Flooding is simply an overflow of water, but there are many different types of flood depending on where that water comes from and why it is overflowing. For example, it could be excessive rain that has nowhere to drain to, or it could be a damaged sewer that stops normal waste water from draining away. The main types of flooding include:
- Tidal or coastal flooding
- Fluvial or river flooding
- Flash flooding
- Groundwater flooding
- Sewer flooding
In each different scenario, there will be different risk factors to examine. The severity of flooding will have an effect on the level of damage caused, as well as the type of recovery and clean-up operation required.
Tidal/Coastal Flooding
Tidal flooding is any flooding that results from the sea, whether that’s tidal rivers overflowing, or large waves crashing the sea front.
This type of flooding is usually very sudden, as the tides can change quickly and with no warning. This means that the resulting floods are extremely dangerous, especially in the case of a coastline that is frequented by pedestrians or vehicles.
Flash Flooding
Flash flooding is usually the result of exceptionally heavy rain that overwhelms drainage systems or breeches flood defences. These floods are very fast moving and unexpected, which means that they can be very dangerous.
This type of flooding is likely to rise as climate change continues. The risk is also increased by more developments being constructed on flood plains and natural drainage systems being concreted over for construction.
Fluvial/River Flooding
Fluvial flooding is any type of flood that results from rivers or waterways. They are usually the result of heavy rain that exceeds river capacity and causes them to burst their banks.
This type of flooding can usually be anticipated, as it results from prolonged rain and often happens regularly in the same areas. Residents can usually see the water level rising over a few days or weeks, signalling that a flood may be imminent.
Other causes include obstructions in the river, such as a buildup of rubbish or a fallen tree, or runoff caused by melting snow.
Groundwater Flooding
Groundwater flooding occurs when the natural water level below ground rises to well above what can be accommodated.
This can happen after prolonged or extremely heavy rainfall, and will result in the ground becoming so waterlogged that it can no longer drain water away naturally. The effects of groundwater flooding are often worsened by construction. Large, open areas are concreted over, removing soil and vegetation that would have contributed to absorbing the rainwater.
Sewer Flooding
Sewer flooding is the overflow of water from the drainage and sewerage system. It can be the result of damage in the sewers, or the capacity of the system may be overwhelmed by heavy rain, flash flooding or groundwater flooding.
Sewer flooding is extremely hazardous, as the water is full of bacteria and contaminants. Wastewater and sewage can overflow into residential areas, posing a real risk to human health and safety.
