Flood Insurance Study and Map

At last night's meeting, many people had questions about the origins of the flood maps. This is technically called a Flood Insurance Rate Map (FIRM). It has been digitized and can be seen as a layer in the Johnson County GIS site and the maps I have produced for the meetings. This flood map should always be used in conjuntion with the 2007 Flood Insurance Study (FIS). This study provides good background on previous floods and how the map got updated, specifically the hydrologic and hydraulic methods used to estimate base flood elevations, floodways, flood zones, etc. You can also find the base flood elevation for your house using the flood profile. This comes in handy if you are wondering if you have to raise your house (only applicable if you are in the 100-year). I've attached the FIRM for the neighborhood and a select number of pages from the FIS since it is a large document. The FIS should be able to answer alot of the questions posed last night, even those regarding changes in land use, or at least you'll find a reference.

As far as the GIS maps, maybe people are wondering why they look off. You may have noticed that flood plain may not resemble the topography or may go through part of your house. Understand that the FIRM has been digitized at a larger scale. Plus, layers used to create the maps, such as parcels, contours, and aerials, come from different sources. That leaves more room for error. Use these maps for general purposes only, not for decision making. If your structure is not clearly in the 100-year or 500-year plain, and you haven't resolved where you structure stands, go to the Housing Inspection or Engineering deparments in City Hall. They have survey drawings with more precise information. Julie Tallman in Housing Inspection is happy to show the maps to you and can help you determine your flood zone and base flood elevation.

I know this is alot of information. If you have any additional questions about the above, email me and I'll do my best to help you out. Feel free to post this on the blog as well.

Africa Espina
828 Normandy Dr.
africaespina@gmail.com


Click on link below to see Flood Insurance Study and Map

http://www.razztech.com/floodmap.html