Flood Warning

When I attended the Lake Lariat Preservation Committee meeting earlier this month, I was told that I should become a member of the committee in order to have legitimacy in the eyes of the HOA. However, I am not sure that lake preservation is what I want to advocate. What about doing away with the lake and letting Mill Creek be what it was 60 some odd years ago? Would removing the Lake Lariat dam eventually lead to cleaner water flowing into the Chesapeake Bay? This is a question any community with a dam should ask about their own watershed.

Photo by Anders Sandberg

Aside from the water quality question, dams can lead to rampant destruction and loss of life, as South Carolina learned in the wake of floods last year causing 36 dam failures! Not all dam failures cause loss of life, but 81 of 336 dams in Maryland (including Lake Lariat) are high risk hazards by virtue of the potential consequences of a failure. Thirty-six dam failures in one state weighed against 71 dam failures nationwide in the five years prior points to a possible tipping point. If it is, three factors can be blamed for placing many at higher risk of flooding catastrophes: more extreme rainfall, more development, i.e. impervious surface, and aging of dams.

Dams have been built over the last 100 years or so with liberal safety factors for maximum probable precipitation. Aging of those dams beyond their 50 year design life makes them vulnerable to rainfall extremes even under their designed capabilities. Add to that the furious climate-driven increase in rainfall in the Eastern U.S. and you get catastrophes like South Carolina's.

We are in the middle of one of those rain spells here in Maryland. After a 4" rain last week, we have totaled almost 5" in the last two days, with lots more to come in the next few days. Rivers are predicted to flood. Hurricane Matthew may drop more rain here next week. I doubt if our dams would be able to hold it all. If you live downstream of one, don't be like one of the 17 people killed by dam failure in South Carolina last year. Take any flash flood warning very seriously.