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 14
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 15
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 16
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 17
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
OCR for page 18
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
OCR for page 19
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
OCR for page 20
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.
OCR for page 21
INTRODUCTION
21
erted such political power within the state that few limits were imposed by statute
or court decision until a catastrophic flood struck in 1881. The flood prompted a
series of lawsuits by property owners, perhaps encouraged by the Moulton case,
against the mining companies. In 1884 the Federal Appeals Court for the 9th
Circuit concluded that hydraulic mining was doing widespread damage and was
a destructive public and private nuisance that must be halted (Woodruff v. North
Bloomfield Gravel Mining Co., 18F.753 (9th Circuit, 1884~.
Throughout the history of the Sacramento-American river flood control saga,
the issue recurs as to what should be the geographical basis for action. The Green
Act encouraged flood protection based on property boundaries, not hydrologic
units. Most nineteenth-century levees were constructed by municipalities, land-
owners, or districts composed of groups of landowners. Seldom was cooperation
achieved among private owners or districts sharing a watershed or facing each
other across a common stream. Nor was flood control planning integrated with
other functions of water resources management until the 1930s.
Gradually, as individual and collective landowners' flood control projects
failed to stem the tide of flood damage and instead often shifted damage to other
properties, more centralized institutions for flood management emerged. Two
examples were the California Debris Commission created by Congress in 1893 to
regulate hydraulic mining and the Sacramento Drainage District established by
the state in 1905. Later in the twentieth century, authority was further concen-
trated under the federal Central Valley Project and the State Water Project. But
local interests, such as those now represented by the Sacramento Area Flood
Control Agency (SAFCA), continue to play a prominent role in advocating flood
protection for particular communities and river reaches. With the advent of more
centralized decisionmaking at the state and federal levels, flood control planning
has increasingly been based on hydrologic rather than political boundaries. Imple-
mentation of plans, however, still depends to a considerable extent on local
political support and local funds.
Competing Strategies of Flood Response
Throughout the history of Sacramento-American river settlement, competing
engineering strategies for controlling floods have been advocated. The funda-
mental debate during the last three decades of the nineteenth century was be-
tween "levees only" and a combination of levees, bypass channels, and overflow
basins. The former position was derived from the influential 1861 USACE report
by Humphreys and Abbot that advocated "levees only" for ensuring navigation
and flood control on the Mississippi River. Local sentiment in the Sacramento
Valley, based on bitter experience, favored bypasses in addition to levees. The
1894 plan for Sacramento, called the Manson and Grunsky plan, developed under
the California Commission of Public Works, advocated bypass channels and the
OCR for page 22
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
OCR for page 23
INTRODUCTION
OCR for page 24
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
OCR for page 25
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.
OCR for page 26
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
OCR for page 27
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
OCR for page 28
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),
OCR for page 29
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
OCR for page 30
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.
OCR for page 31
INTROD UCTION
~ . ~ ~ ~ ~ ~ . . ~ ~ ~ ~ ~ ~ ~ ~ ~ . . ~ ~ . ~ ~ . ~ . . ~ ~ ~ ~ ~ . ~ ~ ~ ~ ~ . . ~ ~ ~ . ~ . ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ . ~ ~ ~ ~ ~ ~ ~ ~ . ~ . . ~ ~ ~ . ~ ~ ~ . ~ ~ . ~ ~ ~ ~ . ~ ~ . . ~ . ~ . ~ ~ ~ ~
I, ~
k~ .,..
,., ,,
.,..,..,
::::
::::::::
31
~ ~ ~ . .
Representative terms from entire chapter:
flood control
