COMFORT - usually boot style footwear is best - get them fitted wearing 2 pair of your thickest socks so they will not be too tight.
Wear two pair of socks, it helps to prevent blisters. Your going to be on your feet alot, and you will have these boots on a very long time. Wear your two pair of socks when being fitted for the boots.
ANKLE SUPPORT - you will more than likely be walking in some very uneven terrain, on or over debris piles, and sliding in mud, etc. the added protection around your ankle will also give some protection from being cut by sheet metal etc. found at many disaster sites.
NON-SLIP SOLE - will help you be sure footed. The big lug soles sometimes don't clean out very well when loaded up with debris and mud. The soles should be easy to shed this debris by simply kicking or stomping your feet.
Some Safety Concerns - a big plus would be if the boots had a steel protective shank in the sole to help prevent roofing nails and other sharp pointed items from puncturing your feet if you step on them.
Also steel toes are a plus especially for damage assessment or CERT teams, it helps to keep your toes from being crushed should something fall on them.
If you can find the boots made of micropore laminates like Gortex etc. would be great. These micropore laminates allow the boot to breathe without letting water in. This makes for a much more comfortable boot in wet environments because your feet will saty drier.
WATER PROOFING - seals the water out - it also seals the perspiration in - causing your feet to be wet. Poor air circulation means it will take a long time for your boots to dry too.
It is suggested that you carry a spare pair of gym shoes or sandals for your down time so your feet can "air out" and give your boots a break too. The all rubber sandal known as "flip flops" are a good idea too. They are great for wearing in public showers etc to prevent foot desease transfer, and to let your feet really air out.
Have plenty of dry socks. Polypropylene or other synthetic socks are the best.
Cotton products absorbs and holds moisture - the one thing you don't want to do is retain moisture in any of your clothing.
