Most homeowners whose homes have been destroyed by Tropical Storm Harvey face financial devastation as well because insurance won't cover any of their losses.

Why do so many people in Houston lack flood coverage? Probably for the same reasons most of us don't have it--but we should. Here are some common reasons why you may not have bought flood insurance, and why you should probably rethink that decision, and why you should probably take the time to buy flood insurance within the next 30 days:

1. You think your homeowner's insurance will cover flood damage.

Nope. Most private insurance policies specifically exclude damage from floods. (If the damage comes from a burst pipe or, say, because a tree fell on your roof, you're probably covered.)

I learned about this having lived through Hurricane Irene in Upstate New York, which caused a lot of damage but, unlike Harvey (and Sandy) affected mostly a very rural area. My husband and I met several people whose homes were destroyed but lacked flood insurance. We didn't have it either and our basement got flooded, but fortunately our basement was an old quarry that would get wet in every heavy rainstorm so the damage was minimal.

2. Your mortgage company didn't require it so it must not be necessary.

That logic got a lot of people in Houston into trouble. If you've ever applied for a mortgage, you know that lenders try to insulate themselves from risk in all kinds of ways, requiring an appraisal of the home, homeowner's insurance, and sometimes mortgage payment insurance that will pay off to them if you stop paying your mortgage. They also, in some cases, require flood insurance so you may be lulled into thinking that if they don't require it, your house is safe from flooding. Take it from the people of Houston: That's not necessarily true. In fact, the head of the National Flood Insurance Program says only half the homes in the United States that need flood insurance have it.

3. You can't afford it.

This is the reason many people in Houston say they didn't get flood insurance, especially since Congress raised rates five years ago. Annual flood insurance rates vary from about $400 for a low-risk home to about $2,500 for a high-risk one. Admittedly, the high end of that range isn't cheap, but you could wind up spending hundreds of thousands of dollars--if you have them--to rebuild a home destroyed by flooding and replace what was inside it. And just because you lost your home in a flood, don't expect your lender to stop expecting you to pay your mortgage on time. They still will.

4. It never floods where you are.

That's another reason many Houstonians did not have flood insurance: Many of them had lived in the same places for decades without ever seeing the slightest flood risk. But, sadly, what we know from the past about the severity of storms and flooding may not be true anymore. Harvey is the third "500-year flood" to hit Houston in the past three years. Just because your location has always been safe from flooding doesn't mean it still is.

5. If disaster strikes, FEMA will help you out.

Yes...up to a point. FEMA (the Federal Emergency Management Agency) does hand out grants to those affected by natural disaster. Those grants are capped at $30,000 and average only about $5,000, however. And they can take months to process, especially during an event like Harvey. They're better than nothing, but nowhere near a repacement for flood insurance.

6. You'll buy flood soon as you get around to it.

That one applies to a lot of us, including me. But if we don't act very soon, we could lose our chance. Flood insurance in most places is only available through the federal National Flood Insurance Program, which is set to end on September 30 unless Congress renews it. Given national concern over Harvey, it might seem likely that Congress won't let the program die. On the other hand, it's operating at a huge loss and Republicans in Congress are committed to cutting taxes and trimming government spending. That's a great reason to pick up the phone and ask your insurance agent about federal flood insurance--today.