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CTFRP data is insufficient to accurately compare failure potential among species. As data accumulates, it is hoped that failure patterns for individual species will emerge. When a question arises about the hazard potential for an an individual tree, it is always best to have an expert analysis done. You can find an expert by consulting the American Society of Consulting Arborists website at http://asca-consultants.org

Eucalyptus globulus data summary:

287 reports of 5322

Mean age: 64 years, mean DBH: 43", mean Height: 81',

Failures at: Trunk: 14%, Branch: 42%, Root: 43%

Major structural defects associated with failures: Heavy lateral limbs 26%, multiple trunks/codominance 10%, dense crown 11%.

Decay was present in 55% of cases.

Precipitation: some 56%

Wind:<5mph 26%, 5-25mph 26%, >25mph 48%

There are 154 reports of P. pinea failures in the database. 57 of those are root failures and only five are from Alameda and San Francisco counties. None of the five report root cutting or root pruning, but kinked/girdling roots are listed as defects twice.

For all 57 of the root failures, two mention root pruning, two root cutting and kinked/girdling roots are listed as defects 12 times.  

London plane is the most widely planted street in the San Francisco Bay area, yet out of 5253 reports to date, only 17 failure reports have been filed for the species. Trunk: 6, Branch: 9 and Root:2

Mean Age: 32 years, Mean DBH: 20 inches, Mean Height: 36 Ft. Mean Crown spread: 22 Ft.

Decay: present at point of failure: none: 9, some: 4, unknown: 4

Other structural defects: failed portion dead: 2, multiple trunks/codominance: 2, dense crown: 1, uneven distribution: 2, kinked, girdling roots: 2 none: 3, data missing: 3

Months of failure: November-April: 8, May-October: 8, data missing: 3

Site use: High: 13

Wind: Some: 9, data missing: 8

Precipitation: none: 6, some: 3, data missing: 8

This phenomenon has occurred in several locations in the Bay Area and a fungus disease may have been involved in some cases. There is no information about it in CTFRP data, however. Your question will be referred to someone who may have better information. Stay tuned.

There are only 22 reports for E. polyanthemos. 8 trunk, 11 branch and 3 root. Mean Ht. 41ft., mean DBH 18 inches and mean age 20 years. 17 failed between November and March. 19 reports originated from northern California counties and 3 from southern California.

For the branch failures, 7 failed at the point of attachment. There was no decay noted in all but one of the branch failures. Most commonly reported defects were included bark and heavy lateral limbs.

For the trunk failures, 2 failed at ground level and the remainder from 6-30 ft. above ground. No decay noted in five trunk failures and multiple trunks and codominance were the most commonly reported structural defects.

Two of the 3 root failures reported no decay.

Weather factors: 19 failed in moderate to high wind. 3 did not report wind speed. 14 failed in the rain.

CTFRP data shows that of 18 redwood branch failures reported, 15 (83%) failed at the point of attachment. Cultural practices such as watering and fertilizing are not reported for branch failures.

CTFRP data on valley oaks is insufficient to answer your question. However, it is not unusual for large old oaks to have decay and other structural defects that can lead to failure. Check the American Association of Consulting Arborists website  http://www.ASCA-consultants.org for someone in your locality who can do a structural assessment of your tree.