Types of Flooding
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 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, and of course the severity of flood will have an effect on the level of damage caused, as well as the type of recovery and clean up operation that needs instigating.
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 the resulting floods, especially if large waves are flooding a coastline that is frequented by pedestrians or traffic, are extremely dangerous.
Flash flooding is usually the result of exceptionally heavy rain, that overwhelms drainage systems or coincides with failed flood defences. The flood are very fast moving and unexpected, which means they can be very dangerous.
This type of flooding is likely to rise as climate change continues. The risk is also increases as more developments are being constructed on flood plains, which is undermining the effectiveness of natural drainage systems and flood defences.
Fluvial flooding is any type of flood that results from rivers or waterways. Usually, they are the result of heavy rain that can exceed the capacity watercourses and cause them to burst their banks.
This type of flooding can usually be anticipated as it results from prolonged rain and often happens in the same areas over and over again. As well as this, people nearby 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 build up of rubbish or a fallen tree as well as melting snow that can worsen the effects of the 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 it can no longer drain water away naturally. Often, the effects of groundwater flooding are worsened by constructions, as large open areas are concreted over and trees and vegetation that would have absorbed rainwater are removed.
Sewer flooding is the overflow of water from the drainage and sewerage system. It can be the result of damage in the sewerage system that stops the water flowing, or the capacity of the system can simply be overwhelmed by heavy rain, flash flooding or groundwater flooding.
Sewer flooding is extremely hazardous as the wastewater and sewage can overflow into residential areas where the bacteria poses a real risk to the health and safety of people in the area.