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River management is when humans take measures to try and ensure that flooding does not happen again in an area.

The answer isn’t always to relocate people from the affected areas to higher ground. What we need are preventative measures that will reduce the sea level rise immediately as well as flood defences that will protect homes, buildings and the natural environment. It’s not one or the other - we need to tackle the root cause of the climate crisis as well as mitigate the devastating effects as much as possible. We want to keep local rivers, such as the River Lagan, at their current level - even a few centimetres rise would leave them susceptible to catastrophic flooding.

What causes a river to flood? There are a number of factors that cause a river to flood:

• no vegetation
• urbanisation
• steep slopes
• rock type
• dry soil or wet soil

It depends on where the river is located and its geographical context. When there is no vegetation that means there are no leaves or trees to take up or hold the water. This means that the water will make its way into the river channel quickly - which can cause a flood.

The construction of many roads and buildings in a confined space, called urbanisation, means that water goes quickly to the river (through pipes and drainage systems) and does not absorb the water as much as a natural habitat would.

Steep slopes in both urban and rural environments can cause the rain to run more quickly downhill to the river. Impermeable rock types (like slate - which does not allow water through) can stop water soaking into the soil.

Sometimes when the soil becomes wet it cannot allow any more water to be stored or stay in the soil. This is when the soil becomes waterlogged and the water will start to move across the surface instead.

So what is the risk of flooding near the River Lagan in Belfast city centre? The flood risk to the city is very high. There are many physical and human factors that have caused this risk.

For example, there is lots of urbanisation near the river, which enables the rainwater to go more quickly into the river. As a result, this increases the risk of flooding because when it rains the water is not able to soak into the soil. There is also no vegetation to take up or store/hold the water.

In 2021, the United Nations Intergovernmental Panel on Climate Change declared a code red for humanity. Between 1901 and 2018, the global mean sea level rose by approximately 20 centimetres.

The report predicts a further 15 to 25 centimetre rise by 2050. If global emissions are not reduced immediately, then this accelerated sea level rise will have devastating consequences for millions of people around the world. Entire, low-lying nations already vulnerable to flooding could be completely submerged in water in 30 years’ time.

There are many of us here in Northern Ireland that think the rising sea level will have its impact in faraway places and not here. However, this couldn’t be further from the truth.

Unless action is taken, non-profit organisation Climate Central predicts that a huge mass of Belfast city centre will be at risk of severe flooding by 2050. This area includes Belfast City Airport, Saint George’s Market and the residential areas situated along the River Lagan.

Other rivers across NI are also liable to breaking their banks and flooding nearby areas if the sea level is allowed to keep on rising.

Flooding can cause damage or destroy people’s homes and built environment, but it can also cause significant pollution - washing chemicals and sewage into the water. The contaminated water will spread quickly over an area, creating health hazards and killing river animals and fish.

There are many ways to prevent and reduce the risk of flooding, or at least lessen its impact.

These ways can be classified into two groups - hard engineering and soft engineering.

Hard engineering is the construction or placement of big objects such as embankments, walls, levees, dams, groynes or boulders to protect areas along rivers or the coast.

To avoid major disruptions to the natural environment, soft engineering works with the landscape and uses techniques to allow floodwater to interact with the land and not with the built environment.

Such techniques take the pressure off urban areas and populations and are more sustainable than hard engineering methods.

Techniques include - washlands, land use zoning and afforestation. Washlands, for instance, sometimes known as flood plains, are created on land upstream away from urban areas for flooding to occur naturally with little damage to property.

Connswater river is located in East Belfast and in 2007 the river flooded and damaged the built environment in Belfast. Even though it is a small river, the flood still managed to close businesses, damage homes and cars. In total, the flood affected 340 homes.

To make sure nothing on this scale ever happened again, the East Belfast Flood Alleviation Scheme was formed to find new ways to protect areas at risk of flooding from the three rivers in East Belfast — Connswater, Knock and Loop — helping to ensure that the community was protected against flooding in the future.

They did this by upgrading the sea defences at Sydenham as well as providing protection from river flooding for approximately 1,700 properties. The scheme improved the ecological environment as well as creating new green community spaces, such as the Comber Greenway and a 9 kilometre park that follows the course of the Connswater, Knock and Loop rivers.

Both soft and hard engineering techniques were used that not only prevented future flooding, but also made the space more liveable for people and for the ecological environment.