FEMA Flood Zones and the 100-Year Event
Each lot, plot, section or tract of land has a designated flood zone regardless of whether it is located in a hazardous flood area. A flood zone is a geographic area that the Federal Emergency Management Agency (FEMA) has defined according to varying levels of flood risk. Each zone reflects the severity or type of flooding in the area. A floodplain is an area subject to periodic flooding. Floodplains are delineated by the expected frequency of flooding. For example, an annual floodplain is expected to flood once each year.
Even the arid desert southwest can have problems with flooding. In Arizona, the County of Mohave Flood Control Division, says that one of the greatest problems the Flood Control District has is convincing new county residents that flooding is a problem. The District says that floods that create major damage in a desert happen for four reasons:
- A large population base;
- Location in a major drainage basin;
- The chance for large storms with greater than normal precipitation; and
- Inadequate drainage conveyance. 1
In rural areas dirt roads and subdivision layouts were often built without taking into account the natural drainage systems of the washes and lands. In the cities, structures, parking lots and asphalt roads do not absorb water like the land as it was prior, resulting in a whole new set of flooding problems.
In the southwest desert areas the most frequent cause of flooding is heavy rain. Intense thunderstorms with heavy rainfall can cause flash floods, common in the desert monsoon months between July and September. Couple these flash floods with inadequate community drainage systems and there is no place for the local runoff to go. This is why adequate drainage facilities must be accounted for when a preliminary plat is submitted for approval.
FEMA maintains flood plain delineations on a set of maps called Flood Insurance Rate Maps (FIRM). Mortgage companies are required to determine if a property they are financing is located within a 100-year floodplain (any zone designation beginning with the letter A). If so, the mortgage company can require the buyer to obtain flood insurance. This information must be disclosed in most State Subdivision Disclosure Reports.
What is a 100-year flood or event? Contrary to what it sounds like, it is not a flood event that happens once in a hundred years. It is a flood that has a one percent chance (or, 1 in 100) of occurring in any given year. A 5-year event has a 20% odds, a 10-year event has a 10% odds, a 50-year event a 2% odds, and a 500-year event a .2% odds. The few and far between floods tend to result in more deep and forceful water flows. The more frequent floods result in more shallow and less forceful water flows, although damage is still possible. The general rule is that water volume increases as the probability decreases.
A 100-year floodplain is also known as a Special Flood Hazard Area (SFHA) and if a lender determines that a property is in a SFHA, they must have flood insurance, or apply for a Letter of Map Amendment (LOMA) or a Letter of Map Revision (LOMR). They may also apply for a Letter of Determination. All of these applications first require the support of an Elevation Certificate. An Elevation Certificate is required in order to properly rate post-FIRM buildings. Post-FIRM buildings are those buildings constructed after the finished flood elevations bring them up out of a flood insurance zone — as in raised house pads. This certificate does not provide a waiver of the flood insurance purchase requirement. Only a LOMA or LOMR from FEMA can amend the FIRM and remove the Federal mandate for a lending institution to require the purchase of flood insurance.
Always determine which flood zone property is located in before you decide to purchase even if the land is located well inland of a body of water. At the very least, you need to know whether flood insurance is going to be a requirement of your lender. In addition, you need to educate yourself as to alternatives that may be available through amending or revising current FEMA maps.
Contact Nancy at nancy@nancysvirtualoffice.com or 928-766-2810 for help in finding flood zone information and other due diligence property research prior to making your purchase.