Some of the things I would recommend other fellas like Wally have already suggested like a good pair of work gloves, and a hat. The hat I have used is from a company called "Sundayafternoons.com" It is a lightweight vented hat with a huge floppy brim and tail that will cover the full length of your neck.
You are building a 48hr go bag to get you from point A to point B, B being a place of safety. Do you plan on keeping this go bag in your vehicle?
I would add in a case of bottled water to your vehicle. It is very cheap security as you can take what you need to fill your personal water containers and either give some away as charity or even barter. Rotate it out every few weeks.
As far as water containers go, the Camelbak water bladders are very popular and I used them in the military however they can be punctured. You want to have at least 1 hard plastic military type canteen with you perhaps in conjunction with a bladder type water container. Another option would be a steel single walled bottle like the popular Kleen Kanteen. The advantage to the steel bottle is that you can boil water in it. Make sure it is a single walled bottle or canteen as a doubled wall bottle can explode when heated.
While I think it is great to have a pair of rugged lightweight sandals with you it is very important to have a pair of rugged broken in hiking boots or military type boots. I suggest the ones with a hard rubber sole versus the tactical sneaker style that you see today.
The concern you had was flooding. You will want to protect your feet with a pair of boots in contaminated water where you would no doubt be stepping on all types of debris. You want to use sandals for allowing your feet to dry out as well as your boots.
You need to pack some foot powder and moleskin for your feet. Remember to massage in the powder to your feet as this will help with circulation. DO NOT shoot powder into your socks as it can clump and blister your feet. When you stop to take a break from walking make sure you check and massage and powder your feet. If you feel a hot spot on your foot, if safety permits stop and address it.
One of the things you will face and it will take you out quickly is something called "Trench foot". Your feet being constantly damp will break down your skin, cause all your toenails to fallout, leave you open for infection and if the infection goes into the bloodstream it can kill you. While all this is taking place something so simple as not caring for your feet will absolutely immobilize you. You will go nowhere.
Medical wise you were not specific enough for me as Adventure Medical Kits makes multiple kits.
If you are slogging along in contaminated water you figure there will be dead animals as well as people, I would see about talking to your family doctor and getting a prescription of antibiotics that would address the type of illnesses that you would encounter under the outlined conditions. If you cannot get antibiotics from the doctor there are other options. Search online for alternatives like fish antibiotics and livestock antibiotics. Many preppers use these means but it takes research and personal responsibility and at your own risk.
Keep your meds in a small waterproof container or bag. Keep your band-aids and other minor 1st aid items separate from your trauma gear.
Pack a laminated map for the areas you operate in, go to school, work, etc. If SHTF take the map/s that apply to you when you grab your bag and go, leave the rest behind. If your budget allows you might consider a handheld GPS but even if you invest in one you still need to carry the map and compass as a backup.
Well in a natural disaster you may face looting, roving bands of people robbing others. You might consider clothing that allows you to blend into your environment. You do not need to wear military camouflage fatigues, that could draw attention from authorities. Subdued earthy tones for clothes is good. It can keep you more low profile and help keep people from wondering what cool items you may have in your pack.
You want to have the clothes made from materials that will wick away moisture and are lightweight. You can find these types of clothing even in places like Walmart (if they have Walmarts in your country). In other words you don't need to blow $400.00 on a tactical pair of pants.
Pants wise I like fatigue pants, you can get them in solid colors and even in shorts if you so choose. If you do decide on camouflage the best single style for all environments is the "Multi-Cam" by Crye Precision.
In a flooded environment should you have to bed down in that, you will want to have a mosquito net. Mosquitos and flies are major disease vectors. And in a flood will be out in full force in such an environment.
SnugPak makes something called the "Jungle Bag" that is meant for tropical environments and has a built in net for insects. I would still pack a full mosquito net separately. A military poncho can complete your shelter system with this bag. The poncho can also be used for collecting rain water if setup properly.
Ditch the canned goods as you will be carrying extra weight for no reason Remember ounces equal pounds and pounds equal pain. I will tell you what a Special Forces Soldier told me about food for a go bag. he said pack bullion cubes. You will not need a lot of food for 48 hours. The bullion will help flavor water that may not taste so good.
You do not want to eat without having water as you will dehydrate yourself, If you want some food for your planned 48hr kit, consider the tuna and chicken breasts that come packed in a heavy foil pouch. for protein. Some M&M peanuts for carbs. Consider some freeze dried foods in foil pouches like Mountain House as they are lighter to carry and you won't be eating unless you have water. For 48hrs or even 72hrs food is not going to be your biggest concern. Military style MREs (Meals Ready To Eat) are yet another option. 1 MRE is designed to give you the calories you need to sustain you for 24hrs. So in theory you only would need 2 in your pack.