Physically an EMP does not really damage homes, buildings, structures, cars, trees, or any living thing directly. It is theorized (rightly so) that some humans, those with pacemakers, for example, will be directly effected. Incidental damage from fires caused by the massive electrical surge, 50KW per meter, are very possible and a real threat, but I am not talking about physical devastation. I am talking about the cost in human life.
In an EMP/Grid down scenario, there will not be tens of thousands leaving the cities, at least not at first. Even when they leave it will not happen all at once, unless a massively nasty occurrence like a firestorm or hurricane drives them out. No single person is going to want to leave the security and safety of their “home” until the food runs out, and even then not right away. Sure they will struggle a few days in the dark, (and if the summer) hot nights. However, they will literally not leave until there is nothing to drink, no water, and no way of getting anything to drink. Some will even stay until they are on the brink of starvation, or dehydration. This would be 3 weeks if they are able to procure drinkable liquids and no food, 3 mere days if they have food, but nothing to drink. Perhaps a week, if they are wise and drink the water from their stockpile of canned vegetables.
These people will be sitting there thinking “The government will drop food”, “They will send FEMA”, “The Red Cross is coming”. Many thoughts along those lines. Normalcy bias, is real, and in this case will cost lives.
Deaths from any serious SHTF scenario will be upwards of 75-80% of any population, the elderly, the critically ill, the ones who must have daily dialysis, those reliant on medications. Within 1 month, 70-80% of the populace, is dead, from what ails them or lack of life saving medical help. In the case of an EMP/Coronal Mass Ejection Solar Event, it could be as little as a couple of weeks.
Add in attrition – murders, falls, infected cuts, lack of potable water, rampant disease like cholera (the lack of electrical power means the sewage systems will stop working, and it has been supposed that they may even run backwards briefly during the surge) going untreated or under treated, fires, people dying of heat stroke (summer) or freezing to death (winter), animal bites (unfed dogs going feral, and attacking in packs), take another 5-15% off of the total populace of any given major city. That is anywhere from 75%-95% of any major metropolitan area’s populace dead within one solid month of a massive SHTF scenario. If the SHTF scenario is an EMP or solar event, and the city is one like Los Angeles that must have almost all of it’s water pumped in from over the mountains, advance the timeline to a mere 3 weeks, barring a decent amount of rainfall that can be collected by wise or canny people.
This is not an attempt to scare anyone, it is an attempt to put some facts out there to be considered. I have said it many times before, and I will likely say it again and again: water and food must top your list of preps.
Just an opinion, YMMV. All postulation anyhow. Fictional, you know…
Got preps? Pray for the best, prepare for the worst.