Flood Map Modernization

Understanding the Effects of Map Changes

Map Modernization Phases

Digital Flood Insurance Maps


Flood Hazard Information Request - County

Flood Hazard Information Request - Nogales



December – March 2009
90-day Public Comment Period (appeals and protests must be filed during this time).

Spring-Summer 2009
Review and resolution of appeals and protests by FEMA.

December 2009
Maps Revised based upon accepted appeals and protests.

January-March 2010
Second 90-day public reviews and comment period.

April-June 2010
Review and resolution of appeals and protests by FEMA.

June 2011
Final Maps issued by FEMA with Letter of Final Determination; county and communities have 6 months to adopt the new flood maps.

December 2, 2011
New digital flood maps become effective.

Flood Map Modernization: Understanding the Effects of Map Changes



Flood hazard maps can be valuable tools in the effort to protect lives and properties. The County’s current flood maps are nearly thirty years out –of-date. The new flood maps provide a much more accurate picture of flood risks and flood elevations to guide in land development and building decisions.

Engineers/Developers/Builders can plan for safer construction

When preliminary flood maps are released, the building industry will need to know the differences between the preliminary maps and the current effective map. The data from the more conservative map is typically used by communities for design and permitting purposes. This will remain the case until the preliminary maps become effective. When the preliminary map shows less restrictive information, it usually cannot be used until that map becomes effective.

The vertical datum is changing

As new flood maps are issued, they will no longer be using the National Geodetic Vertical Datum of 1929 (NGVD29) as the vertical datum (see the Federal Emergency Management Agency’s Procedure Memorandum 41). Instead, they will use the North American Vertical Datum of 1988 (NAVD88). Floodplain managers, surveyors, engineers, builders, and other users of elevation data from multiple sources (e.g., a FIRM and elevation certificate) must take care that the elevation values they use are based on the same vertical datum. If they are not the same, the values need to be converted to the same datum. Failure to do so can result in improper design (e.g., building at the wrong elevation). Note that the property owners’ risk is not affected by a vertical datum change because all elevations in the local area are changed by the same amount.

Additional information can be found on the Resources Page.

For General Information, call:
Santa Cruz Flood Control District
Open 8:00 a.m. to 5:00 p.m.
Monday through Thursday