Flood Risk Management and the American River Basin An Evaluation (1995) / Chapter Skim
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5 FLOOD RISK MANAGEMENT BEHIND LEVEES
5 FLOOD RISK MANAGEMENT BEHIND LEVEES
Pages 164-176
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From page 164... ...
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 securitythat leads to new growth within the area (White, 19751.
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From page 165... ...
. 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; .
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From page 166... ...
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?
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From page 167... ...
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 physically 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.
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From page 168... ...
Local political jurisdiction over Natomas is divided among the city of Sacramento, 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.
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From page 169... ...
As of mid-1994 the only urban facilities in Natomas Basin north of Interstate 80 consisted of the Sacramento International Airport in unincorporated Sacramento 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 basketball team, and to prime the pump of development in North Natomas.
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From page 170... ...
NFIP Status of Natomas The development of the Natomas Basin is further affected by its novel status under the National Flood Insurance Program (NFIP)
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From page 171... ...
of Water Resources, MaD of American River- Sacramento Estimated Potential Flood Depths, June 1 993.
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From page 172... ...
Matsui that viewed the exemption with dismay (PI. Duryea, personal 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]
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From page 173... ...
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)
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From page 174... ...
The American River Project Levee bordering Natomas was constructed by USACE after the completion of Folsom Dam (U.S. Bureau of Reclamation, 1986)
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From page 175... ...
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.
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From page 176... ...
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.
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