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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

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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.

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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.