As the nation's population has grown, more and more people have moved into locations potentially vulnerable to flooding. Major devastating floods have been recorded along the Mississippi and Atchafalaya Rivers in 1927, 1983, and 1995. In addition, in 2005, Hurricane Katrina provided another example of regional and national impacts as a result of a natural disaster, which included flooding. The Mississippi River and Atchafalaya River floods of 2011 again brought to light many of the problems that occurred in 1927 and again in 2005. Thankfully, in 2011, effective mitigation efforts waylaid many adverse impacts in Louisiana.

Given the populations and commerce established along the Mississippi and Atchafalaya Rivers and their tributaries, emergency preparedness activities have become increasingly more prominent. Timely and accurate forecasts and warnings provide critical input to the decision-making of many citizens, either through their personal actions or through governmental efforts. The use of contingency river forecasts provides additional input that can be instrumental in the planning process. Conveying clear, concise information about a range of forecast possibilities using contingency forecasts has proven to be a challenge, since most emergency preparedness officials have come to rely upon the deterministic river forecasts.

This presentation will examine the impact of contingency forecasts on the preparedness efforts within the Mississippi and Atchafalaya river basins during the flood of 2011. We will review the impacts of the floods along the Lower Mississippi River and the Atchafalaya River basins. In addition, we will examine the National Weather Service products issued to convey threats before, during, and after the event, and how they affected the preparedness efforts.