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

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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 44
California Rapid Assessment Method for Wetlands v. 5.0.2 – Chapter 4 Table 4.1: Rating for Landscape Connectivity for all wetlands except Riverine. Rating Alternative States A An average of 76 – 100 % of the transects is wetland habitat of any kind. B An average of 51 – 75 % of the transects is wetland habitat of any kind. C An average of 26 – 50 % of the transects is wetland habitat of any kind. D An average of 0 – 25 % of the transects is wetland habitat of any kind. Riverine wetlands: For riverine wetlands, landscape connectivity is assessed as the continuity of the riparian corridor over a distance of about 500 m upstream and 500 m downstream of the AA. Of special concern is the ability of wildlife to enter the riparian area from outside of it at any place within 500 m of the AA, and to move easily through adequate cover along the riparian corridor through the AA from upstream and downstream. The landscape connectivity of riverine wetlands is assessed as the total amount of non-buffer land cover (as defined in Table 4.4) that interrupts the riparian corridor within 500m upstream or downstream of the AA. Non-buffer land covers less than 10m wide are disregarded in this metric. Note that, for riverine wetlands, this metric considers areas of open water to provide landscape connectivity. For the purpose of assessing buffers, open water is considered a non-buffer land cover. But for the purpose of assessing landscape connectivity for riverine wetlands, open water is considered part of the riparian corridor. This acknowledges the role that riparian corridors have in linking together aquatic habitats and in providing habitat for anadromous fish and other wildlife. Table 4.2: Steps to assess Landscape Connectivity for riverine wetlands. Extend the AA 500 m upstream and downstream, regardless of the Step 1 land cover types that are encountered (see Figure 4.1). Using the site imagery, identify all the places where non-buffer land covers (see Table 4.4) at least 10 m wide interrupt the riparian area Step 2 on at least one side of the channel in the extended AA. Disregard interruptions of the riparian corridor that are less than 10m wide. Do not consider open water as an interruption. Estimate the length of each non-buffer segment identified in Step 2, Step 3 and enter the estimates in the worksheet for this metric. 45
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