The terrain of Houston is best described as a billiard table with a matchbook under one leg. It has an average slope of 0.02%. Thus, any hard rain will cause flooding.ThomasDodd wrote:I don't remember the cause, but I remember I-10 and I 45 being under water in '92 whicle I was there. I think it happend March. I on't remeber any evacuation and few people seamed to care. I lived inside the 610 loop, and still had to go too work the whole time. At teh tim that was security work, as a fill in, so I was all over downtown.
But being flat also means that it doesn't concentrate runoff like hilly areas. Thus, where 10 inches of rain would mean raging walls of water in the creeks and rivers around here (and that would all end up causing the Potomac to spill over into Alexandria--again), 10 inches of rain makes 20 inches of water in the street and none in the houses. Some parts of town flood more easily because the drainage system brings water in quicker than it can leave, which is the source of the storied sewers backing up phenomenon. So, Houston can take lots of rain with minimal damage. The street on which I grew up floods deep enough to prevent cars driving down it several times every year. Spring is a popular time for floods in Texas, because late cold fronts clash with tropical air, often from the Pacific rather than the Gulf, and all the water falls out of the air. The Memorial Day flood in Austin (in the late 70's) is an example.
But Allison was quite different from the typical Spring downpour. Many tens of thousands of houses had water in them, along with the Medical Center, most freeways, and so on. The power was out, the water foul, and the mud it left behind even fouler. You didn't want to buy a used car in the area for a couple of years after that, heh, heh. Houston took 20-35 inches of rain in that storm, depending on where in town you added it up. It still ranks in the top handful of the most expensive cyclonic storms in history, even though it never reached hurricane status. Water is more dangerous than wind.
Rick "who remembers the futility of sweeping water off the front porch with a broom" Denney