Water has created an underground channel in my yard that seem to continue down and under my garage. There is not a lot of drop from the back to the street. Else, we could put a French drain below the channel and divert the water around the garage. One contractor recommends a sump be sunk in the ground and the water be pumped from there. Another contractor says the problem with sump pumps is that in heavy storms, when you most need the drainage, the electricity is likely to go out. How serious a problem is this?