U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2007–5233

Wave-Driven Spatial and Temporal Variability in 

Sea-floor Sediment Mobility in the Monterey 

Bay, Cordell Bank, and Gulf of the Farallones 

National Marine Sanctuaries
This page intentionally left blank
Wave-Driven Spatial and Temporal Variability in 

Sea-floor Sediment Mobility in the Monterey Bay, 

Cordell Bank, and Gulf of the Farallones National 

Marine Sanctuaries

By Curt D. Storlazzi, Jane A. Reid, and Nadine E. Golden

U.S. Department of the Interior

U.S. Geological Survey 

Scientific Investigations Report 2007–5233
U.S. Department of the Interior

DIRK KEMPTHORNE, Acting Secretary

U.S. Geological Survey

Mark D. Myers, Director

U.S. Geological Survey, Reston, Virginia: 2007

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Produced in the Western Region, Menlo Park, California

Manuscript approved for publication, October 4, 2007

Text edited by James W. Hendley II

Layout and design by Stephen L. Scott

Cover—Wave orbital ripples at a depth of 15 m in the Monterey Bay National Marine Sanctuary.
Contents

Abstract -------------------------------------------------------------------------------------------------------1

Introduction---------------------------------------------------------------------------------------------------1

Study Area ----------------------------------------------------------------------------------------------------2

Methods-------------------------------------------------------------------------------------------------------4

Sediment Cover of the Central California Continental Shelf --------------------------------------4

Gridded Coverage of Sediment Grain Size ----------------------------------------------------------5

Wave Data ----------------------------------------------------------------------------------------------7

Wave Modeling--------------------------------------------------------------------------------------- 10

Threshold for the Initiation of Sediment Transport----------------------------------------------- 10

Results-------------------------------------------------------------------------------------------------------- 15

Discussion -------------------------------------------------------------------------------------------------- 30

Geological Implications ----------------------------------------------------------------------------- 30

Biological Implications ------------------------------------------------------------------------------ 30

Conclusions------------------------------------------------------------------------------------------------- 33

Acknowledgments ----------------------------------------------------------------------------------------- 33

References-------------------------------------------------------------------------------------------------- 33

Appendixes 1-41-------------------------------------------------------------------------------------------- 35

Figures

1. Map of the study area -----------------------------------------------------------------------------2

2. Distribution of bathymetry by depth range ------------------------------------------------------3

3. Wave rose for central California -----------------------------------------------------------------3

4. Grid of central grain-size data in mm ------------------------------------------------------------5

5. Grid of central grain-size data by grain-size class ---------------------------------------------6

6. Histograms of surficial sediment distributions--------------------------------------------------8

7. Multivariate El Niño-Southern Oscillation (ENSO) index ------------------------------------ 10

8. Temporal variability in the wave parameters for El Niño, La Niña conditions, 

 and Normal conditions--------------------------------------------------------------------------- 11

9. Delft 3D curvilinear modeling grid for the study area---------------------------------------- 12

10. Example model run showing significant wave height for an El Niño February ----------- 13

11. Example model run displaying peak wave-induced near-bed orbital wave 

 velocity for an El Niño February ---------------------------------------------------------------- 14

12. Example model run displaying peak wave-induced near-bed shear stress--------------- 16

13. Critical shear stresses for the initiation of sediment transport----------------------------- 17

14. Example model run displaying regions mobilized and stable due to wave forcing 

 during an El Niño February ---------------------------------------------------------------------- 18

15. Example model run displaying regions mobilized and stable due to wave forcing 

 during a La Niña October------------------------------------------------------------------------ 19

16. Plots showing the temporal variation in sea-floor disturbance by depth range---------- 20

17. Map of the study area showing the frequency of sea-floor disturbance during 

 a year with Normal conditions.----------------------------------------------------------------- 22

18. Map of the study area showing the frequency of sea-floor disturbance during 

 a year with El Niño conditions.------------------------------------------------------------------ 23

19. Map of the study area showing the frequency of sea-floor disturbance during 

 a year with La Niña conditions.----------------------------------------------------------------- 24

20. Map showing the difference in the frequency of sea-floor disturbance during 

 El Niño and La Niña years. ---------------------------------------------------------------------- 25
 21. Map showing the difference in the frequency of sea-floor disturbance during 

 El Niño and La Niña winter months---------------------------------------------------------- 26

 22. Map showing the difference in the frequency of sea-floor disturbance 

 during El Niño and La Niña spring months ------------------------------------------------- 27

 23. Map showing the difference in the frequency of sea-floor disturbance 

 during El Niño and La Niña summer months ----------------------------------------------- 28

 24. Map showing the difference in the frequency of sea-floor disturbance 

 during El Niño and La Niña fall months ----------------------------------------------------- 29

 25. Plot synthesizing the data on the spatial and temporal variations in sea-floor

 mobility between El Niño and La Niña conditions ---------------------------------------- 31

 26. Map of the study area displaying the mean peak near-bed wave orbital velocity ---- 32

Tables

 1. Monthly climatic model run boundary conditions-------------------------------------------9

 2. Return interval model run boundary conditions-------------------------------------------- 12

 3. Percent of sea floor disturbed by depth range for return interval model run 

 boundary conditions--------------------------------------------------------------------------- 20

 4. Percent of sea floor disturbed by depth range for climatic model run 

 boundary conditions--------------------------------------------------------------------------- 21
1

Abstract

Wind and wave patterns affect many aspects of continental shelves and shorelines geomorphic evolution. Although 

our understanding of the processes controlling sediment 

suspension on continental shelves has improved over the past 

decade, our ability to predict sediment mobility over large 

spatial and temporal scales remains limited. The deployment 

of robust operational buoys along the U.S. West Coast in 

the early 1980s provides large quantities of high-resolution 

oceanographic and meteorologic data. By 2006, these data 

sets were long enough to clearly identify long-term trends 

and compute statistically significant probability estimates 

of wave and wind behavior during annual and interannual 

climatic cycles (that is, El Niño and La Niña). Wave-induced 

sediment mobility on the shelf and upper slope off central 

California was modeled using synthesized oceanographic 

and meteorologic data as boundary input for the Delft SWAN 

model, sea-floor grain-size data provided by the usSEABED database, and regional bathymetry. Differences in 

waves (heights, periods, and directions) and winds (speeds 

and directions) between El Niño and La Niña months cause 

temporal and spatial variations in peak wave-induced bed 

shear stresses. These variations, in conjunction with spatially 

heterogeneous unconsolidated sea-floor sedimentary cover, 

result in predicted sediment mobility widely varying in both 

time and space. These findings indicate that these factors 

have significant consequences for both geological and biological processes.

Introduction

Wind and wave patterns can affect many aspects of continental shelf and shoreline evolution. Although our understanding of the processes controlling sediment suspension on 

continental shelves has improved over the past decade, our 

ability to predict sediment mobility over large spatial and 

temporal scales remains limited. The development, deployment, and continued maintenance of robust operational 

oceanographic systems off central California by the National 

Oceanic and Atmospheric Administration (NOAA) in the 

early 1980s provides large quantities of high-resolution 

oceanographic and meteorologic data, such as wave height, 

wave period, wave direction, wind speed, and wind direction. 

By 2003, these data sets were large enough to clearly identify 

long-term trends and compute statistically significant probability estimates of wave and wind behavior during seasonal, 

annual, and interannual climatic cycles (that is, El Niño 

and La Niña). Although many studies have investigated the 

wave climate along central California (Seymour and others, 

1984; Inman and Jenkins, 1997; Allan and Komar, 2000; 

Bromirski and others, 2005), none have investigated how 

spatial and temporal variations in wave climate influence 

sediment mobility on the shelf and upper slope. Sea-floor 

sediment may be resuspended by these waves, depending 

on their height, period, water depth and the sediment grain 

size. These natural readjustments of unconsolidated seafloor materials may influence both the recovery from human 

perturbations and/or cause short-lived natural disturbances. 

The effect on benthic and pelagic ecosystems will depend on 

local sea-floor conditions, sediment distributions, and ecological balances.

Here we interpolated the oceanographic and meteorologic data synthesized by Storlazzi and Wingfield (2005) 

across the continental shelf, and integrated these with gridded grain-size data held in the U.S. Geological Survey’s 

(USGS) usSEABED compilation (Reid and others, 2006). 

These two data sets, complemented by bathymetry, allowed 

the prediction of seabed suspension and mobility at various 

spatial and temporal scales (months to decades) encountered 

under different climatic regimes (for example, during normal 

“winter” months, a typical El Niño January or a La Niña 

fall) or statistical projections (5-, 10-, 25-, 50- and 100-year 

storms). Understanding the spatial and temporal variability 

of these sea-floor disturbances can provide information to 

managers and planners so that the effects of particular manWave-Driven Spatial and Temporal Variability in 

Sea-floor Sediment Mobility in the Monterey 

Bay, Cordell Bank, and Gulf of the Farallones 

National Marine Sanctuaries

By Curt D. Storlazzi, Jane A. Reid, and Nadine E. Golden
2 Wave-Driven Spatial and Temporal Variability in Sea-floor Sediment Mobility

agement practices, such as dredge material disposal, can be 

forecast. This work would also provide practical scientific 

information to local, State, and Federal permitting agencies 

for use in the consideration of offshore activities such as trawling, dredging, and the placement of sea-floor engineering structures (cables, pipelines, others) that disturb the sea floor.

Study Area

The study area for this project extends approximately 280 

km from just north of Bodega in Sonoma County southward to 

Point Sur in Monterey County and extends from the shoreline 

out past the 2,000-m isobath (fig. 1). Central California has 

Figure 1. Map of the study area showing location names discussed in the text and the bathymetry of the model domain, 

which includes the shelf and upper slope down to depths of 500 m. The 30-m, 60-m, 90-m, 120-m, 150-m, 200-m, and 500-m 

isobaths are shown. Inset: Map of California, showing the locations of the study area and the NOAA National Data Buoy 

Center buoy (yellow dot) used in this study.

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

-450 

-400 

-350 

-300 

-250 

-200 

-150 

-100 

-50 

0 

-500 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

FARALLON 

ISLANDS 

CORDELL 

BANK 

DEEP 

REEF 

MONTEREY 

PENINSULA 

POINT 

SUR 

PORTUGESE 

LEDGE 

MONTEREY 

BAY 

0 100 200 

KILOMETERS 

Pacific 

Ocean 

Cape 

Mendocino 

San 

Francisco 

Point Conception 

Los 

Angeles 

San 

Diego 

California 

LATITUDE (DEGREES NORTH) 

LONGITUDE (DEGREES WEST) 

DEPTH (METERS) 

0 25 50 

KILOMETERS 
3

a rugged coastline characterized by a narrow 

continental shelf and coastal mountains cut with 

high seacliffs and narrow river valleys. The continental shelf, defined here as extending from 

the shoreline out to the 120-m isobath, varies 

significantly in width along the study area, ranging from more than 50 km off San Francisco to 

less than 1 km off of the Monterey Peninsula; 

although spatial area on the upper shoreface 

(depths 0-30 m) is narrow relative to the rest of 

the shelf, in general the distribution of shelf area 

by depth in the study area is relatively uniform 

(fig. 2).

The general offshore wave climate of California is characterized by four regimes (fig. 3): 

North Pacific swell, Northwest wind waves, 

Southern swell and local wind waves (National 

Marine Consultants, 1960; Storlazzi and Wingfield, 2005). The North Pacific swell is caused by 

extra-tropical lows and cold fronts in the North 

Pacific that generate long-period (Tdom) swell 

that impacts the study area from the west and 

northwest, with a general wave direction (WVdir) 

of azimuth 290° and a WVdir range of azimuths 

210° to 330°. These waves have significant wave 

heights (Hsig) of 2 to 10 m and Tdom of 10 to 25 s, 

with the largest Hsig and longest Tdom during the 

winter (October-May). Northwest wind waves 

are generated by winds driven by the California 

High blowing over the open ocean and insolation-driven sea breezes that generate short Tdom

waves; these waves impact the study area from 

the northwest, with a general WVdir of azimuth 

310° and a WVdir range of azimuths 280° to 350°. 

Northwest wind waves have Hsig of 1 to 4 m and 

Tdom of 3 to 10 s. Although they occur throughout 

and common geochemical and geophysical parameters. It 

holds separately lab-determined numerical data (“extracted” or 

“EXT”), numerical data based on written descriptions (“parsed” 

or “PRS”), and estimated values for selected parameters from 

incompletely reported data (“calculated” or “CLC”), as given 

in existing publications, unpublished reports, theses, gray literature, and other unpublished data.

One prominent use for usSEABED data is in a regional 

view of sediment, rock, and biological information in areas 

without a single regional sampling regime such as the ones 

presented in this report. Several factors about usSEABED and 

extrapolation of its data in such a regional view should be considered in order to understand the inherent limitations of the 

resulting coverage.

The sediment grain-size data were derived from 32 original 

sources including those noted above, and are primarily from 

0 

5 

10 

15 

20 

25 

0 - 30 30 - 60 60 - 90 90 - 120 120 - 500 

DEPTH RANGE (METERS) 

PERCENT 

Figure 2. Distribution of bathymetry by depth range for the model 

domain down to 500-m water depth.

Santa 

Cruz 

Monterey 

San 

Jose 

Salinas 

CALIFORNIA 

M a p 

A r e a 

150o 

Local Wind Waves 

GENERATION: 

Storms passing through central California 

OCCURRENCE: 

Generally in October-April; 

typical year: 50 percent of the time 

WAVE HEIGHT: 1-4 m 

WAVE PERIOD: 3-10 s 

210o 

330o 

North Pacific Swell 

GENERATION: 

Storms in the North Pacific, mid-latitude lows, 

and cold fronts 

OCCURRENCE: 

Throughout the year; largest in October-May; 

largest waves to impact the region 

WAVE HEIGHT: 2-10 m 

WAVE PERIOD: 10-25 s 

290o 

280o 

350o 

Northwest Wind Waves 

GENERATION: 

Northwest winds generated by the California 

High blowing over the open ocean; sea breezes 

OCCURRENCE: 

Throughout the year; dominant in April-October; 

summer: 90-95 percent, winter: 55-65 percent of the time 

WAVE HEIGHT: 1-4 m 

WAVE PERIOD: 3-10 s 

310o 

260o 

200o 

Southern Swell 

GENERATION: 

Storms in the South Pacific and off Central America 

OCCURRENCE: 

Throughout the year; generally in April - October; 

typical year: 50 percent of the time 

WAVE HEIGHT: 0.3-3 m 

WAVE PERIOD: 10-25 s 

Figure 3. Wave rose for central California showing the four dominant wave 

patterns that impact the study area. Arcs show the range of direction for a given 

wave pattern, whereas arrows show the mean direction for a given wave pattern. 

Modified from Storlazzi and Wingfield (2005).

Study Area
4 Wave-Driven Spatial and Temporal Variability in Sea-floor Sediment Mobility

published and unpublished work by the USGS, the University of 

California at Berkeley Hydraulic Engineering Laboratory, and 

the U.S. Navy, with sampling dates generally from the 1960s to 

early 2000s (Reid and others, 2006). To gain the best coverage of 

the central California area, three data sets (EXT, PRS, and CLC) 

were combined and assumed the recorded subsample depths 

(here restricted to the upper 0.10 m of the sample) represent the 

water-sediment interface, regardless of sampler type. Rocks and 

rocky areas were excluded from the dataset, although rocky areas 

are well known along the nearshore area, the shelf edge, and 

in “Deep Reef” off Half Moon Bay (Eittreim and others, 2000, 

2002; Orzech and others, 2001; Edwards, 2002; Reid and others, 

2006; unpubl. usSEABED data). 

The grain-size values in usSEABED are called “central” 

grain size; that is, determined from either the median (preferred) 

or mean values across the range of sediment analyzed or noted 

in a written description (see the FAQ section of Reid and others, 

2006). For this work, where both a laboratory analysis and a 

written description of a sample exist, the EXT grain-size value 

was generally chosen; however, if the difference between the 

two was significant (>2 grain-size-class range), the original data 

were compared, modified as appropriate, or discarded. Modifications were usually due to the EXT value excluding noted larger 

objects, such as stones or shells. In these cases, the larger-object 

descriptors were combined with a verbal description of the 

granulometric analyses based on Folk and others (1970) ternary 

diagrams. The new description was reprocessed through dbSEABED, the processing software at the heart of usSEABED, to 

determine a better representative PRS grain-size value.

Of the resultant 3,438 data points used in the gridding, 90 

percent were extracted from lab analyses (EXT) and are well 

distributed throughout the region (fig. 4, inset). PRS values 

contribute about 7 percent, and were primarily on Cordell Bank 

across the shelf to Point Reyes, east of the Farallon Islands, 

along the shelf edge, or well distributed throughout the shelf 

south of San Francisco. The remaining 4 percent of the data were 

calculated (CLC) from reported values for gravel, sand, silt, and 

clay fractions, and are located off northern Point Reyes or south 

of the Monterey Peninsula. Work by Field and others (1992) and 

Eittreim and others (2002) confirm the approximate grain sizes 

in the latter two areas, respectively.

Using solely the modified usSEABED-supplied ungridded data, approximately 57 percent of the Continental Shelf and 

upper slope down to 500 m in the study area is dominated by 

fine and very fine sand. Approximately 22 percent of the samples 

show coarser sediment, although current sampling locations, 

inherent limitations on sampling, and laboratory-induced bias 

towards finer sediment may under represent this value. Cordell 

Bank, for example, is notably underrepresented in usSEABED; 

sampling sediment much larger than pebbles in localities that 

may be part of the excluded rock or in rocky areas is difficult; 

pebbles and larger objects including shells may be discarded 

before laboratory analysis. The mud belts along central California consist primarily of silts with some clay (Edwards, 2002; 

Reid and others, 2006) and represent about 21 percent of the 

samples held in usSEABED for the area.

the year, they occur most consistently (90-95 percent of the 

time) from April to October and less frequently (55-65 percent 

of the time) in the winter. Southern swells are driven by storms 

in the South Pacific and off Central America that generate long

Tdom waves that impact the study area from the south and southwest, with a general WVdir of azimuth 290° and a WVdir range 

of azimuths 150° to 260°. These waves have Hsig of 0.3 to 3 m 

and Tdom of 10 to 25 s. Although they occur throughout the year, 

they occur most consistently and with the largest Hsig from April 

to October when large storms occur in the South Pacific during 

the Southern Hemisphere’s winter and when tropical cyclones 

develop off Central America. Local wind waves are driven by 

storms passing through central California that generate short 

Tdom waves that can impact the study area from all orientations, 

depending on the latitude of the storm’s track. These waves 

have Hsig of 1 to 4 m and Tdom of 3 to 10 s; they are most frequent in the winter months (October-May).

Methods

Sediment Cover of the Central California Continental Shelf

Several regional and site-specific studies have investigated 

the surficial sediment along the central California Continental 

Shelf. Edwards (2002) presents detailed work in the Monterey 

Bay National Marine Sanctuary (MBNMS) and gives detailed 

descriptions of the locations, characteristics, and variabilities 

within the mid-shelf ‘mud-belt’. He also describes the wellsorted, unimodal, generally very fine sand (0.125-0.063 mm) 

except near the San Lorenzo River mouth where they are polymodal, fine (0.250-0.125 mm) to very fine sand, along the nearshore, and slightly finer, less well-sorted, very fine sands along 

the shelf edge. 

North of the MBNMS, Moore (1965), Schatz (1965), and 

Maher and others (1991) provide the largest published studies of 

the area between the Golden Gate and the Farallon Islands. The 

two earlier reports describe the ebb-tidal delta near the Golden 

Gate generally as medium (0.500-0.250 mm) to fine sands, 

fining outward to very fine sands. Maher and others (1991) 

describes the sediments east of the Farallon Islands as pockets 

of coarse (1.000-0.500 mm) and medium sand in a field of fine 

sand, with an overall coarsening trend towards the islands. Most 

of the samples reported by Maher and others (1991) have very 

little mud or gravel; however, a few scattered samples record as 

much as 65 percent as gravel-sized particles. These researchers 

also note a “tongue of silt” that curves around Point Reyes.

Data used to create the grain-size grids are from usSEABED, a U.S.-wide seabed characterization database, and are 

modified from the initial publication for the contiguous Pacific 

Coast (Reid and others, 2006). The usSEABED database, 

designed to provide point data for benthic habitat identification 

and geologic resource use, includes unified data on sediment 

size (gravel, sand, mud, clay) with standard statistical parameters, rock or seabed consolidation, constituent components, 
5

Gridded Coverage of Sediment Grain Size

The sediment grain-size grids shown here are considered 

preliminary and should not be used beyond the scope of this 

report. The gridding technique used (inverse-distance weighted 

[IDW] nearest-neighbor method provided by ESRI® ArcMap) 

forces coverage in areas of sparse or no data and ignores at 

least two notable issues. First, the spatial distribution of points 

varies from less than 0.2 km in the nearshore area off Santa 

Cruz to 12 km off northern Point Reyes (fig. 4, inset). This 

Figure 4. Grid of central grain-size data from the upper 0.1 m of the sediment cover on the central California Continental 

Shelf, using data modified from Reid and others (2006), presented in mm, for the model domain. Warm colors indicate areas 

of finer grained sediment. Gridded using Inverse Distance Weighting (IDW) method at 100-m grid-cell size with a variable 

radius and 12 nearest neighbors. Inset: Sample distributions along the central California coast from Reid and others (2006). 

Localities with extracted (EXT, laboratory analyses) data in red, with parsed (PRS, numeric data from written descriptions) 

data in green, and with calculated values (CLC, derived from incompletely reported data) in blue.

0.9 

0.8 

0.7 

0.6 

0.5 

0.4 

0.3 

0.2 

0.1 

1.0 

0.0 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

= EXT 

= PRS 

= CLC 

LATITUDE (DEGREES NORTH) 

GRAIN SIZE (MILLIMETERS) 

LONGITUDE (DEGREES WEST) 

0 25 50 

KILOMETERS 

Methods
6 Wave-Driven Spatial and Temporal Variability in Sea-floor Sediment Mobility

wide range in data spacing is because the data in usSEABED is 

derived from a number of disparate, noncoordinated sampling 

efforts spanning multiple decades. The grid cell size of 100 

m was chosen to match the resolution of the wave data, and 

every cell may not have the same number of representative 

sediment samples or may lack a sample entirely.

Secondly, water depth is not included as a variable during 

the gridding process. Because water depth is an important 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

Very coarse sand 

and gravel 

Coarse sand 

Medium sand 

Fine sand 

Very fine sand 

Coarse silt 

Medium silt 

Fine silt, very fine 

silt and clay 

Grid cells > 500 m 

depth 

SAND MUD 

GRAINSIZE 

CLASS 

LATITUDE (DEGREES NORTH) 

LONGITUDE (DEGREES WEST) 

0 25 50 

KILOMETERS 

Figure 5. Grid of central grain-size data from the upper 0.1 m of the sediment cover on the central California Continental Shelf, 

using data modified from Reid and others (2006), presented by grain-size class (Wentworth, 1922). Note mid-shelf “mud belts” 

(orange and yellow) in pockets off Bodega, due west of Half Moon Bay, along much of the shelf south of Half Moon Bay as well 

as within Monterey Bay. Gridded using Inverse Distance Weighting (IDW) method at 100-m grid-cell size with a variable radius 

and 12 nearest neighbors.
7

factor in sediment deposition, erosion, and transport, the sediment patterns presented here are approximate. In particular, 

along areas of high bathymetric relief, such as the shelf edge 

or canyon breaks, the sediment patterns are poorly constrained 

in this gridded coverage. Caution should be used in using this 

coverage to strictly predict sediment grain size within one 

Udden-Wentworth class (Wentworth, 1922) at any given site.

Two gridded coverages are presented here to show the 

best estimate of sediment distributions along central California 

as modified from Reid and others (2006). Figure 4 presents a 

smooth continuum of surficial sediment grain size from 0.001 

mm to more than 1.000 mm as used in the mobility model. 

Warmer colors show the areas of finer deposits in generally 

elongated pockets off Bodega and along the mid-shelf south of 

“Deep Reef” in water depths between 60 and 100 m.

Figure 5 presents the same data in textural categories of 

gravels, sands, silts, and clays. This figure shows the same 

mud belts (primarily coarse and medium silts) as figure 4 

(here in orange, red, and brown) and emphasizes the coarsesilt dominated mud-belt pocket noted by Edwards (2002) 

north of “Deep Reef”. Coarser sediments are found adjacent 

to San Francisco, surrounding the Farallon Islands, between 

Half Moon Bay and “Deep Reef”, and in many areas along 

the near shore. Coarser sediments are also suggested along 

the outer shelf near the Farallon Islands north to the pebbly 

deposits of Cordell Bank and as relict deposits along the shelf 

edge (Edwards, 2002). Along the nearshore and the shelf break 

between Año Nuevo and Point Sur, some areas depicted here as 

fine to coarse sands roughly correlate with locations of rocky 

outcrops or relict gravels shown in backscatter imagery (Chin 

and others, 1988; Eittreim and others, 2000, 2002 and references therein; Anima and others, 2002); the size differences 

may be due either to thin sediment cover or to sampling bias 

against larger particles.

The IDW grid suggests that more than 75 percent of the 

central California Continental Shelf shallower than 500 m is 

covered by sand, with approximately 21 percent covered by 

mud (fig. 6A). Medium sand to silt dominate the shelf, with fine 

sand to very fine sand accounting for approximately 60 percent 

of the sediment (fig. 6B). A comparison of samples and the 

resulting grid suggests that areas of very fine sand are underrepresented in usSEABED.

Wave Data

Since the early 1980s, the NOAA National Data Buoy 

Center (NDBC) has deployed several buoys off the U.S. coast 

to monitor various oceanographic and atmospheric conditions. Data from the NDBC Monterey buoy (ID no. 46042) 

online data archive were used; these data are available online 

(National Data Buoy Center, 2006). This buoy, first deployed 

in December 1987, records hourly data for various oceanographic and meteorologic parameters, including significant 

wave height (Hsig), dominant wave period (Tdom), dominant 

wave direction (WVdir), wind speed (WDspd), and wind direction 

(WDdir). The Monterey buoy did not obtain directional wave 

capability until July 1991. More than 150,000 hourly observations per parameter were extracted for the 07/1991–12/2005 

time period investigated in this study. 

The average time between events of a given magnitude 

can be estimated using extreme value statistics (Carter and 

others, 1986). For example, a 2-year recurrence interval for 

Hsig suggests that the probability of an occurrence of a given 

extreme value in any given year is 50 percent. The inverse 

of the recurrence interval is the probability of such an occurrence of a parameter’s value equaling or exceeding the given 

extreme value. Return magnitudes were based on Fisher-Tippet type I distributions (Carter and others, 1986) of monthly 

maxima, and 2-, 10-, 50-, and 100-year return-magnitude 

projections were calculated for Hsig, Tdom and WDspd (table 

1). Note that these projections are for a maximum observed 

wave height for a given return period and thus might only be 

observed for one hour, as compared to the greater durations 

calculated for the monthly data discussed below.

The El Niño-Southern Oscillation (ENSO) cycle is an 

interannual phenomenon composed of episodic El Niño and 

La Niña climatic events at 2- to 7-year intervals. The multivariate ENSO index (MEI), devised by Wolter and Timlin (1998), 

incorporates multiple factors to give a weighted average of 

the main oceanic-atmospheric ENSO-related features. In addition to sea-level barometric pressure, other variables include 

sea-surface water temperature, surface air temperature, total 

cloudiness, and zonal (north-south) and meridional (east-west) 

components of surface winds. Negative values of the MEI (fig. 

7) represent cold ENSO phases (La Niña), and positive values 

represent warm ENSO phases (El Niño).

To understand how these oceanographic and meteorologic 

parameters are influenced by ENSO events, we broke down 

the monthly statistics into three categories based on the corresponding MEIs for each specific month—all months of the 

study period, El Niño months, and La Niña months. Monthly 

MEIs before 1993 were normalized to an average MEI of 0.0 

and a standard deviation of 1.0 (National Oceanic and Atmospheric Administration, Climate Diagnostics Center, 2006). 

Cutoff MEI values were used to separate index values of El 

Niño, La Niña, and “Normal” months, that is months when 

neither intense El Niño nor intense La Niña conditions were 

observed. In this case, all months with an MEI > 1.0 were 

defined as El Niño months (39 out of 174 total months [22.4 

percent]); months when the MEI < -0.5 were defined as La 

Niña months (27 out of 174 total months [15.5 percent]); and 

months with –0.5 < MEI < 1.0 were defined as Normal months 

(108 out of 174 total months [62.1 percent]). These subsets, in 

conjunction with the high temporal resolution and long duration of data collection, made it possible to make statistically 

significant projections of each parameters’ behavior under 

each of the three climatic conditions.

Because the MEI data are at a resolution of one month, it 

was necessary to compile the wave and wind data at a monthly 

rate to make meaningful conclusions on the nature of their 

temporal variability under the different climatic conditions. 

Because the ultimate goal was to understand if the seabed was 

Methods
8 Wave-Driven Spatial and Temporal Variability in Sea-floor Sediment Mobility

Figure 6. Histograms of surficial sediment distributions (upper 0.1 m) from gridded coverage of the Continental Shelf between Bodega and Point Sur, presented by grain-size class (Wentworth, 1922). Areas of rocky 

outcrops are excluded. A, Relative percentages of textural classes show the dominance of sand in the modeled domain. B, Relative percentages of single classes over the same area suggest that fine and very fine 

sand covers nearly 60 percent of the Continental Shelf along central California.

GRAIN-SIZE CLASS 

(GRAIN SIZE, MILLIMETERS) 

Very Coarse Sand and 

Gravel 

(>1 mm) 

Coarse Sand 

(<1 mm to >0.5 mm) 

Medium Sand 

(<0.5 mm to >0.25 mm) 

Fine Sand 

(<0.25 mm to >0.125 mm) 

Very Fine Sand 

(<0.125 mm to >0.0625 mm) 

Coarse Silt 

(<0.0625 mm to >0.0313 mm) 

Medium Silt 

(<0.0313 mm to >0.0156 mm) 

Fine Silt, Very Fine Silt 

and Clay 

(<0.0156 mm) 

PERCENT 

TEXTURAL CLASS 

(GRAIN SIZE, MILLIMETERS) 

Gravel 

(>2mm) 

Sand 

(<2 mm to >0.0625 mm) 

Mud 

(<0.0625 mm) 

PERCENT 

10 

20 

30 

40 

50 

60 

70 

80 

0 

5 

10 

15 

20 

25 

30 

35 

40 

Modified from Reid et al. (2006) IDW Nearest Neighbor Grid 

Modified from Reid et al. (2006) IDW Nearest Neighbor Grid 

A 

B 
9

RUN ID Climate Month Hsig

(m)

Tdom

(s)

WVdir

(deg)

WDspd

(m/s)

WDdir

(deg)

N01 Normal Jan 6.1 15 277 10 287

N02 Normal Feb 6.6 14 288 10 294

N03 Normal Mar 6.1 15 298 9 305

N04 Normal Apr 4.5 14 303 11 320

N05 Normal May 4.2 12 306 11 321

N06 Normal Jun 4.3 10 310 10 319

N07 Normal Jul 3.8 9 314 10 322

N08 Normal Aug 3.3 9 311 9 323

N09 Normal Sep 3.8 9 311 9 319

N10 Normal Oct 4.3 12 302 8 320

N11 Normal Nov 5.6 14 302 10 318

N12 Normal Dec 6.0 15 295 10 274

E01 El Niño Jan 6.5 15 273 5 252

E02 El Niño Feb 7.5 14 276 9 274

E03 El Niño Mar 6.2 15 288 8 303

E04 El Niño Apr 4.9 13 300 9 325

E05 El Niño May 3.9 11 305 11 324

E06 El Niño Jun 4.5 11 307 8 322

E07 El Niño Jul 4.0 9 314 7 322

E08 El Niño Aug 3.3 9 313 7 323

E09 El Niño Sep 3.8 9 308 7 319

E10 El Niño Oct 4.3 12 300 4 326

E11 El Niño Nov 5.5 13 297 4 319

E12 El Niño Dec 6.4 14 292 6 283

L01 La Niña Jan 5.7 15 280 9 281

L02 La Niña Feb 5.9 14 299 9 309

L03 La Niña Mar 6.0 15 299 10 316

L04 La Niña Apr 4.1 14 306 11 315

L05 La Niña May 4.4 12 307 10 313

L06 La Niña Jun 4.1 10 316 7 316

L07 La Niña Jul 3.7 9 314 10 322

L08 La Niña Aug 3.3 9 311 10 323

L09 La Niña Sep 3.9 10 312 8 317

L10 La Niña Oct 4.4 12 306 8 312

L11 La Niña Nov 5.8 15 306 11 310

L12 La Niña Dec 5.7 15 297 8 289

Table 1. Monthly climatic model run boundary conditions.

[Hsig, Significant wave height; Tdom, Dominant wave period; WVdir, Wave direction; WDspd, Wind speed; WDdir, Wind direction]

Methods
10 Wave-Driven Spatial and Temporal Variability in Sea-floor Sediment Mobility

Figure 7. Multivariate El Niño-Southern Oscillation (ENSO) index (MEI; NOAA, 2006) during the time 

period when high-resolution direction wave and wind information for the study area were available. 

Red regions denote months with El Niño conditions, blue regions denote months with La Niña conditions, and the remaining months are classified as those with Normal conditions.

being mobilized or not by surface waves during any given 

month, it was decided that the most useful statistical scenario 

would be the largest sustained wave height, in that a wave 

height that was observed for a minimum period of 7 hours 

each month rather than just the maximum wave height for a 

given month. This choice was made for two reasons. First, if 

a given wave height was only observed for 1 hour (actually 

one 20-minute period when the sensors were collecting data 

that hour), it might not be long enough in duration for the seafloor sediment to be fully entrained by the surface wave orbital 

motions. Second, the 7-hour duration could be compiled statistically, being the mean plus three standard deviations from 

the 720 hours of wave data each month, which is statistically 

the mean of the top 1 percent of wave heights each month. For 

each climatic subset, monthly means, standard deviations and 

top one percent (mean + three standard deviations) statistics 

for the Hsig data were computed; monthly mean Tdom, WVdir, 

WDspd, and WDdir that corresponded to these times of the top 1 

percent of highest waves were also compiled (fig. 8; table 2).

Wave Modeling

Monthly statistics of NDBC buoy data (Hsig, Tdom, WVdir, 

WDspd, and WDdir) provided boundary input to the Delft3D version 3.25.01 (Delft, 2006) SWAN wave model (Holthuijsen 

and others, 1989; Ris, 1997; Booij and others, 1999; Ris and 

others, 1999). SWAN is based on the discrete spectral action 

balance equation and is fully spectral in all directions and 

1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 

-1.5 

-1.0 

-0.5 

0.0 

0.5 

1.0 

1.5 

2.0 

2.5 

3.0 

YEAR 

MULTIVARIATE ENSO INDEX 

El Niño 

La Niña 

frequencies. This third-generation wave model incorporates 

wind-wave growth, whitecapping, quadruplets, frequency 

shifting, and nonlinear triad interactions. The model also 

incorporates shallow-water wave effects such as depthinduced breaking, refraction and JONSWAP (Hasselmann 

and others, 1980) bottom friction (Cd = 0.067). The frequency 

space was set from 0.04-1.00 Hz in 25 frequency bins with 

a standard deviation of 20 degrees in directional spreading. 

Parametric specification of the spectra used a JONSWAP 

shape with a 3.3 peak enhancing factor. The model domain 

extends from the shoreline out ~100 km into water depths 

greater than 2,000 m (fig. 9). The model grid cells are small 

and more densely spread in shallow water and around complex bathymetry so that the model can accurately handle wave 

refraction in shallow water.

Threshold for the Initiation of Sediment Transport

The SWAN wave model was used to calculate Hsig, Tdom, 

and WVdir data for the entire model domain (fig. 10). From 

these data, the dispersion equation was solved iteratively to 

determine the wave number (k) and the radian frequency (σ), 

which were then used to solve the near-bed horizontal wave 

orbital velocity (u, fig. 11) via Stokes second-order waves 

theory (see for example, Komar, 1998). Grain roughness (r) 

was defined following Nielsen (1979) as 2.5 times the mean 

grain diameter, which varied spatially according to the usSEA-
11

Figure 8. Temporal variability in the wave parameters for El Niño (red), La Niña conditions (blue), 

and Normal conditions (black) used as boundary input for the wave modeling. A, Top 1 percent 

(mean + 3 standard deviations) significant wave heights (Hsig). B, The corresponding monthly 

mean dominant wave periods (Tdom) for the top 1 percent wave heights. C, Mean wave directions 

(WVdir) for the top 1 percent wave heights. The largest waves during La Niña events occur early in 

the winter (November), whereas the largest waves during El Niño events occur much later in the 

winter (February) and come from more westerly and southwesterly directions.

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 

3 

4 

5 

6 

7 

8 

8 

10 

12 

14 

16 

270 

280 

290 

300 

310 

320 

330 

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 

SIGNIFICANT WAVE HEIGHT 

[METERS] 

DOMINANT WAVE PERIOD 

[SECONDS] 

WAVE DIRECTION 

[DEGREES] 

MONTH 

= El Niño 

= La Niña 

= Normal 

A 

B 

C 

Methods
12 Wave-Driven Spatial and Temporal Variability in Sea-floor Sediment Mobility

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

LATITUDE (DEGREES NORTH) 

LONGITUDE (DEGREES WEST) 

0 25 50 

KILOMETERS 

Figure 9. Delft3D curvilinear modeling grid for the study area, with dots denoting the grid cells 

vertices. The average cell size is approximately 100 m on a side. The grid extends out into deep 

(>1,000 m) water to propagate the wave field properly on to the upper slope and shelf. The higher 

density, and thus smaller cell size, of the grid on the shelf and upper slope was necessary for the 

model to accurately handle wave refraction in shallow water and around complex bathymetry.

RUN ID Return Interval

(years)

Hsig

(m)

Tdom

(s)

WVdir

(deg)

WDspd

(m/s)

WDdir

(deg)

TWO 2 7.7 16 280 20 280

TEN 10 9.6 18 280 24 280

TFV 25 10.6 20 280 26 280

FIF 50 11.4 22 280 28 280

HUN 100 12.2 24 280 30 280

Table 2. Return interval model run boundary conditions.

[Hsig, Significant wave height; Tdom, Dominant wave period; WVdir, Wave direction; WDspd, Wind speed; WDdir, Wind direction]
13

1 

2 

3 

4 

5 

6 

7 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

SIGNIFICANT WAVE HEIGHT (METERS) 

El Niño February 

Hsig = 7.53 m, Tdom = 13.75 s 

LATITUDE (DEGREES NORTH) 

LONGITUDE (DEGREES WEST) 

0 25 50 

KILOMETERS 

Figure 10. Example model run for the study area showing significant wave height (Hsig), in m, over the model domain for an 

El Niño February. Reduced wave heights are seen in the lee of the Farallon Islands, the ebb tidal delta off San Francisco, 

and the headlands at Bodega, Point Reyes, Half Moon Bay, Año Nuevo, Santa Cruz and Monterey. A subtle, but noticeable, 

decrease in wave heights across the shelf due to wave energy loss by frictional interactions with the sea floor is observed. 

The dominant wave period (Tdom ) is 13.75 seconds.

Methods
14 Wave-Driven Spatial and Temporal Variability in Sea-floor Sediment Mobility

0. 1 

0. 2 

0. 3 

0. 4 

0. 5 

0. 6 

0. 7 

0. 8 

0. 9 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

El Niño February 

Hsig = 7.53 m, Tdom = 13.75 s 

NEAR-BED ORBITAL WAVE VELOCITY (METERS PER SECOND) 

LATITUDE (DEGREES NORTH) 

LONGITUDE (DEGREES WEST) 

0 25 50 

KILOMETERS 

Figure 11. Same example model run shown in figure 10 displaying peak wave-induced near-bed orbital wave velocity (Uorb), 

in m/s, over the model domain for an El Niño February. The largest Uorb values are found in shallow regions where significant 

wave height (Hsig) is large, with substantial Uorb values observed all across the inner shelf and elevated Uorb values observed 

out to the shelf break in water depths exceeding 120 m. The dominant wave period (Tdom) is 13.75 seconds.
15

BED data. The wave friction factor, fw, was defined using the 

Nielsen (1992) formulation:

with the orbital amplitude excursion (A) defined as u/σ. 

The wave friction factor was then used to calculate the peak 

bed shear stress for oscillatory flow under waves (τpeak) using 

the Fredsoe and Deigard (1992) formulation:

with pf as the density of seawater (1,026 kg/m3 at 34 PSU 

and 10 °C). These τpeak values for each grid cell, in units of N/

m2 (fig. 12), were compared to the critical shear stresses for 

the initiation of sediment transport (τcrit, fig. 13) calculated 

using the modified Shield parameter methodology of Madsen 

(1999) for each grid cell for the cell’s grain size (fig. 4) and 

sediment density from the usSEABED database. If τpeak < 

τcrit, then the force per area applied by the waves is not great 

enough to mobilize the sea-floor sediment; if the τpeak >= τcrit, 

however, then the sea-floor sediment is entrained by the wave 

orbital velocities and thus the sea floor is mobilized. Because 

unidirectional currents are not being modeled, sediment fluxes, 

and thus the divergences or convergences that cause erosion 

or deposition of the sea floor cannot be computed. Therefore, 

these calculations can only determine if the seabed sediment is 

mobilized and entrained by the wave-orbital velocities and not 

provide information on sediment transport or depth of disturbance.

Since sea-floor sediment resuspension is driven by the 

total shear stress (wave + current) on the sea floor, these calculations, which only used the wave-induced shear stress, will 

likely under represent the true magnitude of sediment mobility 

on the outer shelf and upper slope due to the equal order of the 

magnitude of the wave-induced stresses and current-induced 

(internal, tidal or subtidal) stresses at these depths. Therefore, 

the results of this study will provide minimum forcing levels. 

The current-induced shear stresses and the resulting combined 

wave-current shear stresses in the study area will be addressed 

in subsequent reports.

Results

Examples of the influence of variations in oceanographic 

and meteorologic forcing on wave-induced sediment mobilization along the central California coast are shown in figures 14 

and 15. Figure 14 displays regions of the study area that are 

mobilized (red) or are stable (blue) for the El Niño February 

model run shown in figures 10 through 12. The red regions 

indicate where the peak wave-induced near-bed shear stress 

(τpeak, fig. 12) exceeds the critical shear stress for the initiation of sediment transport (τcrit, fig. 13); the blue regions are 

where τpeak < τcrit. Almost the entire shelf, except for areas 

characterized by rock and boulders, is mobilized during an 

El Niño February due to the large Hsig, long Tdom and westerly 

WVdir. Figure 15 displays which regions of the study area are 

mobilized (red) and which are stable (blue) during a La Niña 

October. La Niña Octobers are characterized by smaller Hsig

and shorter Tdom than during an El Niño February, resulting in 

a much smaller proportion of the shelf mobilized (fig. 14).

Two general alongshore trends are visible in figure 15 

that are common to many of the model runs. The first trend is 

a band of sediment mobility that extends from the shoreline 

out into water depths of 10 to 30 m. This region, although 

predominantly coarse (sand-sized) sediment (fig. 4), is commonly mobilized due to the shallow water depth relative to 

the Hsig and Tdom, resulting in τpeak greater than the τcrit for the 

sediment. Farther out on the shelf in water depths of 60 to 90 

m, another region of finer-grained (silt and clay) sediment, 

termed the “mud belt,” is more commonly mobilized than 

the coarser sediment in shallower water depths (30-60 m). 

Although the water depth is greater along the mud belt than 

the region of less frequent mobility inshore of it, the much 

smaller grain size lowers τcrit and results in greater mobility 

than the shallower but coarser material inshore. The individual 

monthly model runs detailed in table 1 are shown in appendixes 1 through 36 and the return interval projections outlined 

in table 2 are shown in appendixes 37 through 41. The return 

interval projections suggest that the entire shelf (0-120 m) is 

suspended under these extreme events, and more than 97 percent of the entire study area shallower than 500 m is mobilized 

during a 100-year storm (table 3). 

Modeled sediment mobility in the study area varies by 

depth range, but is also affected by location and time of year

(fig. 16; table 4). Spatially, the shallower regions are generally 

more frequently mobilized than the deeper regions due to the 

dependence of τpeak on water depth. Temporally, the greater 

storminess during the winter months (December–February) 

results in approximately 10 percent of the upper slope (120-

500 m) in the study area being mobilized, whereas in the 

summer months (July-September) only 30 percent of the inner 

shelf (0-30 m) is mobilized by waves. During normal oceanic 

conditions, the regions with highest mobility occur along the 

inner shelf and the mud belt, and sections of the inner shelf 

with westerly exposures are more frequently mobilized than 

those with more southerly exposures due to wave energy loss 

resulting from wave refraction and energy dissipation (fig. 17).

ENSO events have a clear influence on sediment mobility along the central California shelf (table 4). Spatially, El 

Niño conditions cause greater mobilization on the upper slope 

(120-500 m) and the inner shelf (0-30 m), as shown in figure 

18. Although 2 percent of the shelf between the 60 m and 90 

m isobaths is more frequently disturbed during El Niño conditions than during Normal conditions (fig. 17), this relative 

increase in frequency of disturbance is offset by an almost 

equal decrease in frequency of disturbance throughout the rest 

of the shelf and upper slope in the study area. La Niña condiResults

τ peak = 1

2 f fw (Aσ )

2 ρ

f w = exp 5.5 r

A

⎛

⎝

⎜ ⎞

⎠

⎟

0.2

− 6.3

⎡

⎣

⎢

⎢

⎤

⎦

⎥

⎥
16 Wave-Driven Spatial and Temporal Variability in Sea-floor Sediment Mobility

0. 2 

0. 4 

0. 6 

0. 8 

1 

1. 2 

1. 4 

1. 6 

1. 8 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

El Niño February 

Hsig = 7.53 m, Tdom = 13.75 s 

PEAK WAVE-INDUCED NEAR-BED SHEAR STRESS (NEWTONS PER METERS SQUARED) 

LATITUDE (DEGREES NORTH) 

LONGITUDE (DEGREES WEST) 

0 25 50 

KILOMETERS 

Figure 12. Same example model run shown in figures 10 and 11 displaying peak wave-induced near-bed shear stress (τpeak), 

in N/m2

, over the model domain for an El Niño February. Substantial τpeak values are observed all across the inner shelf and 

elevated τ peak values are observed to the shelf break in water depths exceeding 120 m.
17

0. 2 

0. 4 

0. 6 

0. 8 

1 

1. 2 

1. 4 

1. 6 

1. 8 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

more erodable less erodable 

LATITUDE (DEGREES NORTH) 

LONGITUDE (DEGREES WEST) 

CRITICAL BED SHEAR STRESS (NEWTONS PER METER SQUARED) 

0 25 50 

KILOMETERS 

Figure 13. Critical shear stresses (τcrit), in N/m2, for the initiation of sediment transport in the study area calculated using 

the methodology defined by Madsen (1999) based on the grain size and sediment density from the usSEABED database. 

Sediments with higher critical shear stresses require greater force per area to mobilize and thus are less easily erodable.

Results
18 Wave-Driven Spatial and Temporal Variability in Sea-floor Sediment Mobility

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

LATITUDE (DEGREES NORTH) 

LONGITUDE (DEGREES WEST) 

El Niño February 

Hsig = 7.53 m, Tdom = 13.75 s 

BLUE = STABLE

RED = MOBILIZED 

0 25 50 

KILOMETERS 

Figure 14. Same example model run shown in figures 10 through 12 displaying regions of the study area 

mobilized (red) and stable (blue) during an El Niño February due to wave forcing. The red regions are where 

the peak wave-induced near-bed shear stress (τpeak, fig. 12) exceeds the critical shear stress for the initiation 

of sediment transport (τcrit, fig. 13); the blue regions are where τpeak < τcrit. Almost the entire shelf (depths <120 

m), except for areas characterized by rock and boulders, is mobilized during an El Niño February. The significant wave height (Hsig) is 7.53 m and the dominant wave period (Tdom ) is 13.75 seconds.
19

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

LATITUDE (DEGREES NORTH) 

LONGITUDE (DEGREES WEST) 

BLUE = STABLE

RED = MOBILIZED 

La Niña October 

Hsig = 4.43 m, Tdom = 12.25 s 

0 25 50 

KILOMETERS 

Figure 15. An example model run displaying regions of the study area mobilized (red) and stable (blue) 

during a La Niña October. The red regions are where the peak wave-induced near-bed shear stress (τpeak) 

exceeds the critical shear stress for the initiation of sediment transport (τcrit, fig. 13); the blue regions are 

where τpeak < τcrit. A much smaller proportion of the shelf is mobilized during a La Niña October than during an 

El Niño February (fig. 14). The significant wave height (Hsig) is 4.43 m and the dominant wave period (Tdom ) is 

12.25 seconds.

Results
20 Wave-Driven Spatial and Temporal Variability in Sea-floor Sediment Mobility

Return Interval

(years)

120 – 500 m 90 – 120 m 60 – 90 m 30 – 60 m 0 – 30 m

2 34.19 96.50 99.16 99.38 99.03

10 52.14 98.64 99.66 99.70 99.41

25 63.54 99.09 99.76 99.77 99.32

50 75.43 99.50 99.87 99.80 99.37

100 80.71 99.50 99.87 99.67 99.19

Table 3. Percent of sea floor disturbed by depth range for return interval model run boundary conditions.

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 

0 

20 

40 

60 

80 

100 

PERCENT 

-20 

-10 

0 

10 

20 

PERCENT DIFFERENCE 

-20 

-10 

0 

10 

20 

MONTH 

PERCENT DIFFERENCE 

= 0m - 30m 

= 30m - 60m 

= 60m - 90m 

= 90m - 120m 

= 120m - 500m 

Normal Years 

Deviation during El Niño Years 

Deviation during La Niña Years 

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 

A 

B 

C 

Figure 16. Plots showing the temporal variation in percent of sea floor in the study area disturbed by 

depth range. A, Normal years. B, Deviation from normal during El Niño conditions, with positive values 

showing a percentage increase in area disturbed compared to normal conditions and negative values 

showing a percentage decrease in area disturbed than during normal conditions. C, Deviation from 

normal during La Niña conditions. The greatest increase in percentage of sea floor mobilized during El 

Niño conditions occurs late in the winter during the month of February, whereas the greatest increase 

during La Niña conditions occurs earlier in the winter during the month of November.
21

Climate Month 120 – 500m 90 – 120m 60 – 90m 30 – 60m 0 – 30m 

Normal Jan 13.45 77.95 93.02 94.05 95.86

Normal Feb 10.39 73.18 91.50 92.96 94.89

Normal Mar 9.01 65.68 86.78 89.77 91.77

Normal Apr 0.39 29.27 59.39 70.21 82.85

Normal May 0.00 13.55 43.81 46.76 71.41

Normal Jun 0.00 0.41 5.46 6.91 50.00

Normal Jul 0.00 0.00 0.13 0.69 26.77

Normal Aug 0.00 0.00 0.07 0.30 19.64

Normal Sep 0.00 0.00 0.13 0.59 27.11

Normal Oct 0.00 11.23 38.01 37.68 67.31

Normal Nov 2.67 50.00 75.04 82.87 87.37

Normal Dec 9.56 68.50 89.01 91.42 94.05

El Niño Jan 15.34 81.50 94.03 94.34 95.90

El Niño Feb 16.90 86.50 96.42 95.73 96.75

El Niño Mar 11.06 72.91 90.52 92.04 94.51

El Niño Apr 0.17 21.45 52.75 63.50 81.12

El Niño May 0.00 2.59 19.49 24.73 61.49

El Niño Jun 0.00 3.95 17.23 18.78 55.95

El Niño Jul 0.00 0.00 0.20 0.56 20.35

El Niño Aug 0.00 0.00 0.03 0.20 14.53

El Niño Sep 0.00 0.00 0.10 0.49 22.76

El Niño Oct 0.00 9.95 33.79 31.77 64.48

El Niño Nov 0.89 31.82 59.53 74.88 84.84

El Niño Dec 7.45 67.18 86.68 90.17 92.78

La Niña Jan 9.23 70.86 88.23 91.61 94.89

La Niña Feb 3.78 56.73 78.79 85.66 89.44

La Niña Mar 8.84 65.32 86.91 89.84 91.64

La Nina Apr 0.33 21.14 52.95 60.37 77.79

La Niña May 0.00 13.27 42.53 44.52 70.19

La Niña Jun 0.00 0.00 0.47 0.66 28.34

La Niña Jul 0.00 0.00 0.10 0.53 25.38

La Niña Aug 0.00 0.00 0.07 0.30 23.56

La Niña Sep 0.00 0.00 0.27 0.85 32.56

La Niña Oct 0.00 10.86 36.12 33.34 64.27

La Niña Nov 6.84 60.50 83.27 88.19 89.44

La Niña Dec 5.56 58.86 80.37 86.45 90.03

Table 4. Percent of sea floor disturbed by depth range for climatic model run boundary conditions.

Results
22 Wave-Driven Spatial and Temporal Variability in Sea-floor Sediment Mobility

10 

20 

30 

40 

50 

60 

70 

80 

90 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

Normal 

LATITUDE (DEGREES NORTH) 

LONGITUDE (DEGREES WEST) 

FREQUENCY DISTURBED (PERCENT) 

0 25 50 

KILOMETERS 

Figure 17. Map of the study area showing the frequency of sea-floor disturbance (as a percentage of months) during a 

year with normal conditions. Warm colors indicate higher frequencies of disturbance, whereas cool colors indicate less 

frequently disturbed areas. A general trend is seen of greater disturbance along the inner shelf, with lower frequency of 

disturbance along the outer shelf, upper slope, areas of the inner shelf in the lee of headlands, and regions of the sea floor 

characterized by rock outcrops or boulders.
23

10 

20 

30 

40 

50 

60 

70 

80 

90 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

LATITUDE (DEGREES NORTH) 

LONGITUDE (DEGREES WEST) 

FREQUENCY DISTURBED (PERCENT) 

El Niño 

0 25 50 

KILOMETERS 

Figure 18. Map of the study area showing the frequency of sea-floor disturbance (as a percentage of months) during a year 

with El Niño conditions. Warm colors indicate higher frequencies of disturbance, whereas cool colors indicate less frequently disturbed areas. Although 2 percent of the shelf between the 60-m and 90-m isobaths is more frequently disturbed 

during El Niño conditions than during Normal conditions (fig. 17), this relative increase in frequency of disturbance is offset 

by an almost equal decrease in frequency of disturbance throughout the rest of the shelf and upper slope in the study area.

Results
24 Wave-Driven Spatial and Temporal Variability in Sea-floor Sediment Mobility

Figure 19. Map of the study area showing the frequency of sea-floor disturbance (as a percentage of months) during a year 

with La Niña conditions. Warm colors indicate higher frequencies of disturbance, whereas cool colors indicate less frequently disturbed areas. Although 10 percent of the shelf between the 60-m and 90-m isobaths is more frequently disturbed 

during El Niño conditions than during Normal conditions (fig. 17), an almost equal decrease in frequency of disturbance 

occurs over the rest of the shelf and upper slope in the study area.

10 

20 

30 

40 

50 

60 

70 

80 

90 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

LATITUDE (DEGREES NORTH) 

LONGITUDE (DEGREES WEST) 

FREQUENCY DISTURBED (PERCENT) 

La Niña 

0 25 50 

KILOMETERS 

tions cause greater mobilization on the middle and outer shelf 

(30-120 m), as shown in figure 19. Although 10 percent of the 

shelf between the 60 m and 90 m isobaths is more frequently 

disturbed during El Niño conditions than during Normal 

conditions (fig. 17), an almost equal decrease in frequency of 

disturbance occurs over the rest of the shelf and upper slope 

in the study area. The difference in frequency of disturbance 

between El Niño and La Niña conditions is shown in figure 

20. El Niño and La Niña conditions generate similar areas 

with the highest frequency of disturbance (31.6 percent and 

32.7 percent of the study area, respectively). Approximately 

8.4 percent and 3.5 percent more of the upper slope (120-500 
25

Figure 20. Map showing the difference in frequency that the sea floor in the study area is disturbed during 

El Niño and La Niña years. El Niño and La Niña conditions generate similar areas with the highest frequency 

of disturbance (31.6 percent and 32.7 percent of the study area, respectively). Approximately 8.4 percent 

and 3.5 percent more of the upper slope (120-500 m) and inner shelf (0-30 m), respectively, is disturbed more 

frequently during El Niño conditions, whereas La Niña conditions result in more frequent disturbances on 5.8 

percent of the outer shelf (60-120 m).

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

GREEN = No difference 

BLUE = Greater disturbance during La Niña

RED = Greater disturbance during El Niño 

LATITUDE (DEGREES NORTH) 

LONGITUDE (DEGREES WEST) 

ALL MONTHS 

0 25 50 

KILOMETERS 

Results
26 Wave-Driven Spatial and Temporal Variability in Sea-floor Sediment Mobility

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

GREEN = No difference 

BLUE = Greater disturbance during La Niña

RED = Greater disturbance during El Niño 

LATITUDE (DEGREES NORTH) 

LONGITUDE (DEGREES WEST) 

DECEMBER - FEBRUARY 

0 25 50 

KILOMETERS 

Figure 21. Map showing the difference in frequency that the sea floor in the study area is disturbed during 

El Niño and La Niña winter months (December-February). El Niño conditions resulted in a much larger area 

with more frequent disturbance (16.1 percent) than La Niña conditions (<0.1 percent), with 13.2 percent, 24.7 

percent and 8.8 percent more of the upper slope (120-500 m), outer shelf (60-120 m), and inner shelf (0-30 m), 

respectively, disturbed during El Niño conditions. 

m) and inner shelf (0-30 m), respectively, is disturbed more frequently during El Niño conditions, whereas La Niña conditions 

result in more frequent disturbances on 5.8 percent of the outer 

shelf (60-120 m).

There is substantial temporal variation in the influence of 

ENSO events on these general trends (figs. 21 through 24). The 

greatest increase in percentage of sea floor mobilized during El 

Niño conditions occurs during the winter (December-February), 
27

as shown in figure 21. El Niño conditions resulted in a much 

larger area with more frequent disturbance (16.1 percent) than 

La Niña conditions (<0.1 percent), with 13.2 percent, 24.7 percent and 8.8 percent more of the upper slope (120-500 m), outer 

shelf (60-120 m) and inner shelf (0-30 m), respectively, disturbed during El Niño conditions. La Niña conditions resulted in 

a more than twice the area with more frequent disturbance (13.3 

percent) than El Niño conditions (5.9 percent) during the spring 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

GREEN = No difference 

BLUE = Greater disturbance during La Niña

RED = Greater disturbance during El Niño 

LATITUDE (DEGREES NORTH) 

LONGITUDE (DEGREES WEST) 

MARCH - MAY 

0 25 50 

KILOMETERS 

Figure 22. Map showing the difference in frequency that the sea floor in the study area is disturbed during 

El Niño and La Niña spring months (March-May). La Niña conditions resulted in a more than twice the 

area with more frequent disturbance (13.3 percent) than El Niño conditions (5.9 percent). Whereas El Niño 

conditions caused 2.1 percent more of the upper slope (120-500 m) to be more frequently disturbed, La Niña 

conditions resulted in 24.7 percent and 8.8 percent more of the outer shelf (60-120 m) and inner shelf (0-30 m), 

respectively, to be more frequently disturbed.

Results
28 Wave-Driven Spatial and Temporal Variability in Sea-floor Sediment Mobility

months (March-May), as shown in figure 22. Whereas El Niño 

conditions caused 2.1 percent more of the upper slope (120-500 

m) to be more frequently disturbed, La Niña conditions resulted 

in 24.7 percent and 8.8 percent more of the outer shelf (60-120 

m) and inner shelf (0-30 m), respectively, to be more frequently 

mobilized. El Niño conditions resulted in a more than six times 

the area with a higher frequency of disturbance (13.1 percent) 

than La Niña conditions (2.0 percent) during the summer 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

GREEN = No difference 

BLUE = Greater disturbance during La Niña

RED = Greater disturbance during El Niño 

LATITUDE (DEGREES NORTH) 

LONGITUDE (DEGREES WEST) 

JUNE - AUGUST 

0 25 50 

KILOMETERS 

Figure 23. Map showing the difference in frequency that the sea floor in the study area is disturbed during 

El Niño and La Niña summer months (June-August). El Niño conditions resulted in a more than six times the 

area with a higher frequency of disturbance (13.1 percent) than La Niña conditions (2.0 percent). Whereas 

neither set of end-member conditions caused increased mobility on the upper slope (120-500 m), El Niño 

conditions resulted in 10.4 percent and 17.2 percent more of the outer shelf (60-120 m) and inner shelf (0-30 

m), respectively, to be more frequently disturbed.
29

months (June-August), as shown in figure 23. Although neither 

set of end-member conditions caused increased mobility on the 

upper slope (120 to 500 m), El Niño conditions resulted in 10.4 

percent and 17.2 percent more of the outer shelf (60 to 120 m) 

and inner shelf (0 to 30 m), respectively, to be more frequently 

disturbed. The greatest increase in percentage of sea floor mobilized during La Niña conditions occurs in the fall (SeptemberNovember), as shown in figure 24. La Niña conditions resulted 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

GREEN = No difference 

BLUE = Greater disturbance during La Niña

RED = Greater disturbance during El Niño 

LATITUDE (DEGREES NORTH) 

LONGITUDE (DEGREES WEST) 

SEPTEMBER - NOVEMBER 

0 25 50 

KILOMETERS 

Figure 24. Map showing the difference in frequency that the sea floor in the study area is disturbed during El 

Niño and La Niña fall months (September-November). La Niña conditions resulted in a much larger area with 

greater disturbance (18.5 percent) than El Niño conditions (0.3 percent), with 6.0 percent, 27.9 percent and 

14.7 percent more of the upper slope (120-500 m), outer shelf (60-120 m), and inner shelf (0-30 m), respectively, disturbed during La Niña conditions.

Results
30 Wave-Driven Spatial and Temporal Variability in Sea-floor Sediment Mobility

in a much larger area with greater disturbance (18.5 percent) 

than El Niño conditions (0.3 percent), with 6.0 percent, 27.9 

percent and 14.7 percent more of the upper slope (120-500 m), 

outer shelf (60-120 m), and inner shelf (0-30 m), respectively, 

disturbed during La Niña conditions.

The differences in frequency of disturbance between El 

Niño and La Niña conditions are delineated spatially and by 

depth range in figure 25. Spatially, El Niño conditions result in 

greater mobility on the upper slope (120-500 m) and the inner 

shelf (0-30 m), and La Niña conditions cause greater mobility on the middle and outer shelf (60-120 m). Temporally, El 

Niño conditions result in more frequent mobility in the winter 

(December-February) and summer (June-August) months, and 

La Niña conditions cause greater mobility in the spring (MarchMay) and fall (September-November) months. An important 

point is that the entire shelf is being mobilized under both El 

Niño and La Niña conditions, just at different locations at different times.

Discussion

The results of this study suggest that, on a given month, 

just under half of the shelf (0-120 m) and 4 percent of the upper 

slope (120-500 m) is mobilized 1 percent of time. While these 

results do not attempt to address to what depth this mobilization 

occurs, they do show wave-induced shear stresses large enough 

to resuspend the surface sediment layer. These findings indicate 

that these factors have significant consequences for both geological and biological processes.

Geological Implications

One of the important concepts incorporated into numerical models (Hanson and Kraus, 1989; Larson and Kraus, 1989) 

used by engineers and coastal scientists is that of “closure 

depth,” or the depth below which no sediment is transported in 

significant volumes (Hallemeier, 1981; Pilkey and others, 1993). 

Although the definition of “significant volumes” is loosely 

constrained, much of the recent work trying to better define 

the depth of closure has shown that this is not a fixed boundary 

but varies temporally. Our investigation of sediment mobility 

along the central California shelf similarly suggests that sediment mobility varies significantly both in space and time due to 

temporal variations in meteorologic and oceanographic forcing, 

spatial variations in wave properties (Hsig and WVdir), and seafloor sediment material properties.

The relatively high frequency of mobilization along the 

inner shelf of the study area, except in the lee of headlands at 

Point Reyes, Half Moon Bay, Santa Cruz, and the Monterey 

Peninsula, correlates well with the presence of coarser-grained 

material in these locations, suggesting that finer-grained material is unstable in these locations and shallow water depths, and 

thus is likely transported offshore into deeper, more quiescent 

water depths. This has implications on the terrestrial input of 

material to the coastal ocean. Most of the precipitation and fluvial discharge along central California occurs during the winter 

months when 90 percent or more of the coarse material on the 

inner shelf is being mobilized. Hence, the fine-grained sediment 

inputs from coastal streams and rivers are probably short lived 

on the inner shelf and are likely quickly transported offshore into 

greater water depths where the shear stresses are low enough to 

allow deposition. Similarly, fine-grained sedimentary material 

naturally deposited by small coastal landslides into the nearshore 

or dredged to maintain harbor access during the stormy winter 

months is likely not stable for substantial periods of time on most 

of the inner shelf (<30 m depth) of central California.

Conversely, the presence of fine-grained material on the 

middle shelf that is frequently mobilized a good portion of the 

year suggests that the supply of this fine-grained sediment from 

terrestrial sources is greater than the ability of waves to remove 

the fine-grained material from the mud belt, as suggested by 

McCave (1972) and Grove and others (1982). This suggests that 

although most of the streams and rivers draining central California are small by global standards, their steep nature results 

in them supplying much more material to the coastal zone for 

the size of their drainage basins relative to many larger river 

systems, agreeing with the basic tenets found in Milliman and 

Syvitski (1992). This has significant implications on the flux of 

biologically important materials (iron, carbon, others) delivered 

by rivers and streams to the coastal ocean that strongly influence 

coastal ecosystem dynamics.

Biological Implications

The relatively high percentage (>50 percent) of the central California Continental Shelf that is mobilized at least 1 

percent of the time in a given month suggests that the benthic 

infauna and epifauna along the shelf are adapted to a dynamic 

hydrodynamic and sedimentary environment. Even along the 

coarse-grained or rocky sections of the study area, such as 

Cordell Bank off Point Reyes, “Deep Reef” off Half Moon Bay, 

and Portuguese Ledge in southern Monterey Bay, the high frequency of mobilization in these regions suggests that many of 

the deeper bedrock reefs are frequently subjected to moderate 

wave-orbital velocities (>0.2 m/s; fig. 26) and abraded by mobilized seabed sediment. Furthermore, all of the shallow bedrock 

reefs on the inner most portions of the Continental Shelf (<10 m 

depth) except those in the lee of headlands are frequently subjected to strong wave-orbital velocities (>0.5 m/s). The critical 

velocities for the entrainment of coarse sand and fine sand are 

0.5 m/s and 0.2 m/s, respectively, and these wave-orbital velocities will cause the bedrock reefs to be abraded by mobilized 

interstitial sediment.

Benthic communities’ structure is typically determined by 

the sea-floor composition. Research by Grant and others (1991) 

on the Scotian Shelf showed that oxygen demand was approximately 2.7 times higher and carbon consumption was approximately 1.5 times higher in surficial fine-grained sediment than 

in coarser sediment, suggesting links between sea-floor grain 

size and productivity. Recently, to better describe animal-sedi-
-35 -30 -25 -20 -15 -10 -5 0 +5 +10 +15 +20 +

PERCENT DIFFERENCE 

120 - 500 m 90 - 120 m 60 - 90 m 30 - 60 m 0 - 30 m 

Fall (Sep-Nov) 

Summer (Jun-Aug) 

Spring (Apr-May) 

Winter (Dec-Feb) 

All Seasons 

La Niña > El Niño 

(greater disturbance during La Niña) 

El Niño 

(greater disturba

Figure 25. Plot synthesizing the data on the spatial and temporal variations in sea-floor mobility between El Niño and La Niña conditions shown in figures 20 thr

the different depth ranges and the data are plotted for the entire year and each season. Positive values represent the percentage of the sea floor for a given demore during El Niño conditions than during La Niña conditions; negative values indicate the frequency of disturbance was greatest during La Niña conditions. Sresult in greater mobility on the upper slope (120-500 m) and the inner shelf (0-30 m), and La Niña conditions cause greater mobility on the middle and outer shelNiño conditions result in more frequent mobility in the winter (December-February) and summer (June-August) months, and La Niña conditions cause greater mMay) and fall (September-November) months.
32 Wave-Driven Spatial and Temporal Variability in Sea-floor Sediment Mobility

ment relationships, Snelgrove and Butman (1994) suggested that 

hydrodynamics and sediment mobilization be incorporated into 

habitat classification. Their work suggested that sediment mobilization helped to better constrain species distribution. Potential 

future climate change, and the resulting changes in storm patterns and intensity, could modify the sediment distribution and 

mobilization patterns shown here, and thus alter benthic community structure.

Figure 26. Map of the study area displaying the mean peak near-bed wave orbital velocity (Uorb), in m/s, over the model domain 

for all months and conditions. Warmer colors denote regions that experience faster wave-driven oscillatory near-bed currents. 

The greatest Uorb values are found in shallow regions where significant wave height (Hsig) is large, with substantial Uorb values 

observed all across the inner shelf and elevated Uorb values observed out into water depths exceeding 90 m

0. 1 

0. 2 

0. 3 

0. 4 

0. 5 

0. 6 

0. 7 

0. 8 

0. 9 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

LATITUDE (DEGREES NORTH) 

LONGITUDE (DEGREES WEST) 

MEAN NEAR-BED ORBITAL WAVE VELOCITY (METERS PER SECOND) 

0 25 50 

KILOMETERS 
33

Conclusions

Oceanographic and meteorologic data were combined 

with bathymetry and gridded grain-size data held in the USGS 

usSEABED database to predict the mobilization of the unconsolidated sea floor on the Continental Shelf and upper slope 

off central California. Sediment resuspension was investigated 

under different climatic regimes and statistical projections. 

Spatially, the shallower regions are generally more frequently 

mobilized than the deeper regions. Temporally, the greater 

storminess during the winter months (December–February) 

results in approximately 10 percent of the upper slope 

(120-500 m) in the study area being mobilized, whereas in the 

summer months (July-September) only the inner shelf (0-30 

m) is mobilized by waves. El Niño conditions cause greater 

mobilization on the upper slope (120-500 m) and the inner 

shelf (0-30 m); La Niña conditions cause greater mobilization 

on the middle and outer shelf (30-120 m). There is substantial 

temporal variation in the influence of ENSO events on these 

general trends, with the greatest increase in percentage of sea 

floor mobilized during the winter (December-February) of an 

El Niño, whereas the greatest increase during La Niña conditions occurs in the fall (September-November). By understanding the spatial and temporal variability in the disturbance 

of the sea floor, managers and planners can use this information when considering offshore activities such as trawling, 

dredging, and the emplacement of sea-floor engineering structures (cables, pipelines, others).

Acknowledgments

This research was conducted as part of the USGS Benthic 

Habitats Project’s effort to better understand the impact of 

geologic and oceanographic processes on central California’s 

shoreline and nearshore ecosystems. We would like to thank 

Monica Tydlaska (University of California, Santa Cruz), who 

compiled all of the figures presented in the appendices. We 

also thank Steve Lonhart (Monterey Bay National Marine 

Sanctuary), Katie Farnsworth (USGS) and Doug George 

(USGS), who contributed numerous excellent suggestions and 

timely reviews of the manuscript. James Hendley in the USGS 

Menlo Park Publications Service Center worked diligently 

with the authors to get this report into the correct style, grammar, and format and deserves special thanks.

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Pilkey, O.H., Young, R.S., Riggs, S.R., Smith, A.W.S., Wu, H., 

and Pilkey, W.D., 1993, The concept of shoreface profile 

equilibrium – A critical review: Journal of Coastal 

Research, v. 9 no. 1, p. 255-278.

Reid, J.A., Reid, J.M., Jenkins, C.J., Zimmermann, M., 

Williams, S.J., and Field, M.E., 2006, usSEABED – Pacific 

Coast (California, Oregon, Washington) offshore surficialsediment data release: U.S. Geological Survey Data Series 

182, version 1.0 [http://pubs.usgs.gov/ds/2006/182/].

Ris, R.C., 1997, Spectral modeling of wind waves in coastal 

areas: Delft, The Netherlands, Ph.D. dissertation, Delft 

University of Technology, Department of Civil Engineering, 

Communications on Hydraulic and Geotechnical 

Engineering, Report No. 97-4.

Ris, R.C., Booij, N., and Holthuijsen, L.H., 1999, A thirdgeneration wave model for coastal regions, Part II 

–Verification: Journal of Geophysical Research, v. 104, no. 

C4, p. 7667-7682.

Seymour, R.J., Strange, R.R., Cayan, D.R. and Nathan, R.A., 

1984, Influence of El Niños on California’s wave climate: 

Proceedings of the 19th Coastal Engineering Conference, 

American Society of Civil Engineers, vol. 1, p. 577-592.

Schatz, B., 1963, A restudy of bottom sediments near the 

entrance of the Golden Gate: Berkeley, University of 

California, Hydraulic Engineering Laboratory, Wave 

Research Project, Technical Report HEL 4-3, 8 p. with 

appendices. 

Snelgrove, P.V.R., and Butman, C.A., 1994, Animal-sediment 

relationships revisited – Cause versus effect: Oceanography 

and Marine Biology Annual Review, v. 32, 111-177.

Storlazzi, C.D. and Wingfield, D.K., 2005, The spatial and 

temporal variability in oceanographic and meteorologic 

forcing along Central California – 1980-2002: U.S. 

Geological Survey Scientific Investigations Report 

2005-5085, 39 p.

Wentworth, C.K., 1922, A scale of grade and class terms used 

for clastic sediments: Journal of Geology, v. 30, p. 377-392.

Wolter, K., and Timlin, M., 1998, Measuring the strength of 

ENSO – How does 1997/98 rank?: Weather, v. 53, p. 

315-324.
35

Appendixes 1-41
36 Wave-Driven Spatial and Temporal Variability in Sea-floor Sediment Mobility

Appendix 1. Model run for a Normal January. A, Map of significant wave height (Hsig), in m. B, Map of peak wave-induced 

near-bed orbital wave velocity (Uorb), in m/s. C, Map of peak wave-induced near-bed shear stress (τpeak), in N/m2

. D, Map displaying which regions of the study area are mobilized (red) and which are stable (blue) for the modeled conditions. See table 2 for 

information on model run boundary conditions.

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o

36.60o

37.05o

37.50o

37.95o

38.40o

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o

36.60o

37.05o

37.50o

37.95o

38.40o

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o

36.60o

37.05o

37.50o

37.95o

38.40o

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o

36.60o

37.05o

37.50o

37.95o

38.40o

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

Tpeak [N/m Blue = Stable, Red = Mobilized 2]

Hsig [m] Uorb [m/s] 

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

2

3

4

5

6

7

A

C

B

D
Appendixes 37

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

τpeak [N/m Blue = Stable, Red = Mobilized 2]

Hsig [m] Uorb [m/s] 

0. 2 

0. 4 

0. 6 

0. 8 

1.0 

1. 2 

1. 4 

1. 6 

1. 8 

0. 1 

0. 2 

0. 3 

0. 4 

0. 5 

0. 6 

0. 7 

0. 8 

0. 9 

1 

2 

3 

4 

5 

6 

7 

A 

C 

B 

D 

Appendix 2. Model run for a Normal February. A, Map of significant wave height (Hsig), in m. B, Map of peak wave-induced 

near-bed orbital wave velocity (Uorb), in m/s. C, Map of peak wave-induced near-bed shear stress (τpeak), in N/m2

. D, Map displaying which regions of the study area are mobilized (red) and which are stable (blue) for the modeled conditions. See table 2 for 

information on model run boundary conditions.
38 Wave-Driven Spatial and Temporal Variability in Sea-floor Sediment Mobility

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

τpeak [N/m Blue = Stable, Red = Mobilized 2]

Hsig [m] Uorb [m/s] 

0. 2 

0. 4 

0. 6 

0. 8 

1.0 

1. 2 

1. 4 

1. 6 

1. 8 

0. 1 

0. 2 

0. 3 

0. 4 

0. 5 

0. 6 

0. 7 

0. 8 

0. 9 

1 

2 

3 

4 

5 

6 

7 

A 

C 

B 

D 

Appendix 3. Model run for a Normal March. A, Map of significant wave height (Hsig), in m. B, Map of peak wave-induced nearbed orbital wave velocity (Uorb), in m/s. C, Map of peak wave-induced near-bed shear stress (τpeak), in N/m2

. D, Map displaying 

which regions of the study area are mobilized (red) and which are stable (blue) for the modeled conditions. See table 2 for 

information on model run boundary conditions.
Appendixes 39

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

τpeak [N/m Blue = Stable, Red = Mobilized 2]

Hsig [m] Uorb [m/s] 

0. 2 

0. 4 

0. 6 

0. 8 

1.0 

1. 2 

1. 4 

1. 6 

1. 8 

0. 1 

0. 2 

0. 3 

0. 4 

0. 5 

0. 6 

0. 7 

0. 8 

0. 9 

1 

2 

3 

4 

5 

6 

7 

A 

C 

B 

D 

Appendix 4. Model run for a Normal April. A, Map of significant wave height (Hsig), in m. B, Map of peak wave-induced near-bed 

orbital wave velocity (Uorb), in m/s. C, Map of peak wave-induced near-bed shear stress (τpeak), in N/m2

. D, Map displaying which 

regions of the study area are mobilized (red) and which are stable (blue) for the modeled conditions. See table 2 for information 

on model run boundary conditions.
40 Wave-Driven Spatial and Temporal Variability in Sea-floor Sediment Mobility

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

τpeak [N/m Blue = Stable, Red = Mobilized 2]

Hsig [m] Uorb [m/s] 

0. 2 

0. 4 

0. 6 

0. 8 

1.0 

1. 2 

1. 4 

1. 6 

1. 8 

0. 1 

0. 2 

0. 3 

0. 4 

0. 5 

0. 6 

0. 7 

0. 8 

0. 9 

1 

2 

3 

4 

5 

6 

7 

A 

C 

B 

D 

Appendix 5. Model run for a Normal May. A, Map of significant wave height (Hsig), in m. B, Map of peak wave-induced near-bed 

orbital wave velocity (Uorb), in m/s. C, Map of peak wave-induced near-bed shear stress (τpeak), in N/m2

. D, Map displaying which 

regions of the study area are mobilized (red) and which are stable (blue) for the modeled conditions. See table 2 for information 

on model run boundary conditions.
Appendixes 41

Appendix 6. Model run for a Normal June. A, Map of significant wave height (Hsig), in m. B, Map of peak wave-induced near-bed 

orbital wave velocity (Uorb), in m/s. C, Map of peak wave-induced near-bed shear stress (τpeak), in N/m2

. D, Map displaying which 

regions of the study area are mobilized (red) and which are stable (blue) for the modeled conditions. See table 2 for information 

on model run boundary conditions.

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

τpeak [N/m Blue = Stable, Red = Mobilized 2]

Hsig [m] Uorb [m/s] 

0. 2 

0. 4 

0. 6 

0. 8 

1.0 

1. 2 

1. 4 

1. 6 

1. 8 

0. 1 

0. 2 

0. 3 

0. 4 

0. 5 

0. 6 

0. 7 

0. 8 

0. 9 

1 

2 

3 

4 

5 

6 

7 

A 

C 

B 

D 
42 Wave-Driven Spatial and Temporal Variability in Sea-floor Sediment Mobility

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

τpeak [N/m Blue = Stable, Red = Mobilized 2]

Hsig [m] Uorb [m/s] 

0. 2 

0. 4 

0. 6 

0. 8 

1.0 

1. 2 

1. 4 

1. 6 

1. 8 

0. 1 

0. 2 

0. 3 

0. 4 

0. 5 

0. 6 

0. 7 

0. 8 

0. 9 

1 

2 

3 

4 

5 

6 

7 

A 

C 

B 

D 

Appendix 7. Model run for a Normal July. A, Map of significant wave height (Hsig), in m. B, Map of peak wave-induced near-bed 

orbital wave velocity (Uorb), in m/s. C, Map of peak wave-induced near-bed shear stress (τpeak), in N/m2

. D, Map displaying which 

regions of the study area are mobilized (red) and which are stable (blue) for the modeled conditions. See table 2 for information 

on model run boundary conditions.
Appendixes 43

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

τpeak [N/m Blue = Stable, Red = Mobilized 2]

Hsig [m] Uorb [m/s] 

0. 2 

0. 4 

0. 6 

0. 8 

1.0 

1. 2 

1. 4 

1. 6 

1. 8 

0. 1 

0. 2 

0. 3 

0. 4 

0. 5 

0. 6 

0. 7 

0. 8 

0. 9 

1 

2 

3 

4 

5 

6 

7 

A 

C 

B 

D 

Appendix 8. Model run for a Normal August. A, Map of significant wave height (Hsig), in m. B, Map of peak wave-induced nearbed orbital wave velocity (Uorb), in m/s. C, Map of peak wave-induced near-bed shear stress (τpeak), in N/m2

. D, Map displaying 

which regions of the study area are mobilized (red) and which are stable (blue) for the modeled conditions. See table 2 for information on model run boundary conditions.
44 Wave-Driven Spatial and Temporal Variability in Sea-floor Sediment Mobility

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

τpeak [N/m Blue = Stable, Red = Mobilized 2]

Hsig [m] Uorb [m/s] 

0. 2 

0. 4 

0. 6 

0. 8 

1.0 

1. 2 

1. 4 

1. 6 

1. 8 

0. 1 

0. 2 

0. 3 

0. 4 

0. 5 

0. 6 

0. 7 

0. 8 

0. 9 

1 

2 

3 

4 

5 

6 

7 

A 

C 

B 

D 

Appendix 9. Model run for a Normal September. A, Map of significant wave height (Hsig), in m. B, Map of peak wave-induced 

near-bed orbital wave velocity (Uorb), in m/s. C, Map of peak wave-induced near-bed shear stress (τpeak), in N/m2

. D, Map displaying which regions of the study area are mobilized (red) and which are stable (blue) for the modeled conditions. See table 2 for 

information on model run boundary conditions.
Appendixes 45

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

τpeak [N/m Blue = Stable, Red = Mobilized 2]

Hsig [m] Uorb [m/s] 

0. 2 

0. 4 

0. 6 

0. 8 

1.0 

1. 2 

1. 4 

1. 6 

1. 8 

0. 1 

0. 2 

0. 3 

0. 4 

0. 5 

0. 6 

0. 7 

0. 8 

0. 9 

1 

2 

3 

4 

5 

6 

7 

A 

C 

B 

D 

Appendix 10. Model run for a Normal October. A, Map of significant wave height (Hsig), in m. B, Map of peak wave-induced 

near-bed orbital wave velocity (Uorb), in m/s. C, Map of peak wave-induced near-bed shear stress (τpeak), in N/m2

. D, Map displaying which regions of the study area are mobilized (red) and which are stable (blue) for the modeled conditions. See table 2 for 

information on model run boundary conditions.
46 Wave-Driven Spatial and Temporal Variability in Sea-floor Sediment Mobility

Appendix 11. Model run for a Normal November. A, Map of significant wave height (Hsig), in m. B, Map of peak wave-induced 

near-bed orbital wave velocity (Uorb), in m/s. C, Map of peak wave-induced near-bed shear stress (τpeak), in N/m2

. D, Ma p displaying which regions of the study area are mobilized (red) and which are stable (blue) for the modeled conditions. See table 2 

for information on model run boundary conditions.

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

τpeak [N/m Blue = Stable, Red = Mobilized 2]

Hsig [m] Uorb [m/s] 

0. 2 

0. 4 

0. 6 

0. 8 

1.0 

1. 2 

1. 4 

1. 6 

1. 8 

0. 1 

0. 2 

0. 3 

0. 4 

0. 5 

0. 6 

0. 7 

0. 8 

0. 9 

1 

2 

3 

4 

5 

6 

7 

A 

C 

B 

D 
Appendixes 47

Appendix 12. Model run for a Normal December. A, Map of significant wave height (Hsig), in m. B, Map of peak wave-induced 

near-bed orbital wave velocity (Uorb), in m/s. C, Map of peak wave-induced near-bed shear stress (τpeak), in N/m2

. D, Map displaying which regions of the study area are mobilized (red) and which are stable (blue) for the modeled conditions. See table 2 for 

information on model run boundary conditions.

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o

36.60o

37.05o

37.50o

37.95o

38.40o

HALF MOON BAY

ANO NUEVO

SANTA CRUZ

SAN FRANCISCO

POINT REYES

BODEGA

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o

36.60o

37.05o

37.50o

37.95o

38.40o

HALF MOON BAY

ANO NUEVO

SANTA CRUZ

SAN FRANCISCO

POINT REYES

BODEGA

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o

36.60o

37.05o

37.50o

37.95o

38.40o

HALF MOON BAY

ANO NUEVO

SANTA CRUZ

SAN FRANCISCO

POINT REYES

BODEGA

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o

36.60o

37.05o

37.50o

37.95o

38.40o

HALF MOON BAY

ANO NUEVO

SANTA CRUZ

SAN FRANCISCO

POINT REYES

BODEGA

τpeak [N/m Blue = Stable, Red = Mobilized 2]

Hsig [m] Uorb [m/s]

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

2

3

4

5

6

7

A

C

B

D
48 Wave-Driven Spatial and Temporal Variability in Sea-floor Sediment Mobility

Appendix 13. Model run for an El Niño January. A, Map of significant wave height (Hsig), in m. B, Map of peak wave-induced 

near-bed orbital wave velocity (Uorb), in m/s. C, Map of peak wave-induced near-bed shear stress (τpeak), in N/m2

. D, Map displaying which regions of the study area are mobilized (red) and which are stable (blue) for the modeled conditions. See table 2 for 

information on model run boundary conditions.

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

τpeak [N/m Blue = Stable, Red = Mobilized 2]

Hsig [m] Uorb [m/s] 

0. 2 

0. 4 

0. 6 

0. 8 

1.0 

1. 2 

1. 4 

1. 6 

1. 8 

0. 1 

0. 2 

0. 3 

0. 4 

0. 5 

0. 6 

0. 7 

0. 8 

0. 9 

1 

2 

3 

4 

5 

6 

7 

A 

C 

B 

D 
Appendixes 49

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

τpeak [N/m Blue = Stable, Red = Mobilized 2]

Hsig [m] Uorb [m/s] 

0. 2 

0. 4 

0. 6 

0. 8 

1.0 

1. 2 

1. 4 

1. 6 

1. 8 

0. 1 

0. 2 

0. 3 

0. 4 

0. 5 

0. 6 

0. 7 

0. 8 

0. 9 

1 

2 

3 

4 

5 

6 

7 

A 

C 

B 

D 

Appendix 14. Model run for an El Niño February. A, Map of significant wave height (Hsig), in m. B, Map of peak wave-induced 

near-bed orbital wave velocity (Uorb), in m/s. C, Map of peak wave-induced near-bed shear stress (τpeak), in N/m2

. D, Map displaying which regions of the study area are mobilized (red) and which are stable (blue) for the modeled conditions. See table 2 for 

information on model run boundary conditions.
50 Wave-Driven Spatial and Temporal Variability in Sea-floor Sediment Mobility

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

τpeak [N/m Blue = Stable, Red = Mobilized 2]

Hsig [m] Uorb [m/s] 

0. 2 

0. 4 

0. 6 

0. 8 

1.0 

1. 2 

1. 4 

1. 6 

1. 8 

0. 1 

0. 2 

0. 3 

0. 4 

0. 5 

0. 6 

0. 7 

0. 8 

0. 9 

1 

2 

3 

4 

5 

6 

7 

A 

C 

B 

D 

Appendix 15. Model run for an El Niño March. A, Map of significant wave height (Hsig), in m. B, Map of peak wave-induced 

near-bed orbital wave velocity (Uorb), in m/s. C, Map of peak wave-induced near-bed shear stress (τpeak), in N/m2

. D, Map displaying which regions of the study area are mobilized (red) and which are stable (blue) for the modeled conditions. See table 2 for 

information on model run boundary conditions.
Appendixes 51

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

τpeak [N/m Blue = Stable, Red = Mobilized 2]

Hsig [m] Uorb [m/s] 

0. 2 

0. 4 

0. 6 

0. 8 

1.0 

1. 2 

1. 4 

1. 6 

1. 8 

0. 1 

0. 2 

0. 3 

0. 4 

0. 5 

0. 6 

0. 7 

0. 8 

0. 9 

1 

2 

3 

4 

5 

6 

7 

A 

C 

B 

D 

Appendix 16. Model run for an El Niño April. A, Map of significant wave height (Hsig), in m. B, Map of peak wave-induced nearbed orbital wave velocity (Uorb), in m/s. C, Map of peak wave-induced near-bed shear stress (τpeak), in N/m2

. D, Map displaying 

which regions of the study area are mobilized (red) and which are stable (blue) for the modeled conditions. See table 2 for 

information on model run boundary conditions.
52 Wave-Driven Spatial and Temporal Variability in Sea-floor Sediment Mobility

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

τpeak [N/m Blue = Stable, Red = Mobilized 2]

Hsig [m] Uorb [m/s] 

0. 2 

0. 4 

0. 6 

0. 8 

1.0 

1. 2 

1. 4 

1. 6 

1. 8 

0. 1 

0. 2 

0. 3 

0. 4 

0. 5 

0. 6 

0. 7 

0. 8 

0. 9 

1 

2 

3 

4 

5 

6 

7 

A 

C 

B 

D 

Appendix 17. Model run for an El Niño May. A, Map of significant wave height (Hsig), in m. B, Map of peak wave-induced 

near-bed orbital wave velocity (Uorb), in m/s. C, Map of peak wave-induced near-bed shear stress (τpeak), in N/m2

. D, Map displaying which regions of the study area are mobilized (red) and which are stable (blue) for the modeled conditions. See table 

2 for information on model run boundary conditions.
Appendixes 53

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

τpeak [N/m Blue = Stable, Red = Mobilized 2]

Hsig [m] Uorb [m/s] 

0. 2 

0. 4 

0. 6 

0. 8 

1.0 

1. 2 

1. 4 

1. 6 

1. 8 

0. 1 

0. 2 

0. 3 

0. 4 

0. 5 

0. 6 

0. 7 

0. 8 

0. 9 

1 

2 

3 

4 

5 

6 

7 

A 

C 

B 

D 

Appendix 18. Model run for an El Niño June. A, Map of significant wave height (Hsig), in m. B, Map of peak wave-induced nearbed orbital wave velocity (Uorb), in m/s. C, Map of peak wave-induced near-bed shear stress (τpeak), in N/m2

. D, Map displaying 

which regions of the study area are mobilized (red) and which are stable (blue) for the modeled conditions. See table 2 for 

information on model run boundary conditions.
54 Wave-Driven Spatial and Temporal Variability in Sea-floor Sediment Mobility

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

τpeak [N/m Blue = Stable, Red = Mobilized 2]

Hsig [m] Uorb [m/s] 

0. 2 

0. 4 

0. 6 

0. 8 

1.0 

1. 2 

1. 4 

1. 6 

1. 8 

0. 1 

0. 2 

0. 3 

0. 4 

0. 5 

0. 6 

0. 7 

0. 8 

0. 9 

1 

2 

3 

4 

5 

6 

7 

A 

C 

B 

D 

Appendix 19. Model run for an El Niño July. A, Map of significant wave height (Hsig), in m. B, Map of peak wave-induced nearbed orbital wave velocity (Uorb), in m/s. C, Map of peak wave-induced near-bed shear stress (τpeak), in N/m2

. D, Map displaying 

which regions of the study area are mobilized (red) and which are stable (blue) for the modeled conditions. See table 2 for 

information on model run boundary conditions.
Appendixes 55

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

τpeak [N/m Blue = Stable, Red = Mobilized 2]

Hsig [m] Uorb [m/s] 

0. 2 

0. 4 

0. 6 

0. 8 

1.0 

1. 2 

1. 4 

1. 6 

1. 8 

0. 1 

0. 2 

0. 3 

0. 4 

0. 5 

0. 6 

0. 7 

0. 8 

0. 9 

1 

2 

3 

4 

5 

6 

7 

A 

C 

B 

D 

Appendix 20. Model run for an El Niño August. A, Map of significant wave height (Hsig), in m. B, Map of peak wave-induced 

near-bed orbital wave velocity (Uorb), in m/s. C, Map of peak wave-induced near-bed shear stress (τpeak), in N/m2

. D, Map displaying which regions of the study area are mobilized (red) and which are stable (blue) for the modeled conditions. See table 2 for 

information on model run boundary conditions.
56 Wave-Driven Spatial and Temporal Variability in Sea-floor Sediment Mobility

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

τpeak [N/m Blue = Stable, Red = Mobilized 2]

Hsig [m] Uorb [m/s] 

0. 2 

0. 4 

0. 6 

0. 8 

1.0 

1. 2 

1. 4 

1. 6 

1. 8 

0. 1 

0. 2 

0. 3 

0. 4 

0. 5 

0. 6 

0. 7 

0. 8 

0. 9 

1 

2 

3 

4 

5 

6 

7 

A 

C 

B 

D 

Appendix 21. Model run for an El Niño September. A, Map of significant wave height (Hsig), in m. B, Map of peak wave-induced 

near-bed orbital wave velocity (Uorb), in m/s. C, Map of peak wave-induced near-bed shear stress (τpeak), in N/m2

. D, Map displaying which regions of the study area are mobilized (red) and which are stable (blue) for the modeled conditions. See table 2 for 

information on model run boundary conditions.
Appendixes 57

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

τpeak [N/m Blue = Stable, Red = Mobilized 2]

Hsig [m] Uorb [m/s] 

0. 2 

0. 4 

0. 6 

0. 8 

1.0 

1. 2 

1. 4 

1. 6 

1. 8 

0. 1 

0. 2 

0. 3 

0. 4 

0. 5 

0. 6 

0. 7 

0. 8 

0. 9 

1 

2 

3 

4 

5 

6 

7 

A 

C 

B 

D 

Appendix 22. Model run for an El Niño October. A, Map of significant wave height (Hsig), in m. B, Map of peak wave-induced 

near-bed orbital wave velocity (Uorb), in m/s. C, Map of peak wave-induced near-bed shear stress (τpeak), in N/m2

. D, Map displaying which regions of the study area are mobilized (red) and which are stable (blue) for the modeled conditions. See table 2 for 

information on model run boundary conditions.
58 Wave-Driven Spatial and Temporal Variability in Sea-floor Sediment Mobility

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

τpeak [N/m Blue = Stable, Red = Mobilized 2]

Hsig [m] Uorb [m/s] 

0. 2 

0. 4 

0. 6 

0. 8 

1.0 

1. 2 

1. 4 

1. 6 

1. 8 

0. 1 

0. 2 

0. 3 

0. 4 

0. 5 

0. 6 

0. 7 

0. 8 

0. 9 

1 

2 

3 

4 

5 

6 

7 

A 

C 

B 

D 

Appendix 23. Model run for an El Niño November. A, Map of significant wave height (Hsig), in m. B, Map of peak wave-induced 

near-bed orbital wave velocity (Uorb), in m/s. C, Map of peak wave-induced near-bed shear stress (τpeak), in N/m2

. D, Map displaying which regions of the study area are mobilized (red) and which are stable (blue) for the modeled conditions. See table 2 for 

information on model run boundary conditions.
Appendixes 59

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

τpeak [N/m Blue = Stable, Red = Mobilized 2]

Hsig [m] Uorb [m/s] 

0. 2 

0. 4 

0. 6 

0. 8 

1.0 

1. 2 

1. 4 

1. 6 

1. 8 

0. 1 

0. 2 

0. 3 

0. 4 

0. 5 

0. 6 

0. 7 

0. 8 

0. 9 

1 

2 

3 

4 

5 

6 

7 

A 

C 

B 

D 

Appendix 24. Model run for an El Niño December. A, Map of significant wave height (Hsig), in m. B, Map of peak wave-induced 

near-bed orbital wave velocity (Uorb), in m/s. C, Map of peak wave-induced near-bed shear stress (τpeak), in N/m2

. D, Map displaying which regions of the study area are mobilized (red) and which are stable (blue) for the modeled conditions. See table 2 for 

information on model run boundary conditions.
60 Wave-Driven Spatial and Temporal Variability in Sea-floor Sediment Mobility

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

τpeak [N/m Blue = Stable, Red = Mobilized 2]

Hsig [m] Uorb [m/s] 

0. 2 

0. 4 

0. 6 

0. 8 

1.0 

1. 2 

1. 4 

1. 6 

1. 8 

0. 1 

0. 2 

0. 3 

0. 4 

0. 5 

0. 6 

0. 7 

0. 8 

0. 9 

1 

2 

3 

4 

5 

6 

7 

A 

C 

B 

D 

Appendix 25. Model run for a La Niña January. A, Map of significant wave height (Hsig), in m. B, Map of peak wave-induced 

near-bed orbital wave velocity (Uorb), in m/s. C, Map of peak wave-induced near-bed shear stress (τpeak), in N/m2

. D, Map displaying which regions of the study area are mobilized (red) and which are stable (blue) for the modeled conditions. See table 2 for 

information on model run boundary conditions.
Appendixes 61

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

τpeak [N/m Blue = Stable, Red = Mobilized 2]

Hsig [m] Uorb [m/s] 

0. 2 

0. 4 

0. 6 

0. 8 

1.0 

1. 2 

1. 4 

1. 6 

1. 8 

0. 1 

0. 2 

0. 3 

0. 4 

0. 5 

0. 6 

0. 7 

0. 8 

0. 9 

1 

2 

3 

4 

5 

6 

7 

A 

C 

B 

D 

Appendix 26. Model run for a La Niña February. A, Map of significant wave height (Hsig), in m. B, Map of peak wave-induced 

near-bed orbital wave velocity (Uorb), in m/s. C, Map of peak wave-induced near-bed shear stress (τpeak), in N/m2

. D, Map displaying which regions of the study area are mobilized (red) and which are stable (blue) for the modeled conditions. See table 2 for 

information on model run boundary conditions.
62 Wave-Driven Spatial and Temporal Variability in Sea-floor Sediment Mobility

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

τpeak [N/m Blue = Stable, Red = Mobilized 2]

Hsig [m] Uorb [m/s] 

0. 2 

0. 4 

0. 6 

0. 8 

1.0 

1. 2 

1. 4 

1. 6 

1. 8 

0. 1 

0. 2 

0. 3 

0. 4 

0. 5 

0. 6 

0. 7 

0. 8 

0. 9 

1 

2 

3 

4 

5 

6 

7 

A 

C 

B 

D 

Appendix 27. Model run for a La Niña March. A, Map of significant wave height (Hsig), in m. B, Map of peak wave-induced 

near-bed orbital wave velocity (Uorb), in m/s. C, Map of peak wave-induced near-bed shear stress (τpeak), in N/m2

. D, Map displaying which regions of the study area are mobilized (red) and which are stable (blue) for the modeled conditions. See table 2 for 

information on model run boundary conditions.
Appendixes 63

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

τpeak [N/m Blue = Stable, Red = Mobilized 2]

Hsig [m] Uorb [m/s] 

0. 2 

0. 4 

0. 6 

0. 8 

1.0 

1. 2 

1. 4 

1. 6 

1. 8 

0. 1 

0. 2 

0. 3 

0. 4 

0. 5 

0. 6 

0. 7 

0. 8 

0. 9 

1 

2 

3 

4 

5 

6 

7 

A 

C 

B 

D 

Appendix 28. Model run for a La Niña April. A, Map of significant wave height (Hsig), in m. B, Map of peak wave-induced nearbed orbital wave velocity (Uorb), in m/s. C, Map of peak wave-induced near-bed shear stress (τpeak), in N/m2

. D, Map displaying 

which regions of the study area are mobilized (red) and which are stable (blue) for the modeled conditions. See table 2 for 

information on model run boundary conditions.
64 Wave-Driven Spatial and Temporal Variability in Sea-floor Sediment Mobility

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

τpeak [N/m Blue = Stable, Red = Mobilized 2]

Hsig [m] Uorb [m/s] 

0. 2 

0. 4 

0. 6 

0. 8 

1.0 

1. 2 

1. 4 

1. 6 

1. 8 

0. 1 

0. 2 

0. 3 

0. 4 

0. 5 

0. 6 

0. 7 

0. 8 

0. 9 

1 

2 

3 

4 

5 

6 

7 

A 

C 

B 

D 

Appendix 29. Model run for a La Niña May. A, Map of significant wave height (Hsig), in m. B, Map of peak wave-induced nearbed orbital wave velocity (Uorb), in m/s. C, Map of peak wave-induced near-bed shear stress (τpeak), in N/m2

. D, Map displaying 

which regions of the study area are mobilized (red) and which are stable (blue) for the modeled conditions. See table 2 for 

information on model run boundary conditions.
Appendixes 65

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

τpeak [N/m Blue = Stable, Red = Mobilized 2]

Hsig [m] Uorb [m/s] 

0. 2 

0. 4 

0. 6 

0. 8 

1.0 

1. 2 

1. 4 

1. 6 

1. 8 

0. 1 

0. 2 

0. 3 

0. 4 

0. 5 

0. 6 

0. 7 

0. 8 

0. 9 

1 

2 

3 

4 

5 

6 

7 

A 

C 

B 

D 

Appendix 30. Model run for a La Niña June. A, Map of significant wave height (Hsig), in m. B, Map of peak wave-induced nearbed orbital wave velocity (Uorb), in m/s. C, Map of peak wave-induced near-bed shear stress (τpeak), in N/m2

. D, Map displaying 

which regions of the study area are mobilized (red) and which are stable (blue) for the modeled conditions. See table 2 for 

information on model run boundary conditions
66 Wave-Driven Spatial and Temporal Variability in Sea-floor Sediment Mobility

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

τpeak [N/m Blue = Stable, Red = Mobilized 2]

Hsig [m] Uorb [m/s] 

0. 2 

0. 4 

0. 6 

0. 8 

1.0 

1. 2 

1. 4 

1. 6 

1. 8 

0. 1 

0. 2 

0. 3 

0. 4 

0. 5 

0. 6 

0. 7 

0. 8 

0. 9 

1 

2 

3 

4 

5 

6 

7 

A 

C 

B 

D 

Appendix 31. Model run for a La Niña July. A, Map of significant wave height (Hsig), in m. B, Map of peak wave-induced nearbed orbital wave velocity (Uorb), in m/s. C, Map of peak wave-induced near-bed shear stress (τpeak), in N/m2

. D, Map displaying 

which regions of the study area are mobilized (red) and which are stable (blue) for the modeled conditions. See table 2 for 

information on model run boundary conditions.
Appendixes 67

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

τpeak [N/m Blue = Stable, Red = Mobilized 2]

Hsig [m] Uorb [m/s] 

0. 2 

0. 4 

0. 6 

0. 8 

1.0 

1. 2 

1. 4 

1. 6 

1. 8 

0. 1 

0. 2 

0. 3 

0. 4 

0. 5 

0. 6 

0. 7 

0. 8 

0. 9 

1 

2 

3 

4 

5 

6 

7 

A 

C 

B 

D 

Appendix 32. Model run for a La Niña August. A, Map of significant wave height (Hsig), in m. B, Map of peak wave-induced 

near-bed orbital wave velocity (Uorb), in m/s. C, Map of peak wave-induced near-bed shear stress (τpeak), in N/m2

. D, Map displaying which regions of the study area are mobilized (red) and which are stable (blue) for the modeled conditions. See table 2 for 

information on model run boundary conditions.
68 Wave-Driven Spatial and Temporal Variability in Sea-floor Sediment Mobility

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

τpeak [N/m Blue = Stable, Red = Mobilized 2]

Hsig [m] Uorb [m/s] 

0. 2 

0. 4 

0. 6 

0. 8 

1.0 

1. 2 

1. 4 

1. 6 

1. 8 

0. 1 

0. 2 

0. 3 

0. 4 

0. 5 

0. 6 

0. 7 

0. 8 

0. 9 

1 

2 

3 

4 

5 

6 

7 

A 

C 

B 

D 

Appendix 33. Model run for a La Niña September. A, Map of significant wave height (Hsig), in m. B, Map of peak wave-induced 

near-bed orbital wave velocity (Uorb), in m/s. C, Map of peak wave-induced near-bed shear stress (τpeak), in N/m2

. D, Map displaying which regions of the study area are mobilized (red) and which are stable (blue) for the modeled conditions. See table 2 for 

information on model run boundary conditions.
Appendixes 69

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

τpeak [N/m Blue = Stable, Red = Mobilized 2]

Hsig [m] Uorb [m/s] 

0. 2 

0. 4 

0. 6 

0. 8 

1.0 

1. 2 

1. 4 

1. 6 

1. 8 

0. 1 

0. 2 

0. 3 

0. 4 

0. 5 

0. 6 

0. 7 

0. 8 

0. 9 

1 

2 

3 

4 

5 

6 

7 

A 

C 

B 

D 

Appendix 34. Model run for a La Niña October. A, Map of significant wave height (Hsig), in m. B, Map of peak wave-induced 

near-bed orbital wave velocity (Uorb), in m/s. C, Map of peak wave-induced near-bed shear stress (τpeak), in N/m2

. D, Map displaying which regions of the study area are mobilized (red) and which are stable (blue) for the modeled conditions. See table 2 for 

information on model run boundary conditions.
70 Wave-Driven Spatial and Temporal Variability in Sea-floor Sediment Mobility

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

τpeak [N/m Blue = Stable, Red = Mobilized 2]

Hsig [m] Uorb [m/s] 

0. 2 

0. 4 

0. 6 

0. 8 

1.0 

1. 2 

1. 4 

1. 6 

1. 8 

0. 1 

0. 2 

0. 3 

0. 4 

0. 5 

0. 6 

0. 7 

0. 8 

0. 9 

1 

2 

3 

4 

5 

6 

7 

A 

C 

B 

D 

Appendix 35. Model run for a La Niña November. A, Map of significant wave height (Hsig), in m. B, Map of peak wave-induced 

near-bed orbital wave velocity (Uorb), in m/s. C, Map of peak wave-induced near-bed shear stress (τpeak), in N/m2

. D, Map displaying which regions of the study area are mobilized (red) and which are stable (blue) for the modeled conditions. See table 2 for 

information on model run boundary conditions.
Appendixes 71

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

τpeak [N/m Blue = Stable, Red = Mobilized 2]

Hsig [m] Uorb [m/s] 

0. 2 

0. 4 

0. 6 

0. 8 

1.0 

1. 2 

1. 4 

1. 6 

1. 8 

0. 1 

0. 2 

0. 3 

0. 4 

0. 5 

0. 6 

0. 7 

0. 8 

0. 9 

1 

2 

3 

4 

5 

6 

7 

A 

C 

B 

D 

Appendix 36. Model run for a La Niña December. A, Map of significant wave height (Hsig), in m. B, Map of peak wave-induced 

near-bed orbital wave velocity (Uorb), in m/s. C, Map of peak wave-induced near-bed shear stress (τpeak), in N/m2

. D, Map displaying which regions of the study area are mobilized (red) and which are stable (blue) for the modeled conditions. See table 2 for 

information on model run boundary conditions.
72 Wave-Driven Spatial and Temporal Variability in Sea-floor Sediment Mobility

4

4

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

τpeak [N/m Blue = Stable, Red = Mobilized 2]

Hsig [m] Uorb [m/s] 

0. 2 

0. 4 

0. 6 

0. 8 

1.0 

1. 2 

1. 4 

1. 6 

1. 8 

0. 1 

0. 2 

0. 3 

0. 4 

0. 5 

0. 6 

0. 7 

0. 8 

0. 9 

1 

2 

3 

4 

5 

6 

7 

A 

C 

B 

D 

Appendix 37. Model run for a 2-year storm. A, Map of significant wave height (Hsig), in m. B, Map of peak wave-induced nearbed orbital wave velocity (Uorb), in m/s. C, Map of peak wave-induced near-bed shear stress (τpeak), in N/m2

. D, Map displaying 

which regions of the study area are mobilized (red) and which are stable (blue) for the modeled conditions. See table 1 for 

information on model run boundary conditions.
Appendixes 73

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

τpeak [N/m Blue = Stable, Red = Mobilized 2]

Hsig [m] Uorb [m/s] 

0. 2 

0. 4 

0. 6 

0. 8 

1.0 

1. 2 

1. 4 

1. 6 

1. 8 

0. 1 

0. 2 

0. 3 

0. 4 

0. 5 

0. 6 

0. 7 

0. 8 

0. 9 

1 

2 

3 

4 

5 

6 

7 

A 

C 

B 

D 

Appendix 38. Model run for a 10-year storm. A, Map of significant wave height (Hsig), in m. B, Map of peak wave-induced nearbed orbital wave velocity (Uorb), in m/s. C, Map of peak wave-induced near-bed shear stress (τpeak), in N/m2

. D, Map displaying 

which regions of the study area are mobilized (red) and which are stable (blue) for the modeled conditions. See table 1 for 

information on model run boundary conditions.
74 Wave-Driven Spatial and Temporal Variability in Sea-floor Sediment Mobility

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

τpeak [N/m Blue = Stable, Red = Mobilized 2]

Hsig [m] Uorb [m/s] 

0. 2 

0. 4 

0. 6 

0. 8 

1.0 

1. 2 

1. 4 

1. 6 

1. 8 

0. 1 

0. 2 

0. 3 

0. 4 

0. 5 

0. 6 

0. 7 

0. 8 

0. 9 

1 

2 

3 

4 

5 

6 

7 

A 

C 

B 

D 

Appendix 39. Model run for a 25-year storm. A, Map of significant wave height (Hsig), in m. B, Map of peak wave-induced nearbed orbital wave velocity (Uorb), in m/s. C, Map of peak wave-induced near-bed shear stress (τpeak), in N/m2

. D, Map displaying 

which regions of the study area are mobilized (red) and which are stable (blue) for the modeled conditions. See table 1 for 

information on model run boundary conditions.
Appendixes 75

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

τpeak [N/m Blue = Stable, Red = Mobilized 2]

Hsig [m] Uorb [m/s] 

0. 2 

0. 4 

0. 6 

0. 8 

1.0 

1. 2 

1. 4 

1. 6 

1. 8 

0. 1 

0. 2 

0. 3 

0. 4 

0. 5 

0. 6 

0. 7 

0. 8 

0. 9 

1 

2 

3 

4 

5 

6 

7 

A 

C 

B 

D 

Appendix 40. Model run for a 50-year storm. A, Map of significant wave height (Hsig), in m. B, Map of peak wave-induced nearbed orbital wave velocity (Uorb), in m/s. C, Map of peak wave-induced near-bed shear stress (τpeak), in N/m2

. D, Map displaying 

which regions of the study area are mobilized (red) and which are stable (blue) for the modeled conditions. See table 1 for 

information on model run boundary conditions.
76 Wave-Driven Spatial and Temporal Variability in Sea-floor Sediment Mobility

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

123.68o 123.22o 122.78o 122.32o 121.86o 36.15o 

36.60o 

37.05o 

37.50o 

37.95o 

38.40o 

HALF MOON BAY 

ANO NUEVO 

SANTA CRUZ 

SAN FRANCISCO 

POINT REYES 

BODEGA 

τpeak [N/m Blue = Stable, Red = Mobilized 2]

Hsig [m] Uorb [m/s] 

0. 2 

0. 4 

0. 6 

0. 8 

1.0 

1. 2 

1. 4 

1. 6 

1. 8 

0. 1 

0. 2 

0. 3 

0. 4 

0. 5 

0. 6 

0. 7 

0. 8 

0. 9 

1 

2 

3 

4 

5 

6 

7 

A 

C 

B 

D 

Appendix 41. Model run for a 100-year storm. A, Map of significant wave height (Hsig), in m. B, Map of peak wave-induced 

near-bed orbital wave velocity (Uorb), in m/s. C, Map of peak wave-induced near-bed shear stress (τpeak), in N/m2

. D, Map displaying which regions of the study area are mobilized (red) and which are stable (blue) for the modeled conditions. See table 1 for 

information on model run boundary conditions.
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Storlazzi, Reid, and Golden—Wave-Driven Spatial and Temporal Variability in Sea-floor Sediment Mobility—U.S. Geological Survey Scientific Investigations Report 2007–5233

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