You haven't made it clear whether the brook is part of your property, a neighbor's, or is public domain. That being said, if it is part of the Parks Dept., you would notify them of the problem. In any case, you may want to notify EPA since they would want to protect a natural brook and such a problem could endanger other life forms. If it is on your property, you might want to consult with specialists. The site that has water flow clogged should be addressed so you can avoid more of the same with heavy rain or snow which will leave your property subject to water backing up and continue causing problems. Excess water should be drained after clogs are cleared, to avoid added moisture attracting mosquitos in the spring.