Did you know that Dallas has a system of levees that help keep it dry, and that those levees could overflow and cause major flooding in the event of a big storm? Like, say, Hurricane Rita, had it not gone as far east as it did?

Downtown Dallas relies on a much-compromised 30-mile levee system to keep it dry from the Trinity River. Because of extensive development in the counties north and west of the city, the levees, completed in 1958, can no longer handle the severe storm runoff they were designed to contain.

Dallas is therefore now vulnerable to a far less serious storm breaching the levees and flooding business and residential areas that equal about 20 percent of the city's taxable property value.

With only a day or so of warning, city officials would need to coordinate the swift evacuation of an estimated 100,000 people who live or work in flood-prone areas on either side of the Trinity.

The flooding would also complicate the city's standard emergency plan, since key shelters such as Reunion Arena and the Convention Center, as well as the city's emergency command post beneath City Hall, would all be flooded.