Final Branch Clubs & Delegates -24 Jan (Central Rift - North Rift)
Accumulated - University of California, Berkeleyepisodic.ced.berkeley.edu/Hecht_spottedOwl.pdf ·...
Transcript of Accumulated - University of California, Berkeleyepisodic.ced.berkeley.edu/Hecht_spottedOwl.pdf ·...
EpisodicRange
Time (decades)
SedimentAccumulatedon Bed
Degree of HabitatSedimentation(log scale)
orIndex of
Disruptionin
Corridor
CorridorChannel
ChronicRange
Figure 1. Schematic representation of episodic variations in bed sedimentation and/or disturbance in riparian alluvial-scrub corridors of centra or southernl California streams.
Lagunitas Creek
Corralitos Creek
Arroyo Seco, Carmel River,Salinas River
Sisquoc River
Ventura River
San Diego MSCP
San Lorenzo River
Figure 2. Locations of corridors discussed in text.
Ann
ual b
ed-lo
ad s
edim
ent
tran
spor
t (m
illio
n to
ns)
1930 1935 1940 1945 1950 1955 1960 1965 1970 1975 1980 1985 1990
5
4
3
2
1
0
12.6 million tons
5.6 million tons
Sisquoc River near SisquocDrainage Area = 281 sq. mi.
Figure 3. Simulated long-term record of bedload sediment transport in an unregulated episodic stream-- the Sisquoc River, near Santa Maria, California. More than half of the bedload (coarse) sediment transported by the river during the 60 years was probably associated with two events -- the Wellman fire (1966), which burned approximately 35 percent of the watershed, and high-recurrence storms of January and February 1969. Source: Knudsen et al. (1992).
Springs
Mouth orLagoon Ocean
Beach bar
* *
*
*
major tributary
Headwaters
? ?
Frequency of Significant Disturbance
*
= Confluence of*
Longitudinal Profile
Large Landslides
*
Bedrockgorge
Figure 4. Schematic longitudinal variability in the frequency of episodic disturbance in a represen-tative central California corridor. Reaches immediately downstream from channel confluences and other point sources of sediment are more susceptible to frequent disturbances; reaches with gorges or perennial springs tend to be more resilient to the same disturbances. Frequency diminishes from upstream to downstream, but relative severity or extent of disturbance does not.
0 200 400 600 800
Average June + July flows, 1962 to 1986800
700
600
500
400
300
200
100
0
observed pre-fire best fit1962
1977 Fire
1982
San Lorenzo (unburned) flows (cumulative mean cfs in June + July)
Gage 11160500 operated 1937 to present
Arr
oyo
Sec
o (b
urne
d) fl
ows
(cum
ulat
ive
mea
n cf
s in
Jun
e +
July
)G
age
111
5187
0, o
pera
ted
196
2 - 1
986
Figure 5. Increased summer streamflows following the Marble-Cone fire (1977) helped sustain aquatic and near-channel habitat in Arroyo Seco and adjoining streams, which were initially heavily sedimented by post-fire runoff. From 1978 through 1982 or 1983, summer flows in Arroyo Seco were nearly twice values expected based on long-term correlation with the San Lorenzo River (unburned watershed), offsetting some of sediment water-quality and temperature effects on aquatic biota. The double-mass curve shows that the pre-fire relation for June and July flows between Arroyo Seco and the San Lorenzo River resumed after 1982 or 1983.
CREEK
CR
I DE R
C R.
R.
BRO
WN
S
WATSONVILLE
HW Y
1
Qa
Tp
Tp
TeoTe
San Andreas Rift Zone
LONG-TERM STREAM GAGE
MONTEREY
BAY
Figure 6. Location and geologic influences, Corralitos and Browns Creeks.
Upper Corralitos / Browns CreeksWatershed Boundary
Unconsolidated sediments
Semi - consolidated Purisimasandstones and siltstones
Consolidated marine shales,sandstones and shales
Consolidated marine siltstonesand sandstones
Bed - Monitoring Sites
0 3 miles
N
CORR
LIT O
S
A
Tp
Qa
Teo
Te
Pro
bab
ility
of
Occ
urr
ence
in a
Giv
en Y
ear
?
Wild
fires
Te: Hard siltstones and sandstones
chaparral
Teo: Tightly-folded shales,sandstones and mudstones
mixed conifer
Tp: Semi-consolidatedsandstones and siltstones
hardwood, conifer
Predominant Substrate and Vegetation
10%
PRIMARY SECONDARY PRIMARY SECONDARY PRIMARY SECONDARY
Col
luvi
al s
lum
ps
Rea
ctiv
ated
lan
dslid
es
Larg
e r
ocks
lides
Wild
fires
Wild
fires
Bed
ding
pla
ne f
ailu
res
Rea
ctiv
ated
lan
dslid
es
Mud
flow
s
Ove
r-st
eepe
ned
slo
pes
Sw
ale-
fill
mud
flow
s
Land
-use
cha
nge
Geology:
Dominant Vegetation:
Figure 7. Estimated probability of significant sedimentation of steelhead habitat caused by episodic events, in three geologic/vegetative regimes, Corralitos Creek watershed. Probabilities based on estimated or observed frequencies and projected durations of bed sedimentation. Primary disturbances warrant site assessments by knowledgeable specialists and may merit temporary management measures. Secondary influences are more localized or less severe than primary. Source: Hecht and Woyshner (1991).