Hat Creek Restoration Project
Geomorphic Assessment and Preliminary Plans for Woody
Debris Placement and Recreation Access Improvements
Prepared by
Hat Creek Restoration Project
Prepared for
California Trout
HatRAC Presentation
October 29, 2013
Project area/objectives
Hat Creek Restoration Project
PROJECT AREA
• Highway 299 upstream to
Powerhouse riffle
OBJECTIVES
• Provide geomorphic
background for restoration
activities
• Develop designs for
recreation improvements
• Develop designs for
introduction of large woody
debris
PRESENTATION OUTLINE
• Geomorphic overview
• Large wood restoration
• Recreation/access
improvements
HatRAC Presentation
October 29, 2013
Restoration approach/study methods
PROCESS-BASED RESTORATION
• Replicate the geomorphic and ecosystem processes
that create habitat
• Identify and describe processes
• Identify human disturbance
WHY THIS APPROACH?
• Target species likely to
show a positive response
• Restoration measures less
likely to have negative
unintended consequences
• Restoration measures
more likely to function
over long-term
Hat Creek Restoration Project
•
•
•
•
•
METHODS
Review existing information
Stream walk survey
Topographic surveys
Field surveys of existing wood, and
potential wood placement areas
Review of instream wood inventory
conducted by CalTrout
HatRAC Presentation
October 29, 2013
Geomorphic processes: water and sediment
• Channel form is a
reflection of the
balance between
flow and
sediment
Source: Rosgen 1996
Hat Creek Restoration Project
HatRAC Presentation
October 29, 2013
Water
• Flow very consistent
over time
• Floods are not large
• Hydropower has
limited, short-term
effects
• Agricultural
diversion lowers
spring flood peaks,
spring-summer flow
Hat Creek Restoration Project
Sources: Kondolf et al. 1994
HatRAC Presentation
October 29, 2013
Sediment: suspended sediment
SOURCES
• Bank erosion, overland
flows
• Episodic, short-term
inputs from large-scale
events
• Human disturbances that
increase erosion have
likely increased
suspended sediment
supply, but supply
relatively low
EFFECTS OF DISTURBANCE
• Increased sedimentation
in low velocity areas
• Limited effect on
channel form, but may
impact ecology
Hat Creek Restoration Project
HatRAC Presentation
October 29, 2013
Sediment: bedload supply
•
Large body of prior work due to
concerns about sediment wave: Kondolf
et al. 1994; Cook and Ellis 1998; Cook
2000)
Bedload mostly sand; larger sediment
generally can’t be transported due to
low slope and lack of large floods
•
•
•
•
•
TYPICAL SOURCES
Streambank erosion
Erosion of tributaries
Mass wasting upstream
in bypass reaches
General conclusions:
none of these sources
account for bedload
Hat Creek Restoration Project
Source: Kondolf et al. 1994
HatRAC Presentation
October 29, 2013
Sediment: bedload supply
•
•
•
•
•
Volcanic events can
dramatically increase
bedload supply—1915
eruption
Transport through the
system influences the
bedload supply to the
project area
Flatter areas store
sediment, affecting the rate
of sediment supply and the
size of sediment delivered
to the project area
Result—over decades
following a volcanic event,
increase in bedload supply
rates to the project area
Long intervening periods
with low rates of sediment
supply
Hat Creek Restoration Project
Source: Kondolf et al. 1994
HatRAC Presentation
October 29, 2013
Recent sediment wave: influence of human disturbance
• Little effect on overall
magnitude of supply
• Hydropower modifications
have disrupted sediment
transport in the system
• Likely a link between Baum
Lake and the Powerhouse 2
bypass reach (Cook 2000)
• Channelization upstream of
Cassel in 1950’s likely
increased sediment supply,
either by increasing
transport capacity, erosion
of the channelized reach, or
both
• Episodic increases in
sediment likely a natural
process
Hat Creek Restoration Project
HatRAC Presentation
October 29, 2013
Channel sediment reponse
• Hat Creek has limited
transport capability
due to consistent flow
and low slope
• During periods of high
sediment supply,
transport capacity is
exceeded and channel
aggrades
Hat Creek Restoration Project
Source: Rosgen 1996
HatRAC Presentation
October 29, 2013
Recent sediment wave
• Increased sediment supply resulted in a
sediment wave over decadal time scales
• At any point in the channel, the wave
caused an aggradation-degradation
event as it passed
• Total sediment volume in wave 60,000
cy; aggradation average about 1.5 ft
(Kondolf et al. 1994)
• Wave has mostly passed through upper
half of project area, crest likely around
Wood Duck Island; passes out of project
area 2010-2040 (Cook 2000)
Hat Creek Restoration Project
HatRAC Presentation
October 29, 2013
Channel form
• Cross section rectangular, high
width-depth ratio
• Relatively uniform width and depth
• Peaty streambanks in low marshy
areas
• Erosion rates low during periods of
low sediment supply
HUMAN DISTURBANCE
• Introduction of muskrats
significantly increased streambank
erosion rates and channel
widening--possibly exacerbated
by grazing
• Old Carbon Bridge may have
caused widening downstream
• Riparian shrubs may have been
reduced by grazing
Hat Creek Restoration Project
HatRAC Presentation
October 29, 2013
Channel form and periods of high sediment supply
•
•
•
•
•
CHANNEL FORM
Depth variable in space and
time
Width may increase due to
higher streambank erosion
rates (powerhouse riffle
island, Cook 2000)
Avulsion possible during
severe events (backwaters
in historic aerials, Cook
2000)
During recent wave, bank
instability caused by
muskrats may have
increased widening
Widened areas may retain
portions of the wave in
narrow, longitudinal bars
Hat Creek Restoration Project
ECOLOGICAL RESPONSES
• Burial of aquatic vegetation
• Aquatic vegetation reestablishment
constrained due to high bed mobility
• Reduction in habitat diversity and
complexity
HatRAC Presentation
October 29, 2013
Model of channel function
• Infrequent, large-scale waves of sediment occur naturally
• Resulting ADE may last decades
• High rates of streambank erosion during aggradation may
result in widening, or side channels and avulsion during
severe events
• As sediment supply decreases, backwater areas fill in with
aquatic and emergent vegetation, creating peat and lowlying streambanks
• Narrow longitudinal bars may persist in widened areas
after wave passage, likely to be eventually colonized by
aquatic and emergent vegetation and resulting in
narrowing
Hat Creek Restoration Project
HatRAC Presentation
October 29, 2013
Woody debris-processes of large wood recruitment
POSSIBLE MODES OF
LARGE WOOD
RECRUITMENT TO
STREAMS
• Tree fall
• Bank erosion
• Wind throw
• Soil saturation
• Snow load
• Fire
• Disease
• Floating
• Mass wasting
Hat Creek Restoration Project
HatRAC Presentation
October 29, 2013
Large wood: recruitment in the project area
• Trees found on
streambanks in much of
lower half of project
area
• Swampy areas unlikely
to grow large trees
Hat Creek Restoration Project
HatRAC Presentation
October 29, 2013
Large wood: human disturbance and wood supply
• Timber harvest likely
removed potentially
recruitable trees
• Subsequent grazing and
management favored
conversion to meadows
• Areas that are currently
meadow may have
historically had scattered
large trees
• Current load of large wood
(@5 pieces in the project
area, CalTrout surveys) are
likely lower than would
have occurred naturally
Hat Creek Restoration Project
HatRAC Presentation
October 29, 2013
Large wood: restoration opportunities
GEOMORPHIC EFFECTS
• Work with existing
process of narrowing in
wide areas
•
•
•
•
ECOLOGIC EFFECTS
Increase instream
habitat diversity and
complexity
Provide stable
substrates for aquatic
plant colonization
Loafing habitat for
turtles
Substrates for
macroinvertebrates
Hat Creek Restoration Project
HatRAC Presentation
October 29, 2013
Large wood: habitat diversity and complexity I
Hat Creek Restoration Project
HatRAC Presentation
October 29, 2013
Large wood: habitat diversity and complexity II
Hat Creek Restoration Project
HatRAC Presentation
October 29, 2013
Large wood: habitat diversity and complexity III
Hat Creek Restoration Project
HatRAC Presentation
October 29, 2013
Large wood: preliminary wood plan
•
Large woody debris loading
can vary substantially
between streams, even those
with similar surrounding
forest types, climate, and
disturbance histories (Morris
2008)
Final density and location
determined by budget,
aesthetics, fishing access, etc.
•
•
•
•
•
Design/Construction
Considerations
Mimic natural tree
throw
Rootwads will assure
stability
Disturbance of cultural
resources
Construction
access/disturbance
Hat Creek Restoration Project
HatRAC Presentation
October 29, 2013
Large wood: preliminary wood plan
STREAMBANK
STABILIZATION
• Use of wood or
other revetments
to stabilize
streambanks is
not recommended
• Consider
biotechnical
treatments such
as high-density
willow planting
• Control of
muskrats should
be considered
Hat Creek Restoration Project
HatRAC Presentation
October 29, 2013
Recreation Improvements I
Hat Creek Restoration Project
HatRAC Presentation
October 29, 2013
Recreation Improvements II
Hat Creek Restoration Project
HatRAC Presentation
October 29, 2013
Recreation Improvements III
Hat Creek Restoration Project
HatRAC Presentation
October 29, 2013
Recreation Improvements IV
Hat Creek Restoration Project
HatRAC Presentation
October 29, 2013