There are a wide variety of different types of flood defences to prevent flooding and protect your home or commercial property. These range from passive to active measures including sandbags, water dams and inflatable barriers that can be inflated or packed away when the flood waters rise. There is also a large selection of semi-permanent and permanent options like levees, flood gates and sea walls that can be left open during periods of mild weather or closed to mitigate severe flooding events.
Choosing the right type of flood defence for your property depends on what you need it to do and how long you want it to last. A temporary flood barrier is great for preventing flood damage to your home, garden or any outdoor equipment such as sheds and summer kitchens. Sandbags are a cheap, readily available option that can be used to block the outer crevices of buildings or contain rainfall on low-elevation sites.
More permanent flood defences like levees, dikes and berms are designed to prevent flood damage along rivers and coasts. They can be constructed to a specific height or width to ensure that flood waters will not exceed a certain level. This can be beneficial for communities that are prone to frequent flooding. However, studies have shown that these structures tend to disconnect rivers from their floodplains and reduce the natural benefits that they provide. This is due to the fact that they promote urban and agricultural development on the floodplains, which can lead to increased flood risks for the surrounding areas.
Passive flood defences are usually more expensive than their active counterparts. However, they tend to pay for themselves over time due to their high service life, minimal maintenance and true floodproofing capabilities. Some passive barriers require no electricity, personnel or training to activate and can be installed in places where traditional flood defences are unable to reach such as doors and stairwells.
Active measures like flood doors, logs and bladders are relatively cheaper than their passive counterparts but they can be expensive to operate and maintain over time. They must be transported to the area, inflated or packed away between flood events and stored at a safe location. They are also known to be less effective than their passive counterparts in preventing flooding. They have been shown to be only around 30% effective in reducing flood losses during 1-in-5 year events, and even less efficient for 500-year return periods. Moreover, they have been known to disintegrate or breach over time. Therefore, homeowners and business owners should not use these types of barriers for their permanent flood protection.