LOUISIANA - Tropical Storm Allison flooded nearly all of south Louisiana with three months of rain in three days. The storm provided a new opportunity to evaluate the effectiveness of recent mitigation investments by Federal, State and local government. This report explores 11 projects where mitigation proved particularly effective. By reviewing the basis on which Federally funded mitigation activities were approved, the performance analysis details the damages avoided or financial savings that resulted from these activities.
In a sense, Louisiana is the floodplain of the nation. Louisiana waterways drain two-thirds of the continental United States. Precipitation in New York, the Dakotas, even Idaho and the Province of Alberta, finds its way to Louisiana’s coastline. Preexisting high land is often the result of natural levees developing along the banks of historical or present-day waterways.
Despite massive improvements to reduce the impacts of severe weather in the last 100 years, flooding is a constant threat. The State of Louisiana has more flood insurance claims than any other state in the country. Leading the nation, Louisiana has more than 18,000 repetitively flooded structures. Repetitive loss structures are the largest drain on the National Flood Insurance Program (NFIP).
As part of the National Repetitive Loss Strategy, FEMA has ranked all repetitive loss structures. The top 10,000 repetitive loss structures nationwide have received repetitive flooding to the extent that flood claims equal or exceed the value of these structures or, as is the case for most of Louisiana’s structures, have experienced four or more losses in the last 10 years.
Of these top 10,000 structures nationwide, over 3,000 are in Louisiana, more than any other state. Furthermore, the top two parishes (or counties) in terms of repetitive loss structures are in Louisiana: Jefferson Parish and Orleans Parish, both part of the New Orleans Metropolitan area. Over the last 5 years, Louisiana has made excellent progress in addressing repetitive loss issues.
In addition to mitigation, flood prevention is enhanced through regulatory programs such as the Community Rating System (CRS). To date, 38 Louisiana communities have joined CRS, an insurance rating system similar to that of the national fire rating system. From June 6 to June 8, 2001, mitigation measures and flood damage prevention regulations were tested when Tropical Storm Allison brought torrential rains through southern portions of the States of Texas and Louisiana. The storm lingered and moved slowly, dumping up to 20 inches of rain in many of the low-lying parishes of Louisiana. A Major Presidential Disaster Declaration was signed for the State of Louisiana on June 11, 2001, for 28 parishes.
In the report, there are examples of successful and comprehensive hazard mitigation. For selected stories, the cost of damages avoided during Tropical Storm Allison as a result of these mitigation projects has been estimated. These examples show that actions taken to permanently reduce or eliminate long-term risks in the state have been effective and demonstrate the long-term sustainability for communities throughout the state.