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Outside a flooded house© Info

Ask students if they have seen television news pictures of people trying to protect their homes in response to a flood warning.

Very often, they will be seen building a sandbag wall.

Ask students why – and discuss the basics of the flood defence. The idea is to reduce the amount of water that might enter the property.

Split the class into three and give each group one of the following questions for exploration. They can try to find the answers there and then – through discussion or through internet searching, if available. Or it could be set as an out-of-class homework activity.

For some classes, everyone could be invited to tackle all three.

  1. Is it a good idea to put a sandbag in the toilet bowl? Explain.
  2. It can be a very bad idea to arrange sandbags higher than one metre. Why might this be?
  3. Where do you get sandbags? What could you use instead if you do not have enough?


  1. Yes, a sandbag in the loo can be good. Floodwater can enter through drains, toilets and other outlets such as washing machines. The simplest way to prevent this is by putting plugs into sinks and baths and weighing them down with a sandbag or other heavy object. Outlets from washing machines and dishwashers should be disconnected. Place a sandbag in the toilet bowl and block the washing machine drain with a suitable plug (e.g. cloth or towel) to prevent backflow.
  2. Because the pressure of water can damage the structure of the building. In cases of very severe flooding (where the floodwater is more than one metre deep) keeping water out of your property can do more harm than good. Unless your building is specifically designed to withstand such stresses, the hydrostatic pressures involved with deep water can cause long-term structural damage and undermine the foundations of a property. Therefore you should not aim to prevent water from entering your property through any windows, doors, airbricks etc. more than one metre above the level of the ground surrounding the property.
  3. Unfilled sandbags and a supply of sand can be purchased from some DIY stores and builders merchants. But if a flood is forecast, supply may be limited. Some councils may provide sandbags in an emergency. If you have not purchased sandbags and sand in advance, you can use alternatives such as pillow cases or refuse sacks and fill them with garden soil.



This resource was written by PJ White and produced in May 2008.

This resource and other free educational materials are available at






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