2013.03....e 6.1.pdf - Cram

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Worksheet for Assessing Channel Stability for Riverine Wetlands. *Please refer to the CRAM Photo Dictionary at www.cramwetlands.org for photos of each of the following indicators. *Definitions of several of the terms used can be found in the glossary of the CRAM manual. Condition Indicators of Channel Equilibrium Indicators of Active Degradation Indicators of Active Aggradation □ □ □ □ □ □ □ □ □ □ □ □ □ □ □ □ □ □ □ □ □ □ □ Field Indicators (check all existing conditions) The channel (or multiple channels in braided systems) has a well-defined bankfull contour that clearly demarcates an obvious active floodplain in the cross-sectional profile of the channel throughout most of the AA. Perennial riparian vegetation is abundant and well established along the bankfull contour, but not below it. There is leaf litter, thatch, or wrack in most pools (if pools are present). The channel contains embedded woody debris of the size and amount consistent with what is naturally available in the riparian area. There is little or no active undercutting or burial of riparian vegetation. If mid-channel bars and/or point bars are present, they are not densely vegetated with perennial vegetation. Channel bars consist of well-sorted bed material (smaller grain size on the top and downstream end of the bar, larger grain size along the margins and upstream end of the bar). There are channel pools, the spacing between pools tends to be regular and the bed is not planar throughout the AA The larger bed material supports abundant mosses or periphyton. The channel is characterized by deeply undercut banks with exposed living roots of trees or shrubs. There are abundant bank slides or slumps. The lower banks are uniformly scoured and not vegetated. Riparian vegetation is declining in stature or vigor, or many riparian trees and shrubs along the banks are leaning or falling into the channel. An obvious historical floodplain has recently been abandoned, as indicated by the age structure of its riparian vegetation. The channel bed appears scoured to bedrock or dense clay. Recently active flow pathways appear to have coalesced into one channel (i.e. a previously braided system is no longer braided). The channel has one or more knickpoints indicating headward erosion of the bed. There is an active floodplain with fresh splays of coarse sediment (sand and larger that is not vegetated) deposited in the current or previous year. There are partially buried living tree trunks or shrubs along the banks. The bed is planar (flat or uniform gradient) overall; it lacks well-defined channel pools, or they are uncommon and irregularly spaced. There are partially buried, or sediment-choked, culverts. Perennial terrestrial or riparian vegetation is encroaching into the channel or onto channel bars below the bankfull contour. There are avulsion channels on the floodplain or adjacent valley floor. Overall Equilibrium Degradation Aggradation 23
Rating A B C D Table 12: Rating for Riverine Channel Stability. Alternative State (based on the field indicators listed in the worksheet above) Most of the channel through the AA is characterized by equilibrium conditions, with little evidence of aggradation or degradation. Based on the indicators of condition, typical sediment transport processes are occurring. Most of the channel through the AA is characterized by some aggradation or degradation, none of which is severe. The channel may be approaching or moving away from equilibrium. Based on the indicators of condition, typical sediment transport processes are occurring, however the reach is trending toward excess transport or deposition due to moderate disequilibrium conditions. There is evidence of severe aggradation or degradation of most of the channel through the AA or the channel bed is artificially hardened through less than half of the AA. Based on the indicators of condition, typical sediment transport processes are severely altered. The channel bed is concrete or otherwise artificially hardened through most of AA. Metric 3: Hydrologic Connectivity Definition: Hydrologic connectivity describes the ability of water to flow into or out of the wetland, or the wetland’s ability to accommodate rising floodwaters without persistent changes in water level that can result in stress to wetland plants and animals. This metric is scored by assessing the degree to which the lateral movement of floodwaters is restricted. For riverine wetlands, the Hydrologic Connectivity metric is assessed based on the degree of channel entrenchment (Leopold et al. 1964, Rosgen 1996, Montgomery and MacDonald 2002). Entrenchment is a field measurement calculated as the flood-prone width divided by the bankfull width. The concept of bankfull flow is integral to this metric. Assessing hydrologic connectivity requires measuring the ability of flows to leave the channel and flood the surrounding landscape. In the absence of a site-specific flow duration curve, the best estimate of this process is the entrenchment ratio. The method to calculate this ratio requires an estimate of the width of the wetted channel during bankfull flow, based on proven field indicators. Bankfull depth is the channel depth measured between the thalweg and the projected water surface at the level of bankfull flow. The flood-prone channel width is measured at flood-prone depth, the elevation equal to twice the maximum bankfull depth. The process for measuring entrenchment is outlined below. A long metric measuring tape and a stadia rod are required. For non-wadeable streams (i.e., one-sided Assessment Areas) this metric cannot be measured directly and must be approximated using the following procedure. (a) First, identify indicators of bankfull condition on the side of the stream being assessed. Then, using binoculars to visualize the opposite bank, identify the corresponding bankfull location there. (b) Using appropriate tools (e.g., a portable electronic distancemeasuring device) estimate the bankfull width. (c) Estimate, using the best information available, the depth of the thalweg in the stream at the selected cross-section location, with reference to the estimated bankfull elevation. (d) As with the procedure for wadeable streams, double the estimated bankfull depth to yield an estimated flood-prone depth. (e) Estimate the flood-prone width as with the procedure for wadeable streams. If the flood-prone width is obscured from view in the field, use aerial imagery to estimate floodprone width. (f) Divide the estimated flood-prone width by the estimate bankfull width to provide an estimated entrenchment ratio for use in scoring this metric in non-wadeable streams. 24
Page 1: ` California Rapid Assessment Metho
Page 4 and 5: Photo Identification Numbers and De
Page 6 and 7: Identify Wetland Type Figure 1: Flo
Page 8 and 9: Valley Width A B Bankfull Width C D
Page 10 and 11: Figure 3: Diagram of the lateral ex
Page 12 and 13: Attribute 1: Buffer and Landscape C
Page 14 and 15: Table 5a: Rating for Stream Corrido
Page 16 and 17: Figure 5: Diagram of approach to es
Page 18 and 19: Submetric B: Average Buffer Width D
Page 20 and 21: Submetric C: Buffer Condition Defin
Page 22 and 23: Table 11: Rating for Water Source.
Page 26 and 27: Riverine Wetland Entrenchment Ratio
Page 28 and 29: Metric 1: Structural Patch Richness
Page 30 and 31: Structural Patch Type Worksheet for
Page 32 and 33: Worksheet for AA Topographic Comple
Page 34 and 35: Table 16: Rating of Topographic Com
Page 36 and 37: Layer definitions: Floating Layer.
Page 38 and 39: Table 17: Plant layer heights for a
Page 40 and 41: Metric 2: Horizontal Interspersion
Page 42 and 43: Metric 3: Vertical Biotic Structure
Page 44 and 45: Stressor Checklist Worksheet HYDROL
Page 46: CRAM Score Guidelines Step 1: Calcu

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