This week is National Tree Week (23rd November – 1st December), which has always marked the start of the planting season, but this year there’s been another timely reason to give particular thought to tree planting: flood mitigation. Flooding has been in the news again in recent days, with Storm Bert resulting in more than 200 flood warnings in England and Wales, and Storm Conall following on closely behind just days later (with 90 flood alerts in place at the time of writing).
Tree planting can help with stormwater mitigation, and given that intense downpours are anticipated to be four times as frequent by 2080 compared with the previous 100 years (according to research by Dr Elizabeth Kendon at the University of Bristol), it’s more important than ever to consider flood prevention measures such as SuDS (Sustainable Drainage Systems), and how they might be optimised to create long-term benefits.
Healthy trees offer better urban flood mitigation
Healthy trees play a critical role in SuDS because they provide multiple layers of surface water management that other solutions cannot replicate. Firstly, the expansive root systems of trees act as natural sponges, absorbing excess water from the ground, reducing runoff and increasing soil infiltration rates. When stormwater is able to infiltrate more effectively, it minimises surface water accumulation, which is one of the main causes of urban flooding. Unlike impervious surfaces like concrete or tarmac, healthy soil surrounding tree roots can hold significant quantities of water, making trees highly efficient in helping regulate the water cycle in urban environments – but to do this to best effect, the trees must be thriving.
It’s not only a tree’s roots that help reduce flash flooding caused by heavy rain, either. The canopy of a mature tree helps intercept rainfall before it even hits the ground, reducing the volume and speed of runoff, giving stormwater management systems more time to cope with large volumes of water. This can make the difference between a functioning system and an overwhelmed, flooded one.
Benefits of urban trees beyond stormwater management
Trees also offer significant ecological and social benefits to urban environments. They not only improve air quality and enhance biodiversity, but by creating cooler microclimates they also slow down evaporation and help stabilise soil, further decreasing erosion and supporting healthy groundwater recharge. This means that healthy trees within a SuDS framework are not just mitigating floods, but actively contributing to creating more pleasant, enjoyable urban spaces.
As a result, urban areas that incorporate thriving trees into their SuDS designs also see a boost in community well-being and property value. Green spaces and tree-lined streets are proven to reduce stress, increase recreational opportunities, and make neighbourhoods more desirable.
Thriving urban trees for climate resilience
However, simply planting trees into the ground and letting them get on with it is not enough. They need to be planted and maintained correctly in order to deliver the maximum level of benefit. Factors like soil health, root space and irrigation all require careful consideration, especially in urban environments where space is tight, hard landscaping abounds, and competition for resources can be intense. Ensuring trees have uncompacted, nutrient-rich soil and proper root management systems means they can establish robust root networks that contribute more effectively to stormwater absorption.
Urban-specific planting strategies, such as underground guying and advanced irrigation, help trees thrive in challenging settings. Proper root management ensures strong growth, protects paved surfaces, and supports urban infrastructure.
Moreover, innovative attenuation solutions, such as the StormForm™, demonstrate their effectiveness in mitigating peak stormwater flows. As a key component of our ArborFlow tree pit systems, the StormForm™ works alongside other GBU products to create fully compatible and functional SuDS tree pits tailored to site-specific requirements. The ArborFlow system includes all the necessary elements for a successful SuDS installation, offering a versatile approach to urban tree planting that aligns with broader climate resilience objectives.
Incorporating trees into urban flood resilience plans is essential. As storms intensify due to climate change, trees in SuDS offer a proactive, nature-based solution, benefiting both communities and the environment.
