I'm not an Emcomm person, nor do I have have any experience with HF digital modes requiring a computer.
I suggest contacting the local Emcomm groups in your area to see what they're using, as you would likely be communicating with them or using their equipment.
Considerations:
Nature, severity, and duration of disaster?
Infrastructure status?
Availability of equipment and trained personnel at both ends?
Terrain and weather conditions?
Assuming no AC power, Internet, or cellular, and poor atmospheric and weather conditions, I would consider QRP CW. Probably not the type of "digital mode" you're thinking of, but CW makes it through all sorts of poor conditions, and doesn't require a computer or sound-card interface (simpler is better). All HF radios are equipped with CW.
Consider a low-current draw transceiver like the compact, rugged, and waterproof
Lab599 Discovery TX500, coupled to an
end-fed half-wave antenna that can be easily packed, quickly deployed, and configured for horizontal, sloped, or vertical orientation, depending on what's available at the station location. You'd want the lowest current draw possible, assuming you're running off DC power, maybe charged via solar (refueling a generator would be difficult if fuel stations aren't operating).
Greg