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CCH GIS Data Dictionary

Flood Zones- polygons which depict flood zones as defined by the Federal Emergency Management Agency (FEMA).
 
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Notes
References
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Last Update: 2002
Agency/Dept: DPP

ATTRIBUTES:
COLUMN NAME
DESCRIPTION
 SAMPLE
flood_zone the designated flood zone or flood way (AEF), possible values include:
  • A = 100 Year Flood, No Base Flood Elevation Determined
  • AE = 100 Year Flood, Base Flood Elevation Determined
  • AH = 100 Year Flood, 1 to 3 Ft, with ponding
  • D = Undetermined Flood Hazard
  • V = 100 Year Flood, Coastal, Wave Action, No Base Elevation determined
  • VE = 100 Year Flood, Coastal, Wave Action, Base Elevation determined
  • X = Beyond 500 Year Flood Plain
  • XS = 500 Year Flood Plain AEF = 100 Year Flood, Flood Way Area With AE
 
uniform_fld_ht (not used)  

NOTES:
The layer Flood Elevation Labels (Flood_Height_Poly feature class) shows areas with a uniform height (HT).
This is the height above which the first floor must be built.
The layer Flood Elevation Lines (Flood_Contour feature class) also designates the height at which the first floor must be built. The first inhabited floor of a dwelling unit must be above this elevation.

Note: all heights based on mean sea level except where FTZONE = AO and value of 1,2,3 it is based on grade.
The City and County of Honolulu encourages GIS data users to verify the suitability of the data before use. Please report any discrepancies or errors found to gis@honolulu.gov.

Use Constraints:
When using this layer in relation to other layers, the user must exercise caution because the source document was drawn at a scale of 1" = 1000' and other layers, such as parcels, were input at 1" = 40'. Theoretically, the flood layer could have a 40 foot horizontal error. When comparing this layer to other layers which were created from a source document scale of 1:400 or larger (like 1" = 40') it is recommeded to check other available sources and to strongly suggest that a site survey be conducted for those areas where a flood hazard boundary is represented.

LINEAGE:
The flood layer was originally digitized from the 1987 FIRM (Flood Insurance Rate Maps) maps. DPP created a set of manually drafted mylar maps at a scale of 1"=1000' delineating the 1987 flood hazard zones in relation to parcels and topography. These were updated to reflect the 1990 FEMA flood surveys and recent isolated site surveys.

In 2002, specific FEMA Panels with changes identified by an experienced planner in DPP were digitized by using plotted mylar overlays with flood tile tics from FEMA panels as well as flood section tiles set at 1” = 1000’ scale and adjustable to 1” = 500’ as need be as coverages Registering FEMA panels (15003CO030, 035, 045, 237, 239, 240, 310 and 351) corresponds with library section tiles (s1t7, s1t8, s2t8, s6t7, s7t6, s7t9) respectively using a Altex digitizing board with a RMS error of .003.
Next, digitized FEMA panels with all pertinent lines, polygons and points were coded and merged with extracted library section tiles. However a closer scrutiny indicated that most of the other FEMA panels’ line work and related information were affected too, some rather noticeably. A decision was made to go beyond the original project’s parameters to make whatever updating necessary to reflect the latest FEMA panels. As a result nearly 70% of the 2000 FEMA panels’ information were examined and digitized to reflect accurately as possible our flood layer

DPP is currently looking at another round of updates based on the 2006 data delivered to Holis by FEMA.
REFERENCES:
Federal Emergency Management Agency

COVERAGE:




Flood Zones

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