The City of London Dyke System – Vegetation Management Planning

The City of London’s flood protection dykes are barriers made of earth, built along stretches of the Thames River and the North Thames River in London. The dykes help to protect people and properties in areas that would otherwise be at significant risk of flooding.

Many sections of the dykes are covered with a dense mix of trees and shrubs. The impact of this vegetation on the dykes’ ongoing stability and performance during flooding has become a major concern. Large trees or other vegetation may become uprooted, destabilizing the soil, eroding the slope and potentially causing a breach. Hazard trees must be removed to minimize any damage to the dyke, until major repair or replacement works are carried out.

The UTRCA compiled an inventory of trees that may pose a risk to the stability of the earth dykes, to identify which trees should be removed, and completed a three season inventory of vegetation and wildlife to help determine how to remove specific trees in an environmentally sensitive manner.

Approximately 65 trees were removed between October 2013 and March 2014. These trees were the highest priority trees identified for removal. In addition, some smaller trees were removed either to provide safe access for the tree cutters, or because they would have been damaged when the target trees were being removed.

Related Reports

• London Dykes Vegetation Management Plan Preliminary Investigation Phase (Dougan & Associates, 2006)
  • Map 2. Site Location
  • Map 3. West London Dyke – Section A
  • Map 4. West London Dyke – Section B
  • Map 5. West London Dyke – Section C
  • Map 6. Riverview-Evergreen Dyke
  • Map 7. Coves Dyke and Flood Gate
  • Map 8. Byron Dyke
  • Map 9. Broughdale Dyke
  • Map 10. Nelson-Clarence Dyke
  • Map 11. Ada-Jacqueline Dyke
• Riverview Dyke Vegetation Management Plan (UTRCA, 2009)
  • Figure 1. Location of Riverview Dyke in the Upper Thames River Watershed
  • Figure 2. Location of Riverview Dyke in the City of London
  • Figure 3. Property Ownership near Riverview Dyke
  • Figure 4. Location of Riverview Dyke within the Carolinian Canada Big Picture Corridor
  • Figure 5. Vegetation Communities near Riverview Dyke
  • Figure 6a. Location of Hazard Trees on Riverview Dyke
  • Figure 6b. Location of High, Medium and Low Hazard Trees on Riverview Dyke
  • Figure 7. Location of Recreational Infrastructure
• London Dykes Hazard Tree Assessment (UTRCA, 2012) (Broughdale, Byron, West London Cavendish area, Nelson-Clarence)

What is a Hazard Tree?

The UTRCA defines a hazard tree as a tree that has structural or growth defects with the potential to fail (fall) under normal conditions and cause personal injury or property damage, and that would contact an identifiable target. The trees on the dykes were assessed mainly for hazard potential to the structural integrity of the dykes, as well as consideration for personal injury and property damage where applicable.

Most of the hazard trees identified are alive but have one or more characteristics that indicate potential failure. Characteristics assessed to determine hazard potential include: species, overall health, degree of lean, size, position on the dyke, root exposure and erosion, and potential to contact a target.

For information on the London Dyke Vegetation Management Plan, please contact:

• David Charles, Supervisor, Water Control Structures, UTRCA
• Brad Glasman, Manager, Integrated Watershed Management, UTRCA
• Billy Haklander, Environmental Services Engineer, Stormwater Management Unit, Environmental & Engineering Services, City of London