Geographic variation in San Francisco Bay beach forms, sedi
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Geographic variation in San Francisco Bay beach forms, sedi

State of the Sediment Workshop . April 19-20, 2010 . San Francisco Bay Conservation and Development Commission . U.S. Geological Survey . Menlo Park, California. Peter Baye, Coastal Ecologist, . Annapolis, California.

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Geographic variation in San Francisco Bay beach forms, sedi




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Presentation on theme: "Geographic variation in San Francisco Bay beach forms, sedi"— Presentation transcript:

Slide1

Geographic variation in San Francisco Bay beach forms, sediments, and processes: an overview

State of the Sediment Workshop

April 19-20, 2010 San Francisco Bay Conservation and Development Commission U.S. Geological Survey Menlo Park, California

Peter Baye, Coastal Ecologist,

Annapolis, California

baye@earthlink.net

Slide2

Geographic variation in San Francisco Bay beach forms, sediments, and processes: an overview

Summarize geographic distribution and variability of modern San Francisco Bay beach landforms and beach sediment Original purpose: classification of habitat suitability and restoration feasibility for rare/endangered estuarine beach plants Identify provisional subregional “provinces” of beaches with similar sediments, local wave energy climates, backshore settings, profiles, dynamics

Slide3

Classification tools available for documenting geographic variation in San Francisco Bay Beaches

R

ecent fetch-limited beach geomorphology literature:

Pilkey

, O.H

., J. A.G. Cooper, D.A. Lewis.

2009

. Global Distribution of fetch-limited barrier islands.

Journal of Coastal Research

25

:819-837

Jackson

, N.L

. Nordstrom, K.F. Eliot, I. And

Masselink

, G.

2002

. “Low

energy

” sandy beaches in marine and estuarine environments: a review.

Geomorphology 48

: 147-162

classic beach profile and

planform

typologies (Bird 1964, Johnson 1919)

qualitative sediment typing

Approximate historic distribution and

planform

of beaches delineated on T-sheets:

EcoAtlas

synthesis (Robin

Grossinger

, SFEI)

Herbarium and flora records

of beach & dune (strand) plant species

(locality data on presence of estuarine beach, dune habitat)

Slide4

Bay beach types: simplified planform-based classification

Fringing beaches

: mainland-attached beaches, extensive; limited headland influence

Pocket beaches

: mainland-attached beaches, narrowly confined by headlands or resistant shoreline indentations

Barrier beaches

: beach ridges,

tombolos

, or spits sheltering enclosing lagoons, intertidal flats, or marshes

Marsh

berms

, marsh barriers

- “marsh fringe barriers”, perched or fringing beaches along storm-eroded marsh scarps or peat outcrops (cf.

chenier

), usually vegetated

Cuspate forelands

– salient

prograded

or multiple beach ridges or

recurved

spits (rare)

Slide5

Base map credit: Mike

Perlmutter, BAEDN

Beach shorelines▬▬ historic▬▬ modern

Excluded: swell-influenced Golden Gate beaches

Pinole

mixed beaches (sand, shell gravel)

San Rafael

pocket sand beaches

Richardson Bay

pocket beaches

West Berkeley

sand beaches

SE SF

pocket sand beaches

South Bay

oyster shell hash beaches

San Leandro-Hayward

shoreline sand beaches

SF Bay beach provinces

provisional classification prevalent sediment type (sand, shell, gravel, mixed) geomorphic setting (headland, marsh fringe)

Richmond

pocket beaches

Slide6

Point Pinole marsh barrier chains

Mixed beach sediment (erosion of sedimentary headlands, small stream deltas = sand and gravel; nearshore erosion of shell) associated with prehistoric (Whittell) and modern salt marshes boat wake (Vallejo Ferry) and long NW fetch of San Pablo Bay – episodic high wave energy

Transverse bar?

Ebb deltas of tidal creeks

WHITTELL MARSH

1948

BARRIER BEACH

Slide7

2007

Point Pinole marsh barrier

Ebb tidal delta

BARRIER BEACH

Slide8

Point Pinole

– prehistoric

Whittell

Marsh sheltered by barrier beach (crest <0.75 m above marsh plain)

Slide9

Point Pinole (west of Point) – salt marsh peat outcrops, proximal end

Slide10

Slide11

Slide12

Point Pinole cuspate sand & gravel barrier foreland

gravel and coarse sand

west-facing shore

backbarrier

tidal marsh

Bluff erosion sediment source

cobble lag-armored foreshore

updrift

Slide13

Point Pinole – west shore gravel beach and cobble lag foreshore

Slide14

Pinole Creek mouth

Marsh berm

(“Marsh Bar” of Johnson 1919; marsh fringe barrier of

Pilkey

et al

. 2009)

Thin perched sand beach ridge deposit above salt marsh scarp

vegetated: high salt marsh

marsh peat outcrop

Slide15

Active barrier

beach (long fetch)

Active barrier

beach (short fetch)

Multiple relict stabilized beach ridges?(past progradation)

Nontidal

salt marsh

Central San Francisco Bay sand/shell hash beaches:

Brooks Island, Richmond (

tombolo

and barriers)

Slide16

Central San Francisco Bay sand/shell hash beaches:

Brooks Island, Richmond (tombolo and barriers)

Photo: Mike Perlmutter, BAEDN

East Bay Regional Parks District – protected tern colonies

Slide17

Marina Bay, Richmond

South-facing barrier

tombolo

,

mixed gravel-sand-shell

Slide18

Radio Beach, Oakland

(Bay Bridge Toll Plaza)West-facing barrier beach (tombolo)

Rip-rap headland

1 m high

foredune

ridge

Slide19

Radio Beach, Oakland (Emeryville Crescent)

North-facing sand spit (seasonal tern roost)

Slide20

Swash-aligned and drift-aligned bay

beaches(Davies 1978)

Swash-aligned pocket beach: facing dominant waves, confined by (artificial) headlandPotential stable beach planform; symmetric

Dominant local waves (NW)

Longshore

drift

RADIO BEACH COMPLEX – Oakland Bay Bridge Toll Plaza

Riprap headland

Drift-aligned

sand spit: oblique approach of dominant waves, unconfined

longshore

transport

unstable beach

planform

, proximal narrowing, distal

progradation

Slide21

“West Berkeley” -

Eastshore

State Park (University Ave – Powell St) fringing beaches

Slide22

San Leandro-Hayward shoreline

Robert’s Landing “Long Beach”

Salt marsh peat outcrops, foreshore, proximal (N) end

Slide23

San Leandro-Hayward shoreline

Robert’s Landing “Long Beach” –

overwash

transgression of

backbarrier

salt marsh

Slide24

San Leandro-Hayward shoreline

Robert’s Landing “Long Beach” – active washover fans

Slide25

San Leandro-Hayward shoreline

Robert’s Landing “Long Beach”

ridge and runnel (

multibarred

) foreshore profile

(sand, mud)

Slide26

San Leandro-Hayward shoreline

Robert’s Landing “Long Beach”

updrift

shoreline (N)

Slide27

WESTERN SNOWY PLOVER – Pacific population, federally listed as threatened

Roberts Landing sand spit – March 2006

Slide28

Erosion of artificial shore fill nourishes SF beaches:

Brisbane

Bayshore gravel spitHeron’s Head (Pier 98) San Francisco gravel beach

Brisbane spit, south of Candlestick Pt

Pier 98 (Heron’s Head), San Francisco

Slide29

SE San Francisco, Pier 94 constructed gravel-shell beach

Slide30

SE San Francisco, India Basin

Low foredunes, west-facing beach

Slide31

Native

(fossil)

Olympia oyster

(

Ostrea

lurida

, syn.

O.

conchaphila

)

shell hash

Central, South

SF

Bay

nearshore

sources: wave erosion, transport of shell hash eroded from marsh scarps,

shelly

mudflats

swash bar welding?

(onshore migration of shell hash swash bars)

Slide32

SE Bair Island –

Oyster shell hash beach accretion

(2007)

Slide33

SE Bair Island –

prograded

multiple spit

recurves

over salt marsh

Oyster shell hash

– recent beach ridge deposition

Slide34

SE Bair Island –

prograded

oyster shell hash beach ridges

Slide35

SE Bair Island –

prograded oyster shell hash beach ridges

Recent swash bar formed by boat wakes

Slide36

SE Bair Island –

vertical scarp (boat wake erosion) in oyster shell beach ridge

Slide37

Slide38

SE Bair Island –

transgressive

oyster shell hash beach ridges dam tidal creeks

Slide39

SE Bair Island –

transgressive

oyster shell hash beach: perched beach ridge above marsh scarp; beach face below scarp

Slide40

SE Bair Island – perched beach profile and

infilled

relict tidal creek in marsh peat scarp – oyster shell hash

Slide41

2007 Foster City

1998 Foster City

MARSH BERMS

Vegetative stabilization of relict beach ridges – high salt marsh

Analogous with

chenier

beach ridges (Gulf of Mexico)

Slide42

Stabilization impacts of invasive non-native hybrid smooth

cordgrass

(Spartina alterniflora x foliosa) stabilization of nearshore shell-rich muds (marsh conversion)Wave damping

1998

2007

Seal Slough, NE Foster City shoreline

SOUTH SAN FRANCISCO BAY

OYSTER SHELL HASH BEACHES

Slide43

Conclusions

Quartz-rich medium grain sand

fringing beaches

are prevalent from West Berkeley to Hayward, vicinity of Merritt Sands – regenerate in urban shoreline.

Oyster shell hash (fossil sediment

) marsh fringing barrier beaches

are prevalent from Foster City to Ravenswood – esp

. Bair Island

(among largest in SF Bay) – regenerate in marsh and urban shorelines

Mixed sediment (gravel-sand-shell

) marsh fringing barrier beaches

are prevalent in North Richmond to Point Pinole – likely headland and stream mouth sources? – near original marsh and bluff shoreline

Small

pocket and fringing beaches of

quartz-rich sand occur in urban San Francisco shore (vicinity of

Colma

formation) – urban shoreline

Drift-aligned sand spits

occur in Central East Bay (Radio Beach, Roberts Landing) – among largest natural beaches in SF Bay

Slide44

QUESTIONS

Relative importance of

nearshore

erosion, onshore transport, versus headland/bluff erosion,

longshore

transport of beach sediment?

Shoreline armoring, flood channel stabilization effect on bay beach sediment supply?

Oyster shell hash (20

th

c industrial mining and ongoing commercial mining of fossil sediment)

Beach sediment budgets and sea level rise?

Artificial barrier beaches and tidal marsh restoration – engineering alternatives to levee maintenance during sea level rise?