Click here for a printable version of this article.

October 2000: Flood

We've all heard the word, and we all think it won't happen to us. Not to our buildings, our buildings are too well protected. Are they really? For some of you, your plant may be well elevated above local streams and rivers. However, for many of you, your plants are located in areas subject to serious flood losses.

What is a flood and when should you be concerned? Flood is the overflow of natural or man-made barriers where water is supposed to be. You should be concerned anytime this occurs. While it would be impossible to react every time rains fall from the sky, there are guidelines and helpful reference materials that can help you prepare your facilities against flooding. Most often, your local community has Flood Insurance Rate Maps. When looking at these maps, determine what changes have been made since the time the map was produced. The map may be several years old and recent activity may have changed drainage conditions. These maps are produced by FEMA and identify 100-year flood plains, 500-year flood plains and areas not subject to flooding. The 100-year flood is a flood having an average frequency of occurrence on the order of once in a 100-year period, although the flood may occur in any given year. A 500-year flood has an occurrence probability of one-fifth of the 100-year flood. If, during your research of these maps, you find that your site is located in a non-flood prone area, but is situated near a 100-year flood zone, use common sense and determine why your site wasn't included. Errors may have been made in examining prior data, which affects the current map. These errors aren't normally identified until flooding occurs.


If flooding is possible, determine to what elevation the floodwaters are expected. This elevation should be indicated on the flood maps. Next, find out what the finished floor elevations are for your buildings. The difference between these two numbers will either be the height floodwaters will reach inside your buildings or the "safe zone" that you have against interior flooding. Remember, the finished floor elevations give you the elevations of the buildings, not the yard areas. Exterior tanks (both above ground and below ground) and storage, underground piping and utilities are all subject to flood damage.

Floodwaters will naturally strike the exterior of your building before entering the building. Your emergency plans should include, but not be limited to:

- Properly anchor all storage tanks. This also includes underground tanks, which should be filled to resist hydrostatic forces lifting the tanks.

- Raise as much plant utility equipment above the maximum flood level anticipated. This includes transformers, switchgear, electronic control equipment, etc.

- Close all unnecessary openings with masonry.

- Seal all cracks in walls and floors with hydraulic cement.

- Provide valves or check valves in all underground sewer or drainage lines to prevent flood waters backing up into the building.

- Elevate critical machinery inside the plant and make preparations to relocate stock, computers, etc. to a higher elevation.

- Consider construction of a reinforced concrete floodwall or earthen levee to protect the plant.

- Provide sandbags to protect window and door openings. These should be pre-filled and readily available.

- Provide sump pumps to eject seepage. An emergency generator may be necessary to power this equipment in the event of major power outages.

A well-trained and organized flood response team familiar with all aspects of the site can greatly reduce losses. Management must be actively involved to allow time to properly plan for the necessary actions needed. Remember this flood response team should be instructed for both pre-flood and after-flood activities. Salvage operations should begin immediately by drying stock and equipment. Make a list of priorities for clean up. Power supplies are a necessity. If power was turned off, make sure it is safe for it to be turned on again. Determine whether interior hoses can be used to wash down equipment and floors. Finally, examine your flood plan to determine where it can be improved. If you are at all unsure, contact us. We are here to help you.