Yes, it could flood, but you can eliminate that issue by rebuilding it on top of a hill. Just add a few buckets of top soil.
You could still have an escape issue! I would suggest trenching about a foot deep around the outside walls and then fill that with concrete. The quik-crete stuff should work fine. The material cost would be very cheap.
You could still have an escape issue! I would suggest trenching about a foot deep around the outside walls and then fill that with concrete. The quik-crete stuff should work fine. The material cost would be very cheap.