ABSTRACT

Update on the California Levee Database TO #2 Risk Factors Data Collection Task   [open pdf - 1MB]

"The following is an update on California levee database effort and Task Order 2 [TO2] - levee database and the risk factor data collection and prototype application. The levee alignment and attribution collection aspect task within Task Order 2 is complete. PBS&J [former engineering and construction company that has since been acquired and renamed to match its acquirer: 'Atkins'] has collected levees for the entire state including all 58 counties. This effort involved review of approximately 2,770 USGS [U.S. Geological Survey] quads, rectified and reviewed 860 FEMA FIRMs [Flood Insurance Rate Maps] and used Digital Ortho Quads coverage (DOQs - aerial imagery) to check data spatial alignments. Existing digital levee data was merged with the data capture form the USGS quads and FEMA FIRMs and check for location accuracy against the statewide DOQs. The scale of the data collection was done at approximately USGS quad scale (1:24,000) for most of the data. The DOQs are somewhat better then 1:24,000 so the accuracy of the data is some where between +/- 33.3 to 40 feet per national map accuracy standards. Over 147 communities were contacted for collection of data. The levee geodatabase consists of approximate 13,740 miles of spatially located levees, canals, and flood control features totaling 8,712 records. A geodatabase feature class has been developed to house the levee information."

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