We have identified one important failure point, and it wasnt lack of warning. The Kerrville City Manager had the option to send actual help to get people out earlier. Instead, he gave it a hard pass with the excuse that getting more people out onto the roads could be more dangerous, because then you have more vehicles (like buses to get many people at once) on possibly flooding roads, to get swept into the water if the got out too late. Talk about a circular argument by someone who couldve sent vehicles and first responders to actually evacuate people. This guy knew early enough he couldve easily sent buses to the camps, but nah.
But back to warnings: more isnt necessarily helpful. The problem is people SLEEPING through nighttime warnings, or disregarding them, or being new to the area with no idea where to get to safety. Name after name on the lists of the dead were people who were visiting the area and staying in pretty but risky places. Especially important would be companies renting sometimes dozens or more campsites and/or cabins down on the river having evac plans, and communicating them to people who dont know the river in advance. In other words, you do the thing that makes your customers a little scared, and you tell them the risks, how to get out, and where to go, and YOU, as that property owner, have some measures in place to help first responders get to people or some transportation arranged on standby to help people leave.
Camp Mystic was another such failure. To get 725+ people out of the flood itself, they clearly had warning as well as plans, and staff knew those. But the plans werent taking into account this sheer level of flood that would cut them off on high ground and require people to be airlifted out. Not a warning issue, but a problem with choices on how to spend money or whether to plan for the worst case scenario versus milder floods.
If the city manager had made the right call to send HELP to large groups/visitors, that would have probably cut the number of deaths at least in half.