i. Restoration of access to the upper Elwha Watershed
Hypthesis: The construction of the two dams on the Elwha River, without
fish passage capability, has: 1) reduced chinook salmon abundance, through
the loss of available habitat, 2) reduced productivity through the loss
of habitat, as well as reductions in habitat quality below the dams;
3) has diminished diversity through the loss of spring chinook habitat,
and; 4) has reduced spatial distribution of chinook in the Elwha Watershed
through loss of access to the upper watershed.
Explanation: The primary affects of the two dams on the Elwha River,
constructed without fish passage capability, are intuitively obvious.
The construction of the Elwha Dam in 1911 blocked access of Elwha Chinook
to 95% of their historic range. The response of the population, in terms
of abundance, productivity, and spatial distribution was immediate. Further,
diversity was also immediately affected by construction of the dam, as
it is believed that access to all areas previously utilized by the spring
chinook population (upper reaches of the watershed) has been eliminated.
Other affects on the population caused by the dams may not be as obvious.
For example, the two reservoirs behind the dams have captured nearly
18 million cubic yards of sediment. The affect of this has been the
loss of spawnable substrate below the dams, where cobble and boulder
particle
sizes are the norm. In addition, the dams prevent the normal recruitment
of LWD downstream from the upper watershed. Although some wood is passed
through the upper dam, it tends to splinter when it drops the 200 feet
from the spillway to the channel bottom Finally, summer temperatures
in the lower river appear to be 2 – 4o C higher than normal, as
the reservoirs act as a solar “heat sink”, warming the
river (DOI, 1995). The cumulative affect of these changes is a significant
reduction in the productivity of those fish spawning in the lower river.
The prespawning mortality of adults has been as high as 65%, while
returns
to the river can be explained entirely by hatchery production (although
some natural production likely occurs) (PNPTC, 2003).
Action: Removal of the two dams on the Elwha River is the single most
important step in restoring the Elwha chinook population. Specific habitat
changes expected following dam removal include:
1) Restoration of access by anadromous fish to the upper watershed.
2) Natural recruitment of sediment and wood to the lower watershed and
nearshore environment.
3) Restoration of the natural flow regime
4) Restoration of the natural temperature regime.
It should be noted that following dam removal, the Elwha Watershed will
still not be entirely free of impacts. The lower river system, below
the Olympic National Park boundary, is subjected to many deleterious
affects on the habitat (see below).
ii. Protection of Existing Functional Habitat
Hypothesis: Protection of existing functional habitat in the lower river
is critical to maintaining current river productivity, while other restoration
efforts are implemented and maturing. Loss of existing habitat would
affect abundance, productivity, diversity, and to a lesser degree, spatial
distribution.
Explanation: It is widely recognized that the protection of existing
functional habitat is a viable, and often cost effective, means of maintaining
and restoring salmon populations (Roni et al, 2002). In the case of the
Elwha River, the majority of the watershed is protected in perpetuity
within Olympic National Park. However, the lower river is so hostile
for adult spawning and juvenile rearing, that the protection of functioning
habitat is critical to the survival of the population. In particular,
the functional side-channel habitat of the type directly connected to
the mainstem at both the upper and lower end of the channel is essential,
as this habitat type has been shown to be utilized extensively by spawning
and rearing chinook (Pess et. al., in press)
Actions: The following specific projects have been identified to protect
existing high quality habitat within the watershed:
1) Riparian corridor protection/restoration to Olympic National Park,
through acquisition, ownership and/or private stewardship.
2) Implementation of the land use management plan (DOI, 1994) for Lake
Aldwell properties following dam removal.
3) Regulatory protection measures (Clallam County Critical Areas Code
and other County Regulations , Fish and Forest Plan, DNR HCP, Federal
Forest Plan, Shorelines Protection Act, State Hydraulics Code, Tribal
land use regulations, etc.)
iii. Floodplain Restoration/Constriction Abatement
Hypothesis: Floodplain development has reduced off channel habitat through
dikes, increased flood depths and velocities leading to scour of eggs,
reduced or eliminated riparian vegetation restricted normal channel processes
that create salmon habitat (Pohl, 1999) These changes have reduced abundance,
through loss of spawning and rearing habitat; have reduced productivity
through loss of rearing habitat, and; have reduced diversity by limiting
the number of life history pathways available for fish. Aside from loss
of side-channel habitat, spatial distribution is largely unaffected by
these problems.
Explanation: Several important constrictions exist between Olympic
National Park and the river mouth. Seven features constrict the
channel throughout
this stretch of river and reduce the river’s access to its
floodplain. As a result of these constrictions, the river channel
repeatedly experiences
scouring and filling with sediment throughout these reaches, creating
poor conditions for both adult spawning and juvenile fish rearing.
A few pockets of good quality side-channel habitat occur in these
reaches, and are being used by both adult and juvenile salmonids.
Actions: The following specific projects have been identified to alleviate
channel constrictions and thus increasing corresponding channel meanders
and reducing gradient, velocities, scour, and bank erosion:
1) Remove spur dike at RM 8.5. This 300’ dike provides no flood
control function, but redirects water away from historic side-channels
and potential off-channel sites.
2) Remove gabions and RM 3.1. A series of gabions were constructed
on the west side of the river near the infiltration gallery site. These
structures appear to provide no flood protection, but limit lateral
migration.
3) Remove or reconfigure spur dike at RM 2.9. This structure is located
on the east bank of the river below the one-way bridge. It provides
limited flood control function, but affects channel meander for at
least three meander sequences downstream largely by diverting water
away from its historic meander pattern.
4) Remove push-up dikes between RM 1.5 and 3.0. A series of relict
unreinforced dikes from meander truncation activities have been left
in the Elwha floodplain. These structures still represent barriers
to channel migration.
5) Remove dike at Tribal hatchery infiltration site at RM 1.5. This
provides protection for the current Tribal hatchery water supply. However,
alterations to the LEKT hatchery may make this structure unnecessary.
6) Tribal hatchery outfall at RM 0.3. Spoils from the construction
of the hatchery outfall were formed into a perpendicular dike along
the length of the outfall. Alterations to the LEKT hatchery may make
this structure unnecessary, or breaching of the feature in several
locations may allow alternative pathways for floodwaters to flow.
iv. Estuarine and Nearshore Protection/Restoration
Hypothesis: The loss of nearshore and estuarine habitat from diking,
draining, tide-gates, hardening, and fill has decreased the chinook
and bull trout stocks’ abundance and productivity through the
loss of rearing area and the disruption of the food base of the entire
nearshore
aquatic community. The loss of quantity and function of these habitats
has also reduced the diversity by limiting the number of life history
pathways available for these stocks.
Explanation: Healthy estuarine and nearshore habitat is a critical component
of the chinook and bull trout life history. For chinook, it is not unusual
for newly emergent fry to migrate quickly downstream, to rear in the
estuary (Healy, in Groot and Margolis, 1991). When these fry vacate this
area in early June, at a size of about 70 mm, the habitat may then be
taken over by fingerling chinook smolts which will rear through mid-July
or August. These fry and smolts seem to prefer tidal channels with low
banks and many subtidal refugia (Healy, in Groot and Margolis, 1991).
For bull trout, the nearshore and estuarine environment serve as important
feeding areas for maturing and adult fish.
Much of the Elwha estuary has been altered through diking, and the construction
of the Elwha dams, which altered normal sediment transport processes.
The historic low-gradient habitat of the estuary and salt marsh (those
tidal channels so important for chinook rearing) has been virtually eliminated
at the river mouth. Literally hundreds of acres of this type of habitat
have been lost, when one considers the extent of the isolated beach lakes
to the west and east of the river mouth which likely historically served
as estuarine habitat.
In addition to alterations of the estuary, the nearshore habitat to
the east of the river mouth has been hardened with riprap to prevent
beach erosion. The loss of sediment supply from the Elwha River has
increased the need for this beach hardening, in order to protect infrastructure
(industrial water line, mills, and the US Coast Guard Base). This hardening
and loss of sediment has changed the nearshore substrate from one dominated
by sand and gravel, to one dominated by cobble, with related changes
in the vegetated and fisheries community (USF&WS, 1995).
Actions: The following specific projects have been identified to improve
the quantity and quality of estuarine and nearshore habitat:
1) Remove Elwha dams, to restore natural recruitment of sediment to
the nearshore areas.
2) Implement other nearshore restoration/protection projects from the
NOPLE Strategy and the Elwha Nearshore Workshop.
3) Non-federal levee at RM 0.1. This structure provides limited flood
protection to houses on the west bank of the river, at the river mouth.
However the structure could be altered to provide up to an additional
30 acres of historic estuary habitat
v. Water Conservation, Instream Flow Protection
Hypothesis: Diversion of water from the river system accentuates low
flow condition , decreasing functional salmon habitat (particularly side-channel
habitat), (Orsborn and Orsborn, 1999). Additionally, spawning chinook
tend to be concentrated in mid-channel areas which are subjected to scour
during winter high flow events. These changes have reduced abundance,
through loss of side-channel spawning and rearing habitat; have reduced
productivity through loss of side-channel rearing habitat, and increased
redd scour, and; have reduced diversity by limiting the number of life
history pathways available for fish. Productivity of the population has
also been reduced by high water temperatures. Aside from loss of side-channel
habitat, spatial distribution is largely unaffected by these problems.
Explanation: Water rights for municipal and private purposes in the
Elwha River watershed approximate extreme summer low flows (~210 cfs
water rights vs. ~ 200 cfs summer low flow) (DOI and BOR, 1997). Although
these rights have never been fully utilized, it is not unusual for as
much as one-fourth of the stream flow to be withdrawn during summer low
flow periods. Orsborn and Orsborn (1999) found that available fish habitat
dramatically decreased in the mainstem when flows dropped below 400 cfs.
Coincidentally, this also seems to approximate the flow at which important
side-channel habitat is lost (Pat Crain, pers. Com.).
With the closure of the Rayonier Mill in the late 1990’s, water
use from the Elwha was reduced by nearly 50%. However, even with these
reduced diversions, water withdrawals continue to affect salmon spawning
and rearing habitat.
Actions: The following specific projects have been identified to improve
summer low flows and alleviate water quality concerns:
1) Following dam removal, conduct IFIM flow analysis, to
establish flows necessary to maintain fish production in the Elwha
River
2) Implement other domestic/municipal water conservation projects
and
minimum stream flow requirements found in the WRIA 18 Watershed Plan.
vi. Large Woody Debris Placement
Hypothesis: Lack of large woody debris and debris jams has reduced pool
frequency and depth, reduced sediment storage and stability, and has
reduced side-channel habitat. The lack of large woody debris has also
resulted in increased velocities and associated channel instability,
and bank erosion. These problems have decreased abundance through the
loss of suitable spawning and rearing habitat; have decreased productivity
through the loss of side channel habitat, rearing habitat, and diminished
quality of spawning substrate resulting from scour and bank erosion.
Diversity and spatial distribution are relatively unaffected by these
problems.
Explanation: It is broadly recognized that Large Woody Debris provides
a critical function in river forming processes necessary for healthy
fish habitat. “Large woody debris plays a vital role in maintaining
the distribution and frequency of many diverse flow and cover conditions
in small forested streams and in serving to ameliorate the erosive
forces of channel forming and flood flows. It is the condition created
by the LWD e.g. variable velocity regimes, darkness, and overhead shelter,
that fish seek out, and not the structure itself (Shirvell, 1990).
Juvenile coho salmon and older age classes of steelhead and cutthroat
trout strongly prefer the low velocity habitats various kinds of pools
provide (Bisson et al., 1982). For these salmonids a loss of pools
means almost a proportional decrease in their abundance. Seasonal velocity
shadows cast by woody debris may be even more significant in maintaining
salmonid abundance (McMahon and Hartman, 1989)” Without a healthy
riparian forest in the lower river, recruitment of LWD or creation
of LWD-capture locations is not possible. Any LWD present today is
dominated by smaller pieces, which tends to be deposited outside the
main channel. Few key pieces exist that are like to form jams. Specific
locations on the river have been identified where the placement of
LWD is likely to provide a long-term meaningful change in habitat conditions
in the river, while minimizing any risk associated with placement of
the jams.
Actions: The following specific projects have been identified for LWD
placement:
1) Strategic LWD placement from Elwha Dam to the river mouth
2) Strategically place LWD in Indian Creek
3) Strategically place LWD in Little River
4) Following dam removal, evaluate the mainstem channel between the upstream
extent of Lake Mills and the river mouth, to assess need to strategically
place LWD