Suspended Sediments in South San Francisco Bay

By Anna Kunkel

Maidment-GIS

Objective

• To determine how different factors affect the levels of suspended sediments in the South San Francisco Bay.

• Factors examined– Location– Time of the Year– Precipitation

What are Suspended Sediments?

• Sediments--solid particles transported in fluid media or found in deposit after transportation by flowing water, wind, glacier and gravitational action.

• Suspension due to

River Turbidity Wind Waves

Why do we care?

• Transport adsorbed toxic substances

• Block light from reaching submerged vegetation

• Absorb heat from sunlight• Reduces the dissolved

oxygen level• Changes morphology of

an area through sedimentation

Mississippi River Sediment Plume

South San Francisco Bay

363534

3332

31

3030

29

28

27

26

25

24

23

22

21

USGS Testing Sites

• 36 testing sites in San Francisco Bay– Sites 21 through 36 in south– Located along central deep

channel

• Monitored monthly using submersible instrument package– Discrete measurement of

concentration– Optical backscatter sensor

Suspended Sediment Levels Throughout 2001

0

50

100

150

200

250

Testing Station

Su

spen

ded

Sed

imen

t C

on

cen

trat

ion

(m

g/L

)

Dec

Nov

Oct

Sep

July

June

May

April

Mar

Feb

Southern vs. Northern Testing Sites

30

29

28

27

26

25

24

23

22

21

36

35

34

33

32

31

30

Reasons for Difference in Suspended Sediment Levels Closer to Shoreline Farther From Shoreline

River Outlets No River OutletsShallower Testing Sites Deeper Testing Sites

Corte Madera Cr

Stevens Cr Coyote Cr

Suspended Sediment Change with Season

0

20

40

60

80

100

120

140

Testing Station

Su

spen

ded

Sed

imen

t C

on

cen

trat

ion

(m

g/L

)

SpringSummerFallW inter

PrecipitationANGWIN

FAIRF IEL D

ST .HEL ENA

AT LAS PEAK

OAK LAND SOU TH

J OHNSON RANCH

NAP A F IRE DEP T

LAGUNIT AS LAK E

MOUNT HAMIL TON

SAN FRANCISCO AP

ANGWIN P AC UNION

SFF

NSH

LGT

HML

FRF

APUSH4

OSO

JNR

ATL

SFF

NSH

LGT

HML

FRF

APUSH4

OSO

JNR

ATL

For February (Winter) For November (Fall)

Legend

<VALUE>

1.531869769 - 2.784353574

2.784353575 - 4.036837379

4.03683738 - 5.289321184

5.289321185 - 6.541804989

6.54180499 - 7.794288794

7.794288795 - 9.046772599

9.0467726 - 10.2992564

10.29925641 - 11.55174021

11.55174022 - 12.80422401

Precipitation Maps

ConclusionsThe concentration of

suspended sediments depends on – Location

• Sites closer to shore are affected by more river and wind effects

– Season• Higher levels occur during fall

and winter.

– Precipitation• Higher levels occur with more

precipitation.

The Yangtze River as it empties into the East China Sea