Sometimes weather events conspire in such a way that everything that could lead to a worst-case scenario just clicks into place, and when it happens, it’s horrific. U.S. weather history is full of worst-case scenarios.
The one I wish to write about today happened in Colorado, as its citizens were celebrating 100 years of statehood on the weekend of July 31 & Aug. 1, 1976.
That weekend, about 4,000 campers took to the many gorgeous camping sites along the Big Thompson River, which flows through a narrow and very steep canyon, about an hour northwest of Denver.
On the evening of July 31st, a thunderstorm developed and then remained nearly stationary for about 3 hours near the headwaters of the Big Thompson River, high in the Rockies. In that 3-hour period, an astonishing 12 inches of rain fell, with 8 inches falling in a single hour!
It truly was a worst-case scenario, a nightmare storm in the wrong place at the wrong time. A tremendous wall of water, almost 20 feet high, sped down the narrow canyon, sweeping away everything it its path. There were reports of cabins, with people screaming inside, being instantly swept from their foundations, and carried downstream to be smashed to bits.
To get a sense of how sudden this was, there is this, from the Denver Post: “Downstream in the canyon, just above the Narrows, some people were unaware that anything was amiss until they went outside their houses and saw the water rising in their yards. It hadn’t even rained there.”
That is something that always surprises folks, it need not rain where you are along a small river or stream for a flood to occur at your location if heavy rains have fallen upstream. After the Big Thompson disaster, which killed 144 people, remote sensors began to be used to monitor river levels at campgrounds on or near rivers to alert people to sudden changes upstream.
In general though, if you are ever near a river that suddenly starts rising, always move to higher ground at once!
Here in The County, we are certainly not immune to flash floods. Never drive across a road with water flowing across it.
Always treat Flash Flood Warnings with great respect and listen carefully for the areas included in the warning, Such information is on many phone apps, and it is also broadcast on NOAA Weather Radios. I find that the REECOM is a good buy, at about 45 dollars.
Ted Shapiro holds the Broadcast Seal of Approval from both the American Meteorological Society and the National Weather Association. An Alexandria, Va. native, he has been chief meteorologist at WAGM-TV since 2006. Email him at tshapiro@wagmtv.comtshapiro@wagmtv.com.
