Dear Michelle:

Thanks for your question on whether it is safe to apply a strong vinegar for controlling blackberry and bamboo shrubs near a creek.

Herbicidal vinegars are typically 10-20% acetic acid as compared to household vinegar which are about 5% or less. Herbicidal vinegars are effective  contact dessicants in controlling small leafy -herbaceous plants.  However, they are ineffective for controlling large woody shrubs like blackberries (I assume you are trying to control Armenian/Himalayan blackberries) and bamboo where a substantial part of the plant are growing in rhizomes underground.  I have included below several Extension references from OSU Extension and sister Extension programs on ways to control blackberry and bamboos
Is vinegar effective as an herbicide?  Also included are Extension references on the use of vinegar for weed control.

Please note that herbicidal vinegars above 7% are strong acids  (many are 10-20% acetic acid) and must handled as used carefully and according to the product label.

Is vinegar effective for killing weeds?
https://extension.oregonstate.edu/ask-extension/featured/vinegar-effective-killing-weeds
Vinegar, an alternative to glyphosate?
https://extension.umd.edu/resource/vinegar-alternative-glyphosate/
Acetic acid: understanding its uses and precautions
https://chem.garden/herbicides/acetic-acid/

Methods to contol blackberry thickets
https://extension.oregonstate.edu/news/methods-control-blackberry-thickets
NC Extension reference on controlling bamboo
https://content.ces.ncsu.edu/controlling-bamboo-in-landscape-plantings

Please feel free to Extension if we can be of further service.

Sam Chan
Statewide Watershed Health and Aquactic Invasive Species Specialist
Sea Grant Extension, Oregon State University