Like many of our colleagues, we have taken plenty of calls about sometimes large branches breaking and falling from large, mature trees which look otherwise healthy and thriving.
Known as Summer Branch Drop (SBD), there isn’t much research out there to help us understand what it is and why is happens, nor then of how if can be prevented, but with acknowledgement and thanks to Arb Consultant Jeremy Barrell and Barrell Tree Care, here are some pointers about what is known from recorded incidents:
1. Where and when could SBD happen?
- In large mature oak, beech, horse chestnut, and cedar trees, although it does occur in other species
- After heavy rainfall following dry periods longer than three to four weeks
- In the early afternoon, often in calm conditions, immediately following the rainfall
2. Assessing the risk from SBD
- Where people come close to trees, duty holders (any owner of a tree – including householders – or manager of a site where trees could cause harm) have an obligation to assess the risk of harm from tree failures and take proportionate measures to reduce significant risks. SBD is a known mechanism for branch failure and the potential for harm that arises from it should be considered in the risk assessment process.
- In practice, site managers should identify large mature individuals of the most vulnerable species, assess whether harm could arise from a branch failure, and take reasonable and proportionate measures to reduce any significant risk of harm.
3. What are the Practical Management Options?
There are a range of management interventions that are likely to reduce the risk of SBD occurring in vulnerable trees, and the risk of harm arising where it does occur, including:
- Prune to reduce the length of the longest branches on vulnerable trees
- Restrict access to vulnerable trees with barriers during critical periods
- Place notices at public entrances or close to vulnerable trees to warn of the risk of harm during critical periods
- Warn of the risk through website and social media posts.
4. What should duty holders do?
- Duty holders should be aware of the risk from SBD and factor it into their normal risk assessment procedures.
- They should specifically consider whether they have any vulnerable trees, the level of access near those trees, and the elevated risk during critical periods.
- Due to the uneven and erratic distribution of summer rainfall, critical periods will vary across the country, so managers should monitor their local weather patterns and be particularly vigilant shortly after heavy rain follows a prolonged dry period. If a failure that causes harm results in legal proceedings, it is likely that duty holders will be expected to have factored SBD into their risk management processes, and taken reasonable and proportionate measures to reduce significant risks of harm.
For advice and assessment of your trees, contact Andrew on 07771 883061, 01256 817369 or email him at Andrew@PrimaryTreeSurgeons.co.uk