Goals and Objectives For
Geomorphology, Water Quality, and
Fish & Wildlife Habitat
Prepared
by: Bay
Area Water Quality Control Board
GOALS AND OBJECTIVES FOR GEOMORPHOLOGY,
WATER QUALITY, AND FISH AND
WILDLIFE HABITAT
A
LIVING RIVER
OVERALL
GOALS
I. GEOMORPHIC OBJECTIVES
A. River channel ( bankfull channel and channel geometry)
B. River
floodplain
C. Slope
and meander
D. Sediment
transport
E. Flow
and velocity
F. Dynamics of null/entrapment zone
II. WATER
QUALITY OBJECTIVES
A. Dissolved
oxygen
B. Salinity
C. Temperature
D. Turbidity
E. Toxicity
F. Nutrients
and algal blooms
III. HABITAT
OBJECTIVES: SOUTH OF TRANCAS STREET
A. Vegetation
1. Cross section
2. Longitudinal profile
B. Aquatic
species
1. Barriers to migration
2. Complexity of in-stream habitat
3. Minimum flows and velocity
C. Wildlife
IV. HABITAT OBJECTIVES: NAPA CREEK, ALL TRIBUTARIES WITH STEELHEAD
AND TROUT, AND NAPA RIVER (north of Trancas St.)
A. Vegetation
1. Cross section
2. Longitudinal profile
B. Aquatic
species
1. Barriers to migration
2. Complexity of
in-stream habitat
3. Flows, depth, and velocity
4. Substrate composition, habitat, and
water quality
Appendices:
APPENDIX A:
Plant Communities in the Napa Valley
APPENDIX B:
Minimum In-stream Flow Requirements
APPENDIX C:
Glossary
The "Water Quality/Fish
Habitat" design review workgroup created the attached report as part of
the design review process for the Napa River flood management plan. Our goal is
to provide a working definition for a "living" Napa River system. Additionally, we provide specific guidance to
the Design Review Committee and general information to the Community Coalition
regarding the geomorphic, water quality and habitat elements of the Napa River
management plan. This report is intended to serve as a "living",
dynamic document which will be modified as we learn more about the living Napa
River system.
A
"LIVING" NAPA RIVER SYSTEM
The Napa River system is currently a partially degraded, "living"
river. Although it has areas of degraded
habitat and water quality, it continues
to support a diverse array of aquatic and terrestrial wildlife. Many of its degraded elements can be restored
and must be restored to ensure the long term functioning of the river as an
ecosystem. We have defined a healthy and
vital "living" Napa River system as follows:
A "living" Napa River and its tributaries is a
river system with structure, function, and diversity. It has physical, chemical, and biological
components that function together to
produce complex, diverse communities of people, plants, and animals.
The health of the entire watershed, from the smallest headwater trickle
on the slopes of Mt. St. Helena to the
broad expanse of the estuary, is the summation of natural and human activities in the basin
and how they affect certain undeniable physical processes common to all river systems. A "living" Napa River system
functions properly when it conveys variable flows and stores water in the floodplain, balances sediment input with
sediment transport, provides good quality fish and wildlife habitat,
maintains good water quality and
quantity, and lends itself to recreation
and aesthetic values.
A"living" Napa River conveys equilibrium and harmony with all that it
touches and resonates this through the human and natural environment.
To protect, enhance and insure the long term viability of
the "living" river system, our committee developed four goals for the
flood management plan (see figure 1). We
further developed specific objectives for geomorphology, water quality and
habitat to support the goals. In our opinion, if the flood management plan
incorporates these goals and objectives, the "living" Napa River will
be protected and significantly enhanced.
To be self-sustaining in the long-term, the
"living" river must be geomorphically stable; have good water quality
with adequate flows; and have a complex, uninterrupted, linear habitat. All of
these must be present. With regards to the flood management plan, what is the
best means of achieving these objectives? The key is geomorphic stability. Fluvial geomorphology refers to a river's
processes (i.e., sediment transport,
tidal and flood flows) and how they create the forms in a river (i.e.
bends/meanders, point bars and pools).
If the geomorphic objectives are met, then most of the water quality and
habitat objectives will also be met. For
instance, if the River is allowed to take its natural form, meandering, creating point bars and shallows,
etc., the desired wetland vegetation will naturally colonize these areas. The
vegetation will stabilize the banks, reducing erosion and improving water
quality. The vegetation will also provide refuge, food and nesting sites for
wildlife.
Figure I
1. The project should preserve or enhance
the habitats, water quality and natural geomorphic characteristics of the Napa
River system.
2. The project should provide enhancement
of the River system to the fullest extent possible, and not preclude or
eliminate future restoration opportunities.
3. The project should incorporate the
geomorphic, water quality and habitat objectives to the fullest extent
possible.
4. The project should incorporate the
geomorphic, water quality and habitat objectives so that the intended functions
are self-sustaining.
In understanding the Napa River ecosystem, it is important
to realize that the system changes from a freshwater riverine system upstream
to an estuarine system downstream. The
water chemistry, geomorphic and
biological components of riverine and estuarine systems are different. The
freshwater riverine system is characterized by a relatively narrow and shallow
active channel. The channel size and
shape are influenced by flows originating from the Napa watershed. The
vegetation, as seen north of the oxbow, is comprised of riparian scrub
shrub and forest species such as willows, cottonwood, and an adjacent overstory
of valley oak.
In the estuarine reach,
the water is saline and the vegetation within the tidal zone is
characterized by saline tolerant species such as tule or bulrush. The overhead canopy is relatively open. The
geomorphic characteristics of the estuarine reach of the Napa River are
complicated by the influence of the tides in combination with freshwater river
flow from the Napa watershed. The slope
of the channel bed is much less within the
estuarine reach and under normal river flow conditions the depths are
much larger .
The estuarine
processes are not simple (Dyer, 1979). The mixing of freshwater and San Francisco/San Pablo Bay water is accomplished by tidal flows which
change direction four 
Figure
II
times a day; by wind stress on the surface; and by river
discharge forcing its way towards the Bay.
The strength of each of these mixing processes varies depending on the
tide conditions, prevailing winds and river discharge. The salinity difference between the river and
the Bay water is about 20 parts per thousand which creates a density difference
of about 2% (this varies seasonally with
changes in freshwater flow). Even though
this is small, it is sufficient to cause stratification (different salinities
at different depths) and circulation patterns over the depth of flow. (see
Figure II)
The meeting of freshwater and saline water creates a
circulation pattern in which the heavier saline water flows underneath the
lighter, less dense freshwater. The
currents cancel each other out in an area called the null zone. The low
currents in the null zone and the circulation patterns of fresh and salt water
create an "entrapment zone".
Nutrients are concentrated in the entrapment zone which becomes an area of maximum productivity
in the estuary.
The boundary between the estuarine and freshwater reaches is
not clearly defined. Generally, the
reach South of Trancas is considered the estuary because this is the upstream
extent of tidal influence and of "salt water" incursion. However, the situation is complex
because the upstream extent of saline
water varies greatly with the season, due to the great variation of freshwater
flow down the Napa River from winter to summer. It advances to the North of
Lincoln (all the way to Trancas) in late summer (particularly in dry years) and
retreats to the southern part of Kennedy Park and beyond in late winter
(particularly in "wet" years). The location and extent of the null
and entrapment zones also vary seasonally with the seasonal changes in freshwater
flow.
Figure A
The vegetation begins to transition from riparian to
estuarine (from upstream to downstream)
south of Trancas near the oxbow. This is in response to increased soil
salinity as well as average water salinity.
Generally, the location of this vegetative transition zone does not
change significantly seasonally or yearly. Significant shifts may occur if the
water salinity is altered for an extended period, such as during an extended
drought.
The environmental objectives for the Napa River system have
been appropriately tailored for the different reaches, riverine and
estuarine, to reflect the differences
between these systems. The following discussion presents the environmental
objectives which we have developed for geomorphology, water quality and
habitat.
"Rivers are ecological systems with many interacting
variables. Interrelated river system variables include: the size of the
watershed; the amount of sediment; the size of the sediment transported in the
river channel; the channel shape, size, slope, and roughness (trees, bushes,
rocks, stream bed forms, stream bank surface, floodplain obstructions, channel
bends, etc.); and amount and frequencies of flow discharges. A stream in equilibrium is a stream in which
these variables are in balance with each other.
Such a stream is sometimes described as being graded. A condition of equilibrium does not represent
a steady state condition at any one particular stream flow because the
variables change among stream reaches and over time. The dynamic equilibrium of a channel
represents the average condition of a river during its relatively recent
history.
Under conditions of dynamic equilibrium, the stream's energy
is such that the sediment loads entering a stream reach are equal to those
leaving it. Over the long-term evolution
of a river, it will attempt to evolve to
transport the sediment delivered to it with the available run-off. A graded stream refers to one in which over a
period of years, slope and channel characteristics are delicately adjusted to
provide, with available discharge, just the velocity required for the
transportation of the sediment load supplied from the drainage basin. If we
consider a long geologic time scale, the evolution of a stream is governed by
the geology and climate influencing the region.
Viewed against a shorter time scale, in days, weeks or months, streams
seldom achieve a steady state because of the continuous small and large changes
in water, sediment discharges, changes in vegetation, stream bed forms, and
other factors.
Conventional engineering practices often have had the
objectives of stabilizing streams and conveying flood flows. The channel width, depth, slope, and meander
are engineered so as to prevent or minimize changes to these dimensions. This
is done to make the waterway more predictable, erode less, and convey more
flood discharges at lower stages.
Streams and rivers are, however, dynamic systems which are adjusting to
natural or human imposed changes in watersheds" (Riley, 1996).
Efforts to confine, widen or deepen a river often fail and
result in unwanted side effects such as increased sediment deposition,
increased scour (bed erosion) and loss of vegetation (see section I.D).
A successful flood management plan for the Napa River will
be based on geomorphic principles involving river channel geometry and sediment
transport dynamics, and will take into account the differences between
estuarine and riverine reaches. Any alterations
of river channel geometry (width, depth, and width/depth ratio) must be based on these principles and allow
the River to function in a self-sustaining, dynamic equilibrium. Additionally,
the flood management plan must take into account that the river's plan form
(shape of a river as viewed from an airplane) is not fixed over time, but
rather will change its course through a
variety of natural processes (i.e., meandering).
BANKFULL CHANNEL
"The first and most important aspect of the river
channel is that it is self-formed and self-maintained. The flowing water carves the groove in which
it flows. The water fashions the depth,
the cross section, the areal configuration, and the longitudinal
profile" (Leopold, 1962). The
discharge that transports the most amount
of sediment in the long term is called the channel forming flow (or dominant
discharge). In river systems that are close to a dynamic equilibrium, the
bankfull discharge and channel forming discharge are the same. The bankful discharge is approximately the
1.5 to 3 year flood event in many regions of Northern California. This moderate
and relatively frequent flow is responsible for creating the characteristic
morphology (size and shape) of the riverine channel. A river carries flows at the bankfull width
approximately 3-5 days per year.
CHANNEL
GEOMETRY (Width, Depth And Width/Depth Ratio)
The channel geometry (width, depth) is adjusted to carry
tidal flows, normal river flows and the major floods. The channel geometry should be based on
natural, undisturbed sections and observations of similar geomorphically stable
river systems (i.e., reference reaches of a stream or reference river systems).
B. RIVER FLOODPLAIN
A river will not maintain a channel big enough to carry the
largest flow. " The river channel is large enough to accommodate all the
water coming from the drainage area only in the relatively frequent event. The
flat area bordering most channels - the floodplain - must flood to some extent
on the average every other year. To
overflow the floodplain is an inherent characteristic of a river" (Leopold, 1962). Thus,
the river floodplain is an integral part of the river system. A successful flood management strategy will
involve reconnecting the River to its floodplain to the extent feasible.
C. SLOPE AND MEANDER
The slope of a river is developed over a very long time. If
the slope of a river is altered in one reach, the rest of the system will tend
to react and either downcut or aggrade.
When this happens, it will take a long time for the river to
equilibrate. Therefore, this project should avoid significantly altering the
slope of the River.
Slope is by definition a measurement of the change in height
divided by the change in length ( change
height/ change length). Thus, slope can
be altered by a change in river depth (where the water surface elevation is
altered) or a change in river length.
Human activities which alter river depth include: land use changes that
increase sediment delivery to the stream (causing aggradation), and
dredging. The river can be shortened by
straightening or by creating a bypass.
Rivers tend to meander and generally are sinuous rather than
straight (certain reaches of a river may be straight for short distances). The wavelength of the meander and the rate of
meandering across the floodplain are different in riverine versus estuarine
systems. In the Napa River system, it is important to distinguish between the
estuarine reaches and the riverine reaches in determining the geomorphic
components of a stable system.
OBJECTIVES
1. Maintain or
restore the River to a state of geomorphic equilibrium.
2. Maintain the
natural slope of the River. The slope of
the River should not be altered significantly by dredging or straightening.
3. Maintain the
natural width of the River.
4. Maintain the
natural width/depth ratio of the River.
5. To the
maximum degree possible, maintain or restore the connection of the River to its
floodplain. This should be of sufficient Figure III
width to
accommodate river meandering caused by naturally occurring flows.
6. Provide
sufficient setbacks to allow natural meandering processes.
7. Maintain
channel features such as mudflats, shallows, a naturally uneven bottom
configuration, and sandbars.
D. SEDIMENT TRANSPORT
Rivers are agents of erosion and transportation, removing
the water and sediment supplied to them from the land surface to the oceans
(Knighton, 1984). The mechanics of
sediment transport are different in riverine versus estuarine systems. Riverine
channel stability is a relative term often defined in terms of the balance
between sediment supply and transportability.
When the sediment supply exceeds the transport capacity, the river bed
tends to aggrade (the bed elevation increases due to the deposition of
sediment). When the sediment supply is
less than the transport capacity, a river bed tends to degrade (the bed elevation decreases due to scouring,
if the bed materials are transportable).
Generally, the Napa River north of Oak Knoll (riverine) is
degrading. The cause of the degradation is unknown, but may be due to at least
two factors:
1.
Dredging of the navigation channel; and
2.
Channel clearing and excavation.
A state of dynamic equilibrium is desired in which the
amount of sediment that enters the system equals the amount that leaves the
system. A long-term goal of the flood
management plan and an Upper Valley Watershed Plan should be to re-establish a
state of equilibrium for sediment transport.
To the extent that this is not achieved, the River will continue to
downcut in the upper reaches and tributaries.
Sediment transport
becomes more complicated in estuarine systems. Fine sediment particles (clays and silt)
which would normally stay in suspension in a freshwater riverine system, begin to settle out and deposit on the river
bed in an estuarine system. This is due,
in-part to the effects of salinity on clay particles (increased flocculation)
and to tidal backwater effects. The depositional patterns in the estuarine reach of the Napa River are complex
and not yet understood. The issues to be assessed in this reach are:
1.
Whether the
current deposition rate is in equilibrium; and
2.
The effect of
a flood management plan on the deposition rate.
Accelerated degradation or increased aggradation are not
desirable from either an environmental or economic standpoint. Downcutting
(degradation) causes bank erosion, bank
failure, loss of land, loss of habitat, and groundwater depletion. Accelerated
aggradation often requires maintenance
dredging to maintain channel capacity.
Dredging and dredge disposal can be extremely costly with significant
environmental effects.
The water quality impacts associated with excessive erosion
and deposition in a river system are also significant. An increase in the sediment load above the
Napa River's natural load will result in increased water turbidity, the
destruction of steelhead/rainbow trout spawning gravels, and the loss of highly productive macroinvertebrate
habitat (riffles). It can also lead to
an increase in the nutrient load (phosphates are often bound to soil particles)
which may result in algal blooms. Algal blooms often lead to a process called
eutrophication which results in depleted dissolved oxygen levels (see section
II.A & F).
Based on the above discussion, it can be seen that it is
preferable to implement a flood management plan that will not accelerate river
bed/bank degradation or increased aggradation. To the extent possible the plan
should be designed to re-create a stable system in equilibrium.
OBJECTIVES
8. Restore the
River to a state of sediment transport equilibrium as follows:
Upstream
of Trancas (riverine):
·
The amount of sediment entering and leaving the system
should be equal.
·
Restore the natural relationship between the floodplain,
riparian edge and River.
Downstream
of Trancas (estuarine):
·
Re-establish natural deposition rates .
This will
require adequate flow and channel geometry providing appropriate velocity,
slope, width, and depth to transport the sediment load. The project should not increase the sediment
load or alter the settling capacities of the sediment such that there is an
increase in sediment deposition South of Third Street.
9. Quantify the
overall sediment load to the system. Long-term watershed management measures
should be determined to reduce the sediment load to the system to re-establish equilibrium.
10. Design a
project that re-establishes a system in equilibrium and decreases upstream
erosion rates, rather than relying on maintenance dredging to maintain the
channel capacity.
11. Design a
project that minimizes the need for erosion control measures such as rock
rip-rap or other hard structures/materials.
E. FLOW AND
VELOCITY
The flow velocity is proportional to the scouring ability of
the river at flood flows. In a natural flood, some vegetation will be scoured
and lost and some will survive. This natural process ensures a range of habitat
type and age within the system. It is important
that the river is not constricted to such an extent that the increased velocity
removes all vegetation in a given flood event.
This condition leads to a uniformity of habitat age and type and may
favor fast colonizing exotic vegetation. (See III. B3 and appendix for a discussion of minimum in-stream flows).
OBJECTIVES:
12. Maintain
seasonal flows of sufficient magnitude and duration to sustain channel
morphology within a floodplain and sustain estuarine system components.
13. Maintain
adequate flows and velocities for sediment transport.
14. Maintain
velocities in the ranges that might be expected in a natural system.
15. Identify
measures throughout the watershed to increase infiltration and decrease
stormwater runoff.
F. DYNAMICS OF THE
NULL/ENTRAPMENT ZONE
The point at which the freshwater River discharge meets and
mixes with saline water from San Francisco/San Pablo Bay is called the null or
entrapment zone (see Introduction and section II.B). The size and location of the null zone varies
seasonally with changes in freshwater flow from the River. Because this is an area of maximum
productivity in the estuary, the flood management plan should not alter the
natural location or size of the entrapment zone. Example activities which might
have this effect include: activities which would reduce the volume of normal
freshwater flow (dams without adequate water releases); or actions which would increase the relative
volume of saltwater (i.e., altering the tidal prism by channel widening).
OBJECTIVES
16. Preserve the
size and seasonally varying location of the null/entrapment zone and its
ecological characteristics.
II. WATER QUALITY OBJECTIVES
What is the best means of achieving the water quality and
habitat objectives? The key is geomorphic stability. If the geomorphic
objectives are met, then most of the water quality and habitat objectives will
also be met. For instance, if the River
is allowed to take its natural form; meandering, creating point bars and
shallows, etc., the desired wetland vegetation will naturally colonize these
areas. The vegetation will stabilize the banks, reducing erosion and improving
water quality.
The workgroup identified water quality objectives for
dissolved oxygen, salinity, temperature, turbidity, toxicity, and nutrients.
The most important objectives include: 1) to maintain/enhance dissolved oxygen
levels and salinity gradients; and 2) to maintain/reduce turbidity and erosion.
A flood management plan which involves minimal dredging and is based on
geomorphic equilibrium principles, should satisfy these objectives.
A. DISSOLVED OXYGEN
The term "dissolved oxygen concentration" refers
to the amount of oxygen in the water column.
Dissolved oxygen (DO) is important because aquatic organisms need oxygen
to survive and grow. If there is not
enough oxygen in the water, fish populations will be affected by:
1.
Increased
mortality of adults and juveniles;
2.
Reduction in
growth;
3.
Lower survival
rates of eggs and larvae; and
4.
Changes in
species composition.
For example, some
species require high DO (e.g., trout and stoneflies) whereas other species
thrive in lower levels (e.g., catfish, worms and dragonflies). A decrease in
the dissolved oxygen supply may not lead to the death of fish, but rather cause
a shift in species composition, for example from steelhead to carp.
Examples of agents that alter dissolved oxygen levels
include:
1.
Low flows (may
result in increased water temperature
and poor circulation);
2.
Water
temperatures (higher Temp. = lower DO);
3.
Nutrients contained in resuspended sediments (see section II.F);
4.
Suspended
sediment (increased sediment = decreased DO, particularly when sediment is anoxic);
5.
Organic
pollutants;
6.
Sulfides
(released during dredging of anoxic sediments); and 8) algal blooms (section II.F).
QUANTITATIVE OBJECTIVES
17. Tidally Influenced Waters (South of Trancas)
Minimum
at all times: 5.0
mg/L
18. Cold Water Fishery (North of Trancas)
Minimum at all times: 7.0
mg/L
19. All Waters
Minimum (three month
median): 6.8-7.2 mg/l (summer,
80% of saturation)
QUALITATIVE OBJECTIVES:
In order to maintain optimal DO levels, characteristics of
the River system should be maintained or restored that positively contribute to
the oxygen dynamics of the system. The
project should not adversely alter the oxygen dynamics of the system. To maintain healthy oxygen dynamics, the
project should:
20. Maintain or
restore the River to a state of geomorphic equilibrium. This should eliminate the need for extensive
ongoing maintenance dredging.
21. Maintain or
restore a riparian zone to provide shade for the River in order to reduce
temperatures.
22. Maintain or
restore adequate low flows.
23. Maintain
adequate water velocity during low flow months.
24. Maintain
adequate circulation patterns.
25. Maintain or
decrease nutrient loading. Nutrients
should not be increased through discharge of dredge material or sediment
resuspension, such that increased primary production occurs.
26. Maintain water temperatures appropriate
to the needs of the local biota.
B. SALINITY (See introduction and section
I.F )
The Napa River tends to be estuarine below Trancas and riverine above Trancas. The boundary location is not precise and
varies depending on the season and the amount of freshwater flow; moving
towards Trancas St. in late summer/fall and southward to Kennedy Park and
beyond in late winter (particularly in "wet" years). The interface and subsequent mixing zone of
fresh and saline water is called the "entrapment zone". In this zone, during the winter (normal
rainfall) the heavier, saline water sinks to the river bottom and lighter,
freshwater flows on top. This creates a cyclical circulation pattern (see
Figure II).
The size of the zone of entrapment has a large impact on the
aquatic life that the River can support.
The smaller the zone, the fewer species can survive. The majority of species require a gradual
shift in salinity concentration (a mild salinity gradient). Very few species
can tolerate a rapid change in water salinity. Additionally, nutrients are
concentrated in this zone. As a result,
the entrapment zone is the area of maximum productivity for algae and
macroinvertebrates. Thus, the larger
the zone, the more food is available over a larger range. The abundance of food affects the size of the
fish population which the River can support.
QUALITATIVE OBJECTIVES:
27. Water quality
factors should not increase the total dissolved solids or salinity so as to
adversely affect the location of the entrapment zone, or beneficial uses of the
River, particularly fish migration and
estuarine habitat.
28. The project
should not have any the following effects on salinity (seasonally or in worst
case conditions such as summer low-flow or droughts):
1.
Compress or alter the location of the null/entrapment zone;
2.
Steepen the salinity gradient;
3.
Alter the average salinity concentrations (seasonal); or
4.
Alter the location of the seasonally varying upstream extent
of salinity.
C. TEMPERATURE
Temperature is one of the most important water quality
parameters because it affects water chemistry and functions required by aquatic
organisms. Water temperature
influences:
1.
The amount of
oxygen that can be dissolved in water (as temp. increases, dissolved oxygen
levels decrease);
2.
The rate of
photosynthesis by algae and other aquatic plants ( as temp increases,
photosynthesis increases) ;
3.
The metabolic
rates of organisms (as temp. increases the metabolic rates increase); and
4.
The
sensitivity of organisms to toxic wastes, parasites and diseases.
In general, in the Napa River system, lower water
temperatures are better than higher temperatures because of the presence of
steelhead/rainbow trout, which require relatively low temperatures (optimum =
10.0 degrees C or 50 degrees F) and high dissolved oxygen levels. The presence
of steelhead/trout in the tributaries and upper River, signify that conditions
are sufficient to support survival of these fish. However, the limited temperature data available
suggests that the summer temperatures are higher than the optimum. During the summer months, the lower River
becomes more saline and supports fish species which are typically better
adapted for warmer water and estuarine conditions such as striped bass.
Factors that affect temperature include:
1.
The daily and
seasonal fluctuations of direct sunlight
radiation;
2.
The amount of
stream shade or cover;
3.
Water depth;
4.
Inflow of
groundwater (usually colder than stream);
5.
Inflow of
other water (surface water) into stream that is at a different temperature than
the stream (e.g., a drainage ditch, hot tub, or another stream); and
6.
Channel width
(deep, narrow channels help maintain low temperatures and sediment transport).
QUALITATIVE OBJECTIVES
29. The natural
river/creek water temperatures should be maintained.
30. Velocity,
circulation patterns, and mass flow should not be altered in a manner that
causes an increase in temperature.
31. Avoid
increases in turbidity from dredging or other project activities that can cause
an increase in water temperature.
32. Avoid
creating thermal barriers to migration or movement by project activities (e.g.,
dredging).
D. TURBIDITY
Turbidity is a measurement of light penetration through the
water column. Turbidity of the Napa River increases as suspended sediment
concentrations and algal populations increase. Suspended sediment in the Napa
River system originates from river bank and bed erosion, land erosion (both
naturally occurring and human induced), and from the transport of suspended
solids from San Pablo Bay. Water
turbidity affects plant species composition and is important in predator-prey
interactions. For example, in highly
turbid water, a steelhead/rainbow trout cannot adequately see in order to catch
the insects it feeds upon.
Possible sources of the flood management project-related
turbidity include the following:
1.
Resuspension
of sediment through dredging;
2.
Increased
upstream bank and River bed erosion; and
3.
River bank
erosion downstream of any newly created reservoirs or dams.
OBJECTIVES
To minimize the negative effects from these activities:
33. Increases
from normal background light penetration or turbidity should not be greater
than 10 % in areas where normal turbidity is greater than 50 NTU.
34. The flood
control project should not:
·
Increase sedimentation rates in the lower River (below
Trancas),
·
Increase bank and bed erosion upstream or in the
tributaries,
·
Cause resuspension of sediments from dredging,
·
Increase algal growth.
E. TOXICITY
Examples of toxic substances that might be released during
the construction phase of the flood control project or during maintenance
operations from dredging include diesel fuel, metals (mercury, arsenic, lead,
silver, etc.), and pesticides (e.g., DDT).
The kinds of activities that can cause the release of these toxic
substances include:
1.
Disturbance of
contaminated sites adjacent to the River which have not been properly cleaned
up or stabilized;
2.
Resuspension
of contaminated sediment through dredging activities; and
3.
Discharge of
water from dredging dewatering operations (where contaminated sediments are
involved).
QUALITATIVE OBJECTIVE:
35. All waters
should be maintained free of toxic substances in concentrations that are lethal
to or produce other detrimental responses in aquatic organisms. Detrimental responses include decreased
growth rate and decreased reproductive success of resident or indicator species. (See San Francisco Bay Regional Water
Quality Control Board, Basin Plan for specific numeric limits).
F. NUTRIENTS/ALGAL BLOOMS
High levels of nitrates and phosphates may cause excessive
plant growth, known as algal blooms.
This, in turn, may lead to a condition of degraded water quality through
the process of eutrophication. A
simplistic diagram of eutrophication is shown below.
Among other water quality problems, eutrophication usually
results in low dissolved oxygen levels and increased turbidity.
OBJECTIVE
36. The project
should not result in the release or discharge of nitrates and phosphates in
concentrations that promote aquatic growths to the extent that such growths
cause a nuisance or adversely affect beneficial uses.
37. A recommended
maximum level for nitrate is 0.3 mg/L.
38. The project
should not result in a wide, shallow low-flow channel (this would result in
increased water temp., causing increased plant growth).
III. HABITAT
OBJECTIVES: SOUTH OF TRANCAS STREET
A. VEGETATION (See appendix A for detailed description of existing plant
communities)
Generally, if the River is
geomorphically stable and contains features such as mudflats, shallows, sloped
banks and an integrated floodplain, the plant community will respond. It will
create a vegetated continuum with the desired diversity and structure (some intervention to insure the proper seed
sources are present and introduced species do not proliferate may be needed).
RIVER CROSS SECTION (FROM WATER
SURFACE TO UPLAND)
There are three basic vegetative
transition zones from water surface to upland.
These are:
·
Root zone wet
all of the time and plant partially submerged (i.e.,cattails, bulrush)
·
Root zone wet
the majority of the time (i.e.,willows)
·
Root zone wet
periodically - flooded periodically (i.e.,oak, grassland)
OBJECTIVE:
39. The vegetative transition zones should
exist from the low water level to the upper floodplain. Each zone should be of sufficient width to
sustain habitat complexity and ecosystem function. There is no set width. Specific widths will
vary with topography and bank slope. To
create a self-sustaining river system, widths should be set by studying and
mimicking natural conditions to the greatest extent feasible.
40. Design a project that minimizes the need
for erosion control measures such as rock rip-rap or other hard
structures/materials.
RIVER LONGITUDINAL PROFILE (From upstream to
downstream)
Vegetation changes can be seen as you travel from downstream
to upstream along the Napa River. The transitions are represented by pickleweed
- tule- willows -oak (from mudflat to sandbar as you go upstream). The changes
in vegetation are driven by changes in salinity (increasing freshwater
upstream).
Without a linear continuum of habitat, aquatic species and
wildlife cannot successfully travel up and down the river corridor. In the case of juvenile fish, without the
cover provided by vegetation they are very susceptible to predation. The vegetation also provides a source of
food. In the case of terrestrial
wildlife, the lack of a linear continuum
prevents movement along the River.
OBJECTIVE:
41. From
saltwater to freshwater, the vegetation should exist in a linear uninterrupted
continuum. This continuum should have
the successional variation, diversity and structure to provide cover and
habitat for a natural variety of aquatic and terrestrial life.
B. AQUATIC SPECIES HABITAT
B. 1 Migration Barriers
Anadromous fish should have barrier-free access to their
spawning and nursery areas. Other fish
and aquatic species travel up and down the River corridor in response to food
supply, the salinity gradient, etc., and also require unobstructed access to
the entire corridor. Barriers to
movement and migration can be physical (dams, submerged structures, etc.) or
water quality related. Water quality
barriers include zones of high temperature, low dissolved oxygen, or sulfides.
Examples of possible project conditions or activities that
could produce these types of barriers include:
1.
A nick-point moving upstream to a hydraulic control (e.g., a grade
control structure or an
artificially armored bed);
2.
Dredging,
which may create zones of warm temperature, low dissolved oxygen, or turbidity that inhibit fish
migration or movement; and
3.
Levees, which
strand fish behind them after flood waters recede.
OBJECTIVE
42. No physical or water quality barriers to
migration.
B. 2 Complexity of In-stream Habitat
A healthy river ecosystem requires complexity of in-steam
habitat. In-stream habitat complexity is
created by a gradation of water depth from bank to bank which forms areas of
shallow, moderate and deep water. Complexity is also created from the presence
of in-stream structures such as tree roots, logs, boulders and overhanging
banks. Vegetation responds to different
water depths (e.g., wetland vegetation grows in shallow water and phytoplankton
is found floating at many depths.
Channel complexity, which includes meanders, a low flow channel, pools,
mudflats, and sand bars, is the essential building block for creating in-stream
complexity.
The diverse habitats provide food, escape from predation,
corridors for movement, and multiple niches for a spectrum of organisms from
insects to clams to fish.
Fish require different depths of water during different life
stages. Juvenile fish rely on vegetative
cover, tree roots, and overhanging banks to escape predation. Adult fish move from deep water refuges
during the day to shallow water at night for feeding. During migratory periods, anadromous fish
often travel upstream in shallow areas where the water velocity is less than in
the deeper reaches.
Disturbances of the river channel from this flood management
project should be minimal. Ongoing or
frequent dredging destroys complexity by eliminating pools, shallows, mudflats,
and sand bars, and destroying the benthic community. This disturbance results in a benthic
community that is comprised of species more opportunistic and
disturbance-tolerant. These species may
be less important as food for fish and
birds. A diverse macroinvertebrate
population ( insects clams, snails, crayfish, etc.) and a diverse plant
community require water of different depths and lack of disturbance. Ongoing disturbances of the water column or
benthos would result in a long-term reduction in the biological productivity of
the River.
OBJECTIVE
43. Post-project
conditions should include:
·
geomorphic features (e.g., meanders) that will foster
continued development of varying water
depths over mudflats, sand bars, pools;
·
gradation of depth from bank to bank;
·
presence of pools, low flow channels, mudflats, and sand
bars;
·
banks at a slope and with appropriate substrate to support
vegetation;
·
minimal maintenance dredging or other disturbances that
eliminate structural complexity.
B. 3 Minimum Flows and Velocity
Flows in the winter months are currently sufficient to attract
migrating steelhead and to maintain a natural variation in flow characteristic
of a living river. Flows in the spring
months are sufficient for out-migrating young steelhead trout (typically 1-3
years old). Summer and fall flows should
be preserved and restored for sufficient steelhead/rainbow trout habitat, and for estuary water quality
enhancement.
The project should strive to reduce peak flows during major
flood events while not significantly altering the winter migration flows which
serve to attract the steelhead and allow access into small tributaries. If water detention facilities up the valley
are incorporated into the project, then they should be designed to release
sufficient storm flows to ensure upstream migration of adults in the winter
(Jan-Mar), outmigration of juveniles (Dec-May), and to provide augmentation for
sufficient life sustaining "summer" flows (Jun-Nov, particularly
Aug-Sep) (F.Kerr, see appendix B ). They should additionally be designed to
allow fish migration where applicable and to not trap fish.
OBJECTIVE
44. Maintain
seasonal flows in the Napa River and its tributaries that permit upstream
migration, summer residence, and outmigration of steelhead.
C. WILDLIFE
The Napa River and surrounding areas support a great
diversity of bird species, both resident and migratory. These include raptors, wading birds,
waterfowl, and shorebirds. Numerous
mammals inhabit the area, such as raccoon, muskrat, blacktail dear, jack
rabbit, brush rabbit and vagrant shrew.
Additionally, the various cover types in the area provide habitat for
many amphibians and reptiles (e.g., western pond turtle, western aquatic garter
snake, and Pacific tree frog).
Wildlife are dependent on the various habitats for food,
cover, burrowing habitat, nesting sites, and access to water. The presence of a linear continuum of
vegetation is necessary to allow wildlife movement up and down the River
corridor.
In the area south of the Oxbow, mudflats and shallow water
areas are used for wintering habitat as well as resting areas during migration
by shorebirds. Tidal mudflats are an
important feeding habitat for shorebirds (e.g., willets, godwits and
sandpipers). Specific species of concern
include the black rail, clapper rail, and Mason's lilleopsis.
An evaluation of much of the wildlife habitat south of the
Oxbow will reveal that there has been degradation of this resource and
tremendous opportunity for enhancement exists.
However, it must be noted that even in this degraded state, the Napa
river and its surrounding areas are supporting a diverse array of species and
play a critical role in the ability of these species to exist in the area.
OBJECTIVES:
45. Restore or
maintain riparian and wetland habitat.
Re-establish a linear continuum of vegetation and a buffer of sufficient
width to protect plants and animals from human disturbance.
46. Maintain
mudflats and shallow areas.
47. Restore or
maintain a riparian corridor that is predominantly undisturbed by human
activity. Minimal disturbance can be
achieved by creating a trail system that is not located directly along the
River banks in most places. Rather, the trail should be located a distance away
from the River, with discrete access points for viewing, fishing, etc. (Exceptions to this would be within the City
downtown area where parks, trails could be located as enhancements to that
area).
IV. HABITAT
OBJECTIVES: NAPA CREEK, ALL TRIBUTARIES
WITH STEELHEAD/RAINBOW TROUT, NAPA RIVER
NORTH OF TRANCAS STREET
Napa Creek should not be altered in any manner that would
place the existing steelhead run at risk.
The geomorphic goals and objectives stated in the previous
sections apply to these reaches.
Additionally, the following more specific objectives apply due to the
presence of steelhead, trout, and other cold water fish species.
A. VEGETATION :
North of Trancas and on Tributaries
Figure IV
In understanding the Napa River ecosystem, it is important
to realize that the system changes from a freshwater riverine system upstream
to an estuarine system downstream. The
water chemistry, geomorphic and
biological components of these systems are different. The freshwater riverine
system is characterized by a relatively narrow and shallow active channel which
has significantly downcut from the valley floor. The channel size and shape is influenced by
flows originating from the Napa watershed.
The vegetation , as seen North of
the oxbow, is comprised of riparian scrub shrub and forest species such as
willows, cottonwood, and an adjacent overstory of valley oak.
The estuarine reach can be broadly defined as where the
freshwater river discharge is mixed with tidally influenced saline water from
San Francisco /San Pablo Bay. In this reach,
the water is saline and the vegetation within the tidal zone is
characterized by saline tolerant species such as tule or bulrush. The overhead canopy is relatively open. The channel shape is influenced both by freshwater flows from the upper watershed and
the tides. Therefore, the channel is
relatively wide and deep.
The meeting of
freshwater and saline water creates a circulation pattern in which the heavier
saline water flows underneath the lighter, less dense freshwater . The currents cancel each other out in an area
called the null zone. The low currents in the null zone and the circulation
patterns of fresh and salt water create an "entrapment zone". Nutrients are concentrated in the entrapment
zone which is an area of maximum
productivity in the estuary.
A boundary between the estuarine and freshwater reaches is
not clearly defined. Generally, the
reach South of Trancas is considered the estuary because this is the upstream
extent of tidal influence and of "salt water". However, the situation is complex as the upstream extent of saline water varies
greatly with the season, due to the great variation of freshwater flow down the
Napa River from winter to summer. It advances to the North of Lincoln (all the
way to Trancas) in late summer (particularly in dry years) and retreats to the
southern part of Kennedy Park and beyond in late winter (particularly in
"wet" years). The location and extent of the null zone also varies
seasonally with the seasonal changes in freshwater flow.
The vegetation begins
to transition from riparian to estuarine (moving downstream) south of Trancas
near the oxbow. This is in response to soil salinity as well as average water
salinity. Generally, the location of
this vegetative transition zone does not change significantly seasonally or
yearly. Significant shifts may occur if the water salinity is altered for an
extended period such as during an extended drought.
The environmental objectives for the Napa River system have been appropriately tailored for
the different reaches, riverine and estuarine,
to reflect the differences between these systems. The following
discussion is a brief summary of the environmental objectives which we have
developed for geomorphology, water quality and habitat.
B. AQUATIC SPECIES HABITAT
B.1 BARRIER-FREE MIGRATION
Examples of possible conditions that could produce barriers
include hydraulic control structures (i.e. weirs or dams), grade control
structures, wide shallow channels,
narrow constricted channels. Successful
migration requires both upstream and downstream resting areas such as pools,
eddies, and backwater zones.
OBJECTIVE
47. No physical
or water quality barriers to migration.
B.2 COMPLEXITY
The complexity of Napa Creek and other tributary ecosystems
is one of its most important characteristics.
The channel bottom, in‑stream vegetation, riparian vegetation,
submerged structures such as logs and boulders, and overhanging banks create
habitat for all lifestages of aquatic species.
OBJECTIVES
48. The project
should provide for a gradation of depth from bank to bank.
49. Maintain
existing riffle:run:pool ratios in the upstream areas, and try to replicate
this in the downstream areas. Maintain
a low flow channel and gravel bars.
50. Maintain geomorphic features (e.g., meanders) that foster
continued development of varying water depths, pools, etc. (See Figure V).
Figure
V
51. Provide for
sufficient cover for various fish life stages, particularly nursery habitat for
steelhead and contiguous bank escape cover for outmigrating steelhead smolts
(wooden snags, rootwads, large rocks and submerged vegetation).
52. Design river
banks at a slope and with appropriate substrate to support vegetation.
53. Allow for
only minimal maintenance dredging or other disturbances.
B.3 IN-STREAM FLOWS, WATER DEPTH AND VELOCITY
(USFWS 1986)
Preferred minimum depth for upstream migration of steelhead
is 0.75 ft. Preferred spawning depth is
1.0 ft or greater. The depth required by
rearing steelhead is most closely associated with food production. The most productive areas in terms of aquatic
insect production are shallow areas typical of rifles..
QUALITATIVE OBJECTIVES:
54. Restore or
maintain flows that will preserve and enhance habitat.
55. Restore or
maintain minimum flows that create sufficient water depth and volume (see water
depth).
56. Restore or
maintain minimum flows sufficient to sustain adequate water quality during the
low-flow months (see water quality).
57. Maintain
flows sufficient to provide adequate recruitment and transport of gravel and
cobble through the system. Clean gravels
are critical to successful spawning and incubation of steelhead eggs and
producing food for young fish.
QUANTITATIVE OBJECTIVES
58. During the
migration period (primarily Jan-Feb.) the minimum depth should be 0.75 ft.
59. Spawning
depth should be 1 foot or greater.
B.4 SUBSTRATE COMPOSITION
Substrate for spawning steelhead/rainbow trout should
consist of clean, well rounded gravel.
Excessive sand and silt in the gravel reduces survival and emergence
rates. Embeddedness should be less than
25%.
During the rearing phase of steelhead/rainbow trout, the substrate composition affects
steelhead/rainbow trout production mostly by regulating the production of
invertebrates, an important food source.
The highest production of invertebrates is in habitats with coarse
gravel.
QUANTITATIVE OBJECTIVES
61. Ensure
conditions that create clean, well rounded gravels for spawning.
62. Embeddedness less than
25%.
APPENDIX A
The Napa Valley is a mosaic of grassland, woodlands,
vineyards, and other cultivated agricultural crops. The majority of the valley bottomlands are
dedicated to the production of wine grapes. A number of vernal pools still dot
the grasslands on the valley floor and hillsides in the southern portion of the
drainage. The hills in the upper Napa
Watershed support a foothill-woodland community dominated by oak, Douglas fir, and
digger pines. Chaparral dominates
mountain slopes on the eastern side of the valley, while a large portion of the
western valley consists of fir/hardwood forest (CRWQCB, 1992).
A dense canopy of riparian habitat dominated by cottonwoods
and willows historically lined the Napa River along most of its upper
reaches. Today the majority of the
gallery forest bordering the riparian zone is gone, and most of the vegetation
is restricted to near the channel. A
large portion of this area is farmed right up to the very edge of the river
(CRWQCB, 1992). Near downtown Napa, streamside vegetation consists of riparian
scrub and herbaceous vegetation with small patches of brackish marsh (CRWQCB,
1992). Throughout downtown Napa, riprap
and concrete rubble are vegetated with herbs and shrubs (CRWQCB, 1992). Farther downstream, oak and mixed woodlands
line the banks, while diked pasturelands and tidal marsh flank the river to its
mouth at San Pablo Bay (CRWQCB, 1992).
Riparian Vegetation Within the City of Napa:
The following description of vegetation along the Napa River
between Trancas Street and Kennedy Park has been adapted from the USFWS
Coordination Act Report (1993). A list
of flora expected along the Napa River within the City of Napa is presented in
Table 1.
The Napa River from Trancas Street to Lincoln Avenue and
Napa Creek provides freshwater stream habitat, including a narrow but dense
corridor of mature riparian forest and scrub-scrub habitat. Native riparian tree species include
cottonwood (Populus spp.),black walnut (Juglans hindsii), black
locust (Robinia pseudoacacia), valley oak (Quercus lobata), and
California buckeye (Aesculus californica) and high marsh (at or above
MHHW). The low marsh is dominated by
California bulrush (Scirpus californicus); the middle marsh is a mixture
of cattails and bulrushes; and the high marsh is a variety of halophytes,
including saltgrass and baltic rush.
Native shrubs and vines include sandbar willow (Salix hindsiana),
arroyo willow (Salix lasiolepis), elderberry (Sambucus sp.),
poison oak (Rhus diversiloba), wild rose (Rosa californica), and
blackberry (Rubus ursinus).
Nonnative tree and shrub species include eucalyptus (Eucalyptus
spp) and acacia (Acacia spp.).
Nonnative vegetation provides cover for wildlife and perching and
roosting sites for birds, but is of minimal forage value to native wildlife
species.
The riparian vegetation along the Napa River from Trancas
Street to Lincoln Avenue and along Napa Creek provides important forest habitat
components, such as snags and debris, dense cover, and high botanical
diversity. Shaded riverine aquatic
cover, also known as SRA, is an
important component of this habitat along the upper Napa River. SRA cover is defined as the nearshore aquatic
area at the interface between a river and adjacent woody riparian habitat.
The principal attributes of this cover type include
1.
Streambanks
composed of naturally eroding substrates supporting riparian vegetation that either overhangs or
protrudes into the water and
2.
Instream
habitat characterized by variations in depth, velocity, current, and the amount of woody debris.
These attributes provide high-quality feeding areas,
burrowing substrates, escape cover, and reproductive cover for numerous
regionally important fish and wildlife species.
The density and quality of the riparian habitat decreases
downstream from Lincoln Avenue through the City of Napa. Most of the native riparian vegetation along
this portion of the river has been displaced by residential and commercial
developments, rock riprap, and concrete rubble vegetated with nonnative
species.
The riparian habitat downstream from Kennedy Park still
supports patches of brackish emergent marsh vegetation. Marsh vegetation has
been divided into three zones of plant growth by the USFWS: low marsh (mean tide
level or lower), middle marsh (mean tide level to mean higher high water),
mixture of cattails (Typha latifolia) and bulrushes, and the high marsh
with a variety of halophytes, including saltgrass (Disticlis spicata)
and baltic rush (Juncus balticus).
Intertidal mudflats also are present in the vicinity of
Kennedy Park as an exposed linear band of river bottom at low tide between the
river and the riverbanks. Emergent species grow at the landward edges of the
mudflats. Mudflats provide habitat for a
variety of aquatic invertebrates which serve as a primary food source for a
number of fish and animal species.
A limited amount of oak woodland is found in the vicinity of
the City of
Napa. Oak woodland is
characterized by an open tree canopy (10-50% cover) of valley and live oak
species ranging from 25 to 75 feet tall (USFWS, 1993). Oak woodlands in this area support a
herbaceous layer characteristic of annual grasslands and little to no shrub
understory layer.
Rare, Threatened, and Endangered Vegetative Species: Two
plants, Baker's stickyseed (Blennosperma bakeri) and Sebastopol
Meadowfoam (Limnanthas vinculans), were identified during USFWS Section
7(c) Endangered Species Act consultation as listed endangered species that may
grow in the project area. Surveys of the
project area failed to locate individuals of either species. Therefore, no plant species which are
currently listed as
endangered or threatened are considered to be present in the
project area.
Fourteen plant species which are candidates for Federal
listing and/or considered sensitive by the California Native Plant Society may
grow in the Project area (Table 2). Two
species, Mason's lilaeopsis (Lilaeopsis masonii) and soft bird's beak (Cordylanthus
mollis), are listed by the State of California as rare species, but only
Mason's lilaeopsis is present in the project area.
TABLE 1. Flora
Expected Along Napa River Within City of Napa (Compiled from: COE, 1975; USFWS, 1993).
Acacia
Box elder
Yarrow
California buckeye
Anise
Dutchman's pipe
Mugwort
Slender wild oat
Coyote bush
Mule fat
Mustard
Yellow star thistle
Chicory
Bindweed
Bermuda grass
Jimson weed
Salt grass
Eucalyptus
Fig
Gum plant
Foxtail
Black walnut
Baltic rush
Prickly lettuce
Mallow
Horehound
Salt cedar
Bristly oxtongue
Plantain
Fremont cottonwood
Valley oak
Coast live oak
Wild radish
Poison oak
Black locust
Wild rose
Blackberry
Curly dock
Pickleweed
Weeping willow
Sandbar willow
Arroyo willow
Sage
Elderberry
Common tule
California bulrush
Olney bulrush
Alkali bulrush
Milk thistle
Cord grass
California bulrush
Olney bulrush
Alkali bulrush
Milk thistle
Cord grass
Common snowberry
Cattail
American elm
California bay
Wild grape
Spiny clotbur
TABLE 2. Species Considered Candidates for Federal Listing and/or
Sensitive by the California Native Plant Society
Which May Occur in the Project Area
COMMON
NAME SCIENTIFIC
NAME STATUS
Mason's lilaeopsis Lilaeopsis
masonii FC2,
Rare, CNPS 1B
Delta tule pea Lathyrus
jepsonii spp. FC2,
CNPS 1B
Suisun Marsh aster Aster
chilensis var. lentus FC2,
CNPS 1B
Soft bird's-beak Cordylanthus
mollis var. mollis FC1, Rare,
CNPS 1B
Legenere Legenere
limosa FC2,
CNPS 1B
Contra Costa goldfields Lasthenia
conjugens FC1,
CNPS 1B
Marin knotweed Polygonum
marinense FC2, CNPS
1B
Showy Indian clover Trifolium
amoenum FC2,
CNPS 1A
Mudwort Limosella
subulata CNPS
1B
Dwarf downingia Downingia
humilis CNPS
1B
Calistoga ceanothus Ceanothus
divergens FC3,
CNPS 1B
Bakers manzanita Arctostaphylos
bakeri ssp. bakeri FC2
Alkali milk-vetch Astragalus
tener var. tener FC2
Rincon ridge ceanothus Ceanothus
confusus FC2
Sonoma ceanothus Ceanothus
sonomensis FC2
Few-flowered navarretia Navarratia
leucocephala
ssp.
pauciflora FC1
Definition of species status is as follows:
FC1: Category
1 Candidate for Federal listing (Taxa for which the
U.S.
Fish and Wildlife Service has sufficient biological information to
support
a listing as either threatened or endangered)
FC2: Category 2 Candidate for Federal
listing (Taxa for which
existing
information indicates may warrant listing, but for which substantial biological information
to support a proposed rule is lacking)
FC3: Widespread
or not threatened
CNPS 1A: Plants presumed extinct by the California
Native Plant Society
CNPS 1B: Plants rare, threatened, or endangered in
California or
elsewhere
APPENDIX B
REFERENCES
Dyer,
K.R.,1979: Estuarine hydrography and sedimentation, Cambridge University Press: p230.
Cohen, A.N. and Lows, J.M., 1991: An Introduction to
the Ecology of the San Francisco
Estuary: San Francisco Estuary Project.
Jacobs, D.,
1993: California' s Rivers, A Public Trust Report. California State Lands Commission.
Kerr, F. 1996:
Minimum In-Stream Flows, personal report to the WQ/Habitat workgroup.
Knighton D. ,
1984: Fluvial Forms and Processes.
Arnold:New York.
Leopold, L.B.,
1962: Rivers. American Scientist, Vol.
50, No. 4.
Phillip
Williams and Associates and Goodwin, P., 1996: From a Conceptual Design For the Napa River Flood Management Plan Draft
Report.
Riley, A.L.
and Mcdonald, M., 1996: Urban Waterways Restoration Training Manual for Youth Service and Conservation Corps:
Produced by Coaliton to Restore Urban Waters
in cooperation with USEPA and NRCS.
.
San Francisco
Bay Regional Water Quality Control
Board, 1995: San Francisco Bay Basin Plan.
US Fish and
Wildlife Service, 1986. Steelhead Trout;
Biological Report 82 (11.62).
USFWS
Coordination Act Report For the Napa Flood Control Project. 1994.
WET (Water
Engineering & Technology), 1990: Napa River Sediment Engineering Study.
[2] The term steelhead/rainbow trout is used
throughout this document to highlight that these fish are the same species. A
rainbow trout is a landlocked steelhead.
This rainbow trout could have become an anadromous steelhead, migrating
to the ocean, given the proper conditions.
Steelhead/rainbow
trout will not spawn and/or the eggs do not survive when silt/sand/clay become
heavily embedded between the gravels. This is because these fine materials
prevent adequate water flow through the gravels and the dissolved oxygen levels
become too low to support the eggs. Additionally, the young fish (fry) may be
prevented from leaving the gravel.
These lower
oxygen limits are based on the oxygen requirements of the different species of
fish. Fish residing in the estuary are
generally more tolerant of lower oxygen levels than cold water fish such as
steelhead/ rainbow trout.
This is an oxygen standard required by the San Francisco
Bay Regional Water Quality Control Board Basin Plan. The Napa River system will
need to be evaluated to determine if the system currently meets this standard.
This standard is a median value, rather than an instantaneous value as in the
previous standards.
range in values
provided to account for varying temperature and levels of salinity.
This refers to a location where the river is
artificially deepened. This deepening
causes the river to erode the river bed in an upstream direction. The river bed
continues to erode upstream until it encounters something in the river bed
(i.e., a cement sill associated with a bridge or grade control structure) which
will not erode. At this location the upstream erosion stops, but river bed may
scour, thus lowering the downstream elevation relative to the upstream. The
change in elevation may be great enough that it impedes fish migration.
the degree that larger particles (boulders, rubble, or
gravel) are surrounded or covered by fine sediment. Usually measured in classes according to
percentage of coverage of larger particles by fine sediments.
