Councillor Raphael Hill
Green Party Councillor, Brighton and HoveHow can surface water flooding be combatted?
Every city in the UK is, to a greater or lesser degree, susceptible to surface water or pluvial flooding from extreme rainfall. According to the Met Office earlier this year, extreme rainfall events could be four times as frequent by 2080 compared to the 1980s. Unlike other forms of flooding, you do not need to live near a body of water to be affected by this type of flooding.
The Frequency of Flooding
In the early morning of June 10th 2023 in Brighton, we experienced what is considered a โone in 200-yearโ flood event caused by a brief but exceptionally intense downpour. This event caused a huge amount of property damage and stopped traffic on major arterial roads. However, calling it a โone in 200-yearโ flooding event is a bit of a misnomer, given our future will be characterised by erratic weather patterns. It might be more accurate to say that without climate change, this would be likely to happen once in 200 years, but in practice, the frequency depends on our collective custodianship of our planet. As well as improving our planetary custodianship, we also have to make urban environments more resilient in light of this change. Sadly, not all of Brighton is well designed to deal with even smaller flood events than the one in June. In my ward of Round Hill, a number of residents live in fear each time there is heavy rain. This is because of a confluence of issues that lead to them being repeatedly at risk of flooding. The flood risk is normally at its greatest in autumn due to the blockage of drains by autumn leaves. These are not only issues affecting Brighton & Hove, and all councils must now consider their flooding response.
Implementing Solutions
Streets particularly affected in my ward span a large hill up to Brighton Racecourse. In times of extreme rainfall, this hill goes from being a busy neighbourhood street to a river-cum-log flume for bins, as pictured. Part of the reason for this is the fact that it is largely a concrete impermeable surface. This means that unlike in a rural environment where water soaks into the soil, the water instead rushes down the hill at speed. One solution proposed to ameliorate this is putting in rain gardens, a type of sustainable drainage solution, or SuDS, which involves planting special water absorbent plants into beds. These plants stem the flow of the water and, according to the Edinburgh Royal Botanic Gardens, can be 30 per cent more absorbent than a normal lawn. This has the added benefit of looking nicer than concrete and creating more green spaces, which are carbon sinks. They also need to be maintained, which is not always easy given current labour shortages and the lack of funding for local government. Although an effective tool, this would be insufficient to stop the events seen in June. There are permeable pavements out there that are like concrete minus the sand. However, permeable pavements are only as good as the material underneath them and may not be appropriate in many instances, such as this.
Effective storm drains are, of course, an essential part of the solution. During high-intensity rainfall, they can get blocked, particularly by autumn leaves or when bins empty into them. The cleansing of these is a constant battle, made harder again by cuts – so there is a need to prioritise the drains that matter most to avoid flooding. Even seemingly small things like litter picking and leaf sweeping can make all the difference in ensuring effective drainage. More drains would certainly help but there is also a need for better system capacity as this would lead to more pollutants – which threaten marine habitats – being discharged elsewhere. Like many cities, Brightonโs poor capacity in its stormwater collection systems stems from years of neglect by its water company, Southern Water. Any improvements they make to this capacity will cost billions, the cost of which will be seen in far higher water bills for consumers in the near future.
The Importance of Collaboration
Sometimes flooding is made worse by other unintentional changes to roads. It is vital that councils consider water flow when making even seemingly minor changes in roads and other places. Minimising the effects of surface water flooding requires a high degree of collaboration across council departments, which too often work in silos.
There is no silver bullet solution to surface water flooding in urban environments, but it has to be at the forefront of planning changes to urban environments, even where water is not normally present. The costs of mitigation are vastly less than the damage from surface water flooding.