When communities accept Federal Emergency Management (FEMA) flood maps, they also adopt appropriate code regulations for properties mapped within the 100-year floodplain. The rationale: municipalities should be concerned with the safety and welfare of their resident and businesses; complying with codes should reduce the enormous cost of flood damage; if there were no limitations to increases of impermeable surfaces (like roofs and pavement) in flood zones there would be greater flood damage; and, anyone who buys a home on the floodplain needs to understand the risk they are taking.
Landowners of property within a 100-year floodplain are not restricted from building, however structures must comply with the adopted codes. New homes should have basement waterproofing or be elevated above the base flood level. Roads, driveways, fill, and utilities cannot hinder - thereby increase - water surface elevation or diminish flood carrying capability. Mobile homes and fuel tanks need to be anchored. These codes generally require a design by a licensed architect or engineer. All codes are meant to connote that those who occupy flood hazard areas should assume responsibility for their actions, for what they do could very well endanger themselves or others.
Unfortunately, many of the FEMA maps are inaccurate. They were a quick attempt by the federal government to identify areas most likely to be hit by floods. Only by re-mapping flood zones, taking into consideration historical documents, information from eye-witnesses, specific geomorphological factors, and particular hazards like areas of ice jamming, can towns begin to have maps that reflect possible flood hazard areas. This takes time and money.
Also, many property owners don't want to be put into a flood hazard zone because their insurance rates will be higher, they'll have to follow codes, and they believe re-sale value will be lowered. All those things may be true, but look at the alternative: homes will be built or expanded with little thought toward flood protection; the flood carrying capability of the river will likely be diminished; there could be more deaths and destruction; and costs for everyone will increase. And we haven't even begun to talk about the repercussions to the ecological health of the river. Floodplains are nature's way of providing natural flood and erosion control, helping to purify water, sustaining groundwater supplies, and providing habitat for many plant and animal species.