How well served by railroads is the area ?

Basic repairs to a railway line following earthquake damage are often easier than repairing a freeway for heavy truck traffic.
A single train can transport several million litres of water either in tankers or packaged water in cans or bottles.

Some breweries are equipped, in an emergency, to can drinking water on a vast scale and some dairies can package drinking water in milk jugs. Such firms are well equipped for handling vast numbers of cans, bottles or jugs.
Railroads can transport such supplies economically in bulk over hundreds or even thousands of miles.

Here in the UK the army train in emergency repair of railways, I presume that this is also the case in the USA.