Disaster operations are probably the weakest link in the militia system for two reasons (1) capital equipment needed to be effective (2) the need to work with other organizations, civil and military who will also be in the AO at some point.

(1) requires setting up local security, and a squad can just have enough people to protect itself in a total chaos, much less set up a secure water and food operation or manage organizing a "tent city". It really takes a unit with some logistical capability to operate effectively, and especially for any length of time while the community proceeds to take stock and rebuild.

(2) means being the de facto government until the civil authority is present, and then depending on circumstances, that civil authority may be difficult to work with. If part of a coordinated effort with other military based organizations,we would need to be able to interface with their logistics and command structure. (Don't count on ammo resupply for your AK).