d a m r e m o v a l joseph c. greene research biologist greene environmental services may 2006...

D A M R E M O V A L

Joseph C. GreeneResearch Biologist

Greene Environmental ServicesMay 2006

Panaceaor

Pandorafor Rivers

Original background illustration from: Gregory Stewart, Ph.D. http://www.collbett.org/greg/

Some Facts Hydropower is the most plentiful and efficient renewable energy resource. It contributes more than 90 percent of all renewable electric energy produced in the U.S.;

If all the energy produced by hydropower was produced by coal instead, pollutants from coal would increase by 16 percent;

A third of countries depend on hydropower for over half their electricity, and over a third of irrigated land depends on dams; and,

much of the world's food is subsidized by cheap irrigation water provided by dams.

The reservoir or lake created by a dam may cover many thousands of acres of forest that once served as habitat

for wild animals and plants.

The Argument Against Dams

Large dams have contributed to:

the extinction of many fish and other aquatic species;

the disappearance of birds in floodplains;

huge losses of forest, wetland, and farmland; and,

the erosion of coastal deltas.

Dam RemovalPanacea or Pandora for Rivers

The debate is playing out against a backdrop of power crises, cycles of flood and drought, endangered ecosystems, and changing societal expectations and demands for water.

Grant, G., 2001, Dam Removal: Panacea or Pandora for Rivers?, Hydrological Processes 15, 1531-152.

The idea that dams are not necessarily permanent features of the landscape, but can and should be removed, has emerged as a rallying cry, political

lightning rod, and unparalleled scientific opportunity for understanding the behavior of rivers

Why is dam removalemerging as an issue?

Increased hazard of aging dams;

Open policy window because of the large number up for re-licensing;

Response to concerns about physical fragmentation of river systems;


Why is dam removalemerging as an issue?

Response to concerns about threatened and endangered fish species;

Response to calls for the return to a more “natural” hydrologic regime to restore ecological

and geomorphic (surface configuration ) function; and,

Finally, dam removal has great symbolic value in terms of representing our good intentions toward our environment.


Dam Removal

A striking conclusion from a number of recent workshops was ………………

“We actually know very little

about the biological and physical consequences of removing dams”.


The response to dam removal is intrinsically complex!

Because of the longevity of dams, channels typically adjust to the altered hydrologic and

sediment transport regimes that dams impose;

consequently,

Dam removal itself represents a land surface re-configuration disturbance to a quasi-

adjusted river system.


“We know that this disturbance tends to propagate both upstream and downstream through cascades of

erosional and depositional processes that are coupled in time and space.”

“Typically, the upstream response

drives the downstream response.”

Stewart, G, S. Hayes, G. Grant, and C. Bromley, 2003, Where did all the dam sediment go, Predicting the effects of dam removal on channel morphology and ecology.

From: Gregory Stewart, Ph.D. http://www.collbett.org/greg/


Key upstream unknowns are:

The rate and mechanisms of removal of sediment from the upstream

reservoir in relation to …..

Flow regime;

Grain size;

Channel and deposit geometry;

Method of dam removal.


Downstream of the Dam:

Sediment will be transported through a channel system already

altered by the presence of the dam.

A complex array of storage features and associated residence times limits our ability to accurately predict how long it will take

for sediment to be routed downstream.


Downstream of the Dam:

Even more challenging to predict are the interactions among …

Sediment transport and deposition;

Vegetation establishment;

Responses to aquatic ecosystems to elevated sediment loads; and,

Transformed channel morphology.


Needs:

On how dams function in the landscape;

On impacts and consequences of past removals, including analysis of dam removal analogues, such as natural and artificial dam failures; and,

Studies that are rigorous pre- and post-removal monitoring schemes for those dams slated for removal.

We need coordinated retrospective laboratory and field studies ….

The studies should be targeted at resolving key uncertainties.


From Past Work on theEffects of Dams on Rivers

“We know that all dams

are not

created equal!”

The Same May Be TrueFor Dam Removal

Some will stimulate dramatic effects on river and ecosystem processes;

Others will have no effects;

Some may open Pandora’s boxes of new problems.


The National Academies' National Research Council committee estimated that

the research, monitoring, and remediation outlined in its report, on the Klamath River

Basin, would cost about

$25 million to $35 million

over the next five years ….

excluding costs for major projectsexcluding costs for major projectsSUCH AS DAM REMOVAL!SUCH AS DAM REMOVAL!

National Research Council, 2003, News Release, Broader Approach Needed for Protection And Recovery of Fish in Klamath River Basin, http://national-academies.org

Grants Pass Daily Courier, "Savage Rapids Total: $30 Million."

Savage Rapids DamRogue River, Oregon

The design for the removal of Savage Rapids dam is proceeding, slowly. The

completion date isn't moving up, but the cost sure is.

The Bureau of Reclamation estimates a cost of $30 million to remove part of

Savage Rapids Dam and install pumps

J. C. Boyle Dam Copco 1 Dam Copco 2 Dam Iron Gate Dam

Klamath River Dam Removal Investigation

G&G Associates developed a report for American Rivers, Trout Unlimited, California Trout, Friends

of the River, and the Klamath River Intertribal Fish and Water Commission.

G&G Associates, 2003, Investigation of Removal of Four Lower Klamath River Dams, J. C. Boyle Dam, Copco 1 Dam, Copco 2 Dam and Iron Gate Dam

Numerous issues require more investigation before final costs estimates can be completed. The objective of this report is to determine whether removal of the

four lower Klamath River dams is feasible from a construction and cost perspective.

The scope of this investigation is feasibility level only.

Specific information regarding volume, location, and size of trapped sediment, specific dimensions of structures, nature

and extent of water use downstream of the dams, and location of spoils sites was either not available or developing such

information was beyond the scope of this report.


Studies conducted as part of the hydropower re-licensing proceeding indicate that cumulatively, all four

dams trap approximately 14.4 million 14.4 million

cubic yards of sedimentcubic yards of sediment, of which approximately 87% is silt and clay

and 13% is sand or larger material.


Information regarding the volume of sediment trapped appears to be well

developed but information regarding grain size distribution of trapped sediment appears

to be insufficient to determine how quickly the eroded sediment would move through

and out of the river system.

Cost estimates developed for this study are based on the assumption that sediment

trapped behind the dams would be naturally eroded downstream.


Based on assumptions stated in this report, the cost for removal would be $19.2, $1.9, $8.5, and $6.2 million respectively for Iron

Gate, Copco 2, Copco 1, and J.C. Boyle dams.

Review of available information regarding the dams, trapped sediment, and river

characteristics indicates that removing the dams is feasible and that the cost would be

approximately $40 million.


Thomson, 2005, Effects of removal of a small dam on downstream macroinvertebrate and algal, J. N. Am. Benthol. Soc., 2005, 24(1):192–207

There is little empirical data on which to base predictions about ecological responses to dam

removal. Less than 5% (~20) of all dam removals in the United States have been

accompanied by published ecological studies.

Most of the dams removed to date were relatively small structures (usually <15 ft. high).

Effects of removal of a small dam on downstream macroinvertebrateand algal assemblages in a Pennsylvania stream


The authors examined the responses of benthic macroinvertebrate and algal assemblages in

downstream reaches to the removal of a small, run-of-river dam on Manatawny Creek, Pennsylvania.


Benthic macroinvertebrates, algae, and habitat characteristics were monitored upstream and

downstream of the dam for 4 months before removal, 3 months after partial removal (i.e., when the

impoundment was largely eliminated but sediment remained trapped behind the remaining structure),

and 12 months after complete dam removal.



Macroinvertebrate density, algal biomass, and diatom species richness declined significantly downstream of the

dam following complete dam removal.

Downstream impacts occurred only after the dam structure had been completely removed and

sediments had been transported downstream from the former impoundment by high flows.

Our results and other studies of dam removal suggest that downstream sedimentation following dam removal can reduce densities of macroinvertebrates and benthic

algae and may reduce benthic diversity,

Biotic impacts persisted for the duration of the study (12 months after complete removal).

but for small dams such impacts may be relatively minor and will usually be temporary.


Mouth of the Klamath River from Requa, CA.

d a m r e m o v a l joseph c. greene research biologist greene environmental services may 2006...

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