The Act credated a coordinated National Flood Insurance Program, incorporating: (1) Risk identification/assessment: mapping of flood prone areas in communities which joined the NFIP. (2) Risk mitigation: adoption of a set of floodplain management regulations that cmmunities must agree to adopt and enforce as a condition to their participation in the NFIP. (3) Insurance: the federal government was authoized to arrange for the sale of federally supported flood insurance in communities which have joined the program. (4) Subsidization: insurance premiums for properties in existence when a community joins the NFIP are subsidized (acturarial premiums for many of these older, high risk properties were considered unaffordable). Insurance for properties constructed after a community joins the program (and thus have presumably been constructed in accordance with flood plain management ordinances) is intended to be set at acturarial levels. (5) Attrition of high risk properties: while existing properties were grandfathered from compliance with new floodplain ordinances and could be insured at subsidized rates, a structure damaged more than 50% by flooding must be relocated or reconstructed in compliance with current floodplain management regulations. (Abbott, pp. 132-133)