Colorado Flooding

A cold front clashed with the warm, moist air from monsoons in the south. As the warm air was cooled by the cold air, large clouds formed. The resulting rain began on the afternoon of September 10th where I live.

It started out as a thunderstorm, like all of the other storms that we had this summer. This thunderstorm, however, was particularly impressive; there was crackling thunder and it just kept raining. I didn't think much of it, as we had been getting a few thunderstorms lately. The next day we had another thunderstorm. This one was special, because once the rain began it continued for the rest of the day. It stopped raining for a couple of hours around nightfall and I thought it was over, but I was wrong; the rain started up again later in the night, gently pouring from the sky.

The next morning was cold and grey. I probably would have slept in if it weren't for the fact that I take part-time college courses. As it was, the rain was gently falling as we drove to the building where I would be taking my classes that day. One of my friends commented on how the weather suited the day perfectly, since it was September 11th, the 12th anniversary of the terrorist attack on the World Trade Center and the Pentagon.

Caption: A sparrow enjoying himself during a break in the rainfall

The rain continued all that day and all the next, almost without stopping. This was highly unusual, since we rarely get rainstorms that last more than a few hours. I was enjoying it very much; with all the sun we normally get, a little bit of moist, cool, rainy weather really hits the spot. The consequences of all the rain, however, were enormous.

Creeks and streams all over Colorado overflowed, destroying hundreds of homes and flooding thousands. Hundreds of bridges were destroyed by the massive amount of water. To illustrate the amount of water there was, take Boulder Creek as an example: normally the water in the creek flows at a rate of around 150 – 200 cubic feet per second, but at its peak during the flood it flowed at more than 5,000 cubic feet per second. In the rest of Boulder, the rainfall in 5 days exceeded the average amount for a year.

Where we live, flooding isn't a problem. We live at the top of a hill, and our neighborhood has a good drainage system, so the road leading out of our community was clear and we could easily drive places. The rain at our house wasn't actually all that heavy, either; it was just light drizzling. We did have a decent-sized stream running through our very large yard, but it was rather far from our house so it didn't cause us any trouble. I was kind of glad that we live where we do.

Caption: The rainstorm approaches

The rain at my house stopped during the night of September 12th/13th, and the ground quickly dried. The stream disappeared. After all that rain, it seemed a little odd that things could return to normal so quickly. My dad went out and started mowing, enjoying the sun. But the flood wasn't over yet, and dark clouds began to fill the sky. Raindrops started to fall. It got harder and harder. At this point, my dad stopped mowing and came inside. It was a good thing he did, because before long the rain was so heavy we couldn't even see our neighbor’s house. Meanwhile, we also had hail and lightning. That lightning was amazing – the patterns zigzagged in all kinds of crazy ways. I think I saw one bolt strike somebody’s house.

A stream formed again in our backyard, but it was larger than the one we had had earlier. There were also smaller branches running down the hill and joining the stream. It exited our property by going through a drain pipe under the road leading through our community. On the other side of the road, it came out of the pipe and entered our neighbor’s property. He has a 500-foot long paved driveway, with a drainage pipe leading under it. There was so much water that it couldn't drain through the pipe fast enough, so it rose higher and higher until it started flowing over his driveway. Fortunately he had another gravel driveway that went a different way off his property, and that one was not flooded.

After about an hour, the rain settled down to a light sprinkle. Taking advantage of the calm, I went to the creek and snapped some photos. The creek started out slow, but as it progressed it narrowed and became very strong and fast. There was even a small waterfall. Then the creek widened into a pond. By the time I got back it was raining harder and I was wet, but I had the photos I needed so I was happy. The rain was over the next day, and the stream was gone.

Caption: Considering the fact that this waterfall wasn't there an hour ago, it's pretty impressive.

Caption: Who would have thought that a little gunk
could tell you so much?

A few nights later I went walking in the moonlight with my dad, exploring the marks left by the rain. We went to a valley that was not visible from our house. There had actually been a second stream in that valley, but I had never seen it. I had guessed that there was probably a second stream there, but hadn't checked to see. By the time we explored the valley, the stream was gone, and there was a lot of gunk everywhere – including grass clippings, tennis balls, and horse patties. From looking at the position of the gunk, we concluded that the water had backed up around a drain pipe and formed a small lake. We were also able to tell how deep the lake had been: 6 feet! I was very disappointed that I had not seen it.

I later learned more about the damage caused by the flooding. Besides the broken bridges, flooded houses, and destroyed highways, there were also fossil fuel tanks that were damaged and leaked thousands of gallons of fuel into the water. At least 8 people were killed, and more than 600 are still unaccounted for.

The chances of another flood like this happening in Colorado in a given year are only 1 out of 100. In other words, a flood like this only occurs once every hundred years on average. For some cities, the flooding was even worse, and on average would only occur every thousand years. The rain had such a big impact, and yet it's over already. Or is it?