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OCR for page 164
Flood Risk Management Behind Levees
THE FLOOD PROTECTION/DEVELOPMENT SPIRAL
Federally subsidized flood control projects, including upstream storage and
local levee projects, were the prevalent form of national response to flood hazard
between the mid-1930s and the late 1960s. Nevertheless, flood losses one
measure of flood hazard-continued to rise throughout this period despite the
spending of billions of dollars to store and deflect floodwaters. In 1960, Gilbert
F. White warned: "Probably the most important reason for the rising trend in
flood losses fas measured in constant dollars] is to be found in the continuing
encroachment of human occupance upon floodplains" (White, 1986~. The 1966
Report of the Task Force on Federal Flood Control Policy, also authored by
White, further charged that ". . . some flood plain encroachment is undertaken in
ignorance of the hazard, that some occurs in anticipation of further federal protec-
tion, and that some takes place because it is profitable for private owners even
though it imposes heavy burdens on society" (U.S. Congress, 19661. The trend of
rising flood losses continues today.
Average annual losses have continued to rise in protected floodplains as well
as unprotected ones. This occurs in part because construction of flood control
projects can engender an illusion of total protection a false sense of security-
that leads to new growth within the area (White, 19751. If unrestricted develop-
ment is allowed in the floodplain behind or downstream from a flood protection
project, the overall value at risk becomes much greater than would have been
likely in the absence of such protection. Although damage from moderate floods
may be successfully averted, any structural project may fail owing to a design
164
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FLOOD RISK MANAGEMENT BEHIND LEVEES
165
flaw, lack of maintenance, or exceedance of its design capacity. When that
happens, the newly developed floodplain reverts to its natural role, and structures
located there can experience massive damage (White, 1975~.
The Pearl River Flood of 1979 at Jackson, Mississippi, provides a case in
point. After a long history of floods, Jackson and its neighboring communities
collaborated with USACE to build a local protection project including construc-
tion of levees and straightening of the river channel. At groundbreaking ceremo-
nies for the project in 1964, local officials promised that it would " . . . mark the
end of the devastating floods which almost annually have inundated thousands of
acres, forced hundreds from their homes, and threatened to destroy major indus-
tries vital to the flocal] economy. . ." (Jackson Daily News, 19641. The project
was completed in 1968 and was soon followed by commercial and public devel-
opment worth tens of millions of dollars in the floodplain behind the new Jackson
levee. In April 1979 the entire area flooded to depths of up to 14 feet as the Pearl
River spilled over and through the new levee. Although the discharge of this
flood was less than the design capacity of the project, the levee failed. The
resulting devastation was far more costly than if the levee had not been built and
the floodplain had remained unoccupied (Platt, 1982~.
Although benefit-cost analysis rules exclude counting future development as
a project benefit, the prospect of new development in the "protected" area often
stimulates such projects. As the 1966 Task Force report warned, "The major
purpose of engineering projects is changing from the protection of established
property to the underwriting of new development. Federal funds are used to
support projects justified on the basis of protection of lands for future use" (U.S.
Congress, 1966~.
The flood protection/development spiral was repeated at Chesterfield, Mis-
souri, which experienced a catastrophic levee failure during the 1993 Missis-
sippi-Missouri River floods. (See Box 5.1.)
Levees are inherently unreliable for large areas of intensively developed
land, as stated by the Federal Interagency Flood Management Task Force (1992b):
.
Many levees . . . are designed to provide protection only from smaller
floods . . . or were built immediately before or during a specific flood event;
· Only a portion of all earthen levees built with crown elevations equal to
the design flood elevation can provide the expected flood protection because of
changing hydrologic conditions and the possibility of structural failure before
overtopping;
· Areas behind levees and floodwalls are often subject to severe internal
drainage problems; . . . surfacing of ground water may be another problem.
.
A levee breach or floodwall failure is similar to a dam break and can
release flood waters with high velocity. After a breach, the downstream portion
of the levee/floodwall system may also act as a dam, prolonging the flooding
behind it.
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FLOOD RISK MANAGEMENT AND THE AMERICAN RIVER BASIN
The actual or prospective failure of levees inevitably stimulates demands for
additional flood protection, either through higher levees, upstream storage, or
other means. Flood protection thus begets new development, which in turn
begets more flood protection and more development. This spiral occurred at both
Jackson, Mississippi, and Chesterfield, Missouri, with disastrous results. The
question for those involved in flood hazard reduction for the American River
basin is: Will this sequence of events be repeated in the Natomas Basin?
THE NATOMAS BASIN
The Setting
The Natomas Basin is a flat lowland of about 55,000 acres near the con
OCR for page 167
FLOOD RISK MANAGEMENT BEHIND LEVEES
....
.. ~
,. I, ~ ~ ~ ~
.~,~,,.,,~..
., ,
::::::::
167
fluence of the American River and the Sacramento River at the city of Sacra-
mento. In its natural state, the basin lies entirely within the 100-year floodplains
of those rivers and associated local drainage systems. Today, the basin is physi-
cally bounded by a 41-mile ring of levees bordering the American River to the
south, the Sacramento River to the west, the Natomas Cross Canal to the north,
and the Natomas East Main Drainage Canal on the east.
Reclamation of the basin for agriculture began with various local levee
schemes during the late nineteenth century and more formally dates back to the
Federal Flood Control Act of 1917. Currently, most of the basin is devoted to
agriculture, including extensive areas of irrigated rice cultivation and other grain
crops on drier soils. Existing levees and agricultural drainage within the basin are
operated by Reclamation District 1000. That district is a member of the Sacra
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68
FLOOD RISK MANAGEMENT AND THE AMERICAN RIVER BASIN
TABLE 5.1 Population Growth of Sacramento Metropolitan Statistical Area
and the City of Sacramento, 1970 to 1990
1970 1980 1990
1980 to 1990
Change
Sacramento MSA 848,0001,100,0001,481,000
Sacramento City 257,000276,000369.000
34.7%
34.0~o
SOURCE: Bureau of the Census, 1991.
mento Area Flood Control Agency (SAFCA), formed in 1986 to serve as a
regional voice and catalyst for upgrading of flood protection in the Sacramento
region.
The basin lies partly within the Sacramento Metropolitan Statistical Area
(MSA) and also partly within the incorporated area of the City of Sacramento.
Both the MSA and the city have experienced rapid development and population
growth since 1970 (Table 5.14.
Local political jurisdiction over Natomas is divided among the city of Sacra-
mento, Sacramento County, and Sutter County. Existing urban development in
the basin occupies about 7,200 acres in the southern part of the basin between the
American River and Interstate 80, which extends diagonally across the lower part
of Natomas Basin. This developed area, known locally as South Natomas, lies
within the city limits of Sacramento and directly across the American River from
the city's business and governmental center. It includes about 13,700 structures
and has a resident population of about 31,000. Interstates 5 and 80, two of the
nation's primary highways, intersect at the northern edge of South Natomas.
An area of about 47,600 acres (75 square miles larger than the District of
Columbia), which makes up 86 percent of Natomas Basin, remains undeveloped
at this time. Ultimately, full build-out of the basin could add 170,000 residents,
with total development value exceeding $15 billion (Sacramento Bee, 1993a).
The portion of the basin of immediate interest to Sacramento is a 7,000-acre area
of agricultural land known as North Natomas directly to the north of Interstate 80.
The city's general plan designates North Natomas as a major growth area for new
housing and commercial development. It is projected to account for about 35
percent of new housing and 30 percent of new jobs in the city when fully built-out
(City of Sacramento, 1993b).
Pressure to develop the Natomas area began in the early 1980s with propos-
als for industrial and commercial projects. These were opposed by the small
group of existing residents in South Natomas, who sought more balanced, better
planned new growth. In particular, they desired to upgrade their own area from a
moderate income neighborhood to a more upscale locale.
Location provides the primary impetus for developing North Natomas. The
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FLOOD RISK MANAGEMENT BEHIND LEVEES
169
area adjoins two interstate highways and is a few minutes of driving time from
both downtown Sacramento and the airport. It would adjoin and expand on the
present development in South Natomas. Under the North Natomas Community
Plan, adopted by the Sacramento City Council on May 3, 1994 (amending earlier
plans from 1993 and 1986), development is planned to take the form of 14
neighborhood areas, served by light rail, schools, parks, and retail centers. The
plan also calls for a town center to be anchored by a regional park and a sports
complex (Sacramento Bee, 1994b). The plan has been developed over several
years by the North Natomas Working Group, which includes city and county
planning officials; the Environmental Council of Sacramento; the Natomas Com-
munity Association; and the North Natomas Landowners Association, represent-
ing the 10 largest ownerships in the area.
One objective of the North Natomas Community Plan is to promote the
fulfillment of federal and state air quality goals through the provision of light rail
and the creation of new housing and employment opportunities convenient to
each other and the central city, potentially reducing the need for longer distance
commuting by car. Also, like most central cities, Sacramento seeks to stem
middle-class flight and the loss of taxes and jobs to outlying areas beyond its
. . . .
Jurlsc .lchon.
As of mid-1994 the only urban facilities in Natomas Basin north of Interstate
80 consisted of the Sacramento International Airport in unincorporated Sacra-
mento County and the Arc o Arena, standing amid the still open fields of North
Natomas. The sports arena was built in the mid-1980s by one of the area's major
landowners to accommodate Sacramento's newly acquired professional basket-
ball team, and to prime the pump of development in North Natomas. Since then,
however, further development in North Natomas and throughout the Natomas
Basin has stalled for a variety of reasons. Among these have been the national
and state recession, unresolved questions of financing proposed infrastructure in
North Natomas, and the need to develop an approved habitat conservation plan to
protect the Swainson's Hawk and the Giant Garter Snake (state-listed threatened
species found in the Natomas Basin). But overshadowing other impediments to
development has been the unresolved issue of flood hazard.
Natomas Flood Hazard
Although lessened to some degree by its 41-mile ring of levees, the risk of
flooding in the Natomas Basin remains significant. Much of the land surface of
the basin lies below the levels of the American and Sacramento rivers at flood
stage, and also below the elevation of the surrounding land. According to
USACE: "flooding from levee failure would be similar in Natomas, downtown
Sacramento, and to some extent North Sacramento regardless of the frequency of
the flood event because: 1) the ground elevation adjacent to the levees in these
locations is lower than the water surface in the river, and 2) the volume of water
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170
FLOOD RISK MANAGEMENT AND THE AMERICAN RIVER BASIN
in the American River . . . and Sacramento River in the case of Natomas . . .
would fill the flood plains to similar depths" (USAGE, Sacramento District,
1991) (emphasis added).
In other words, the basin could fill like a bathtub to the level of the bordering
rivers in the event of a flood exceeding the design capacity of the Natomas
levees, or a lesser event that breaches weaknesses in the levees (as occurred
widely in the Mississippi River floods of 1993~. Critics point out that a flood of
any frequency, if gaining access to the area within the levees, would inundate
over 59 percent of the basin to a depth greater than 13 feet, 32 percent to a depth
between 8 and 13 feet, and 9 percent to a depth of less than 8 feet (Estes, 1993~.
(See Figure 5.1.)
The level of protection provided by the existing Natomas levees is uncertain.
The American River levees in conjunction with Folsom Dam upstream were
thought to provide approximately 100-year protection until the flood of February
1986 compelled reconsideration of that assumption. Releases from Folsom Dam
in that event reached a peak flow of 132,000 cubic feet per second (cfs), which
exceeded the design target of 115,000 cfs of the downstream levees. The levees
were not overtopped, but the flow encroached into the design freeboard and
caused erosion in certain areas. A few more hours of rain would have resulted in
major disaster. The 1986 flood was rated as a 70- year event (City of Sacra-
mento, 1990~. USACE subsequently downrated the available level of protection
along the American River below Folsom Dam to 40 to 70 years. The Sacramento
River levees bordering Natomas were estimated by USACE after the 1986 flood
to protect only against a 40-year flood (City of Sacramento, 19901.
Repair and renovation of existing levees along both the American and the
Sacramento rivers have been in progress since 1986. Congress authorized further
upgrading of the levees and internal pumping and drainage facilities for Natomas
in 1992 (in P.L.102-396, which also created this committee), as recommended in
the 1991 ARWI. This congressional authority, however, was subject to the
condition "that such construction does not encourage the development of deep
floodplains" (Section 9159(b)~1~. (The act did not define the term "deep flood-
plains.")
Even without a levee failure, internal drainage remains a serious problem for
development in the Natomas Basin. Mechanical pumping systems are inadequate
to remove surface drainage when river levels are higher than the land surface of
the basin, so local shallow flooding may occur even during storm events that do
not threaten the levee system.
NFIP Status of Natomas
The development of the Natomas Basin is further affected by its novel status
under the National Flood Insurance Program (NFIP). Normally, where new
construction is built in "special flood hazard areas" (100-year floodplains mapped
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FLOOD RISK MANAGEMENT BEHIND LEVEES
17
FIGURE 5.1
NATOMAS BASIN
ESTIMATED
FLOOD DEPTHS
Flood depths are estimated
from 33-foot flood elevation
derived from Flood Insur-
ance Rate Map issued by
the Federal Emergency
Management Agency in
March 1993.
Map developed from:
California Dept. of Water Resources,
MaD of American River- Sacramento
Estimated Potential Flood Depths,
June 1 993.
U.S. Geological Survey, Topographic
Maps (7.5 Minute Series) with 5-foot
contour interval, various years.
:2 : . ~.''', :2r ~.~.~.~.~.~.'
' ~;
LEGEND
Depth of Water and Acres Flooded
O to 8 feet 4,700 acres
8 to 13 feet 17,600 acres
13 to 18 feet 14,900 acres
18 to 23 feet 16,600 acres
over23 feet 1,100 acres
13to 18ft.
. . ~
8to 13ft.
...............
....... ...
............ .
............
...............
...............
................
................ . _
...................... ~
.................................. , _ ~ a
· ' ' ' ' ' ' ' - ' ' - ':' - ':-: . .':' .-. 1 _
_
. _
2"'~'¢"'.~.~.'2-..'."'" ~
it:: ~ :':':.'''. it: :'~'''''''' ~ ~ ~ ~ .: .,
'. -.'.'.' '. - -.' '.' - ' ' .'.' ' - ' ' ' ' ' ' ' ' ' ' - ' - ' ' - ' ' '1
, .',.,2,:,:2.:,::,:,:::::::::,::,::::::.::~:::,:.:,::~,:,1
_"~""'e2"2."""2""~2."""~"2."2 :1
N
.. , ,1
over ...................
_ ,,,, L'''~'2'2" ~ ,2,'.1 ,
_:,:: :,:: :::::::: :~: :~:: ::::::: :::::: :::::: A:::::.:.:::. r ::::: :~:: :~:~:~:~:
~.. ... , ~.............
- ~
. ~
l #t
l
- ~
- ~
- ~
FIGURE 5.1 Natomas basin flood depths. SOURCE: G. Estes, 1993.
OCR for page 172
72
FLOOD RISK MANAGEMENT AND THE AMERICAN RIVER BASIN
by NFIP), NFIP (1) requires residential structures to be elevated at least 1 foot
above the estimated 100-year flood level and nonresidential structures to be
floodproofed or elevated to that level; (2) requires owners to purchase flood
insurance if they borrow money from a "federally related source" for purchase or
construction of structures in such areas; and (3) charges "actuarial rates" for flood
insurance coverage reflecting the actual risk of flood damage at the site in ques-
tion. Outside of special flood hazard areas, NFIP does not require elevation or
insurance purchase, but makes coverage available in eligible communities at
nominal rates.
Areas protected by levees certified to provide "100-year" protection, are
considered by NFIP as not within a special flood hazard area, although floods
exceeding the design standards of the levees may still inflict catastrophic dam-
age. Natomas was thus exempted from NFIP requirements until the downrating
of its levees after the 1986 flood. In 1988, special legislation attached to the
McKinney Homeless Assistance Act (P.L. 100-628) specifically exempted
Natomas and certain other floodplains in the Sacramento area from the imposi-
tion of NFIP elevation requirements for a period of 4 years. The rationale for this
special exemption for Sacramento the first in the history of the National Flood
Insurance Program was the concern that a change in flood elevation require-
ments " . . . will cause severe disruption in the Sacramento region and could
precipitate the breakup of the political, institutional, and economic relationships
sustaining the high level, comprehensive flood protection efforts" (P.L. 100-628,
Section (a)S). The act further stated that "the City and County of Sacramento
have each provided assurances to the Congress that they will not designate any
increases in urbanization beyond lands already so designated in their general
mans . . ." during the 4 year period of exemption (Section (add. Further, they
committed themselves to consider (P.L. 100-628, Section (a)71:
a) an evacuation-emergency response plan;
b) mechanisms by which to attempt to provide notice to all buyers of new
structures;
c) retention of natural floodways; and
d) recommendations to all buyers of new structures to purchase flood insur
ance.
The Federal Insurance Administrator sent a letter to Congressmen Vic Fazio
and Robert T. Matsui that viewed the exemption with dismay (PI. Duryea, per-
sonal communication, January 3, 19891:
Although the statute does not directly address the issue of insurance rates, the
estoppel on the establishment of new base flood elevations effectively prohibits
FEMA [Federal Emergency Management Agency] from charging actuarial (risk
based) rates within the areas specified. Since risk data is available from the
Corps of Engineers' study, but Congress has prohibited the establishment or
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FLOOD RISK MANAGEMENT BEHIND LEVEES
alteration of base flood elevations based upon it, the assignment of insurance
rates becomes somewhat arbitrary. In light of this situation, FEMA will act in
accordance with your position that the statute prohibits changes to insurance
rates within these areas, and continue to make flood insurance available at rates
normally utilized outside areas of special flood hazard.
I am sure you recognize that maintaining the status quo with regard to insur-
ance rates in these areas will create a significant subsidy for new construction,
as actuarial rates are likely to be considerably higher than the current rates.
This subsidy will be further increased because FEMA will be unable to enforce
the program requirement that new construction be elevated to base flood levels.
This subsidy could exist well beyond the maximum 4-year moratorium period
specified in the statute, if the anticipated structural flood control solutions are
not realized in the near future. In this situation, other flood insurance policy
holders and taxpayers in California and the remainder of the country would be
paying for the expected flood losses to new construction which will be built in
these areas during the next four years.
173
In compliance with the statute, FEMA remapped Natomas as an "A-99 Zone"
within which federal floodplain management requirements are minimal. Lenders
must notify borrowers of a potential flood risk, and the latter must purchase flood
insurance, but rates are those applicable outside special flood hazard areas (i.e.,
rates are very low).
In fulfillment of their commitment to Congress, the City and County of
Sacramento adopted a "Land Use Planning Policy Within the 100-Year Flood
Plain" and its accompanying environmental impact report on February 6, 1990
(City of Sacramento, 1990~. The policy (1) allows approved development in
areas of the 100-year floodplain outside of Natomas; (2) imposes a de facto
temporary moratorium on residential development in the Natomas area during the
period of Sacramento River levee instability by conditioning building permits on
compliance with regulations applicable to development in a flood hazard zone;
(3) conditions all nonresidential building permits on compliance with structural
design and planning criteria aimed at minimizing the risks due to flooding; and
(4) reaffirms the city's commitment to Congress not to designate any increases in
urbanization in floodplain areas beyond lands already so designated in the city's
general plan (City of Sacramento, 1993bJ.
Congress in 1992 amended the National Flood Insurance Program to create a
new "flood restoration zone" for areas where levees have been downrated but are
being expanded to restore 100-year flood protection. Within a flood restoration
zone, modified NFIP requirements would apply to areas (1) that previously were
accredited by FEMA as protected by levees to the 100 year level; (2) whose flood
protection had been decertified by a federal agency, and (3) that are in the process
of restoring such 100-year protection using federal funds (P.L. 102-550, Section
928, amending Section 1307 of the National Flood Insurance Act). Senator Alan
Cranston, chair of the Senate Housing and Urban Affairs Subcommittee respon-
sible for the bill, stated on the floor of the Senate: "The flood restoration zone is
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74
FLOOD RISK MANAGEMENT AND THE AMERICAN RIVER BASIN
not intended to allow the development of undeveloped areas including the
Natomas basin area in Sacramento" (Congressional Record, 19921.
Proposed regulations concerning the AR zone were published by FEMA on
April 1, 1994, in the Federal Register (p. 15351-15361~. Essentially, the amend-
ment and proposed rules would limit mandatory elevation of new structures to 3
feet above grade in "developed areas" or where expected 100-year flood eleva-
tions would be 5 feet or less in "undeveloped" areas. Where expected elevations
would exceed five feet in undeveloped areas, new construction would be el-
evated to the actual estimated level. No elevation requirements would be im-
posed on substantial improvements to existing structures in flood restoration
zones.
However, the regulations also provide for "dual zone" designations (e.g.,
AR/A1-30, AR/AK, etc.) that reflect residual risk from flooding even when the
levee system is restored to 100-year level of protection. In such dual zones, new
construction and substantial improvements would have to be elevated as other-
wise required for the underlying zone.
Mandatory purchase of insurance requirements under the Flood Disaster
Protection Act of 1973 would apply within AR or dual zones. However, premi-
ums for coverage would be charged at rates applicable to those for C zones (i.e.,
pre-FIRM subsidized rates). Eligibility for flood restoration zone status is lim-
ited to "communities where construction and restoration of a flood protection
system is a Federally funded project and the existing flood protection system was
constructed with Federal funds . . ." (Federal Register, April 1, 1994~. The
American River Project Levee bordering Natomas was constructed by USACE
after the completion of Folsom Dam (U.S. Bureau of Reclamation, 1986), but
current improvements are being conducted by SAFCA, a nonfederal agency. It is
therefore unclear whether Natomas will qualify for flood restoration zone status,
and if so whether portions of it will be designated as dual zones where elevation
to applicable levels would continue to be required. Clearly, most of Natomas
outside the existing development in South Natomas is currently agricultural and
would be designated "undeveloped."
The city and county moratorium was partially lifted on October 12, 1993, by
the City Council, which voted to allow master parcel plans to be approved for
Natomas. That action would potentially allow developers to qualify for loans to
finance infrastructure. Individual building permits, however, will not be issued
until the federal government certifies that the area is protected against a 100-year
flood (Sacramento Bee, 1993b).
The City Council, at the urging of Friends of the River, the Sierra Club, and
the State Reclamation Board, on December 7, 1993, ordered a comprehensive
floodplain management plan for the city to be prepared within 12 months (R.
Stork, personal communication to R.H. Platt, May 19, 1994~. The goals of this
effort as defined by the Council (City of Sacramento, Department of Utilities,
1994 are to (1) . . . provide the areas designated for urban development within the
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FLOOD RISK MANAGEMENT BEHIND LEVEES
175
City of Sacramento with at least 100-year level of flood protection on a short term
basis; (2) . . . provide the City with the highest level of flood protection, minimum
200 year, along the Sacramento and American Rivers on a long term basis; and
(3) "utilize] all secondary flood protection measures needed to address the re-
sidual risk of uncontrolled flooding in Sacramento.
The long-term goal of "minimum 200-year" level of protection, while desir-
able, is unlikely to be achieved through reconstruction of local levees within the
immediate control of SAFCA and its constituent local government agencies.
This policy, as stated by the City Council, thus implies an expectation that 200+
year flood protection will be provided externally, through reoperation of Folsom
Dam, through construction of an Auburn dam, or by other means. Indeed, recent
recalculation of expected flood flows on the Sacramento River may even jeopar-
dize the achievement of 100-year protection through levee improvements cur-
rently in progress (Sacramento Bee, 1994a).
The City Council has thus established a goal 200+ year protection that is
beyond the capability of the city to achieve within its own boundaries and through
local actions. Yet it is poised to approve the development of North Natomas and
other floodprone areas despite the unresolved, and perhaps unresolvable, issue of
ongoing flood hazard. The city tends to blame external entities, principally
Congress and federal agencies, for its inability to move ahead with development
of Natomas free of any consideration of residual flood risk. In a report dated
October 12, 1993, the city declared that the only obstacles to development of its
floodplains were the lack of action by Congress and the uncertain future status of
Natomas under the National Flood Insurance Program (City of Sacramento,
1993a).
The Land Use Planning Policy EIR [approved 1990] assumed that by the time
the Sacramento River levee stabilization project was completed in 1992, Con-
gress would have authorized a long-term flood control project and all obstacles
to achieving at least a 100 year level of protection for the Natomas area would
be removed. Instead, Congress failed to authorize a long-term project and
although SAFCA has proceeded with levee improvements . . . it is still uncer-
tain when these improvements will be completed. Despite this uncertainty,
Natomas' existing A-99 zone designation persists because no new zone has
been designated to take its place. FEMA expects to provide a new designation
by the end of 1994. If at that time, the Local Levee Project meets FEMA's
adequate progress criteria, Natomas' existing A-99 zone designation could be
formally extended. This designation would allow building permit issuance with-
out structural elevation.
However, if adequate progress criteria are not met, FEMA is likely to desig-
nate Natomas as a flood restoration zone. In that event, it is unclear whether
and to what extent building permit issuance could proceed. Congress has pro-
vided in committee language attached to the AR zone legislation that this zone
designation is specifically not intended to facilitate widespread development in
Natomas.
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176
FLOOD RISK MANAGEMENT AND THE AMERICAN RIVER BASIN
CONCLUSION
Clearly, as a site for growth the Natomas Basin is well situated in terms of
proximity to urban development, but it is poorly situated in terms of chronic flood
risk. The recorded history of the Sacramento-American river system has been a
long chronology of greater than expected floods, the latest of which in 1986
nearly overwhelmed the local flood protection facilities (Kelley, 19891. Im-
provements in the existing flood protection system including the reoperation of
Folsom Dam and levee expansion are in progress or foreseeable. Other mea-
sures, such as construction of a dry flood storage dam at Auburn, are hypothetical
and speculative at this writing. Environmental, fiscal, and political contingencies
are likely to continue to delay that option and perhaps render it entirely moot.
The future level of reliable flood protection therefore is difficult if not impossible
to assess in light of both hydrologic and sociopolitical uncertainty.
Because of this continuing uncertainty, the committee makes the following
recommendations: Whatever development proceeds within the 41-mile ring of
levees surrounding the Natomas Basin should be subject to prudent floodplain
management requirements under federal, state, and local authority. Unless the
levees are certified to protect against a "standard project flood," the basin should
be designated as subject to a residual flood risk on NFIP flood insurance rate
maps. This may require the specification of a new "AL zone" classification as
recommended by the Federal Interagency Floodplain Management Task Force.
Within the area so designated, appropriate requirements concerning minimum
elevation, building design, and mandatory insurance purchase should be adminis-
tered. Flood warning and evacuation capabilities should be developed by respon-
sible local authorities. In areas subject to possible deep flooding, the designation
of in situ shelters in taller structures should be considered. The public should be
informed of the flood risks that exist in the Natomas Basin despite the presence of
the levee system. It is essential that federal agencies, and particularly the Na-
tional Flood Insurance Program, not accede to local desires to develop the
Natomas Basin under the illusion that the threat of flooding can be eliminated.
As stated by Doug Plasencia, chair of the Association of State Floodplain
Managers, in testimony to the U.S. Senate Committee on Environment and Public
Works, Subcommittee on Transportation and Infrastructure, on February 14, 1995:
If we as a nation are going to bring escalating disaster costs under control, we
need to embrace the concept of hazard mitigation. Our flood policies have not
embraced hazard mitigation, and in part are to blame for escalating disaster
damages. On an individual project basis, flood control projects have reduced
flooding for design floods. But at the same time these policies have enticed
additional development, increasing the damage potential for severe floods, or
have silently promoted the transfer of flood damages from one property to
another. Likewise, with a benevolent federal government, there has been little
incentive at the local and state levels of government to minimize the creation of
new flood hazards.
Representative terms from entire chapter:
natomas basin
