Levees, Hydrologic Uncertainty, and Floodplain Development: A Longitudinal Analysis of Yuba County, California

Authors: Burrell Montz*, East Carolina University, Graham Tobin*, University of South Florida
Topics: Hazards, Risks, and Disasters
Keywords: floodplan, levee effect, uncertainty
Session Type: Poster
Day: 4/5/2019
Start / End Time: 3:05 PM / 4:45 PM
Room: Lincoln 2, Marriott, Exhibition Level
Presentation File: No File Uploaded

Prolonged, heavy rain in Northern California led to the evacuation of over 180,000 residents in Butte and Yuba counties in 2017 after the capacity of Oroville Dam, which spills into the Feather River, came into question. Since the completion of the dam, the highest flows along the Feather River occurred at the confluence with the Yuba River in January 1997, resulting in levee breaks, extensive flooding and the evacuation of 85,000 residents. Hydrographs, including probabilistic ensembles, are helpful in anticipating and therefore preparing for flooding but their impact on long term decision-making is unknown. Thus, despite this information and the history of flooding, development of the floodplain along the Yuba and Feather rivers south of Yuba City, California continues. The levee system has been extended and additional embankments were erected between 2004 and 2011 to accommodate the 200-year flood event. In part reflecting the levee effect, Olivehurst, among other communities, has experienced high population growth and increased housing values in newly developed and revitalized areas despite the history of flooding and failed mitigation structures. Analyses of census data, land cover change, FEMA flood zone designations and county development plans indicate that several factors have precipitated expansion other than available land: (i) population pressure and the need for housing; (ii) certification of the levees that now confine the extent of the official floodplain; and (iii) the fact that flood insurance is no longer a requirement for homeowners.

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