Although working in floods is essentially the same as working in water, flooding brings some specific issues. River levels vary greatly depending upon factors such rainfall, snowmelt, release from dams, etc. Most of the time, river level will be within the river channel and therefore its flow and features are relatively predictable. However, as river levels rise they will eventually reach a point where they are “bankfull” and any subsequent rise will see the riverbanks overtopped and the water flowing through the adjacent low areas of land also known as the floodplain.
Generally, the increased volume of water means that most previously-existing river hazards, such as low head dams, become more powerful and dangerous, although some may actually become “washed out” or less dangerous. At high water, there is a new range of hazards as water flows through and around obstacles that were not designed to be in the water. Major hazards are created by parked cars, fences, hedges, gates, road signs, and park benches. In addition, there may no longer be enough clearance for boats to pass under bridges.
Flood water will carry large amounts of debris that can build up against houses and bridges, etc. causing structural damage and presenting a significant risk to anyone in the water.
As water flows through the flood plain, there is an increased chance of contamination by hazardous materials such as sewage, agricultural waste, and pesticides.
It is worth noting that once the water overflows the riverbanks and spreads across the flood plain, this may result in an apparent reduction in the speed of the water. However, the water flowing in the area of the original river channel will still be flowing at its previous rate.
These factors combine to make working in floods a hazardous and arduous task.
The “100 Year Flood”
Massive Floods are often referred to as the “one in a hundred year flood”. This does not mean that they will occur once every hundred years, but rather, there is a one-in-a-hundred or one percent chance of such a flood occurring every year.
A “one in two hundred year flood” represents a one-in-two-hundred or 0.5 percent chance of the flood waters reaching a certain height in any given year. It is even possible for two “one in a hundred year” floods to occur on the same river, in the same year, or even in the same month. Looking at historic flood data and river flow measurements allows for computer models to be developed which can be used to produce flood return statistics and detailed flood mapping to aid in the pre-planning process.
Most recently, in May 2010, 100 year floods hit parts of Tennessee, Kentucky and Mississippi as the result of torrential rainfall. The Cumberland River in Nashville, TN reached levels not seen since 1937.
Although floods may appear to be random natural catastrophies to some. We have a goo understanding of what the requirements will be for rescue teams involved. We know that By their very nature floods are:
- Multi-agency events
- Multi-jurisdictional events
- Hazmat and public health events
- Long-term events
Rescue teams and emergency planners must understand that floods have their own set of characteristics that differentiate them from other moving water incidents, and therefore also have specific response requirements. With effective pre-planning, specific training and the appropriate equipment designed for these incidents, members of the public will be better protected from the effects of flooding.
At any major flood event, there will be many agencies on-scene. It is essential that these agencies communicate effectively, and work together efficiently.
Flood water does not respect any authority’s jurisdiction or county boundaries. As a result, rescue teams will often work with teams from other areas. By establishing common training techniques and equipment in advance, this mutual aid process can be greatly simplified.
The public health implications of large-scale flooding are clear given that large numbers of people may be exposed to contaminants. The very young and the very old are most at risk. Health services in the area may be stretched to capacity.
The long-term nature of flooding cannot be overstated. Flood response can easily exhaust emergency personnel and community members emotionally, mentally, and physically. Inspective of the resources available, there will always be a call for more. The reality is that years after the rescue response has been completed, members of the public may still be living in temporary accommodation, waiting for their homes to be rebuilt or refurbished.