Clallam County Feeder Bluff Mapping for SMP Update For: ESA/ Clallam County December 2012 By: Jim Johannessen, LEG, MS & Andrea MacLennan, MS Coastal Geologic Svcs, Bellingham, WA www.coastalgeo.com Outline Objectives Previous work Geomorphic processes Methods Feeder bluff results Study Area Objectives Definitively map coastal drift sediment sources (feeder bluffs), “neutral” areas (transport zones), & accretion shoreforms-in N and E County Review and modify drift cell mapping if needed Mapping within drift cells only Littoral (drift) cells = Net shore-drift cells Determined by wave exposure & shoreline configuration Represent independent sediment compartments Over 800 cells in Puget Sound May share Divergence Zones w/ adjacent cells Eroding bluffs (feeder bluffs) are critical components to each cell Divergence Zone West Clallam County Current Net shore-drift (“drift cells”) Previous net shore- drift mapping: Coastal Zone Atlas of WA – (1978-79) East Clallam County Bubnick, through Schwartz of WWU, Shell 1986 CGS 2007 (for USACE) CGS 2011 32 drift cells = 90 miles 24 NAD (no appreciable drift) areas Other Previous Clallam County Work Previous Mapping—Other: WDNR Shorezone database – Dethier habitat classification and Howe’s geomorphic classification. Emphasizes substrate and intertidal morphology rather than larger scale processes. PSNERP Change Analysis Mapping – Hugh Shipman’s typology in current and historic (circa 1850-80) conditions. Coarse scale, shoretypes lumped together, sediment source function not characterized. Coastal Geologic Services – Mapped feeder bluffs/ geomorphic shoretypes within most of 8 other Puget Sound counties • Recent Clallam Co feeder bluff mapping applied same methods as previous mapping. • These data will soon be compiled to create Sound-wide dataset Current Geomorphic Shoretype Mapping - Methods Field Methods -GPS points collected at start and end point, shore normal (90 degree angle) -Surveys conducted at mid-high tide at close range, and notes collected with GPS points -GPS imported into GIS, all mapping snapped to shorezone highwater shoreline Digitized at 1:3000, vertical and oblique images referenced during process Remote Methods -Interpretation of geomorphic shoretypes using vertical and oblique air photos, as well as surface geology and landslide mapping -Field truthing was conducted randomly and in areas with low level of confidence Current Geomorphic Shoretype Mapping - Field Indicators Feeder Bluff Exceptional Mapping Presence of (priority in order): Absence of: 1. Bluff/ bank 1. Shoreline bulkhead/ fill 2. Recent landslide scarps 2. Backshore 3. Bluff toe erosion 3. Old/ rotten logs 4. Abundant sand/gravel in bluff 4. Coniferous bluff vegetation 5. Colluvium/ slide debris 5. Bulkhead 6. Primarily unvegetated or vegetated slumps 7. Trees across beach 8. Boulder/ cobble lag 9. Steep bluff (relative alongshore) Feeder Bluff Mapping Presence of (priority in order): Absence of: 1. Bluff/ bank 1. Shoreline bulkhead/fill 2. Past landslide scarps 2. Backshore 3. Intermittent toe erosion 3. Old/rotten logs 4. Moderate amount sand/gravel in bluff 4. Coniferous bluff vegetation 5. Intermittent colluvium 5. Bulkhead 6. Minimal vegetation 7. Trees across beach 8. Boulder/ cobble lag 9. Steep bluff (relative alongshore) Current Geomorphic Shoretype Mapping - Field Indicators Feeder Bluff –Talus Mapping Presence of (priority in order): Absence of: 1. Bluff/ bank 2. Past landslide scarps, mapped landslides 1. Shoreline bulkhead/fill 3. Bedrock lithology with particle size relevant to 2. Backshore beach material, bedding or jointing conducive to breaking and abrasion 4. Intermittent toe erosion 3. Old/rotten logs 5. Intermittent colluvium 4. Basalt 6. Minimal vegetation on bluff face 5. Bulkhead 7. Trees across beach 8. Boulder/ cobble lag 9. Steep bluff (relative alongshore) Transport Zone Mapping Presence of (priority in order): Absence of: 1. Coniferous bluff vegetation 1. Visible landslide scarps 2. Apparent relative bluff stability 2. Toe erosion 3. Gentle slope bluff (relative alongshore) 3. Backshore & backshore vegetation 4. Unbulkheaded transport zone adjacent 4. Old/rotten logs 5. Colluvium 6. Trees across beach 7. Bulkhead Current Geomorphic Shoretype Mapping - Field Mapping Nearshore Sediment Sources South of Dungeness Northwest Sequim Bay Feeder Bluff Exceptional Feeder Bluff Current Geomorphic Shoretype Mapping - Field Mapping Nearshore Sediment Sources - Aerials South of Dungeness Northwest Sequim Bay Feeder Bluff Exceptional Feeder Bluff Current Geomorphic Shoretype Mapping - Field Mapping East of Salt Creek HarrisonHarrison Beach Beach Feeder Bluff - Talus Transport Zone Current Geomorphic Shoretype Mapping - Field Mapping Dungeness Spit West of Hoku River Accretion Shoreform Modified Current Geomorphic Shoretype Mapping - Field Mapping No Appreciable Drift (NAD) Areas Inner Sequim Bay West of Sekiu Inner Embayment Shore Bedrock Shore Insufficient energy to transport sediment No sediment to transport Shallow Landslides Drawings: Hugh Shipman WA Ecology Large Slumps and Landslides Drawings: Hugh Shipman WA Ecology Results of CurrentSequim Conditions Bay Mapping feeder bluff mapping Results of Current ConditionsDungeness Mapping Spit area feeder bluff mapping Freshwater BayResults area offeeder Current bluff Conditions mapping Mapping Twin Rivers areaResults feeder of Current bluff mapping Conditions Mapping CGS Shoretypes (by percent) Drift Cell Drift Cell length (ft) FBE FB FB-TS TZ AS MOD JF-18-5 11,313 26 48 0 0 17 9 JF-18-4 15,381 0 50 0 12 19 19 JF-18-1 18,036 10 60 0 1 29 0 JF-17-6 11,683 0 34 0 12 54 0 Results by JF-17-7 17,384 0 30 0 28 26 16 Drift Cell JF-17-3 19,271 0 31 0 28 14 27 JF-17-2 9,865 10 18 0 4 11 57 JF-17-1 17,678 35 5 0 5 53 2 JF-16-6 32,954 0 1 0 0 98 1 JF-16-5 8,208 0 29 0 34 8 29 JF-16-4 11,254 0 0 0 0 100 0 JF-16-1 107,355 35 4 0 7 48 6 JF-13-3 4,754 0 0 0 0 34 66 JF-12-1 36,234 3 22 1 39 31 4 JF-10-2 8,879 0 6 12 11 47 24 JF-10-1 36,908 0 3 38 39 10 10 JF-7-7 1,555 0 0 86 14 0 0 JF-7-6 16,919 15 16 53 4 13 0 JF-7-5 16,543 0 0 38 36 16 10 JF-7-4 8,773 0 0 65 30 0 4 JF-7-3 24,467 0 0 65 26 5 4 JF-7-2 3,732 0 0 0 13 87 0 JF-7-1 2,223 0 0 77 23 0 0 JF-6-1 2,393 0 0 50 50 0 0 JF-4-5 5,352 0 0 0 5 95 0 JF-4-4.2 4,541 0 0 0 0 44 56 JF-4-4.1 5,756 0 0 0 25 7 67 JF-4-3 8,060 0 0 24 58 18 0 JF-4-2 5,453 0 0 0 84 0 16 JF-4-1 33,970 0 0 0 24 29 47 JF-3-1 1,643 0 0 0 55 30 15 JF-2-2 3,027 0 0 0 38 52 9 Summary Feeder bluff (FB) function is critical for both formation and maintenance of all beach and nearshore habitats in drift cells Highest sediment input is along Strait of Juan de Fuca in FBEs and FBs, some FB-talus reaches have substantial sediment input Sequim Bay has FB reaches of critical local importance, even though they have less sediment input than reaches along the Strait Ensure adequate setbacks are used for new development at all FB sites, with greatest coastal hazards at FBE, to protect human safety and nearshore species Conserve remaining feeder bluffs .