PNW Pacific Northwest INSIDE Research Station Relicensing Scrutiny ...... 2 Context is Everything ...... 3 Scaling up the Flood Event ...... 3 FLOODS, Floods, and Floods ...... 4 Is This Predictable? ...... 4 Facing the Relicensing Process ...... 5 FINDINGS issue twenty-five / june 2000

“Science affects the way we think together.” Lewis Thomas

SEEN ONE DAM, SEEN ‘EM ALL?: THE SURPRISING STORY OF THE

IN SUMMARY In the next few decades, hundreds of private dams will be relicensed by the Federal Energy Regulatory Commission. Many of them are on or influence Forest Service lands. Relicensing requires rigorous technical assessments of the effects of dams on critical resources, including channels, aquatic habitat, water quality, and recreation. Dams differ widely in their Photo credit: Portland Electric General influence on these resources, and Deschutes River just downstream of Whitehorse Rapids. The landslide dam that formed at ➢ Whitehorse Rapids breached and released floodwaters over the terrain shown in the area predicting their consequences is about in the right center of the photo. critical. Researchers at the Pacific Northwest Research Station examined “You can’t step twice Dams differ widely, he notes, in their influ- the effects of the Pelton-Round Butte ence on downstream resources, depending into the same river.” on their geologic—and ecologic—setting and Dam complex on the geomorphology of Heraclitus 513 B.C. the degree to which their operation modi- the Deschutes River in central . fies predam flow and sediment regimes. The purpose was partly to study the n the heated debate about removal of dams from the Columbia and Snake The Deschutes River of effects of this particular dam on this spills into the between The I Rivers, an interesting twist emerges particular river, but also to develop from the rapids of another famous river. It Dalles and John Day Dams and is home to and test theory, concepts, and tools that turns out that not all dams are created the Pelton-Round Butte Hydroelectric equal. Project. A geomorphological study of the would apply to dam assessments privately owned three-dam complex was anywhere. The results—minimal “We’ve learned that dams must be evalu- commissioned by current license-holder ated on a case-by-case basis, with peer- Portland General Electric (PGE). The U.S. impacts on the channel downstream— reviewed science as a primary tool,” says Geological Survey, PNW Research Station, surprised researchers and revealed Gordon Grant, a research hydrologist with and Oregon State University contributed to how close are the lines between the PNW Research Station in Corvallis, a scientific review of the downstream physi- Oregon,. “It is scientifically unsound simply cal effects of the dam. geomorphology and hydrology in this to tar them all with the same brush.” river system. “This study yielded some of the biggest research surprises I have encountered,” says KEY FINDINGS Grant, who led the Deschutes study. “We didn’t know going in where the Deschutes • The Deschutes is a remarkably stable river, and was so before dam construc- was in the spectrum of downstream tion, based on analyses of bed-load transport, historical channel changes, and effects. But we found that the change in longitudinal patterns of sediment size.Thus channel position is largely fixed; flow and sediment regimes before and after islands, bars, and flood plains are well vegetated; and record floods cause only the dam complex was built were minor. minor physical changes. Consequently, changes to the channel itself • Because of the intrinsic stability of the Deschutes basin, the dam complex were almost undetectable.” studied has had virtually no detectable effects on the physical structure of After more than 40 years, he says, there the downstream channel. No evidence of increased channel erosion, changes are few obvious effects to channel and in grain size, or other channel changes could be found. valley morphology that are traceable to the dam complex. Researchers attributed this • These results, surprising in comparison with other rivers, are consistent with to the fact that the dam did not substan- the magnitude of changes predicted by a conceptual model, which relates the tially change the flow of the river, and type and extent of geomorphic change downstream of a dam to the relation although it trapped sediment, the back- between the predam and postdam flow and sediment regimes. ground supply from the surrounding area • In spite of decadal stability, the Deschutes has experienced previously unrecog- upstream of the dam had always been so nized gargantuan floods many times during the past 100,000 years from events small anyway that the effects brought about including volcanic eruption, collapse of glacial dams, and large landslides from by the dam are only minor. the walls that temporarily dammed the river.

• Related fisheries work suggests that the islands and surrounding back chan- nels created by large and rare floods provide core habitats for diverse fish populations.

RELICENSING SCRUTINY on-Federal dams are licensed— plain habitats will be considered by FERC and relicensed, or not—by the or by Forest Service land managers, says Purpose of N Federal Energy Regulatory Com- Grant. Whether restoration is needed, PNW Science Findings mission (FERC), usually for 30 to 50 years. however, is largely based on what the To provide scientific information Relicensing thus requires a long-term view effects of the dam actually are. Clearly, he to people who make and influence and rigorous technical assessments of the says, science-based assessments of dam- decisions about managing land. effects of dams on critical resources, includ- imposed regimes on downstream resources ing channels, aquatic habitat, water quality, are critical to managers, power companies, PNW Science Findings is published and recreation. and all users of regulated, or dammed, monthly by: rivers. Pacific Northwest Research Station In the next few decades, hundreds of USDA Forest Service private dams face relicensing; many of these What puts this famous river into a category P.O. Box 3890 are on or influence Forest Service lands, that allows a dam to block its normal flow Portland, Oregon 97208 which gives the Forest Service “condition- and yet produce virtually no detectable (503) 808-2137 ing authority;” that is, it can specify some of effects on the physical structure of the Sherri Richardson-Dodge, Editor the conditions of the licensing process. downstream channel? [email protected] In the licensing process, aggressive efforts Carlyn Mitas, Design & layout to supplement sediment loads and possibly [email protected] design floods to restore channel and flood-

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2 CONTEXT IS EVERYTHING “ he Deschutes River is fed by a large hydrologic sponge, otherwise LAND MANAGEMENT IMPLICATIONS T known as the Cascade mountains, a porous environment that makes the river • Only by examining historical and modern changes to and processes operating behave much like a big spring-fed creek,” in the physical channel and riparian environment can the true effects of a dam Grant explains. Thus most precipitation be evaluated, and mitigating measures put in place. enters the ground-water system, rather • The conceptual model may provide managers with a diagnostic tool for distin- than flowing through well-defined channels. guishing different types of dam effects. Specific resources likely altered by dam The geology of the Deschutes basin has operations can be targeted for more intensive studies. dictated its sediment and water regimes. Key attributes of the basin include a • Rivers and dams are complicated, each requiring its own close scrutiny. remarkably stable hydrologic system, a • Independent scientific investigations are an important part of relicensing and muted response to weather events, and should be designed to pass rigorous standards of technical scrutiny and review. little sediment production from vast areas of the basin.Together, these factors—as well as climate, vegetation, and land use— ultimately affect critical resources such as To give the basin’s hydrologic stability control the quantity, timing, and type of aquatic habitat,” Grant says. meaning, consider that the average maxi- sediment transport through the basin. mum flow for a given year in the As early as 1923, the U.S. Geological Survey Deschutes, both before and after the dam The links between the overarching geology recognized the Deschutes River as having complex was installed, is reached when the and hydrology, which are fundamental one of the most stable hydrologic regimes river carries only about three times as controls, and local channel and habitat anywhere in the country, as reflected in the much water as it does at low flow. In other conditions, operate through a set of hierar- magnitude and limited variation of the flows rivers, this factor can be closer to 100 chical relations from the basin scale and the throughout the year. The flow regime in times; in other words, a winter peak flow millennial timeframe, down to instream turn affects sediment transport from the might be 100 times higher than a summer habitats and the most recent high-water river’s surroundings—the boulders, rocks, low flow. event. gravel, and sand that are routinely carried “This is a remarkable system in that the downstream by streams and rivers. Because One result is that this river responds to what geology plays right through to the river that the flows are so stable and generally remain we humans quaintly call “historic floods” the fish see. Understanding these links at levels below what would be required to with something of a geomorphic shrug. allows us to understand how any changes move much sediment, the amount of sedi- to the system may ripple through it and ment moved also stays low.

SCALING UP THE FLOOD EVENT ost of the building activity of a Subsequent research of archives, and also boulders, islands, and very big gravel bars. river normally occurs during first and incomplete observations of the “What on earth must it take, I wondered, M floods. Boulders are moved, geologic record of flood deposits in the to get this river to respond?” woody debris piles up or changes position, Deschutes River canyon, revealed that at Well, the answer is, REAL floods. Gar- gravel bars are made and unmade and least 8 to 10 floods of comparable size to gantuan ones, beyond our imagining, and moved, and sand is carried from one reach the 1996 flood have occurred in the last over scales of tens of thousands of years, to another. Grant has previously character- 1,000 years. If the river’s response to these not mere centuries. ized the flow of rivers and their defining floods was similar to that in 1996, there flood events as “decades of boredom punc- would be some small changes to islands and Grant called in Jim O’Connor of the U.S. tuated by hours of chaos.” channel banks, erosion of riparian zones, Geological Survey, a world authority on and deposits of wood and fine sediment on large floods, and together they took “For the Deschutes, however, it’s more like low surfaces adjacent to the channel. another look at the area. What happened, millennia of boredom punctuated by all hell he says, is that they began to adjust their breaking loose,” he laughs. “You see, I flew But nowhere after the 1996 flood, Grant eyes to what they were seeing. over that river after the 1996 flood, one of emphasizes, was there substantial channel our historic, so-called 100-year events. migration or alteration of the valley bottom When the game of musical chairs was over, geometry. When he had ridden down the and everybody sat down, there was really river at other times, however, he had seen very little change to the river.” much evidence of flood action, such as large

WRITER’S PROFILE Sally Duncan is a science communications planner and writer specializing in forest resource issues. She lives in Corvallis, Oregon.

3 FLOODS, FLOODS, AND FLOODS he Deschutes River has historically (buildup) features, and downstream flood Analyses of movement of materials along experienced floods caused by liter- features all can be reasonably linked,” says, the riverbed, historical channel changes, and T ally every mechanism known to O’Connor.“Boxcar Rapids also may be part longitudinal patterns of sediment size were man, Grant says. This includes volcanic of an accumulation of huge, 20- to 30-foot completed by former Oregon State eruption, collapse of glacial dams, and large diameter boulders, deposited during the University graduate students Ellen McClure landslides from the canyon walls. breach of the nearby channel blockage.” and Heidi Fassnacht. These studies under- score the remarkable stability of the “It turns out that the well-known rapids on The size of materials transported along the Deschutes: channel position is largely fixed; the river, such as Whitehorse and Boxcar Deschutes and their elevation above the islands, bars, and flood plains are well vege- Rapids, lie at the base of what were once present river level seem to require tated; and floods such as the one that huge landslides. Huge landslides, that discharges several orders of magnitude occurred in 1996 cause only minor physical blocked the river and backed it up as much greater than historical discharges, the changes. as 20 miles,” Grant says. Dams formed by researchers agree. This indicates either the landslides are intrinsically unstable and typi- type of catastrophic release suggested or a “A meteorological flood like in 1996 does cally fail rapidly and catastrophically soon significantly different climactic regime. not have the energy to make a mark on a after formation, thereby resulting in large channel that has been sculpted by huge Compared with other, more “normal” discharges immediately downstream from events,” says O’Connor. “The geometry has rivers, the Deschutes has experienced so- the breach. been set by the large-scale floods, and called sediment-moving flows—flows capa- these smaller events just dress it up a little.” “On the Deschutes River, several such ble of moving riverbed materials—only dam-break floods have occurred—the land- once every 5 to 10 years, Grant says. A slide at Whitehorse Rapids is one where typical alluvial river might do this two or the landslide, upstream aggradation three times per year.

IS THIS PREDICTABLE? he mild reaction of the Deschutes River to most flood events, and to Channel aggradation Poorly developed armor T the flow constraints imposed by a High Textural shifts at confluences Textural shifts at confluences dam complex, contrast sharply to down- Island and bar construction stream effects of dams on other large rivers, such as the Snake or Colorado. Textural adjustment Well-developed armor There, ample documentation shows exten- Low Gravel cementation Bed scour sive erosion of beaches and sandbars Below-dam Gravel compaction Bar and island erosion downstream of dams caused by reduced sediment supply No change sediment supply and transport. Low High Given that this river’s history has so clearly Frequency of bed-mobilizing flows dictated its current sediment-transport Conceptual model of the channel below dams in relation to the predam and postdam flow

responses, is there a way to predict a river’s ➢ regime and frequency of bed-load transport. reactions to interference? Remember, all those private dams on all those rivers await and written about. The most common mately provide managers with a diagnostic similar relicensing analysis. effect of a dam is to dramatically reduce tool for distinguishing different types of dam “While these results are surprising when both the peak flows and the sediment load effects.” But, he adds, the model can only compared with other rivers, they are of the river, thereby resulting in coarsening, serve this purpose if used in conjunction consistent with the magnitude of changes and degradation of the channel bed in the with rigorous technical studies conducted to predicted by the model we developed as reaches closest to dams.The Deschutes the accepted high standards of science. part of this research,” Grant says. The River represents an unusual case among the By knowing the degree to which a dam has model relates the type and extent of four general quadrants of river response altered the water and sediment transport geomorphic change downstream of a dam (see figure), but its geomorphic dynamics regimes, he points out, managers could to the relation between the predam and were adequately captured by the model. target for more intensive study those postdam flow and sediment regimes. “The results from the Deschutes River specific resources likely to have been Other studies of dammed rivers tend to increase our confidence in the model and its affected by dam operation. For example, support this model, he notes. Most dams ability to predict downstream changes in dams that dramatically reduce sediment have such a marked effect on sediment other rivers, and emphasize how different loads without changing peak flows are likely loads or on flows capable of moving sedi- rivers respond quite differently to the pres- to degrade, and thus potentially change fish ment that their effects are widely known ence of dams,” he says.“This model may ulti- habitat.

4 Grant points out, however, that what is In other words, the model in its current Columbia River really needed to strengthen the potential of crude form could be used to predict where Portland Lower basin the model as a diagnostic tool is the type of more empirical evidence needs to be Salem Harris Canyon “case lore” that helps in medical diagnosis: if collected from the broad universe of dams, Mud Springs you get enough unusual cases around the and the growing body of empirical evidence Ferry Canyon Macks Canyon country, you become gradually aware of would provide a database on which to build OREGON Oak Canyon Rattlesnake patterns, then increasingly able to diagnose an increasingly robust tool. Canyon Jones Canyon effectively. Buck Hollow Creek

Bakeoven Creek FACING THE RELICENSING PROCESS Nona Creek ecause one of the issues usually a blue ribbon trout fishery,” Grant says. “It’s addressed during the FERC relicens- amazing how the legacy of past geologic ing process is the maintenance of events is strongly influencing the quality of B Shitike Creek the downstream channel environment, find- today’s fish habitat.” This does not, of Trout Creek Reregulating Dam ings from analyses like these provide the course, mean that building the dam has had Pelton Dam data against which the proposed operating no effect on migrating fish. It simply shows regime for the dam can be evaluated, that the physical workings of the down- N according to Grant. stream channel are little changed. 505km He notes that these geomorphological find- “The model as yet offers just a way of ings are just one small part of the data thinking about these kinds of relations. Map of three dams in the lower Deschutes required by FERC of operators of dams. We’re at the edge of what we know, and ➢ River basin: Round Butte Dam impounds Under the FERC process, the effects of vari- the time to start building up case lore is , which holds over ous factors such as fish habitat, water qual- now,” he says. “The relicensing process 40 percent of the water stored in the ity, recreation effects, aesthetics, and wildlife could provide a worthwhile opportunity for Deschutes basin. Just downstream is are studied. real adaptive management, with close and Pelton Dam, responsible for daily peaking power production, then the constant communication between the Related fisheries work in the lower Reregulating Dam, which provides con- people who think they know how the Deschutes by Chris Zimmerman of Oregon stant discharge to the lower Deschutes system works—the scientists—and the State University and Gordon Reeves of the River, evening flow on a daily basis. people on the ground at a particular dam.” Pacific Northwest Research Station is show- ing that the islands and surrounding back Independent science such as this research channels created by the extremely large requires that all data be made public, all process to high standards is crucial to and rare floods provide core habitats for results and conclusions subject to scrutiny having our rivers managed for a wide range diverse fish populations. by peer review. “The relicensing process is of purposes.” To that end, results from the intended to ensure that the past, present, Deschutes study now are being prepared “Fish in the Deschutes system have differ- and potential future impacts and benefits of for a book. ent habitat opportunities than fish in a dams are fairly and honestly evaluated. more active alluvial system. Nonetheless, it’s Given the long-term nature of dam licenses, Independent science conducted in an open the Deschutes findings also might serve as the basis for developing a long-term moni- FOR FURTHER READING toring strategy, he says, which includes Collier, M. [and others]. 1996. Dams and rivers: primer on the downstream effects of dams. measurement of bed-load transport and [Place of publication unknown]. U.S. Geological Survey Circular 1126. channel change to confirm study results. Fassnacht, H. 1998. Frequency and magnitude of bed-load transport downstream of the Thus a dam could be watched for bad Pelton-Round Butte Dam complex, lower Deschutes River, Oregon. Corvallis, OR: Oregon behavior and monitored to ensure that State University. M.S. thesis. possible future effects are detected early and incorporated into ongoing manage- Grant, G.E. [and others]. 1999. Downstream effects of the Pelton-Round Butte hydroelectric project on bed-load transport, channel morphology, and channel-bed texture, Deschutes ment decisions. River, Oregon . FERC No. 2030. Prepared for Portland General Electric. Portland, OR: “I’ll have the current in Portland General Electric. this place dammed up, McClure, E.M. 1998. Spatial and temporal trends in bed material and channel morphology And here the smug and below a hydroelectric complex, Deschutes River, Oregon. Corvallis, OR: Oregon State University. M.S. thesis. silver (river) shall run In a new channel, O’Connor, J. et al. 1999. Geomorphology of the Deschutes River below the Pelton-Round Butte Dam complex, Oregon. Portland, OR: Portland General Electric. 102 p. FERC relicens- fair and evenly.” ing report. On file with: Portland General Electric, 121 SW Salmon St., Portland, OR 97204. Henry IV, Part 1 (William Shakespeare)

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SCIENTIST PROFILE GORDON GRANT, a research hydrologist with GRANT can be reached at: the PNW Research Station, has been studying Pacific Northwest Research Station rivers for nearly 20 years. Before that, his USDA Forest Service Forestry Sciences Laboratory interest in fluvial processes was sparked by 3200 S.W. Jefferson Way a decade-long career as a white-water river Corvallis, OR 97331 guide. His research now focuses on the struc- E-mail: [email protected] Phone: (541)750-7360 ture and behavior of mountain streams and the effects of forest land use, dams, floods, and CO-PRINCIPAL INVESTIGATOR other disturbances on rivers and watersheds in the Pacific Northwest Jim O’Connor, U.S. Geological Survey and elsewhere. He is also a courtesy associate professor of COLLABORATORS geosciences at Oregon State University. Heidi Fassnacht, Oregon State University Ellen McClure, Oregon State University Janet Curran, U.S. Geological Survey

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