(FORTUNE Small Business) – For my business, Rhodes Architectural Stone, I travel frequently to China and India. I'm often setting up factories in remote areas where I can't count on having electricity or clean water. I was never a Boy Scout, but managing to get by in reliably unreliable Third World countries has been an education. When I went to New Orleans on business in August, I found out just how relevant that knowledge would become.

Hurricane Katrina wasn't supposed to make landfall until Monday, Aug. 29, and my meetings ended Sunday morning. I was confident I could fly home before it hit. I called the airport every half-hour. They kept saying, "No problem, Mr. Rhodes. You have a confirmed seat. Sit tight." By Sunday morning, New Orleans was under mandatory evacuation, and there were no rental cars or bus tickets to be had. My flight, now the only option, was at 7 P.M. on Sunday; by then, the airport was closed.

A friend told me that the Ritz-Carlton had just installed hurricane-proof glass and that its generator was on a higher floor to keep it above potential floodwaters. I managed to finagle a room, and after signing a waiver that, yes, I knew I was staying at a hotel in the path of a Category 5 hurricane, I checked in.

Immediately I hit the streets to gather supplies. When the power goes down, ATMs and credit cards are useless. Banks normally let you take out only $300 a day from an ATM, but what they don't advertise is that you can ask them to lift the limit. In an emergency, $300 is not enough. I was able to take out $2,500.

In the French Quarter people were laughing and joking. It was an odd feeling, as if I were watching people dance in the ballroom of the Titanic. When I found a convenience store that was still open, the people inside were buying beer, soda, potato chips, and cigarettes. I was stupefied. The shelves were nearly empty, but I was able to buy four cans of beans, four cans of nuts, six liters of water, two limes, and a small bottle of bleach.

The bleach was for a trick I picked up in China. In remote areas there you can't get bottled water. Even the locals stick to tea, which they boil for 15 minutes. After a while, I got tired of brushing my teeth with tea, and I learned that two drops of bleach in a liter of water makes it potable. If you put a slice of lemon or lime in it, it doesn't taste like a city pool. Now when I travel in developing countries, I always pack a vial of bleach. (This also works for bathing--one teaspoon in a gallon of water.) In the hotel room I filled every vessel I could find with tap water: the bathtub, the trash can, the coffeepot, the vase, all the glasses. Then all I could do was wait.

After the hurricane, it was more than 100 degrees and humid in the hotel. None of the windows broke, but, then, none of them opened either. The winds created a hole in the penthouse, allowing in the torrential rains. Everything was damp. We had no running water, and after the diesel backup generator ran out of fuel, we were without electricity too. There was three or four feet of flood water outside. Toilets backed up. From the mold, the humidity, and the close quarters, people started getting diarrhea. Babies all had fevers. One of the guests was a doctor, and he set up triage in the hotel for what he estimated was 2,000 people. With police help, he raided a pharmacy for supplies.

In business an alliance gives you twice the Rolodex, twice the resources, and twice the knowledge. I teamed up with a TV news reporter from Los Angeles, Kurt Knutsson. He shared a very useful fact--analog phones work even without electricity. We swiped one from the hotel lobby and wired it into my room, which gave us an intermittent ability to call out. We had the only working phone in the hotel, and we were able to take down people's names and get word to their families. I shared my food and bleach with Kurt. Through the whole crisis, we were a team.

The scariest time came Tuesday afternoon when there was gunfire outside and we could see looters in the streets. Two nearby buildings were on fire. Sitting in the dark hotel, the fire alarm started going off, repeating over and over, "Mandatory evacuation of the building. This is not a test." Everyone was burning candles in their rooms, so we wondered if the hotel was on fire. We couldn't leave--the water outside was visibly fouled with sewage. People were panicking. I was truly terrified.

It was then that we finally got through to Los Angeles. KTLA TV, for whom Kurt regularly reports, and the Tribune Co., its corporate parent, agreed to send a helicopter. I pitched an idea to the hotel manager, the same way I've pitched business plans: We needed a way onto the adjacent roof so that the helicopter could bring supplies in and get people out. I explained to him that I'm in construction and architecture. I could evaluate whether that roof was sound. We needed a crew and paint to mark out a helipad. He agreed and found us passageways that led to the roof. My lightweight plastic compass--another thing I always pack to orient myself in new cities--allowed me to tell the pilots our location relative to the Superdome.

We got picked up about 9 o'clock on Wednesday morning. As we cleared the buildings, the water came into view, extending as far as we could see in all directions. We saw bodies floating in the water, people standing on cars waving white T-shirts. We didn't see any Army, any trucks, any police. There was nobody in control. At the hotel we had had no idea of the scale of the disaster.

It takes a tremendous amount of energy to stay calm and clear during a crisis. Back with my wife and five daughters, I finally allowed myself to be exhausted. For a week I could barely form a coherent sentence. I'm grateful that the Ritz-Carlton staff kept order and lawfulness when many other hotels did not. But I also know that the experiences I learned through my business--leveraging a network, having a plan, revising that plan as necessary, and staying clear-headed during times of fatigue and drama--pulled me through Katrina.