[verb (plain)] + 恐れがある [noun] + の + 恐れがある
恐れがある means "there is a risk that ~": something bad could happen. A verb goes before it in the plain form, a noun with の. It is the wording of news reports, weather warnings and official notices, which often write it in kana, おそれがある.
A conditional in front often names what will bring the risk on.
恐れがある is only for outcomes nobody wants. For something good or neutral, use かのう可能せい性がある, "there is a chance".
The phrase is formal and written. In conversation the same warning is かもしれない: かわ川があふれるかもしれない. The negative おそれ恐れはない means "there is no risk", and おそれ恐れもある adds a risk to one already mentioned.