Here’s a diagram of a river before reservoir impoundment
https://www.researchgate.net/figure/Landscape-transformation-from-a-river-to-a-reservoir-A-Pre-impoundment-conditions-the_fig2_320955675
Apparently there’s another dam on the Guadalupe river it’s called Dittmar falls it’s about 22 miles from Canyon lake dam does anyone know if it flooded too? maybe more attention should be on the US army corps of engineers and whoever runs these dams because every time there’s a flood it’s not really an act of nature but there’s a reservoir and dam involved that should have been lowered anticipating flooding