Population immunity is described as the number of individuals in a given population that is sufficient to prevent the transmission of a disease from the infectious to the susceptible. Although high population immunity usually prevents epidemics, we have seen many epidemics that were caused by infectious agents such as the Severe Acute Respiratory Syndrome (SARS) and Influenza type A H1N1 viruses.

Although the 2004 Indian Ocean tsunami was the most devastating in history, tsunamis are a recurring peril for all coastal communities. This experiment evaluated the possibility of using an undersea trench, offset from the shore, to physically reduce wave amplitude at the shoreline.