3.2.3 Rolling Bay-Point Monroe Management (MA-3) (Reaches 3176-3192, Reach 6002) |
Qualitative Rating = Moderate Impact
Mean CF Score (Normalized) = -0.42 (Range: -0.8 to -0.13)
Median CF Score (Normalized) = -0.43
Number of Reaches = 18
Mean EF Score = 22.7 (Range: 18 to 26)
Median EF Score = 23.5
Description
Rolling Bay-Point Monroe (MA-3) comprises 29,707 ft of shoreline that encompasses Point Monroe, Point Monroe Lagoon, as well as Rolling Bay to Skiff Point (Table A-1, Figure 2). Rolling Bay-Point Monroe (MA-3) comprises 18 reaches broken into the following categories: high bluff (11), spit/backshore (5), low bank (1), and a large marsh/lagoon (1) (Figure B-28). Much of MA-3 contains extensive tideflats. MA-3 is defined by two drift cells that converge at Point Monroe (Figure 3). The smaller drift cell begins at a divergence zone located on the eastern shore of Port Madison and moves southeast into Point Monroe Lagoon; high bluffs on the landward margin of the lagoon have exhibited some recent instability. The larger second cell begins to the south at a divergence zone located near Skiff Point, with northerly alongshore drift that terminates at the end of Point Monroe. Relative to wave exposure, shorelines along the eastern shore facing Puget Sound are considered “semi-protected,” with “very protected” shorelines within Point Monroe Lagoon (Figure B29). MA-3 receives most upland flows from Dripping Water Creek (WRIA 15.0320) and unnumbered 28, which drain upland areas with low levels of land use (1% TIA).
Overhanging riparian vegetation covers approximately 29% of the MA-3 shoreline (Table A-1, Figure B-34). However, within the 200-ft riparian zone, naturally vegetated surfaces (coniferous and deciduous trees, shrubs, and wetlands) compose 57% of land cover (Figure B-33). Impervious surfaces (e.g., roads, roofs) represent 17% of the riparian zone land cover.
Shoreline development in MA-3 is primarily residential in nature. Many of the homes built along the spit at Point Monroe are built on fill that directly abuts the shoreline, where encroachment is likely underestimated. However, MA-3 shorelines also include Fay Bainbridge State park, which is a stretch of relatively undeveloped sandy beach with shoreline access for recreation. Approximately 38% of shoreline is modified by armoring and 27% of the shoreline has armoring that encroaches into the intertidal zone (Table A-1, Figure B-30).
A total of 291 point modifications were recorded along MA-3 shorelines, at an average of 10 modifications per 1000 ft (Table A-1, Figure B-31). Most of these modifications are structures at the waterline (112), as well as docks (33) and overwater structures (28). A total of 8 outfalls were also recorded in MA‑3.
Limiting Factors
The average normalized CF score within MA-3 was -0.42, within the middle range of MA scores on Bainbridge Island (Table A-2, Figure B-10, Figure B-13). The wave-energy metric for MA-3 scored particularly low (poor) relative to all other MAs (Table A-3, Figure B-16). Low (poor) wave-energy scores were influenced not only by extent of shoreline armoring within each reach, but also by the prevalence of vertical concrete-type bulkheads that encroached into the intertidal zone along shorelines with higher wave exposure.
Conversely, the artificial shade and hydrology metrics in MA-3 scored high (good) relative to other MAs (Table A-3, Figure B-16). Artificial shade scores were high (good) primarily because of the low density of shading structures, such as docks and piers, present along MA-3 shorelines. In part, the poor shoreline access (high bluffs) and higher relative wave exposure of this MA is not conducive to mooring and accessing boats. The only multi-boat pier (marina) along this stretch of shoreline was located in the lagoon behind Point Monroe (Figure B-32). Hydrology scores were also relatively high (good), despite the influence of impaired tidal hydrology as a result of armoring encroachment. Much of this can be attributed to low TIA (17%) within the marine riparian zone, the lack of artificial tidal constrictions along the shoreline, and relatively low density of outfalls.
Two of the most highly affected high-bluff reaches on Bainbridge Island (Reaches 3177 and 3178) are located within Rolling Bay (MA-3) (Figure B-38). These reaches are feeder bluffs (at least historically); however, each has homes and bulkheads built at the base of the bluffs, with high rates of armoring (>90%), high densities of point modifications, no overhanging riparian vegetation, and a relatively high %TIA in marine riparian zone.
Opportunities
One of the least-impacted spit/barrier/backshore reaches on Bainbridge Island (Reach 3186) encompasses Fay Bainbridge State Park, which has no linear or point modifications along the shoreline, low backshore/dune or riparian vegetation, and LWD accumulation on the backshore (Figure B-38).
The most obvious opportunities for improving scoring of controlling factors metrics include removal or modification of unnecessary armoring structures, especially those that encroach into the intertidal zone. These actions may reduce reflective wave energy, allow resumption of natural sediment processes, preserve intertidal and subtidal vegetated habitats such as eelgrass, and enhance forage-fish spawning functions (Figure B-14).
The EF scores were moderate-to-high in MA-3 relative to the rest of Bainbridge Island (Table A-4, Figure B-11, Appendix D) because of the prevalence of documented herring and sandlance spawning areas, principally in the northern region near Point Monroe (Figure B-34). Cutthroat trout are also documented to spawn in Dripping Water Creek (WRIA 15.0320), and efforts should be made to maximize functions of juvenile rearing areas, both in-stream and in nearby shoreline habitats. Continuous-to-patchy eelgrass beds are found along much of the shoreline, as are geoduck resources (Figures B-35, B-37).
Individual Reaches within MA-3 (Figure B-38, Appendix C, Appendix D)
Reach 3176
CF Rating = Moderate Impact; Normalized score = -0.467
Most impacted CF metric: pollution
Least impacted CF metric: hydrology
Geomorphic class: High Bluff; Shoreline length: 427 ft
Sediment source: Alongshore; Wave exposure: semi-protected
Overhanging vegetation: 12.3%; Riparian zone land use: 22.6% TIA, 34.1% forested
Total shoreline armoring: 52.2%; Total encroaching: 0%
Total point modifications: 2; Density: 4.7/1000 ft; most common is upland structures at waterline, with 2.3/1000 ft
Other: shellfish closure present
EF Score: 20
Reach 3177
CF Rating = Moderate/High Impact, Normalized score = -0.8
Most impacted CF metrics: wave energy, natural shade, substrate type, depth/slope, pollution
Least impacted CF metric: artificial shade, physical disturbance
Geomorphic class: High Bluff; Shoreline length: 1311 ft
Sediment source: Alongshore; Wave exposure: semi-protected
Overhanging vegetation: 0%; Riparian zone land use: 39.2% TIA, 36.8% forested
Total shoreline armoring: 89.1%; Total encroaching: 89.1%
Total point modifications: 24; Density: 18.3/1000 ft; most common is upland structures at waterline, with 12.2/1000 ft
Other: shellfish closure present
EF Score: 18
Reach 3178
CF Rating = Moderate/High Impact, Normalized score = -0.756
Most impacted CF metrics: wave energy, natural shade, sediment supply, depth/slope, pollution
Least impacted CF metric: physical disturbance
Geomorphic class: High Bluff; Shoreline length: 852 ft
Sediment source: Backshore, with feeder bluff activity; Wave exposure: semi-protected
Overhanging vegetation: 0%; Riparian zone land use: 25.4% TIA, 48.3% forested
Total shoreline armoring: 100%; Total encroaching: 100%
Total point modifications: 6; Density: 7/1000 ft; most common is upland structures at waterline, with 2.3/1000 ft
Other: shellfish closure present
EF Score: 20
Reach 3179
CF Rating = Low Impact, Normalized score = -0.178
Most impacted CF metric: sediment supply
Least impacted CF metric: natural shade, hydrology, physical disturbance
Geomorphic class: High Bluff; Shoreline length: 5675 ft
Sediment source: Backshore, with feeder bluff activity; Wave exposure: semi-protected
Overhanging vegetation: 81.4%; Riparian zone land use: 13.6% TIA, 81.8% forested
Total shoreline armoring: 26.5%; Total encroaching: 18.4%
Total point modifications: 10; Density: 1.8/1000 ft; most common is upland structures at waterline, with 0.7/1000 ft
Other:
EF Score: 25
Reach 3180
CF Rating = Low/Moderate Impact; Normalized score = -0.4
Most impacted CF metrics: natural shade, sediment supply
Least impacted CF metric: artificial shade, physical disturbance
Geomorphic class: High Bluff; Shoreline length: 905 ft
Sediment source: Backshore, with feeder bluff activity; Wave exposure: semi-protected
Overhanging vegetation: 8%; Riparian zone land use: 14.1% TIA, 74.3% forested
Total shoreline armoring: 34.2%; Total encroaching: 34.2%
Total point modifications: 1; Density: 1.1/1000 ft; most common is outfalls, with 1.1/1000 ft
Other:
EF Score: 22
Reach 3181
CF Rating = Moderate Impact; Normalized score = -0.578
Most impacted CF metrics: wave energy, depth/slope
Least impacted CF metric: artificial shade, physical disturbance
Geomorphic class: High Bluff; Shoreline length: 583 ft
Sediment source: Alongshore; Wave exposure: semi-protected
Overhanging vegetation: 10.7%; Riparian zone land use: 36.6% TIA, 44.5% forested
Total shoreline armoring: 99.9%; Total encroaching: 99.9%
Total point modifications: 3; Density: 5.1/1000 ft; most common is upland structures at waterline, with 5.1/1000 ft
Other:
EF Score: 23
Reach 3182
CF Rating = Low/Moderate Impact; Normalized score = -0.325
Most impacted CF metrics: wave energy, sediment supply, depth/slope
Least impacted CF metric: natural shade, artificial shade, physical disturbance
Geomorphic class: Spit/Barrier/Backshore; Shoreline length: 944 ft
Sediment source: Foreshore; Wave exposure: semi-protected
Overhanging vegetation: 6.6%; Riparian zone land use: 29.2% TIA, 51.3% forested
Total shoreline armoring: 42.8%; Total encroaching: 42.8%
Total point modifications: 3; Density: 3.2/1000 ft; most common is upland structures at waterline, with 1.1/1000 ft
Other:
EF Score: 22
Reach 3183
CF Rating = Moderate Impact; Normalized score = -0.533
Most impacted CF metrics: wave energy, sediment supply
Least impacted CF metric: artificial shade, physical disturbance
Geomorphic class: High Bluff; Shoreline length: 616 ft
Sediment source: Backshore, with feeder bluff activity; Wave exposure: semi-protected
Overhanging vegetation: 11.6%; Riparian zone land use: 19.4% TIA, 65.8% forested
Total shoreline armoring: 68.8%; Total encroaching: 63.8%
Total point modifications: 4; Density: 6.5/1000 ft; most common is upland structures at waterline, with 4.9/1000 ft
Other:
EF Score: 21
Reach 3184
CF Rating = Moderate Impact; Normalized score = -0.511
Most impacted CF metrics: sediment supply, depth/slope
Least impacted CF metric: artificial shade, pollution, physical disturbance
Geomorphic class: High Bluff; Shoreline length: 2485 ft
Sediment source: Backshore, with feeder bluff activity; Wave exposure: semi-protected
Overhanging vegetation: 17%; Riparian zone land use: 7.6% TIA, 64.8% forested
Total shoreline armoring: 66.4%; Total encroaching: 66.4%
Total point modifications: 1; Density: 0.4/1000 ft; most common is stairs, with 0.4/1000 ft
Other:
EF Score: 24
Reach 3185
CF Rating = Low Impact, Normalized score = -0.178
Most impacted CF metric: natural shade
Least impacted CF metric: wave energy, sediment supply, substrate type, depth/slope, hydrology
Geomorphic class: High Bluff; Shoreline length: 915 ft
Sediment source: Alongshore, with feeder bluff activity; Wave exposure: semi-protected
Overhanging vegetation: 9.2%; Riparian zone land use: 22.3% TIA, 47% forested
Total shoreline armoring: 0%; Total encroaching: 0%
Total point modifications: 4; Density: 4.4/1000 ft; most common is buoys, with 2.2/1000 ft
Other: LWD on beach backshore
EF Score: 25
Reach 3186
CF Rating = Low Impact, Normalized score = -0.125
Most impacted CF metrics: artificial shade, physical disturbance
Least impacted CF metric: wave energy, natural shade, sediment supply, substrate type, depth/slope, hydrology
Geomorphic class: Spit/Barrier/Backshore; Shoreline length: 2782 ft
Sediment source: Alongshore; Wave exposure: semi-protected
Overhanging vegetation: 0%; Riparian zone land use: 20.8% TIA, 35.6% forested
Total shoreline armoring: 0%; Total encroaching: 0%
Total point modifications: 12; Density: 4.3/1000 ft; most common is upland structures at waterline, with 2.5/1000 ft
Other: borders Fay Bainbridge State Park,
EF Score: 24
Reach 3187
CF Rating = Low/Moderate Impact, Normalized score = -0.225
Most impacted CF metric: physical disturbance
Least impacted CF metric: natural shade, artificial shade, pollution, hydrology
Geomorphic class: Spit/Barrier/Backshore; Shoreline length: 712 ft
Sediment source: Alongshore; Wave exposure: semi-protected
Overhanging vegetation: 0%; Riparian zone land use: 1.7% TIA, 0% forested
Total shoreline armoring: 13.7%; Total encroaching: 0%
Total point modifications: 3; Density: 4.2/1000 ft; most common is upland structures at waterline, with 2.8/1000 ft
Other: Fay Bainbridge State Park, backshore dunes and LWD
EF Score: 20
Reach 3188
CF Rating = Moderate Impact; Normalized score = -0.6
Most impacted CF metrics: substrate type, depth/slope
Least impacted CF metric: natural shade
Geomorphic class: Spit/Barrier/Backshore; Shoreline length: 1711 ft
Sediment source: Alongshore; Wave exposure: semi-protected
Overhanging vegetation: 0%; Riparian zone land use: 30.6% TIA, 0% forested
Total shoreline armoring: 87.4%; Total encroaching: 66.5%
Total point modifications: 47; Density: 27.5/1000 ft; most common is upland structures at waterline, with 17.5/1000 ft
Other: Point Monroe
EF Score: 26
Reach 3189
CF Rating = Low/Moderate Impact; Normalized score = -0.325
Most impacted CF metric: physical disturbance
Least impacted CF metric: natural shade, hydrology
Geomorphic class: Spit/Barrier/Backshore; Shoreline length: 1764 ft
Sediment source: Alongshore; Wave exposure: semi-protected
Overhanging vegetation: 0%; Riparian zone land use: 26% TIA, 1.2% forested
Total shoreline armoring: 15.5%; Total encroaching: 7%
Total point modifications: 17; Density: 9.6/1000 ft; most common is buoys, with 5.1/1000 ft
Other: outer half of Point Monroe
EF Score: 24
Reach 3190
CF Rating = Moderate Impact; Normalized score = -0.6
Most impacted CF metrics: natural shade, physical disturbance
Least impacted CF metric: wave energy, hydrology
Geomorphic class: Marsh/Lagoon; Shoreline length: 3447 ft
Sediment source: Unknown; Wave exposure: very protected
Overhanging vegetation: 0%; Riparian zone land use: 29.2% TIA, 2.3% forested
Total shoreline armoring: 36.6%; Total encroaching: 0%
Total point modifications: 109; Density: 31.6/1000 ft; most common is upland structures at waterline, with 9.3/1000 ft
Other: 1 marina(s) present; inside of Point Monroe, encroachment likely underestimated
EF Score: 22
Reach 6002
CF Rating = Low/Moderate Impact, Normalized score = -0.225
Most impacted CF metrics: artificial shade, substrate type
Least impacted CF metric: wave energy, natural shade
Geomorphic class: High Bluff; Shoreline length: 1976 ft
Sediment source: Unknown; Wave exposure: very protected
Overhanging vegetation: 92.7%; Riparian zone land use: 2.8% TIA, 82.9% forested
Total shoreline armoring: 8.3%; Total encroaching: 0%
Total point modifications: 16; Density: 8.1/1000 ft; most common is floating docks, with 3/1000 ft
Other: High bluffs inside Point Monroe
EF Score: 24
Reach 3191
CF Rating = Moderate Impact; Normalized score = -0.467
Most impacted CF metric: substrate type
Least impacted CF metric: pollution, hydrology
Geomorphic class: Low Bank; Shoreline length: 1432 ft
Sediment source: Foreshore; Wave exposure: protected
Overhanging vegetation: 29.8%; Riparian zone land use: 6.3% TIA, 71.7% forested
Total shoreline armoring: 36.3%; Total encroaching: 8%
Total point modifications: 21; Density: 14.7/1000 ft; most common is piers, with 2.1/1000 ft
Other: broad beach in shallow bay
EF Score: 24
Reach 3192
CF Rating = Low/Moderate Impact; Normalized score = -0.289
Most impacted CF metrics: sediment supply, substrate type
Least impacted CF metric: hydrology, physical disturbance
Geomorphic class: High Bluff; Shoreline length: 1168 ft
Sediment source: Alongshore; Wave exposure: semi-protected
Overhanging vegetation: 66.2%; Riparian zone land use: 16.3% TIA, 61.7% forested
Total shoreline armoring: 39.7%; Total encroaching: 17.6%
Total point modifications: 8; Density: 6.9/1000 ft; most common is stairs, with 2.6/1000 ft
Other:
EF Score: 24
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