Northwest Environmental Advocates--Channel Deepening

Columbia and Willamette Channel Deepening Project, cont.

Channel Deepening and Estuary Habitat

The Vital Columbia River Estuary
A History of Habitat Loss and Habitat Alterations
Deepening Threatens Further Deterioration of Estuarine Habitat
Northwest Science Center Report

The Vital Columbia River Estuary

From the mouth of the Columbia River, tides move cold salt water upriver beneath the river's fresh water outflow. Where the two mix and mingle is called the estuary, roughly 38 miles of complex flow patterns supporting an intricate food web and varied fresh and salt water habitat for wildlife. The turbulent area in the river where the strong tidal forces interact with the fast-flowing fresh river waters creates a cloud of organic matter and resuspended sediment from the riverbed. This is called the Estuarine Turbidity Maximum (ETM,) and it supports populations of small organisms including zooplankton that form the base of the estuary food web.

Features of the estuary include islands, peninsulas, tidal channels, large woody debris, plants, floodplains, sandflats, shallow bays, marshes and swamps. These features hold nutrients and provide nursery habitat for the many tiny organisms that support larger organisms like salmon, bald eagles, and humans.

For salmon, the estuary offers protection from predators, food sources, and a place to make the transition from fresh to salt water. Slack water habitat with vegetation and organic debris provide salmon a place to escape from predators. Salmon use the estuary to forage for food that will fortify them against disease and predators at sea. Growth is rapid while the fish reside in the estuary; chinook salmon can triple in size over a period of two months. During their transition from fresh to salt water, enough habitat must be available for the fish to move freely up and downstream with the ever-changing salt water gradient, …and still have places to escape predators and forage for food. By providing these critical survival tools, the estuary and its associated features provide vital nursery grounds that prepare migrating fish for their departure to the Pacific.

Salmon populations have persevered under the varying conditions of freshwater, estuarine, and ocean environments by evolving different timing and strategies of migration and rearing. This means that different stocks of salmon will react differently to different estuary conditions, such as floods, temperature fluctuations, prey availability and predation. The flexibility also helps salmon survive human induced changes in habitat caused by dams, poor forestry techniques, and water diversions for irrigation and power production.

What allows salmon's evolved flexibility to work is the availability of diverse habitat and food sources. When estuary habitat is altered, salmon stocks that evolved to depend on the existence of that particular habitat are displaced. The fish are forced into less suitable habitat and required to compete with other fish populations, thus weakening those species as well. These discoveries have led scientists to realize the true value of a diverse and healthy estuary in the survival of endangered salmon and other estuary species.

A History of Habitat Loss and Habitat Alterations

The estuary has lost 75% of its wetlands due to diking and filling activities. This leaves the estuary more vulnerable to pollution from industrial discharges and run-off, and decreases the capacity of the estuary to support fish and wildlife. Before the estuary lost significant amounts of riparian areas, marshes, swamps, and other slack-water habitat, salmon benefited from what is known as a "macro-detrital" food chain: a food chain based on the presence of marshes, woody debris, and the resulting volume of decaying matter that supported a thriving population of small organisms called Corophium. As a consequence of the degradation of this type of habitat, the Corophium-based food chain has been replaced by the less productive "micro-detrital" Estuarine Turbidity Maximum (ETM).

Historically, the spring freshets that flowed through the estuary carrying salmon smolts to sea were roughly 50% greater than they are now, due to the extensive network of hydroelectric dams in the Columbia River Basin. These decreased spring flows along with decreased sediment discharges have fundamentally altered and reduced the plume that once extended out far into the ocean from the mouth of the river during the spring and summer months.

Deepening Threatens Further Deterioration of Estuarine Habitat

Current Corps' estimates for the channel deepening project predict further losses of 200 acres of agricultural lands, 67 acres of riparian habitat, and 20 acres of wetland habitat, all of which will be smothered beneath almost 100 million cubic yards of sediment. In addition, of the total 418 million cubic yards forecasted for removal during the 50-year project, the Corps plans to dump 7.25 million cubic yards of dredged spoils within a three mile stretch of the river itself in the first 20 years, raising the estuary floor by 20 feet over 400 acres. Much of this area is deep-water habitat used by sturgeon and their primary food source, invertebrates that live on the river bottom.

The extensive alteration to the estuary resulting from the channel deepening project will have an impact on the biological productivity of the estuary in ways that extend beyond the direct impacts of dredging operations. The deeper channel can cause the wedge of cold salt water that protrudes into the estuary to shift in location. This shift can cause the ETM to move as well, both vertically and horizontally, changing the availability of suitable habitat for migrating salmonids. Despite increasing data on the estuary's ETM, the Corps' Final Environmental Impact Statement (Final EIS) presents no conclusive documentation that these detrimental effects will or will not occur. Nor does the Final EIS address the cumulative effects of past channel deepenings based on historical data and reasonably foreseeable trends in the future.

Changes in the ETM can also have impacts on non-aquatic species, a point the Corps ignored. The U.S. Fish and Wildlife Service believes this could have serious consequences on habitat and prey availability, especially for sturgeon, which are believed to be more abundant in deep areas of the river. However, there are little data available about the potential impacts of this planned activity, and the Corps has not evaluated it. Instead, the Corps proposes to study the impacts of dredging as it takes place. This demonstrates that the Final EIS does not adequately evaluate the impacts of current dredging practices and those that would precipitate from further channel deepening.

NMFS SCIENCE CENTER REPORT

The National Marine Fisheries Service (NMFS) called upon the Northwest Fisheries Science Center for an independent analysis of the potential for impacts on threatened and endangered fish in the Lower Columbia River that would result from the channel deepening project. The science center report, released two weeks before NMFS issued its own Biological Opinion, stated that the deepening project is "an incremental insult to an estuarine system that has been grossly altered by previous dredging," and that the most predictable impacts from the proposed action rest in changes to the physical dynamics of the estuary. The scientists concluded that the project has the potential to change circulation patterns, influence the location and timing of sea water intrusion, alter rates and locations of sedimentation, and cause changes to the Estuarine Turbidity Maximum (ETM). (see above)

Though the scientists believed that those changes would have biological ramifications, they could not predict the degree to which they would cause effects on endangered fish species and their prey, and strongly advised NMFS to take a precautionary approach when drawing up its Biological Opinion. Their rationale was simple: at the time planning was begun for this project, only 3 runs of Columbia Basin salmon stocks were listed. Now there are 12, with another proposed for listing, and the estuary has been widely identified as a critical component of their survival.

The report criticized the Corps' Final Environmental Impact Statement (EIS) analysis for not taking into account the cumulative effects and history of dredging activities in the estuary, and suggested that using the historical baseline could substantially alter the Corps' assessment of impacts on salmon. In an appendix, the science center report addressed the matter of inaccuracies in the forecasts of dredged materials. The primary issues raised in the report were:

It is clear that the estuary provides tangible benefits to salmon survival, but it is not clear what features of the estuary benefit salmon.
Changes in the physical features of the estuary combined with likely flow scenarios need to be included in evaluation of impacts to listed species.
The physical changes to the estuary will alter the amount and type of nutrients and the type of organic matter that feed into the estuary, influencing prey availability and the timing and abundance of the small organisms that support larger life forms like fish and birds. These factors need to be more appropriately considered and weighed with respect to salmon recovery potential.
The analysis of changes to the location of salt water in the Final Environmental Impact Statement was inappropriate because it limited evaluation to the effects of salinity changes on immobile aquatic plants and invertebrates and discounted the critical role of salinity changes for mobile species like fish.
Turbidity levels may be sufficient to increase straying of returning adult salmon, but was not included in the Corps' analysis.
Contaminated sediments from upriver sites could be expected to settle out in depositional areas in the estuary, but this risk was not adequately assessed in the Final EIS. Studies have shown that exposure to contaminants increases risk of disease and decrease growth rates in fish species. In fact, salmon are so sensitive to toxins that they are used in standardized testing procedures to measure the toxicity levels of hydrocarbons.

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