The problem states that I have to come up with best possible predictor of a 100yr flood plan. Well I found that best projection and I have to state why.

Could I say: The projection from the power trend line is a better indicator because with the probability of 0.9638 this calculation foretells an increased chance of a flood.

I know it shouldn't be hard but its confusing me.

I'm not a "math person," but I have a couple of questions for you that might help you re-think your wording.

The projection from the power trend line is a better indicator better than what? because with the probability of 0.9638 this calculation foretells an increased chance "increased" in relation to what? of a flood.

Math teachers may have further ideas for you.