SANTA CLARA RIVER PARKWAY FLOODPLAIN RESTORATION FEASIBILITY STUDY

Integrating invasive species management with riparian-floodplain restoration in the lower Santa Clara River

Zooey Diggory, Bruce Orr, Amy MerrillS T I L L W A T E R S C I E N C E S

Gretchen Coffman, and Tom DudleyU C S A N T A B A R B A R A

S A N T A C L A R A R I V E R W A T E R S H E D & A N A L Y S I S A R E A

P R E S E N T A T I O N OV E R V I E W

1. Historical Changes in Riparian Vegetation Extent

2. Influences on Riparian Vegetation Distribution & Composition

3. Vegetation-Process Linkages

4. Restoration & Invasive Species Removal Strategies

H I S T O R I C A L C H A N G E S I N R I P A R I A N V E G E T A T I O N E X T E N T

1. Literature Review

2. Flood Mapping

LITERATURE REVIEW

>floodplain was as much as two miles wide in lowermost reaches (Simons, Li & Associates 1983)

>dense, multi-stored stands of broadleaf trees that extended from a few to several miles wide (Roberts et al. 1980, Holland and Keil 1995, Boughton et al. 2006)

FLOOD MAPPING

>Bare, partially- and highly-vegetated areas mapped after 6 major floods

Year Flow (cfs)Flood

Recurrence Interval

1938 120,000 14 year

1969 165,000 24 year

1978 102,200 11 year

1992 104,000 12 year

1995 110,000 13 year

2005 136,000 16 year

I N F L U E N C E S O N R I P A R I A N V E G E T A T I O N D I S T R I B U T I O N & C O M P O S I T I O N

1. Riparian Vegetation Mapping

2. Vegetation Dynamics Analyses

RIPARIAN VEGETATION MAPPING

>Accurate and current map of riparian vegetation (post-2005 flood)

VEGETATION DYNAMICS ANALYSIS

>Canonical Correspondence Analysis (CCA)

V E G E T A T I O N – P R O C E S S L I N K A G E S

Change background photo?

1. Climate

2. Flood Dynamics

3. Groundwater Availability

4. Floodplain Development

5. Invasion by Arundo

CLIMATE

>Semi-arid, Mediterranean climate>Arid inland and moister, cooler coast

0

10

20

30

40

50

1820 1830 1840 1850 1860 1870 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000

Water Year

Pre

cip

itation (in

ches)

Dry Years

Wet Years

a)

b)

0

10

20

30

40

50

1820 1830 1840 1850 1860 1870 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000

Water Year

Pre

cip

itation (in

ches)

Dry Years

Wet Years

0

10

20

30

40

50

1820 1830 1840 1850 1860 1870 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000

Water Year

Pre

cip

itation (in

ches)

Dry Years

Wet Years

a)

b)

CLIMATE

0

25,000

50,000

75,000

100,000

125,000

150,000

175,000

200,000

Dist

ance

from

rive

r mou

th (f

eet)

>Correlation between distance from river mouth and species distributions

FLOOD DYNAMICS

FLOW

JUNE 2002

pre

-hig

h fl

ow

>Vegetation reset after large floods, particularly in El Niño years

FEB 2005

hig

h fl

ow

FLOOD DYNAMICS

FLOW

>Vegetation reset after large floods, particularly in El Niño years

SEPT 2005

post

-hig

h fl

ow

FLOOD DYNAMICS

FLOW

>Vegetation reset after large floods, particularly in El Niño years

FLOOD DYNAMICS

>Relative elevation and vegetation alliance distribution

0

5

10

15

20

25

Rel

ativ

e el

evat

ion

(ft

)

GROUNDWATER AVAILABILITY

>Gaining vs. losing reaches

GROUNDWATER AVAILABILITY

>Vegetation alliances in gaining vs. losing groundwater reaches

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%%

of p

lots

withi

n ga

inin

g or

losi

ng re

ache

s % occurring in losing reaches

% occurring in gaining reaches

FLOODPLAIN DEVELOPMENT

>Agriculture>Levees and urban development

FLOODPLAIN DEVELOPMENT

>60 percent reduction in historical floodplain extent

INVASION BY ARUNDO

>Replaces native vegetation

>Alters ecosystem processes

RESTORATION & INVASIVE SPECIES REMOVAL STRATEGIES

1. Increase & Improve Floodplain Connectivity

2. Promote Revegetation via Natural Recruitment & Active Planting

3. Implement Strategic Actions to Control Arundo

INCREASE & IMPROVE FLOODPLAIN CONNECTIVITY

> Acquisition & levee setbacks

PASSIVE & ACTIVE REVEGETATION

> Allow natural recruitment in active floodplain> Focus active revegetation in areas not subject to frequent,

resetting floods> Match target restored plant community types with site physical

conditions

1969 flood extent

500-year floodplain

25-year floodplain(largest mapped flood on record)

PLANTING

(active)

NATURAL RECRUITM

ENT(passive)

STRATEGIC ACTIONS TO CONTROL ARUNDO

Remove arundo:>in an upstream to downstream direction>in fire-prone shrub lands>from watersheds and reaches with low

nutrient levels>In the summer following major floods

ACKNOWLEDGEMENTS

Bruce Orr, Amy Merrill, Gretchen Coffman, & Tom Dudley

Coastal Conservancy & Santa Clara River Trustee Council

Bill Sears, Sebastian Araya, & Tami Cosio