How Is the Severity of a Flood Measured?
Floods are the most common natural disaster plaguing Americans, according to the Federal Emergency Management Agency (FEMA). Floods are particularly insidious in that cleanup and recovery can take weeks or months after a flood event. Some effects such as mold may pose long-term human health hazards. According to FEMA, there is no measuring system for floods that is similar to those that measure hurricane and tornado speeds. Measuring the severity of a flood is therefore possible on many different fronts.
According to a report by the National Climatic Data Center, floods cost Americans more than $500 billion between 1980 to 2005. One of the worst events during this span was the Great Flood of 1993, which occurred in the Upper Mississippi River Valley. Cost estimates from this flood alone are over $20 billion.
Floods typically don't cause great losses of human life, primarily due to advanced warning systems. Floods can take days or weeks to reach maximum levels. Flash floods, however, can occur within seconds. Flash floods are caused by excessive rainfall or other source of water such as snow melt that occurs in a short period of time. According to National Weather Service, floods caused 43 deaths in 2005.
It is harder to place a monetary value on the costs of flooding for the environment. Impacts may include soil erosion, especially in the case of fast-moving flood waters. Oftentimes, sewers or septic tanks will flood, introducing a host of contaminants into the environment. Organic waste can continue to impact the environment long after the flood. For example, waste may cause an algal bloom in surface waters such as lakes and ponds. As the algae dies off, decomposing bacteria deplete the available dissolved oxygen. The decay also lowers the pH and raises the ammonia level in these waters, creating ecological dead zones that cannot support any life.
Some floods create ripple effects in terms of the other areas they impact. Floods occurring over major transportation routes can disrupt interstate commerce. Floods can last for hours or even weeks, compounding the financial costs, which can often affect people in areas where flooding did not occur.
An unfortunate consequence of floods lies within the cleanup costs, not only to communities, but to individuals as they struggle to bring their lives back to a sense of normalcy. According to Flood Smart, even a 3-inch flood can cost a homeowner more than $7,000 in cleanup and replacement costs. Often, floods destroy items that do not have a monetary value, such as family photographs and other heirlooms. Sometimes, the loss of these personal items supersedes the financial loss.