According to FEMA, a Base Flood Elevation is

“The elevation of surface water resulting from a flood that has a 1% chance of equaling or exceeding that level in any given year.”

But what does this mean exactly?

Well just think about how water rises in a pond during a storm event, it functions the same as water in a bathtub.

Consider this, there is a 1% chance you might forget to stop the flow of water, and which can flood the room

This funny analogy is exactly what Base Flood Elevation is, it is the percent chances of a base level flood each year. Sometimes it ranges from a 10% minor flood event to a catastrophic event of a 0.2% or 500-year flood event.

The translation from percentage a “year” event is often misleading as a 500 “year” event can happen multiple times during that 500-year cycle.

While we would like to have only one 500-year event, it unfortunately can happen multiple times during that same 500 year period.

This is why we seldom use year events and is more accurate to say the percentage of a type of rain event happening every year.

How GIS comes into play

As it pertains to GIS, you can identify what areas of your property are with flood maps. FEMA offers FIRM maps or (Flood Insurance Rate Maps), but there is a problem as this can often be confusing to see your location with these maps especially if they are scaled out on a city or county level

GIS professionals can assist with making it easier to identify and view hazardous flood areas, and providing solutions of where you can build drainage structures.

Going back from the previous analogy, a drainage structure is a like a “bathtub stopper” that can mitigate the flood has on your area. The stopper is like flood mitigation measures, such as elevating your home or business.

It can effectively decrease your chances of flooding and can make the base flood elevation (BFE) be a lower elevation in your local area.

In layman’s terms, it takes a larger storm event to flood your property with proper drainage structure implementation.

Conclusion

Base Flood Elevation is a measurement by FEMA (Federal Emergency Management Agency) that can be confusing at first glance but is just the elevation of 1% chance flood event each year. Knowing this is very useful as it can allow you to see where it might flood when you know the elevation of the BFE. Anything under this elevation might flood during a high rainstorm event.

GIS professionals can identify these hazardous locations easily with digitizing established FEMA firm maps. They also can allow you to mitigate the effects of floods by identifying areas where drainage structures can be installed or built.

With the utilization of GIS, you can save yourself from the rising rates of floods that are increasing in strength every year.

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