Week 12 - Physical (Flap Gates and LWD) and Chemical in Estuaries Flashcards
Tidal Gates - Salinity Gradient
Changes to estuary channel form will change salinity gradient
Additional salinity impacts due to tidal flap gates, primarily installed for agriculture, also flood control
Tidal Flap Gates - Traditional
Tide gates are doors or flaps mounted on the downstream end of culverts in dikes or under roads, that allow upstream waters to drain while preventing inflows from tidal surges or flooding
Flap opens with positive hydraulic head
Flap closed most of the time
Fish passage?
Salinity/fluvial gradients?
Tidal Flap Gates - Upgrade Options
The critical issue is fish passage. The secondary issue is circulation and restoring fluvial/salinity
gradient.
Tide gate has buoyant door which floats on the incoming tide and remains open until the water elevation reaches the floats, which closes the door.
The door is open most of the time
Columbia River - Salmon Recovery
Example of jetty (levee) breach and removal of flap gate to restore fluvial/tidal gradients and connectivity to off-channel marsh habitat
Evaluation Criteria -
1, Opportunity/Access for salmon
2. Capacity/Complexity
3. Certainty of Success (self- maintaining, proven, subjective)
Pitt-Addington Marsh
Four tidal gates, entirely diked marsh
Former floodplain of the Pitt River
Upper chinook (COSEWIC)
Widgeon Sockeye (endemic)
Incredible restoration opportunity!
LWD in Estuaries - Where does it come from?
LWD is transported from the upper watershed to the estuary/ocean
Then ‘recycled’ by the actions of tides, wind and currents
The ocean is another source of wood
Winter storms blow wood into river mouths and onto
coastal beaches
Where did all the LWD go?
Snags and driftwood presented obstacles for river traffic, fishers, etc.
US Army Corps of Engineers during the late 1800’s removed wood to improve and maintain the navigability of rivers
Snags removed from rivers by US Army Corps of Engineers, 1891-1917
Woody debris in Restoration - Ecological functions
release organic carbon
provide habitat for fish and invertebrates
sediment accumulation
Estuary Wood Dynamics
Wood-boring crustacea (gribbles)
Bivalve mollucs
Marine fungi
Bacteria
Wood recycling - isopods
Wood-boring isopod crustacea (gribbles) of the genus Limnoria are major reducers of wood Pacific Northwest estuaries
Two species involved, L. lignorum, the endemic northern species, and L. tripunctata, the introduced species that is predominantly southern in distribution
Wood Recycling - Wood-Boring mollucs
Other than gribbles, the only shallow-water, wood-boring animals in the Pacific Northwest are two species of shipworms.
The most important reducers of wood in estuarine and shallow marine waters of PN region
Bankia setacea
most common species of shipworm, a coldwater native
the major marine, wood destroying animal in open ocean, embayments and estuaries
Terado nevalis - a smaller introduced warm water species of restricted distribution in PNW
Wood Recycling - Fungi
Marine fungi degrade cellulosic materials, but their ability to rapidly or extensively degrade large pieces of wood appears to be much less than that of terrestrial fungi
Wood Recycling - Bacteria
The role of cellulose-degrading bacteria in the sea is obscure, but many species of marine bacteria have been identified as active degraders of cellulose
Log Booms in the Fraser Estuary
Legacy of historical forestry practices - convenient, slow decomposition
Regulations prohibit boom grounding, but no enforcement
Significant damage to marsh habitat from repeated grounding with mixed tidal cycle
Will require a govt policy shift and bold, courageous action to force industry change
Campbell River Estuary
Heavy industry, dredging, infilling, log storage
1999 City, Nature Conservancy, Tula Found. Purchased Baikie Island
Land purchases
40,000 m3 of fill for habitat creation, shoreline restoration
Community stewardship with Greenways Land Trust provides funds for ongoing maintenance
Final Note on Wood
In estuaries, fast carbon is eel grass decay; medium carbon is decaying salmon, and slow carbon is from decaying LWD
But decay of LWD in estuaries is many times faster than in freshwater, and in the forests
Fresh water – LWD decay is slow
Terrestrial forest – LWD decays is medium – but can still last 100+ years
Estuaries - LWD decay is relatively fast due to crustaceans and molluscs
LWD for Estuary Restoration
- Most people have no idea how much wood used to be in estuaries
- The effects of LWD on fish growth, survival and production has not been demonstrated. Many pressing research questions.
- Treat wood applications in estuaries as an experiment. Rigorous monitoring of hydrologic, geomorphic and fish community responses.
- Use whole logs with root wads to ensure the wood remains in place, or attach logs to the ground using anchors or ballasted with boulders (this tech is going out of “fashion”)
- Wood structures will not last long in an estuary so replacement required at ~10-15 year intervals
Chemicals in Estuaries - Legacy Contaminants
Direct sewer outfalls and combined sewer overflows discharged into estuaries and industrial effluents were building a legacy of :
Metals - chromium, cadmium, copper, lead, zinc
pentachlorophenol (PCP), polychlorinated biphenyl (PCB), polycyclic aromatic hydrocarbons (PAH), halogenated hydrocarbon contamination
Urban/Legacy Contaminants
Non-point source urban run-off continues to be a problem in restoring industrialized estuaries
Mackay Creek Estuaries
stainless steel push corer to collect cores
cores extruded on site in 1 cm increments
Source of copper
Brake pads - 5% copper, contributed 47%
Brick and wood siding - contributed 27%
Copper and salmonids
high concentrations of copper can be toxic
lower concentrations can damage olfactory sensors (important to fish for feeding, predator avoidance, schooling, migration, recognition of natal spawning grounds and mating)
Impacts of remediation
Restoration team must decide whether the site is suitable for restoration in its current state
Some sites might be so contaminated they cannot be restored without a site decontamination step or they cant be “restored” but rather “remediated” or “mitigated”
Super-Fund sites in Washington
48 superfund sites, 17 others have been cleaned up and remove from the list
Elliot Bay Action Plan
Pacific Sound Resources (PSR) site, 83 acres, 58 are which are tidal
wood treating facility released creosote and related hazardous contaminants 1990 - 1994
- soil and sediment excavation
- construction of upland slurry wall
- a low permeability cap
Restoration Challenges with chemicals
- Restricted land access
- Abandoned properties and mess
- Established industry
- Limited opportunities
- Cost of restoration prohibitive
- How to attract funding and resource for these projects?
Change your template with restoration with chemicals
Rather than “use nature as your template”, you may need an entirely “new template”
Consider rehabilitation or mitigation as often the best that can be expected
Recognize that impaired ecosystems will always require active, long-term management of this new ecosystem, support native species, and at least emulate a naturally functioning system
Human Element and Going forward
Public values can completely redefine urban restoration, where it is often valued more for its passive recreational uses than the less-defined concept of ecosystem function.
i.e. Make a canoe park, rather than restore natural function
need to counter humanistic, community-oriented, and recreational demands on an estuary with economic arguments based on natural capital and ecological services recovered by restoration
Duwamish Estuary
Restoration actions in the Duwamish River estuary over the past decade have in aggregate, formed a landscape approach consisting of clusters of sites in strategic locations along the estuarine gradient that are perceived
to be critical for migrating juvenile salmon
Cumulative restoration projects may provide habitat linkages that create landscape-scale habitat function for migrating salmon that exceeds site-specific levels
Significant outcome in the Duwamish River estuary is not ecological or geochemical, but…
Citizen support, investment, and direct involvement in estuarine restoration has flourished. Citizens taking “ownership” will
then take care of it
Final Lessons with Chemicals in Estuaries
- Understand key processes that originate from the watershed and receiving coastal waters, as well as from within the estuary
- Use landscape connectivity, both proximally and at regional scale, to maximize the constrained array of restoration options available.
- Explore innovative and adaptive approaches
- Plan for long-term stewardship, with small and many sites over the years
- Expand social and cultural connections, institutional commitments
- Document how and why estuary ecosystem function can persist, to change perceptions about whether it’s worthwhile investing in restoration
- Promote ecologically functioning estuaries as a social, economic, and cultural investment
