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boundaries and SFHAs, FIRMs will often show areas behveen the 1 DO-year and SOD-year flood boundaries, areas called "moderate flood hazard areas." These areas are designated for advisory purposes only, and no flood plain management or insurance purchase requirements apply. The remaining areas on the map are above the SOO-year flood level. There may be localized flooding in these areas due to storm\vater or small \vatercourses that have not been studied by FEMA. SFHAs are further subdivided into flood zones for floodplain management and insurance purposes. Generally, these zones indicate the type and/or depth of flooding. Most floodplains are designated as zones AE, AI-3D, or A. Zones AE and AI-3D include areas that have been studied using detailed engineering methodologies. Zone A includes areas that have been designated as SFHAs but for which no BFEs have been established. These areas are usually not subject to sufficient development pressure to warrant the expense of a detailed study. The FIRM may also display zones VE, VI-3D, AO, or AH. Zones VE and VI-3D are coastal high-hazard areas subject to high-velocity \'.:aves. Zones AO and AH are areas of shallow flooding due either to sheet flooding or ponding. Zone AO has depth numbers in place of BFEs that indicate the depth of water above grade. Zone AH is also a ponding area, but it does have BFEs designated. In riverine areas, FII'{Ms will shmv designated flood ways. The regulatory flood way is defined as the channel of a river or other waten-vay and the adjacent land areas (Le., the floodplain) that must be reserved in order to discharge the base flood without cumulatively increasing the water surface elevation more than a designated height. (See Figure 1-3.) Regulation of development in a flood,,,,'ay is important because obstructions there \vill increase flood levels, resulting in more damage to upstream and adjacent property owners. NFlP standards allow for a reasonable amount of development in the floodplain outside of the flood\vay to minimize the potential for increased damage due to constriction of the natural floodplain. Local officials have the responsibility to revie".... all proposed development within the tlood\vay to determine whether proposed actions have any adverse impact on the floodway's carrying capacity. This requirement is intended to protect other property owners in and adjacent to the floodplain from increased flood damages as a result of inappropriate development. Furthermore, NFIP minimum criteria require that buildings in the floodway meet the same design standards as buildings elsewhere in the floodplain. Specifically, new residential construction must be elevated above the BFE designated on the FIRM. (See the section on minimum NFIP requirements bellHv for a more detailed description.) More than half of the states also do their o\\'n mapping of flood hazard areas. In many cases, state maps are able to provide communities ""7ith greater detail and better scale than FIRMs. State maps often also reflect specific changes in developed land and hydrology within flood hazard areas (Federal Interagency Floodplain Management Task Force [19921, 6-28). FEylA has invested more than $1 billion in developing FIRMs and studies. Despite this investment, many experts warn against overreliance on the maps by local government and property owners to determine which lands are risk free. There are instances in '\vhich the original study or map did not accurately reflect flooding conditions. There are also instances where the study or map does not reflect changes in hydrology or man-made activities in and adjacent to the floodplain. Floods of a greater magnitude than the lOO-year flood do occur. Finally, due to funding limitations and other policy reasons, not all floodplains have been mapped by FEMA. For example, small \\'atersheds or localized drainage problems are often not mapped, in part because they are complex storm"\'ater management problems best dealt '\vith at the local level. In rural areas, floodplains were often not mapped because there was no development pressure \-\Then the study was done. As a result, significant losses can and do occur outside of FEMA-designated floodplains. For all these reasons, communities are encouraged to evaluate their flood study and maps to ensure that they fully reflect the flood risk and are an adequate basis for planning and regulation. Communities can request that FEMA initiate a restudy of their floodplains, or they can conduct flood studies of their own. Local goverments may also \-vish to recommed that property owners outside but \-vithin close proximity to the mapped floodplain also purchase flood insurance. NFIP l\1inimum Requirements To make flood insurance available for their residents, communities participating in NFIP must agree to regulate new development in the floodplain. NFIP has four major requirements for new construction in the these areas. FEMA encourages states and communities Figure 1-4. When the Maps Are Wrong To accommodate changes within floodplains that may render maps inaccurate and to maintain its investment, FEMA has establisned a number of procedures to revise or appeal maps, or to restudy areas of communities. These procedures are available for those cases in "vhich a FIRM has shmvn the flood hazard incorrectly or contains other errors so that it can be redra,'\'n to incorporate new data and to recognize new flood control measures (e.g., reservoirs, levees, cnannels, fills, and any otner type of development that llJS the effect of removing a property from the floodplain or lo\-vering BFEs). Changes or corrections to a FIRM can be made through a Letter of Map Amendment (LOMA), a Letter of ~'lap Revision (LOMR), and physical map revision. Information on map revisions is available from FEMA regional offices or the local floodplain management coordinator. 7