3.2.4 Murden Cove Management Area (MA4) |
Qualitative Rating = Low/Moderate Impact
Mean CF Score (Normalized) = -0.33 (Range: -0.64 to 0.00)
Median CF Score (Normalized) = -0.34
Number of Reaches = 20
Mean EF Score = 20.2 (Range: 13 to 26)
Median EF Score = 20.5
Description
Murden Cove (MA-4) comprises 28,843 ft of shoreline that encompasses all of Murden Cove, as well as Yeomalt Point and part of Wing Point (Table A-1, Figure 2). Murden Cove comprises 20 reaches broken into the following categories: high bluff (11), spit/backshore (6), marsh/lagoon (2), and low bank (1) (Figure B-39). Most of MA-4 also contains extensive tideflats. MA-4 is defined by two drift cells that converge at the head of Murden Cove, forming the Murden Cove Creek subestuary (a spit and marsh/lagoon area) that lacks appreciable alongshore drift (Figure 3). The northern end of the first drift cell begins at a divergence zone located at Skiff Point and moves south into Murden Cove, encompassing high feeder bluffs south of Skiff Point. The second cell begins to the south at a divergence zone located near Wing Point and moves in a northerly direction, encompassing a number of feeder bluff areas below Yeomalt Point and southern Murden Cove (Figure B-40). Relative to wave exposure, almost all shorelines along the eastern shore facing Puget Sound are considered “semi-protected,” with a small stretch of “protected” and “very protected” shorelines within Murden Cove (Figure B-40). Murden Cove receives upland flows from Murden Cove Creek (WRIA 15.0321), which drains upland areas with low-to-moderate levels of land use (6% TIA), as well as a number of small coastal streams.
Overhanging riparian vegetation covers approximately 36% of the MA-4 shoreline, tying it with MA-1 for the highest value observed of any MA (Table A-1, Figure B-45). Within the 200-ft riparian zone, naturally vegetated surfaces (coniferous and deciduous trees, shrubs, and wetlands) compose 58% of land cover (Figure B-44). Impervious surfaces (e.g., roads, roofs) represent 18% of the riparian zone land cover.
Shoreline development in MA-4 is primarily residential in nature, with some shoreline backed by public roads. Only 34% of the shoreline is modified by armoring and 19% of the shoreline has armoring that encroaches into the intertidal zone, both values that compare favorably with all other MAs on Bainbridge Island (Table A-1, Figure B-41). Most of the homes along this stretch of shoreline are built on the high bluffs, which generally make the shoreline inaccessible; armoring is generally composed of rip-rap at the toe of bluffs.
A total of 86 point modifications were recorded along MA-4 shorelines (unpublished data, COBI 2002), at an average of three modifications per 1000 ft, by far the lowest density of all MAs on the Island (Table A-1, Figure B-42). Most of these modifications are stairs (29) and structures at the waterline (14). A total of 10 outfalls were also recorded along MA-4 shorelines.
Limiting Factors
The average normalized CF score within MA-4 was -0.33, the second highest (best) MA score on Bainbridge Island (Table A-2, Figure B-10, Figure B-13). MA-4 had no particularly low (poor) scores relative to other MAs, but rather, had among the highest (best) scores in four metric categories: artificial shade, substrate type, depth/slope, and physical disturbance (Table A-3, Figure B-16). Artificial shade scores rated well primarily because of the low density of shading structures, such as docks and piers, along MA-4 shorelines. As was seen in MA-3, poor shoreline access (predominance of high bluffs and extensive tide flats) and higher relative wave exposure of this MA is not conducive to mooring and accessing boats. In addition, no marinas or multi-boat piers were documented along this stretch of shoreline (Figure B-43). Substrate type and depth/slope scores were also good because the percentage of shoreline armoring was fairly low in this MA. As well, the substrate metric reflected the relatively low density of point modifications, whereas depth-slope reflected the lack of dredging activity and moderately low level of armoring encroachment. Finally, physical disturbance scores were high (good) primarily because of the low-density residential setting, high-forested cover in the marine riparian zone, and low number of docks, mooring buoys, and ramp densities of most reaches.
Opportunities
Murden Cove (MA-4) encompasses one of the least-altered high bluff reaches (Reach 3165) and two of the least-altered marsh/lagoon reaches (Reaches 3170 and 3171) on Bainbridge Island (Figure B-49, Appendix C). Reach 3165 is a feeder bluff, with downed trees at the based of the bluffs, high forest cover in the landward riparian zone, and no linear or point modifications along shoreline. Reaches 3170 and 3171 are located near the outlet of Murden Cove Creek and have abundant LWD accumulation, intact tidal flats, abundant overhanging and marsh vegetation, and no point or linear modifications along the shoreline.
At an MA level, the most obvious opportunities for improving scoring would be to enhance processes and functions at reaches with particularly low (poor) scores (Figure B-14). This may include targeting removal of encroaching armoring structures in front of feeder bluffs or backshore sediment sources to allow natural sediment processes, modifying or softening armoring structures in front of roads, and removal of constrictions to remnant tidal marshes in Reach 3173 (Figure B-49). Additionally, historic maps and photographs show an extensive backshore marsh along Manitou Beach, which is now fragmented and impacted by development (Peter Namtvedt Best, personal communications). Restoring and reconnecting this marsh to Murden Cove would provide additional functional benefit.
The EF scores were moderate in MA-4 relative to the rest of Bainbridge Island (Figure B-11, Appendix D). There are some small documented areas of surf smelt and sandlance spawning (Figure B-47). Cutthroat trout, coho, and chum salmon are also documented to spawn in Murden Cove Creek (WRIA 15.0321) (Haring 2000), and efforts should be made to preserve spawning access and functions of juvenile rearing areas, both in-stream and in nearby shoreline habitats. Continuous-to-patchy eelgrass beds are found in parts of Murden Cove, and geoduck resources are abundant throughout the MA (Figure B-46 and B-48).
Individual Reaches within MA-4 (Figure B-49, Appendix C, Appendix D)
Reach 3156
CF Rating = Moderate/High Impact; Normalized score = -0.622
Most impacted CF metrics: natural shade, depth/slope, pollution
Least impacted CF metric: artificial shade
Geomorphic class: High Bluff; Shoreline length: 267 ft
Sediment source: Alongshore; Wave exposure: semi-protected
Overhanging vegetation: 0%; Riparian zone land use: 14.8% TIA, 39.3% forested
Total shoreline armoring: 100%; Total encroaching: 100%
Total point modifications: 0
Other: shellfish closure present; Wing Point
EF Score: 18
Reach 3157
CF Rating = Moderate Impact; Normalized score = -0.422
Most impacted CF metrics: natural shade, pollution
Least impacted CF metric: artificial shade, hydrology, physical disturbance
Geomorphic class: High Bluff; Shoreline length: 717 ft
Sediment source: Alongshore; Wave exposure: semi-protected
Overhanging vegetation: 0%; Riparian zone land use: 27.2% TIA, 43.7% forested
Total shoreline armoring: 37%; Total encroaching: 14.5%
Total point modifications: 4; Density: 5.6/1000 ft; most common is stairs, with 5.6/1000 ft
Other: shellfish closure present; broad backshore with LWD recruitment
EF Score: 18
Reach 3158
CF Rating = Low/Moderate Impact; Normalized score = -0.311
Most impacted CF metric: pollution
Least impacted CF metric: hydrology, physical disturbance
Geomorphic class: High Bluff; Shoreline length: 3639 ft
Sediment source: Backshore, with feeder bluff activity; Wave exposure: semi-protected
Overhanging vegetation: 57.3%; Riparian zone land use: 17.2% TIA, 59.5% forested
Total shoreline armoring: 17.2%; Total encroaching: 13.1%
Total point modifications: 12; Density: 3.3/1000 ft; most common is stairs, with 2.2/1000 ft
Other: shellfish closure present; LWD recruitment on beach from bluffs
EF Score: 26
Reach 3159
CF Rating = Low Impact, Normalized score = -0.133
Most impacted CF metric: natural shade
Least impacted CF metric: wave energy, artificial shade, sediment supply, depth/slope, hydrology, physical disturbance
Geomorphic class: High Bluff; Shoreline length: 387 ft
Sediment source: Alongshore; Wave exposure: semi-protected
Overhanging vegetation: 6.3%; Riparian zone land use: 13.3% TIA, 61% forested
Total shoreline armoring: 0%; Total encroaching: 0%
Total point modifications: 2; Density: 5.2/1000 ft; most common is upland structures at waterline, with 5.2/1000 ft
Other:
EF Score: 24
Reach 3160
CF Rating = Moderate Impact; Normalized score = -0.6
Most impacted CF metric: depth/slope
Least impacted CF metric: natural shade, artificial shade
Geomorphic class: Spit/Barrier/Backshore; Shoreline length: 287 ft
Sediment source: Alongshore; Wave exposure: semi-protected
Overhanging vegetation: 0%; Riparian zone land use: 44% TIA, 9.6% forested
Total shoreline armoring: 100%; Total encroaching: 100%
Total point modifications: 1; Density: 3.5/1000 ft; most common is boat ramps, with 3.5/1000 ft
Other:
EF Score: 26
Reach 3161
CF Rating = Low/Moderate Impact; Normalized score = -0.325
Most impacted CF metrics: wave energy, artificial shade, substrate type, pollution, physical disturbance
Least impacted CF metric: natural shade
Geomorphic class: Spit/Barrier/Backshore; Shoreline length: 2013 ft
Sediment source: Alongshore; Wave exposure: semi-protected
Overhanging vegetation: 10.5%; Riparian zone land use: 38% TIA, 25% forested
Total shoreline armoring: 14.3%; Total encroaching: 3.1%
Total point modifications: 16; Density: 7.9/1000 ft; most common is upland structures at waterline, with 2/1000 ft
Other:
EF Score: 20
Reach 3162
CF Rating = Low/Moderate Impact; Normalized score = -0.244
Most impacted CF metric: sediment supply
Least impacted CF metric: artificial shade, physical disturbance
Geomorphic class: High Bluff; Shoreline length: 1980 ft
Sediment source: Alongshore, with feeder bluff activity; Wave exposure: semi-protected
Overhanging vegetation: 47.6%; Riparian zone land use: 11.2% TIA, 66.2% forested
Total shoreline armoring: 22.8%; Total encroaching: 14.6%
Total point modifications: 4; Density: 2/1000 ft; most common is stairs, with 1/1000 ft
Other:
EF Score: 24
Reach 3163
CF Rating = Moderate Impact; Normalized score = -0.578
Most impacted CF metric: sediment supply
Least impacted CF metric: physical disturbance
Geomorphic class: High Bluff; Shoreline length: 1730 ft
Sediment source: Alongshore, with feeder bluff activity; Wave exposure: semi-protected
Overhanging vegetation: 13.6%; Riparian zone land use: 18.6% TIA, 59.4% forested
Total shoreline armoring: 86.5%; Total encroaching: 39.5%
Total point modifications: 10; Density: 5.8/1000 ft; most common is outfalls, with 2.3/1000 ft
Other:
EF Score: 22
Reach 3164
CF Rating = Low/Moderate Impact; Normalized score = -0.356
Most impacted CF metric: sediment supply
Least impacted CF metric: pollution, physical disturbance
Geomorphic class: High Bluff; Shoreline length: 1208 ft
Sediment source: Backshore, with feeder bluff activity; Wave exposure: semi-protected
Overhanging vegetation: 77.8%; Riparian zone land use: 5.6% TIA, 76.5% forested
Total shoreline armoring: 57%; Total encroaching: 51.9%
Total point modifications: 7; Density: 5.8/1000 ft; most common is stairs, with 3.3/1000 ft
Other:
EF Score: 26
Reach 3165
CF Rating = Low Impact, Normalized score = -0.067
Most impacted CF metric: natural shade
Least impacted CF metric: wave energy, artificial shade, sediment supply, substrate type, depth/slope, hydrology, physical disturbance
Geomorphic class: High Bluff; Shoreline length: 182 ft
Sediment source: Backshore, with feeder bluff activity; Wave exposure: semi-protected
Overhanging vegetation: 43.8%; Riparian zone land use: 18.2% TIA, 66.2% forested
Total shoreline armoring: 0%; Total encroaching: 0%
Total point modifications: 0
Other:
EF Score: 22
Reach 3166
CF Rating = Moderate; Normalized score = -0.467
Most impacted CF metrics: sediment supply, depth/slope
Least impacted CF metric: artificial shade, physical disturbance
Geomorphic class: High Bluff; Shoreline length: 1434 ft
Sediment source: Backshore, with feeder bluff activity; Wave exposure: semi-protected
Overhanging vegetation: 67%; Riparian zone land use: 13.7% TIA, 66% forested
Total shoreline armoring: 89.1%; Total encroaching: 89.1%
Total point modifications: 3; Density: 2.1/1000 ft; most common is pilings, with 2.1/1000 ft
Other:
EF Score: 22
Reach 3167
CF Rating = Moderate/High Impact; Normalized score = -0.644
Most impacted CF metrics: substrate type, depth/slope
Least impacted CF metric: pollution, physical disturbance
Geomorphic class: High Bluff; Shoreline length: 636 ft
Sediment source: Backshore; Wave exposure: semi-protected
Overhanging vegetation: 14.2%; Riparian zone land use: 15.5% TIA, 53.6% forested
Total shoreline armoring: 100%; Total encroaching: 72.4%
Total point modifications: 10; Density: 15.7/1000 ft; most common is upland structures at waterline, with 3.1/1000 ft
Other: large shallow tide flats
EF Score: 14
Reach 3168
CF Rating = Moderate Impact; Normalized score = -0.425
Most impacted CF metrics: wave energy, sediment supply, substrate type
Least impacted CF metric: natural shade, artificial shade, hydrology
Geomorphic class: Spit/Barrier/Backshore; Shoreline length: 438 ft
Sediment source: Alongshore; Wave exposure: semi-protected
Overhanging vegetation: 0%; Riparian zone land use: 17.5% TIA, 58.2% forested
Total shoreline armoring: 78.6%; Total encroaching: 19.9%
Total point modifications: 3; Density: 6.9/1000 ft; most common is boat ramps, with 4.6/1000 ft
Other:
EF Score: 13
Reach 3169
CF Rating = Low Impact, Normalized score = -0.125
Most impacted CF metric: wave energy
Least impacted CF metric: natural shade, artificial shade, pollution, hydrology, physical disturbance
Geomorphic class: Spit/Barrier/Backshore; Shoreline length: 1483 ft
Sediment source: Alongshore; Wave exposure: semi-protected
Overhanging vegetation: 0%; Riparian zone land use: 7.2% TIA, 80.8% forested
Total shoreline armoring: 4.8%; Total encroaching: 0%
Total point modifications: 0
Other: LWD accumulation on spit
EF Score: 16
Reach 3170
CF Rating = Low Impact, Normalized score = -0.05
Most impacted CF metric: natural shade
Least impacted CF metric: wave energy, artificial shade, sediment supply, substrate type, depth/slope, pollution, hydrology, physical disturbance
Geomorphic class: Marsh/Lagoon; Shoreline length: 760 ft
Sediment source: Alongshore; Wave exposure: semi-protected
Overhanging vegetation: 56.3%; Riparian zone land use: 5.3% TIA, 88.3% forested
Total shoreline armoring: 0%; Total encroaching: 0%
Total point modifications: 0
Other:
EF Score: 21
Reach 3171
CF Rating = No Impact, Normalized score = 0
Most impacted CF metrics:
Least impacted CF metric: wave energy, natural shade, artificial shade, sediment supply, substrate type, depth/slope, pollution, hydrology, physical disturbance
Geomorphic class: Marsh/Lagoon; Shoreline length: 3929 ft
Sediment source: Foreshore; Wave exposure: very protected
Overhanging vegetation: 95.7%; Riparian zone land use: 5% TIA, 88.4% forested
Total shoreline armoring: 0%; Total encroaching: 0%
Total point modifications: 2; Density: 0.5/1000 ft; most common is outfalls, with 0.3/1000 ft
Other:
EF Score: 24
Reach 3172
CF Rating = Low/Moderate Impact, Normalized score = -0.222
Most impacted CF metric: natural shade
Least impacted CF metric: artificial shade, hydrology, physical disturbance
Geomorphic class: Low Bank; Shoreline length: 1173 ft
Sediment source: Alongshore; Wave exposure: protected
Overhanging vegetation: 4%; Riparian zone land use: 10.2% TIA, 54.8% forested
Total shoreline armoring: 6.7%; Total encroaching: 0%
Total point modifications: 1; Density: 0.9/1000 ft; most common is upland structures at waterline, with 0.9/1000 ft
Other: small shallow embayment
EF Score: 17
Reach 3173
CF Rating = Low Impact, Normalized score = -0.175
Most impacted CF metric: hydrology
Least impacted CF metric: wave energy, natural shade, artificial shade, sediment supply, substrate type, depth/slope, physical disturbance
Geomorphic class: Spit/Barrier/Backshore; Shoreline length: 2150 ft
Sediment source: Alongshore; Wave exposure: semi-protected
Overhanging vegetation: 0%; Riparian zone land use: 10.8% TIA, 50.3% forested
Total shoreline armoring: 0%; Total encroaching: 0%
Total point modifications: 2; Density: 0.9/1000 ft; most common is outfalls, with 0.9/1000 ft
Other: tidal constriction (culvert) to remnant tidal marsh; backshore is taken up by road, LWD recruitment along entire shoreline
EF Score: 16
Reach 3174
CF Rating = Moderate Impact; Normalized score = -0.5
Most impacted CF metric: sediment supply
Least impacted CF metric: natural shade
Geomorphic class: Spit/Barrier/Backshore; Shoreline length: 1632 ft
Sediment source: Alongshore; Wave exposure: semi-protected
Overhanging vegetation: 1.5%; Riparian zone land use: 37% TIA, 29.2% forested
Total shoreline armoring: 80.3%; Total encroaching: 6.4%
Total point modifications: 4; Density: 2.5/1000 ft; most common is overwater structures, with 0.6/1000 ft
Other: backshore dominated by road, LWD recruitment good
EF Score: 17
Reach 3175
CF Rating = Moderate Impact; Normalized score = -0.422
Most impacted CF metric: pollution
Least impacted CF metric: artificial shade, hydrology
Geomorphic class: High Bluff; Shoreline length: 2799 ft
Sediment source: Backshore, with feeder bluff activity; Wave exposure: semi-protected
Overhanging vegetation: 22.4%; Riparian zone land use: 31.7% TIA, 35.3% forested
Total shoreline armoring: 60.5%; Total encroaching: 24.7%
Total point modifications: 5; Density: 1.8/1000 ft; most common is pilings, with 1.4/1000 ft
Other: shellfish closure present
EF Score: 18
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