start with looking at your route(s) home.  find multiple ways to get home, and see what terrain (and how much of it) you'll be going through...  figure out how many days it'll take you, and you've got a good base to plan from... once you know how far you have to go, you'll know how much you need but also how light you'll need the pack to be...  carrying stuff for 5 miles is one thing; carrying stuff for 30 miles is a whole other story...  

definitely first aid, and an N95 mask, flashlights, and an FRS radio...  

ETA:  and read BOB - what it should be

I've posted my GHB/BOB contents here towards the bottom of the page.
Start from the first page of that same thread for a lot of great ideas.
 
 

river crossing makes a whole new game...  find every bridge within a couple of miles up and down from where you would most readily cross and figure out which other bridges would most likely be the best one to use...  waterproof bags for your gear (they make big ziplocs now that would work) and a change of clothes for you are now essentials, as is a strong rope...  

ETA:  wow - just looked at the satellite map of your AO...  not a lot of choices...  you're going to want to blend in with the college look as much as possible...  one of those bridges is going to have to work for you...  but you won't be the only one crossing on foot, I'm sure...

Isn't  possible that you could just walk across the bridge if you have to hump it back home?  I mean if you're on foot there is usually a little space that a person could walk along the bridge, or if traffic is jammed up just walk around cars. Easy as that. I would suggest getting 9mm [or whatever caliber you prefer] handgun of your choice brand and carry two fully loaded magazine and enough secured ammo to refill them both once. If you're going to need more ammo than that well you would have needed a rifle in the first place.

In mine I have the following:

3 X 20rd mags for Sig P226
1 X Surefire G2
2 X MREs
1 X Nalgene water bottle (I should probably have more)
1 X Map
1 X Compass
1 X Cleaning kit (just a small field kit)
1 X Fire starting kit

I probably should add some first aid stuff, but haven't gotten to that yet.

As far as the area specifically, as someone else mentioned, even though the bridges may be clogged, they should still be traffic able on foot, so if need be, I'll hoof it over the bridge to get back home.

An idea for river issues in the Portland/Vancouver area woud be to have a small 2 man inflatable boat in your car and a way to inflate it.
just saying

I would pack extra boxes of ammo in a GHB or magazines, but not a gun.  You will hopefully have your gun ON you.

Maps of your AO––street and aerial/topo

Compass

flashlight + keychain light in red + batts

TP

paracord + duct tape

fak

poncho or 2 thick garbage bags (used as poncho)

Cliff bars

h20

knife/leatherman

While it may seem trivial, you'd be surprised at how much people don't know there surroundings. So, if you are always between point A (home) and point B (work), every day or as time allows, try a different route, make note of interuptions - such as the bridges, or trains, or pending construction. Stop by a visitor's bureau and get some maps and tune into what could be coming up (events, etc) that may disrupt travel along your regular route and between points A and B.

Also, review of what would be needed if you had to make that trip and if it were to take several days - protection, food, water, shelter. You might take a weekend and test some routes or camping out between point A and B. the "test weekend" might allow you to better prepare your GHB to insure it's usefullness.

Ask yourself do you need extra clothes that might be more rugged than your normal clothing? how about shoes vs boots? seasonal weather may throw a hiccup too. For shelter, what would shelter require for you? bivy/blanket/rain fly/heavy jacket? Each person and every AO is different.

Now for food - MRE's are good, but they are bulky - would freeze dried food serve you better? that might require a stove. You might consider the super energy bars or survival bars - things that back a days worth of calories in a small package. You might also want to consider stimulants or energy gells to supplement your adrenaline. For water, you should have several quarts with you but also be prepared to purify additional water.

First Aid Kit - you want to cover the basics but do need to be prepared for emergencies. You may want a more involved "trauma" kit in your vehicle just in case.

Search around on the site and online - eveyone has a different list of things to include - reviewing these may help you realize a need that hadn't materialized at first. They may also mislead you to carry additional crap that won't work for you or your AO.

don't be afraid to post more questions.

Mike

If it happens, call me.  If I'm on the south side like you, you'll have backup.  If I happen to be on the north side, I'll come pick you up.