Over the years, the climate has changed causing sea levels to rise and more and more people are moving to cities in search of work and opportunities leading to a decrease in land in the urban areas. For this reason, coastal cities around the world are at increasing risk of dangerous flooding (both economically and physically). Coastal cities have various defenses in place to prevent flooding, but these defenses are adapted to the current state. As sea levels rise these defenses will no longer be applicable and the city will flood. It is important that something is done now to prevent these floods in the future. If cities wait too long, the loss of life and economy will cause a disaster for cities. For the first time in history, approximately half of the world's population is classified as living in urban areas. Between now and 2050, the human population is expected to continue to grow. Forecasts predict more growth in urban areas than in rural ones. Over the course of the 20th century, the United States grew most rapidly near the coasts and around large cities. California, Texas, Florida, and New York are the four states with the largest populations and where 38% of America's population growth occurred during this time period. These states are also the most vulnerable to sea level rise and other global climate changes. While many small and intermediate cities are experiencing the fastest growth rates, large cities continue to expand in size, density and population. In these cities, the poor are most at risk. Rapid urbanization has forced them to take refuge in vulnerable neighborhoods in low-lying areas and along flood-prone waterways. More than a third of the world's population lives in the urban area of... half of the paper... highest risk of damaging floods? New Study Crunches the Numbers,” The World Bank, August 19, 2013, http://www.worldbank.org/en/news/feature/2013/08/19/coastal-cities-at-highest-risk-floods ( accessed January 17, 2014) Joel E. Cohen, “Population and Climate Change,” Proceedings of the American Philosophical Society Vol. 2 (June 2010) Michael C. Barth, James G. Titus, Kenneth J. Gregory, “Greenhouse Effect and Sea Level Rise; A challenge for this generation”, The Geographical Journal, vol. 154, n. 1 (March 1988), pp. 118-119 Edward D. Murphy, “Architects plan two-day event to explore sea level rise: Their goal is to create proposals for southern Maine and inform the public about vulnerable areas.” Maine Today , Local and state; page B1, 12 May 2011. Reuters, “Rise of the sea threatens US cities: new study”. La Stella Fenice, World; page C14. 2011