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$32.00 • #### Table of Contents • #### FRONT MATTER R1-R14 • #### SUMMARY 1-12 • #### 1 INTRODUCTION 13-31 • #### 2 IDENTIFICATION AND EVALUATION OF ALTERNATIVES 32-84 • #### 3 ENVIRONMENTAL ISSUES 85-113 • #### 4 RISK METHODOLOGY 114-163 • #### 5 FLOOD RISK MANAGEMENT BEHIND LEVEES 164-176 • #### 6 FLOOD RISK MANAGEMENT: IMPLICATIONS FOR THE AMERICAN RIVER AND THE UNITED STATES 177-202 • #### 7 FINDINGS AND RECOMMENDATIONS 203-218 • #### REFERENCES 219-230 • #### A BIOGRAPHICAL SKETCHES OF COMMITTEE MEMBERS 231-234 • #### B GUIDE TO ACRONYMS AND ABBREVIATIONS 235-235 The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001 Copyright Â© National Academy of Sciences. All rights reserved. Terms of Use and Privacy Statement Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole. Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages. Do not use for reproduction, copying, pasting, or reading; exclusively for search engines. OCR for page 13 1 Introduction THE AMERICAN RIVER BASIN In western lore, it is said that "Whiskey is for drinking and water is for fighting." California, with its long, dry summers, has seen its water dammed, diverted, channeled, and fought over for years. Such conflicts over water can be expected to continue, and even increase, as more people (30 million state-wide and rising) and more uses (agriculture, residential, municipal, industrial, power, flood control, recreation, and environment) compete for a fixed, although renew- able, supply. Today most, if not all, of the water in California is highly regulated and controlled by a patchwork quilt of laws, regulations, institutions, and facilities. The states's water supply is now so manipulated and interconnected that any changes in management policies should take into account the broad physical and historical context of the affected region, and sometimes the whole state. This chapter provides a brief introduction to the American River basin for readers unfamiliar with the area and its need for flood protection. The first section provides background on the physical setting and historical context within in which any flood management policy in the area should be considered. The second section provides an overview of the planning and decisionmaking process used by the U.S. Army Corps of Engineers (USAGE). The application of this process in the American River basin is described in more detail in Chapter 6. 13 OCR for page 13 4 FLOOD RISK MANaGEMENT AND THE AMERICAN RIVER BASIN Physical Setting The American River Basin is located east of Sacramento in the northwestern Sierra Nevada (Figure 1.11. The watershed encompasses about 2,000 square miles. Elevations range from 10,400 feet in the high peaks on the Siesta crest to only 30 feet at Sacramento. A range of meteorological, topographic, and hydro- logic conditions contribute to the basin's current flood problem. The climatic regime of California is Mediterranean, with cool, wet winters and dry summers. At high elevations some modest summer precipitation occurs but does not generate regional flooding. The steep, west-facing slopes of the upper basin present an orographic barrier that extracts moisture from the prevail- ing maritime westerlies. Mean annual precipitation varies with elevation, form- ing a steep precipitation gradient from the Sacramento Valley up to the Sierra crest, from 18 to 70 in./yr, respectively (USAGE, Sacramento Districts, 1991, Appendix K). Annual precipitation also varies greatly from year to year, and precipitation in the upper basin can be quite intense. For example, during the severe storms of 1986, rainfall intensities in the mountains reached as much as 0.75 in./hr, and many daily totals exceeded 10 inches (California Department of Water Resources, 1988~. Knowledge of the region's past climates remains qualitative and incomplete, introducing hydrologic uncertainty that cannot be quantitatively incorporated into a risk analysis. It is clear that climatic variability has been substantial. Dendroclimatologic data from 1560 to 1979 A.D. suggest that more recent years have been moist and that the 1930s represent the driest period of the entire record in the Sacramento basin (Earle, 19931. Prolonged departures from the mean are commonplace. Factors affecting flood hydrology include geology, soils, vegetation, and artificial impoundments in the upper basin. Basin topography varies from ex- tremely rugged in the mountains to very flat in the Sacramento Valley. Much of the upper basin above Folsom Dam drains into a network of deep ravines sepa- rated by high, steep-sided ridges. The drainage network can be divided into three primary branches: the North and Middle Forks, which meet near the town of Auburn, and the South Fork, which joins the American River at Folsom Reser- voir (Figure 1.1~. The steep, rocky canyons of the upper basin afford little natural storage of the intense rainfalls that may occur during the rainy season. Except in dense forest or where there is a deep snowpack, most precipitation is quickly 1USACE (U.S. Army Corps of Engineers) as used herein refers to actions taken by the Washington D.C. headquarters of the Corps of Engineers (e.g., Corps wide policies, procedures, etc.) or com- ments by the headquarters on subordinate activities by subordinate elements such as Sacramento District. Field activities, reports, work in progress, meetings, etc. by Sacramento District should be identified as the "District" or "Sacramento District" unless and until specifically acted upon offi- cially by "USAGE." OCR for page 13 INTRODUCTION 15 delivered to channels and conveyed downstream. The elevation of the snowpack, therefore, is critical to runoff response. Vegetation in the American River basin is strongly related to topographic position and has much bearing on spatial characteristics of rainfall-runoff rela- tionships. The upper third of the basin is dominated by glacially polished bed- rock and thin vegetation ranging from alpine tundra to subalpine forest communi- ties (Munz and Keck, 1973~. Much of the basin is at moderate elevations, where gentle slopes are colonized by thick mixed coniferous forests. A grove of giant sequoia on the Middle Fork indicates the ample moisture available in the forest belt of the basin. In general, forested areas do not produce as much runoff as other surfaces. At lower elevations, vegetation thins out to grassland, chaparral, and woodland species in the foothills, and grassland savanna or riparian hard- woods in the Sacramento Valley. Folsom Dam, the largest dam on the American River, has a low volume-to- runoff ratio, and given its current design and operations it is incapable of storing and then releasing the bulk of a major flood on the river. Several small privately owned reservoirs in the basin's upper tributaries are operated primarily for power generation. Five of these reservoirs account for about 90 percent of the total storage capacity above Folsom Dam and collectively control about 14 percent of the drainage area above Folsom (USAGE, Sacramento District, 1991~. The lower basin is distinctly different from the upper basin. Below the town of Folsom, the American River emerges onto an alluvial plain with high, steeply dipping bluffs on the north side. Tributaries on the northern upland drain west- northwest to the Sacramento River. Downstream, below Rancho Cordova, the topography flattens out, and the American River ultimately joins the Sacramento River. Historically, the Sacramento area was marshy and prone to flooding in most years (John Work, 1833, as described in Dillinger, 1991; Lt. Derby, 1849, as described in Farquhar, 1932~. Historical sedimentation by hydraulic gold mining altered the lower American River channel system from its natural state (Gilbert, 1917), but the area remained marshy, and a 1907 topographic map (California Debris Commission, 1907) represented the Natomas area as "Lake American." Historical Context of the Flood Control Controversy The Sacramento River has of course flooded since time immemorial. But the starting point of flood control in the Sacramento Valley was the decision of the City of Sacramento to remain in the floodplain after a major flood in 1850, rather than moving to higher ground (Table 1.1~. As towns grew and prospered along the river, and larger landowners drained swamplands for agriculture, the preven- tion of flood damage became a dominant issue in the politics of the valley. Despite construction of significant flood control features (Figure 1.2) and a long series of studies, reports, and laws designed to reduce the area's risk, the Sacra- mento River has continued to experience devastating floods. OCR for page 13 16 FLOOD RISK MANAGEMENT AND THE AMERICAN RIVER BASIN . DOl:: i VITO ~ ~ ~ ~ A ~C 04: ~ ~_ ~ < _~l I,, :__ - ~ V IC INITY MAP 8CALI lN HILIt ~1~00 \~: T! ~ 1/ it, REMONT WEIRc. ~ of,"'' ~' dl \ ~ HI. ~ AUBURNS ~ ~ ·GEORGETf ~r ~ GREENWOOD , ~ L I NCOLN -NATOMAS EAST MAIN ~-~> ~ L DRA I NAGE CANAL it / ~; 11~ :\_¢ ~ -~ =E A I R ~/~ WOODLAND GH OAK FOLSOM ~ ~ NA\OMAS~ ~ot ~ARM.CHAE~ j \ \ ~ A\A ~ =~ N I MBUS DAM S ACRRAAMETNoT Oy~5 ~ v~ /:D O V A WEST SACRAMEN7O~ ~AM(~\~/ >-r '~'' ~ ~';: f~ t PLYM FIGURE 1.1 Main features of the American River Watershed. SOURCE: Sacramento District, USACE, 1991. OCR for page 13 INTRODUCTION ' it' --<' N_ ~ -IT R U C K E E N LAKE TAHOE ) i\ iSOUTH U ~ K E T ~ H O E Amok ' ~ ~ I Urn' ~ ALl t i r ~ / ~~ ~ _ ~ ~$~\~ ~: S I L ~ ~ R r ~Or _'~ ~3) STA IE H I GH#AY ~ ~ I ~ TERSTATE H I GH.AY S --- COUN TY BOUNDARY ~ AMERICAN RIVER ORAINAGL BASIN BOuNOARY ___ LO.ER RIVER FOLSOV RESERVOIR DRAINAGE SEPARAllON ~1 Main Features of the American River Watershed

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18 FLOOD RISK MANAGEMENT AND THE AMERICAN RIVER BASIN TABLE 1.1 Chronology of Sacramento/American River Flood History 1848 Discovery of gold near Sacramento 1850 Major flood Sacramento stays put, starts building levees 1861 Humphreys and Abbot report for the Mississippi River "levees-only" policy 1862 Major flood Sacramento begins to elevate streets and improve levees 1868 Green Act adopted authorizes local levee districts 1881 Major flood aggravated by hydraulic mining 1883 Moulton v. Parks upholds suit against levee causing overflow onto adjacent land 1884 1891 1893 Woodruff v. North Bloomington Gravel Mining Corp bans hydraulic mining Major flood destroys hydraulic mining infrastructure in mountains California Debris Commission created by Congress; small-scale, licensed hydraulic mining resumes 1894 Debate between "levees only" and combination approach continues 1905 Sacramento Drainage District established 1907 Great flood exceeding 600,000 cfs peak flow discredited "levees only" policy 1910 Jackson plan levees, bypasses, channel widening 1911 California Legislature adopts Jackson plan 1917 Federal Flood Control Act adopts Jackson plan 50-50 cost sharing 1935 Central Valley Project authorized by Congress 1956 Folsom Dam completed 1962 Lower American River Parkway established 1965 Auburn dam authorized by Congress 1975 Auburn dam construction suspended due to Oroville earthquake 1986 Major flood-nearly overtops downstream levees at Sacramento 1991 American River Watershed Investigation Feasibility Report published 1992 P.L. 102-396 authorizes Natomas elements and mandates this study 1993 NRC Committee on Flood Control Alternatives in the American River Basin formed 1994 American River Alternatives Report published Several long-standing issues continue to complicate present-day efforts to achieve safety from floods in the lower American River basin. These include: . the scale of decisionmaking and the problem of externalities, · competing strategies of flood management, · intergovernmental cooperation and cost sharing, and · scientific uncertainty. The Scale of Decisionmaking and Externalities The politics of flood control in the Sacramento Valley reflect a recurrent debate between the advocates of centralization and decentralization in decision- making. During the second half of the nineteenth century, California Republi- cans favored centralized management based on technical expertise, while Demo- crats favored a more laissez-faire approach. The latter prevailed when the state legislature adopted the Green Act in 1868, which authorized the creation of local

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19 v i C) ;- , ._ an In, o \ ~to it ~ ~·~ ~1 o ZJ O ,1 Z C ~ W ~N 3 -( Zip to _ > =>,~4 ~ ~ ~ ~ ~O o :s ~ ED ~ O 3 \ \W ~ to ~ aO Si So ~ ~ ~ O ~C 10000o . ~ ~ ~ ~ ~ Z-~=Z ~" ' \ ~ tat- g ~ · ~ \ 00V ~ = ~ ~\N ~ ~ Cg:W ~ ~ 0~~,~,~ ° -~ W11\\~11 1IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII!IIIIIIIIIIIIIIIIIIIIIIIII ~) YE ~,~ ~ ~Ni- a\\\\\ scow -~ ~, o 11lllilil t)~( wN\111~1lill lillt i\, pL) !111 11 ~ 1 11111 111UtS r>~ \\1\l 11/1' \\\it\\ _ _ , 6' ~_ ill\\t>'~'' ~ ~ PA V AL

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20 FLOOD RISK MANAGEMENT AND THE AMERICAN RIVER BASIN swampland reclamation districts upon petition of one or more property owners. For almost 50 years, flood control was in the hands of local landowners (Kelley, 12 The Green Act . . . completely atomized flood control planning and construc- tion down to the individual reclamation district. The Jeffersonian passion for localism, and for putting people on their own, had been entirely satisfied. The result was that for most of the next half-century, the Sacramento Valley would be scissored into a crazy-quilt of small reclamation districts whose levees fol- lowed property lines, not the Valley's natural drainage pattern. Flood control anarchy, and therefore massive flood control failure, would be the result. In the absence of cooperative approaches to respond to the common flood hazard, each property owner, drainage district, and municipality historically sought to protect itself with levees to deflect floodwaters on its neighbors. In the 1870s, this precipitated a "levee building spiral" in which "each project responded to each other' s threat by building further upstream and thus outflanking the other side. . ." (Kelley, 19899. There was no statutory or judicial remedy for affected parties to prevent this from happening. Water law, such as it was, regarded rivers as a "common enemy" to be resisted by each property owner and town as best they could, regardless of consequences to each other. In fact, the Green Act authorized unilateral efforts by property owners to protect themselves. In 1876 a private landowner, Levi Moulton, sued another owner, William Parks, to prevent him from rebuilding and enlarging a dam/levee that threatened to raise and retain floodwaters on Moulton's land (Moulton v. Parks, 64 Cal. 166,30 p. 613 (1883~3. Although the structure had been erected under authority of the Green Act, the local court granted a permanent injunction against the rebuilding of Parks's struc- ture. This was upheld by the California Supreme Court in 1883 and set a prece- dent for judicial scrutiny of the reasonableness of piecemeal flood control mea- sures in California. Hydraulic mining at the headwaters of Sacramento River tributaries, which had begun in the 1850s, also contributed to the confusion. Miners washed away overburden to reach gold-bearing gravel, thereby clogging stream channels with debris, endangering navigation, and aggravating flooding. Mining interests ex 2The definitive history of flood control in the Sacramento River basin is Robert Kelley's, Battling the Inland Sea: American Political Culture, Public Policy, and the Sacramento Valley 1850-1986. University of California Press, Berkeley, 1989. The committee is indebted to Martin Reuss, USACE senior historian, for his presentation and paper, "History of Flood Control in the Sacramento Valley" in which he summarized this complex history, drawing on Kelley's seminal study. 3The California Supreme Court actually decided for the plaintiff on the narrow ground that the Sutter County Board of Supervisors had no power to approve impoundment of floodwaters in an- other county, where the plaintiff's land was located.

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22 FLOOD RISK MANAGEMENT AND THE AMERICAN RIVER BASIN widening of the Sacramento River. But the Dabney Commission in 1904, headed by a USACE officer, embraced the "levees only" doctrine. A disastrous 1907 flood with a peak discharge of 600,000 cfs far surpassed prior estimates and discredited the "levees only" doctrine. The state in 1911 adopted a new plan by Thomas Jackson that incorporated levees plus bypasses and channel widening. Congress provided 50 percent federal funding to imple- ment it in the 1917 Flood Control Act. Except for the lower Mississippi River basin, this was the first federal financial participation in flood control project construction prior to the 1936 Flood Control Act. With the addition of upstream storage after 1936 at Shasta, Folsom, Oroville, and other dams, paid for almost entirely with federal funds, the Jackson plan has been the blueprint for flood control in the Sacramento Valley. Early approaches to flood control in the Sacramento/American River basin and elsewhere were entirely structural in nature. ~ ~^~^ ~ ~~ ~ In the 1930s the National Resources Planning Board began to explore nonstructural alternatives to flood control, for example, conserving natural wetlands, land use planning (floodplain zoning), warning and evacuation systems, and financial mechanisms to offset the costs of flood losses. These types of approaches were strongly advocated in the 1966 report of the Task Force on Federal Flood Control Policy (U.S. Congress, 19661. The concepts of nonstructural floodplain management and flood insur- ance were adopted by Congress in the National Flood Insurance Act of 1968. But the debate over competing strategies continues, as evidenced by attitudes toward proposed new development in the Natomas Basin. While structural measures are unquestionably necessary in already developed areas, some argue that new devel- opment should be located and designed to avoid harm from floods without plac- ing total reliance on structural protection measures. Intergovernmental Cooperation and Cost Sharing Recurring throughout the history of flood control in California, and through- out the United States, is the question of which levelts) of government should take initiative and bear the costs of achieving protection. Initially, in the absence of state or federal interest, costs were assumed by local communities, groups of landowners acting through a drainage district, or individuals. With the adoption of the Jackson plan in 1910, both the state of California and, in 1917, the federal government agreed to share the costs equally of building new levees, weirs, channels, and other facilities. In 1935, Congress authorized USACE to build the Central Valley Project (see Box 1.1~. This task was reassigned by Congress in 1937 to the Bureau of Reclamation. Thereafter in the Sacramento Valley, and across the United States, the federal government assumed the major share of the costs of building storage dams such as Shasta and Folsom. Nonfederal interests were required only to provide land, flood easements, and maintenance. The pendulum of cost bearing

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INTRODUCTION

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24 FLOOD RISK MANAGEMENT AND THE AMERICAN RIVER BASIN thus swung almost entirely in the federal direction. Congress subsequently pared back the federal role. The Water Resources Development Act of 1986 expanded the nonfederal cost share for certain projects. The present situation on the lower American River is complex, with local interests that are acting through the Sacra- mento Area Flood Control Agency (SAFCA) taking primary responsibility for levee improvements, but thereby gaining credit toward the nonfederal share of possible construction of a new upstream storage project, which would remain predominantly a federal project. Scientific Uncertainty Two interrelated issues have plagued flood control efforts for the Sacra- mento-American river system. One is the question of how much protection should be provided to occupants and investments in floodplains. The other is how reliably we can estimate the level of protection afforded by an existing or proposed flood control project. In the past, it was difficult to determine a sense of what would be an accept- able level of protection, since it was impossible even to estimate the risk of future extreme events. Empirical experience the "flood of record"-provided the only guidance to levee builders. As each generation of levees was overwhelmed, the response was to build them higher, to stand up to a flood of the magnitude just experienced. But this approach failed to recognize the effects of human activities such as hydraulic mining on channel capacity. Floods in 1881 and 1907 far surpassed prior expectations in part because channels were clogged with debris. The "flood of record" approach also cannot accommodate the outlier natural event that exceeds recorded experience, especially in a region of short historical record such as the Sacramento Valley. Since the development of modern statistical models for estimating peak discharges of extreme hydrologic events and hydraulic models for calculating the corresponding water levels, flood planners now can estimate the peak discharge, stage, and approximate geographic expanse of large floods that may not have occurred within the period of historical record. The Flood Insurance Rate Maps prepared by the National Flood Insurance Program are based on these techniques to determine areas subject to an annual chance of flooding of 1 percent ("100- year") and 0.2 percent ("500-year"~. Floodplain management and mandatory purchase are required within the 1 percent flood zones. Yet, despite the appear- ance of precision, such estimates are still far from exact. The law is tolerant of scientific uncertainty and generally allows government the benefit of the doubt regarding floodplain management judgments (see Dingman and Platt, 1977; Platt, 9941.4 4In 1994, the U.S. Supreme Court in Dolan v. City of Tigard (No. 93-518, 62 U.S. Law Week 4576) held invalid a local requirement that a property owner dedicate a portion of her property that lay

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INTROD UCTION :: ::::::: 1 ::~:: :~: ::: 1 ~ it. . 1 : ~ I: :,'~: . ~ I..... ~ . :::::::: 25 ~,~. ~,~.,, ~.,.,~,. ~. ~ it, I ~,~,.~,~,~.,~.,~.~.~. ~. ~...... , I ~ : ~ ail.: "'''~,"'r''"'4"'7."'"''"' " ' i""'': ' ' ''' ' ' '' '' ' ' ' " . ~ I. ,., ,. ~ I. ~ I ,. ~ a., .:,. - I. ~ , I, ~ .,,. ~ ~ ~ I: ~ ~ . ~... . it ~me Amencan people! Wed hea;r minces. to a.~. lOO.;y.e,ar. 00.4.~but the .me~. . tn.g ~.,,..~e,~:h~ ~ ; ~ ; I.: et has a geq al ¢rexceededina31 Even ar. It has a 2Sperc~enteha~ov~life~a~yea ga e. T e te''=.'''','2'''.x'.22'''.''''''''! ' se' ' .~ be ~ . ~ ~ p 4.~.~ ~ 'ment..~n ~ ~5~116 ~d~ ~ ~5iaigh;;4 .~ ~ sm tt. ~ ~ ~ -.~. ~ ~...~- -.. i. .~ .~m i =n be.. .. . .I ~ . r.. .. . ; .. ........... i ; c e .~ =~? Blip-. .. ..-l = do . .~ a: i: .: . I.: ~ ::: :. ::: a: :::~.: ~ :~ i:: I.:: I: :~: :~ :::::: :::.:: ::: :::: :::. ::::: :: ::: ::: :::: :: . ~...................................................................................................................................................................................................... : :. .: A - : : : Am:: .... yeast fib i ~ 6;l~ It (S,u,2'x"'~h~'' 1~"2' ~ ' ' ' '' .. I2'E'''''''''x'""''''''''"'''"'""'""'"' "' ''''"'' ' ' '"' ' '' ""I"'' ' ' '" '''"' '''"" '" ' ""''' ' ' :: ~.. ........ ........................................... ..... . .. d; ~ wow t ha ~ i . ~, . x ..................... ;. fit . Even~fa~. ~t - ~. ""~."'"''~''u'I'''~"''8 "' '' ' " ' A"'' '"' ' ' ''' ''' . i. ~. ~. ~ .~ ~ i ~,.,~,,~, ~ ... ... . . ~ . . . . . . . . . . . . . ~ ~ . · ~c ~A::: Am:: :::::::: i: :~ :::: A: :: ::: i:: : x} ~ : ail: ~ ~ :. ::: ~:::~::: I: : : ~ ~ : ::::::::: : . . ~ : ~ i: ~ :: : : ~ :~ ~( : AL . : :: ~ :: : ~ : ~ : . :: : : :: ~ In: . .~ ~ . : Such calculations of course must be revised in light of actual experience. Thus the estimated level of protection provided by Folsom Dam and downstream levees on the American River was revised downward from the 100-year event to about a 70-year event after the 1986 flood. (See Box 1.2 for an explanation of the term "100-year flood.") Estimates of future rare events also may be affected by uncertainty resulting from climate change and land use change in the watershed. within a floodplain plus an additional strip for a bikeway. The Court, however, did not question the method of determining the extent of the floodplain nor the need to limit development in such areas. The issue narrowly related to the requirement that the owner dedicate such eas to public use and access without compensation.

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26 FLOOD RISK MANAGEMENT AND THE AMERICAN RIVER BASIN Folsom and Auburn Dams Another element of the historical context that plays a part in understanding the current debate over flood control in the American River basin is the role of dams in the system. The flow of the American River upstream of Sacramento is regulated by Folsom Dam, a 340-foot-high, concrete-earthfill multipurpose struc- ture completed by USACE in 1956 and operated today by the Bureau of Recla- mation as part of the Central Valley Project. Folsom regulates runoff from about 1,860 square miles, receiving drainage from all three forks of the American River. Its maximum storage capacity is about one million acre-feet, of which 400,000 acre-feet is allocated to flood storage during the fall and winter months (Figure 1.3~. Beyond the portion reserved for flood storage, the reservoir pool is allocated to power, irrigation, water supply, recreation, and releases to maintain minimum flows in the lower American River. Lower American River flows are also regulated by Nimbus Dam, a small regulating structure just downstream of Folsom Dam. Together with an auxiliary dam and eight dikes, Folsom Dam impounds a reservoir with a shoreline of about 75 miles and a maximum surface area of some 12,000 acres. The nearby Sacramento Metropolitan Area, with a 1990 population of 1.48 million (up from 848,000 in 1970), makes heavy use of Folsom Lake as a recreational resource. The 18,000-acre Folsom Lake State Recreation Area is the most heavily used year-round facility in the state park system, with average annual user-days exceeding 3.4 million (Water Education Foundation, 1988; USACE, Sacramento District, 1991~. When Folsom Dam was planned in 1949, it was designed to protect against a flood characterized by a peak inflow rate of 340,000 cfs (680,000 acre-feet per day) and a 6-day inflow volume of 978,000 acre-feet, which at the time was thought to be a 500-year storm. The 6-day inflow (978,000 acre-feet) was about 2.4 times the size of the flood pool (400,000 acre-feet). Under these conditions, maximum releases would be 115,000 cfs (230,000 acre-feet per day), the stan- dard to which the downstream levees were designed (U.S. Bureau of Reclama- tion, 1986~. A series of floods in 1955, 1963, 1964, and 1986 radically changed the understanding of Folsom's estimated level of protection. As discussed in Chapter 2, the flood protection estimated to be provided by Folsom as currently designed and operated was subsequently downgraded to about a 70-year flood, a flood with a 1.4 percent chance of occurrence in any year (SAFCA, 19931. In 1965 a second, larger dam was authorized by P.L. 89-161 to be con- structed about 12 miles upstream from Folsom Dam near the town of Auburn. The proposed Auburn dam would have impounded runoff from the North and Middle Forks, controlling 973 square miles of the American River watershed and creating a two-pronged lake about 25 miles long. The originally proposed Au- burn dam would have been another multipurpose structure, a concrete arch dam twice the height of Folsom (653 feet from base to crest) with a potential storage

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INTRODUCTION Gates Spillway crest Power house outlet ~ Outlets ,, Low level outlet 27 Folsom Reservoir Existing flood space . 400,000 acre-feet Variable flood space o7~ con =^r^_f~L^t ==: ~ I U.V~v GL-! ~ l~GL Pool required to release 1 15,000 CFS . . ~ ~ Spillway crest,elev.418 feet 1 1 1 1 1 400 0 200 - 480 440 a) a) - C~ 400 _ > a' 360 au C' ~5 320 20 - C~ 280 ._ 240 G 200 1 1 1 1 600 800 1000 Reservoir capacity 1,000 acre-feet FIGURE 1.3 Flood storage space at Folsom Reservoir. SOURCE: Murray, Burns and Kienlen, 1993. capacity of 2.3 million acre-feet, more than double that of Folsom. The full pool would have occupied 10,000 acres, and a total of 42,000 acres of land were scheduled to be acquired for the project. Construction of the originally proposed Auburn dam by the Bureau of Recla- mation began in 1967, despite strong opposition. A diversion tunnel and coffer- dam to carry the American River past the construction site were completed in 1972. Work on the dam stopped in 1975, however, when an earthquake register- ing 5.7 on the Richter scale occurred near Oroville, about 45 miles north of Auburn. Subsequent study revealed a fault near the Auburn site. Some evidence suggested that the newly completed Oroville Dam may have triggered the earth- quake, and the Auburn dam was put on hold indefinitely by the Bureau of Recla- mation. About one-third of a billion dollars was invested at the Auburn dam site and average maintenance costs for the site amount to \$1.5 million annually (USAGE, Sacramento District, 1991~. Although the planned Auburn dam was redesigned to reduce seismic risk, the project as originally conceived lost support. According to USACE (USAGE, Sacramento District, 1991), this was the result of two factors: (1) a 1986 change in federal policy concerning cost sharing of water development projects that would have raised the nonfederal share of the costs substantially and (2) more aggressive and effective opposition by environmental interests. The scenic and

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28 FLOOD RISK MANAGEMENT AND THE AMERICAN RIVER BASIN recreational values of the North and Middle Forks have indeed attracted wide- spread opposition to a permanent impoundment at Auburn. Ironically, the acqui- sition of over 30,000 acres for the Auburn dam impoundment actually helped to consolidate opposition to its completion. This area is now operated as the Au- burn State Recreation Area and is heavily used for white-water rafting, camping, fishing, and hiking. Reevaluation of the American River flood risk following the 1986 flood inevitably reopened the question of whether an Auburn dam should be built. SAFCA and other flood protection advocates offered a dry dam as a compromise alternative to the full-pool, multipurpose dam. As proposed, this dry dam would be used for flood storage only when needed; "frequency of impoundment" would depend on its design. No water would be permanently impounded, and the recreational use of upstream canyons would be largely unaffected except for impacts to valley walls and vegetation caused by occasional inundation. While considerably smaller than the originally proposed multipurpose Auburn dam, it would be the largest dry dam in the United States, and it has added an additional layer of controversy to this already complex decisionmaking process. The issues to be resolved include not only whether the dam is necessary and cost-effective, but whether the dam should have gates to control flow or remain ungated to discourage its conversion to multipurpose use. The committee shares complete consensus, however, that a dry dam of the size proposed for the Auburn site requires the safety margin and flexibility afforded by operational gates. THE USACE PROJECT PLANNING AND DECISIONMAKING PROCESS To have a full understanding of the American River flood control planning process, some familiarity with the USACE planning process in general is helpful. USACE studies for individual project planning move through a highly structured process that begins with a congressional study authorization, requires congres- sional and presidential approval, and ends (if successful) with project implemen- tation (see Box 1.34. USACE planning is expected to provide technical analysis of the merits of different alternatives and the recommended plan to support informed decisionmaking at the local level (where the project will be imple- mented), in the executive branch, and in Congress. The US ACE district office has the primary responsibility for all aspects of project planning. After receiving congressional authorization to conduct a study, a district office is provided with a budget and assigned responsibility for recom- mending a plan for implementation, or recommending that no action be taken. In executing these responsibilities, the district office follows detailed planning pro- cedures mandated by USACE Washington, D.C., headquarters. In addition, the district is expected to subject its planning to the myriad requirements of federal and state laws, such as the National Environmental Policy Act of 1969 (NEPA),

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INTRODUCTION 29 the Clean Water Act, and the Endangered Species Act. Compliance with these various acts is reported in the study and, if appropriate, in an environmental impact statement (EIS) filed under NEPA. In response to NEPA and similar legislation, by the mid-1970s USACE had introduced expanded public participation efforts in planning and made efforts to recognize the concerns of a broader array of interests. The district now is ex- pected to solicit advice, and perhaps request particular technical studies, from other federal and state agencies. Extensive public participation is expected, often through formal public hearings at certain steps in the planning process. All of this external advice is expected not only to meet a legal requirement for consultation under different laws, but also to direct the study process and the resulting recommended plan of action. Indeed, there were many procedural and substantive planning requirements in the various laws passed during the 1970s to provide a foundation for legal and political challenges to USACE planning and recommended plans. Over time USACE critics focused on environmental concerns have succeeded in slowing and then reversing the growth of the federal water development program. By the late 1970s the program had come to a near halt no new construction projects being authorized-largely because of a congressional impasse over cost-sharing issues and other differences between the administrative and legislative branches over water planning. The program was restarted only after passage of the Water Resources Development Act of 1986 (WRDA, 1986~. WRDA 1986 is best recognized for dramatically increasing the required payment for the costs of USACE projects by nonfederal interests who benefit from the projects. For example, prior to 1986 the beneficiaries of a local flood control project would be expected to provide only the lands, easements, and rights-of-way necessary for the proposed project to be implemented. A major flood control reservoir required no local contribution. After 1986, cash payments were required in addition to the lands, easements, and rights-of-way requirement. Nonfederal costs could rise quite high, so high in fact that the law capped the nonfederal contribution at 50 percent of total costs, a substantial increase over the pre-1986 situation. Another significant change was the requirement that the costs of feasibility studies be shared as well. Prior to 1986, study costs were a full federal responsi- bility. With WRDA 1986 the initial study is paid at full federal cost, but the costs of feasibility studies must be shared. For example, a nonfederal sponsor paid 50 percent of the costs of the 1991 American River Watershed Investigation. These cost sharing requirements have put pressure on USACE to open its planning and decisionmaking to even more scrutiny than in the past. Those who pay for a study demand a greater say in all phases of the study process, and, as project implementation costs rise, the demands for influence on the recommended plan also increase. As a consequence of the recent challenges to USACE projects and of WRDA 1986, the USACE planning process not only is increasingly open

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30 FLOOD RISK MANAGEMENT AND THE AMERICAN RIVER BASIN ., ....... .. .. i. . ~ ~ , ~ .... . ,.~.- ~.~.~.~ . ~, . ~ ~..~ i.. ~.~.~. . .. ... ....~... ~..~ .~ it.. . . .... .. .. .... .~..~ .. hi. ~ ~ .. ~ . .... ~ .. i.. i.. .. ... .. ~ ~ ~ ~ ~ . ~ . ~ ~ ~ ~ ~ ~ ~ . ~ . ~ . . ~ . . ~ . . ~ ~ ~ ~ ~ . . ~ . ~ ~ ~ ~ . ~ to environmental and other interests, but it also is a joint product of USACE and a local sponsor (such as SAFCA). It was the degree of openness (or perceived lack of openness) of this plan- ning process for the American River that provided the opportunity for critics to challenge the analysis of the Sacramento District and the plan preferred by the local sponsor. The fact that these challenges were made suggests that, although the process was open to inspection and comment after it was completed, it did not provide opportunity for significant, early input or fully incorporate the concerns of the interests who challenged the study. Of course, opposition may materialize no matter how open the planning process may be, but early identification of disagreements typically increases the opportunities for resolution.

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INTROD UCTION ~ . ~ ~ ~ ~ ~ . . ~ ~ ~ ~ ~ ~ ~ ~ ~ . . ~ ~ . ~ ~ . ~ . . ~ ~ ~ ~ ~ . ~ ~ ~ ~ ~ . . ~ ~ ~ . ~ . ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ . ~ ~ ~ ~ ~ ~ ~ ~ . ~ . . ~ ~ ~ . ~ ~ ~ . ~ ~ . ~ ~ ~ ~ . ~ ~ . . ~ . ~ . ~ ~ ~ ~ I, ~ k~ .,.. ,., ,, .,..,.., :::: :::::::: 31 ~ ~ ~ . .