wetlands or other habitats
do not have intervening obstructions that could inhibit the movements of wildlife.
C. Seasonality: This metric is not sensitive to seasonality.
D. Office and Field Indicators: For the purposes of CRAM, 500 m has been surmised as the
maximum distance between wetlands and other water-dependent habitats that does not by itself
function as a barrier to the easy regular movements of small mammals, birds, amphibians, or
reptiles. Greater distances between the wetland of interest and neighboring habitats are
considered breaks in landscape connectivity. Similarly, any permanent physical alteration of the
landscape surrounding the wetland that would preclude the movements of wildlife between
habitat types or patches, or that would substantially impound or divert surface water flow
between the wetland of interest and other water-dependent habitats are also considered to be
breaks in connectivity.
All wetlands except riverine: On digital or hardcopy site imagery, draw a
straight line extending 500 m from the AA boundary in each of the four
cardinal compass directions. The lines should intercept the approximate
centroid of the AA. Along each transect line, estimate the percentage of the
segment that passes through wetland or aquatic habitat of any kind, including
open water. Vernal pool systems should be considered aquatic habitat. Use the
worksheet below to record these estimates.
Worksheet 4.1: Landscape Connectivity Metric for All Wetlands Except Riverine
Percentage of Transect Lines that Contains
Wetland Habitat of Any Kind
Segment Direction
North
South
East
West
Average Percentage of Transect Length
That Is Wetland
Percentage of Transect Length
That is Wetland
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