Cranfield University has used the an aerial tree map to assess the link between the roots and sewer damage
A team from Cranfield University has used an aerial mapping service to produce data on the relationship between trees and damage to sewers in East Anglia.
The researchers were able to establish the extent of the correlation between tree roots and sewer blockages by combining the Bluesky National Tree Map and long term data from Anglian Water, along with the location of infrastructure such as pipes and manhole covers.
According to Bluesky, the Cranfield team has been able to show the likely zones of root intrusion, that bigger trees have less impact than medium sized trees, and that foul sewer systems were most prone to intrusion.
A postgraduate researcher, Jan Vodicka, has created a spatial database of trees, sewers, manholes, blockages, flooding incidents, pollution events and sewer maintenance jobs using the water company data and the National Tree Map, which details the location, height and canopy cover of more than 280 million trees around the country.
The study showed that sewers near trees are 1.4 times more likely to be intruded compared with those with no trees nearby, and 1.8 times more likely where there are three or more trees.
Blockages are 30% more likely in areas with more than 200 trees per kilometre of sewer than in those with less than 150 trees, and 40% more likely where trees are 3-7 metres high compared with where they are over 12 metres high.
The research also found that foul sewer systems and pipes with small diameters are the most prone to tree intrusion.
The researchers hope that the project will pave the way for such data to be used in tree planting strategies, urban planning and proactive maintenance programmes for sewers.
Dr Timothy Farewell, senior research fellow at the Cranfield Soil and Agrifood Institute, said: “Tree roots are very good at exploiting weaknesses in sewer joints. Root intrusion into sewers can cause significant problems including blockages and significant serviceability issues.
“Trees can also impact on other underground assets by exacerbating soil related ground movement through fluctuations in soil water content.”
Image: Street trees in central Peterborough, from Bluesky