A couple days ago I read a Facebook post by an Ellicott City resident describing how the unfettered development in the Tiber River watershed upstream of Old Ellicott City had contributed to the recent flooding.
Having lived in Columbia for 28 years, I assume that what he wrote about the development is true, and that it absolutely contributed to the flood. However, he concluded by saying "this is a horrible disaster but nature had nothing to do with it." That's nonsense.
In an area that receives some 45 inches of rain annually, 6-and-a-half inches of rain falling in under two hours — with 2 inches falling within 15 minutes — is a seriously extreme event that the National Weather Service estimated happens only once every 1,000 years.
Rainfall of that intensity will cause major flooding anywhere it occurs. Like California's drought, this flood was clearly caused by nature, but its effects were magnified by human activities.
Old Ellicott City is tailor-made to be flooded for two reasons. First, it sits on the Patapsco, with buildings only a short vertical distance from the river. Moreover, the Tiber watershed is very hilly with a lot of impervious surface.
The impervious area causes more runoff; the hilly terrain causes water to flow faster, contributing to higher peak flows, and the streets are convenient conduits for runoff, further exacerbating the flooding.
Thus Old Ellicott City can be flooded by rising water on the Patapsco, an overflowing Tiber River, or both. The Hurricane Agnes flood in 1972 was largely due to the rising Patapsco. The damage from this last flood was largely caused by water raging down the Tiber and into Main Street, and not so much by the Patapsco water.
What to do? At the risk of sounding like a Grumpy Old Man or a Nattering Nabob of Negativism (thank you Spiro T.), rebuilding Old Ellicott City would be an expensive mistake.
Wikipedia states that there have been 11 "major devastating floods" in the last 100 years. The flooding cannot be stopped other than by extraordinary means that no one would or should want.
It's not important to control flooding; it is important, however, to control the damage caused by flooding. The most foolproof and cheapest way to avoid flood damage is to convert flood-prone areas to a land use that won't be badly damaged.
Some 50 years ago, Lafayette, Ind., where I used to live, moved a warehouse district out of the Wabash River flood plain and turned it into a golf course, thus reducing the flood damages to nearly zero. Smart! It was cheap (relatively) and pretty much foolproof.
I understand that moving homes and businesses out of Old Ellicott City will be expensive and fraught with pain. But recurring flooding will be even more expensive and still fraught with pain. Nothing will be gained. Change is inevitable, and as much as we may want to, we can never go back.
Dean Randall, Columbia
The writer is a longtime civil engineer and hydrologist.