Don't build your house below the floodplain

If they don't, they could find themselves underwater, both literally and financially, as any insurance claim they make for flood loss or damage is likely to be rejected if the home has been built below this floodline.  

But what is the 100-year floodline, and how is it determined? Well, there are actually several floodlines for every river, which are determined by scientific modeling to show various levels that the water is likely to reach if there is an unusual amount of rain and the river breaches its banks and floods the surrounding area, which is then called the floodplain.

The modeling takes into account the local topography as well as weather records and forecasts to also work out how often these various sizes of floods are likely to occur, such as once in every 100 years, and the line indicating the level of the water in that rare type of flood is the known as the 100-year flood line.

Looked at another way, though, there is a 1% chance in any given year that a 100-year flood will occur, and given the rate of climate change, that probability may have increased substantially in many areas since their floodlines were drawn.  

However, the 100-year line is the floodline referred to in the National Water Act, and for safety's sake, most local authorities around the world as well as in SA do currently provide that nothing should be built below the relevant 100-year floodline. The plans for any new property or infrastructure development, for example, will usually have to show that it is above the flood line.

This type of town planning reduces the risk of people losing their homes and even their lives due to flooding and reduces the risk of damage to infrastructure such as powerlines, pipelines, cell phone towers, underground cables and fiber-optic networks.

Unfortunately, though, it is clear that rapid urbanisation in SA and the urgent need for more housing in many municipalities has resulted in an erosion of standards and controls, and in many people being put at risk by both formal developments and informal settlements being allowed on floodplains well below the 100-year lines. 

 And this is why it is important for all homebuyers, and especially those buying into new property developments that are close to rivers or streams, to ask to see an approved building or site plan showing the 100-year flood line and reassure themselves that they will not be acquiring a home in a danger zone.