I was flooded in a campground on a weekend trip. I had gone overnight to Lockhart State Park when a storm came through and dropped ~6" in Lockhart and up to 14" in parts of east Austin. The site was grassy and pretty level and as I awoke, my pad was still above the water but there was perhaps ~1/2" of water underneath the tent that I could mostly push down on. I waited a bit and then dashed to nearby shelter and waited until it got light. Once light, I retriever and packed up my belongings and cycled back home. On the path home there were three spots where water went over the road. One of them I could wade through, one was a raging torrent of several feet that I detoured and the last was barely so I could ride.
During that storm several hundred houses in Austin were flooded by Onion Creek in what eventually turned out to be a buyout. After the flood and 14" they redrew the flood maps and decided these houses were now in a 25 year flood plain where-as prior they had estimated it as a 100 year. From a variety of funds, the city ended up buying out the houses.
Not bicycling, but I had an incident when hiking in Canyon country of Utah. Our trip went through a canyon where prior to the rainstorm we could mostly walk in bottom of the canyon including occasional wading in shallow puddles. We had camped well enough so we weren't flooded, but we had to replace our normal method of travel to instead walk along banks of the canyon which took a lot more bushwacking. Eventually we got to a spot where things narrowed and we had to cross. In that case, we got a line across and ended up carefully bringing the party through the water one by one while tied to the line and making sure nobody got swept away.
Then there is my childhood memory:. Each Spring Break my family would take our pickup truck camper and travel for a week. Since it was typically cold in CO, this meant a trip to south or west. This was a year that we went to see Big Bend National Park and then on the way back via Dallas. I was perhaps 10 years or so and was enthused enough to want to camp in my tent rather than sleep in the camper. Things started out fine an evening when we were camped in a State Park near Dallas, but a severe thunderstorm came through with thunder and lightning as well as a bunch of rain and wind. It dropped over my tent pole and a lot of rain came in to make everything wet. I was fine and holding the tent pole back up as part of the adventure. However, my parents thought otherwise and made me come back into the camper. I was not happy with that. The next day driving back with the camper, we ended up with a flat tire on the truck. While this was being fixed, we got out my tent and sleeping bag and strung out a line to dry in the sun. So here we were like gypsies along I-35 with a truck tire being replaced while we had a clothesline and tent with things drying in the sun and breeze.