Long road

This road has been affected by rain and flash flooding. Just by looking at the terrain either side of the road, you can see that the road is the lowest area with what looks like swamp on one side. I can imagine that it was a raging river flowing thru.
Some lower areas around here are constantly going under water every time we have a large dump of rain. The ground is just so wet. Thankfully flood waters in the mountains don't hang around long... But I do wonder - how often can we get flash floods before coastal towns get more major flooding??