Influences on Adaptive Planning to Reduce Flood Risks among Parishes in South Louisiana
Among all natural hazards, floods pose the greatest threat to the property, safety, and economic well-being of human communities in the United States. The economic impact from floods is estimated in the billions of dollars annually (Association of State Floodplain Managers [ASFPM], 2000; Pielke, 1996). According to data from the Spatial Hazard Events and Losses Database for the United States (SHELDUS), the average number of floods per year has increased six-fold, from 394 floods per year in the 1960s to 2,444 floods per year in the 1990s. SHELDUS data also show that in the 1960s floods caused $41.69 million dollars of damage a year. By the 1990s, average annual property damage from flooding increased to $378.12 million dollars a year (in 1960 dollars). It is our proposition that rising flood-related property damage may not be fully explained by inflation or population growth or even by increases in annual mean precipitation. In addition to these factors, increasing costs of floods might also be driven by the manner in which humans plan for and subsequently develop their communities. Individual and community-based decisions pertaining to where buildings and impervious surfaces are distributed, and the degree to which hydrological systems are altered, may be exacerbating losses. Increasing development associated with residential, commercial, and tourism activities, particularly in coastal and low-lying areas, has diminished the capacity of hydrological systems to naturally store surface water runoff. As a result, private property, households, and the economic well-being of coastal communities are increasingly vulnerable to the risks of flooding events. In his book Disasters by Design, Mileti (1999) states that disasters do not simply happen, but largely result from how we design and build human communities. We aim to test this central thesis through a quantitative model that will isolate the effects of specific built environment characteristics on flood damage. Despite its importance, few studies addressing this issue have been conducted longitudinally, over large spatial scales, while controlling for multiple biophysical and socioeconomic variables. We examine 383 individual flood events within coastal counties in Florida between 1997 and 2001 in an effort to better understand how planning decisions and resultant features of the built environment influence flood damage levels over time. These decisions may involve federal, state, or local governments and have varying degrees of public The rising economic cost of floods in the United States cannot be explained solely by monetary inflation or growth in coastal populations. Damaging flood events are also influenced by the way society plans for and physically develops its communities, influencing where structures and impervious surfaces are concentrated and how hydrological systems are altered. We analyze 383 nonhurricane flood events in Florida counties between 1997 and 2001 to isolate how planning decisions and their effects on the built environment affect property damage caused by floods. Our results suggest that alteration of naturally occurring wetlands significantly increases the property damage caused by floods, all else equal. Also, nonstructural methods such as the Federal Emergency Management Agency’s Community Rating System, while providing inexpensive means of reducing property damage directly, may also indirectly encourage more development in hazardous areas.