When many Earthen dams were built not many people lived downstream like now

So, they were not perceived as that great a threat to human life then. However, now with Atmospheric rivers in California (or other states Global Weather concerns) there is more danger during Global Climate change and more people buying land downstream from earthen dams across the U. S.  And many of these dams have no emergency plans in place at all because it wasn't thought they were needed when the dams were originally built because people had a different criteria for danger then because it was between 1900 and 1960 or 1970 when most dams were originally built. Most dams in California are not safe in an Earthquake by the way because they were built before big quakes like the 1971 San Fernando Quake, and the 1989 Loma Prieta Quake, and the 1994 Northridge quake drastically changed building codes here in California.