Here's an "innovation challenge" that I believe is very relevant:
To save crops in drought situations, one needs to get water to the affected areas. There are potential solutions to this problem and its perhaps more of a (non)implementation issue today. So let's put that aside for now.
Consider the converse situation, however: Saving crops when there is excess or untimely rainfall or hailstones coming down. This, I believe, requires a technological innovation.
Can this be done? If so, how? What might be some of the short term options that can be implemented say from next year itself? And long term options that may perhaps take a few years to deploy but are better/more economical.
This might be something cool to work on, get it patented and see it through to deployment. This might also be one heck of a final year project for Civil Engineering students :)!
Note: I don't think the real challenge in the above scenario is deploying roofs/shelter in quick time. One can potentially think of solutions to that part. Rather, the challenge, in my opinion, lies in the following questions: How would one take away all that water coming down from the skies and do so fast enough? Where would one take it? What would one do with it? Store it? Or take it all the way to larger water bodies such as rivers or seas/oceans? How?
From what it seems like to me, we are quite possibly talking about the need for a pretty large scale and a very very well thought out solution! Good luck :).