One Less Thing to Worry About in Latest Storm: How Seasonal Lowering of Lake Conroe Helped

Storms during the last two days were traumatic for virtually everyone in the Kingwood area. Tragically, one person lost her life when her car hit a downed tree.

  • Others lost vehicles, trees, and sleep.
  • Torrential rains for a brief period – at the rate of 4-5 inches in an hour – flooded streets and vehicles.
  • They also brought water near or into homes.
  • Parents picking children up from school waited in rising waters as their students sheltered in place.
  • A small tornado may have briefly touched down near Town Center.
  • Kingwood Drive was shut down for hours during the Friday afternoon rush hour.
  • People traumatized by Harvey were re-traumatized.
  • People without power waited and wondered for hours about what was going on around them.

Lake Conroe: One Less Worry This Time

Despite all that, we did NOT have to worry about one thing: Lake Conroe opening its flood gates again during this storm. The seasonal lowering policy established last year worked.

The SJRA board voted to lower the lake’s level one foot to 200 mean feet above sea level (MSL) from April 1 to May 31.

That action may have saved the Lake Houston area from additional flooding in the last round of storms.

Releasing Water Continuously At Low Rate Created Extra Capacity

Lake Conroe had released water continuously since April 1 at a slow, controlled rate of 350 to 550 cubic feet per second. However, because of spring rains, Lake Conroe had only dropped about a half foot from 201 to 200.66 feet MSL. Had the releases not happened, the lake would have been an estimated 1-1.5 feet higher, according to Mark Micheletti, an SJRA board member from Kingwood. That means the lake level would have been approaching 202 feet, the level at which the SJRA automatically begins releasing water, when the storm hit. That would have forced the SJRA to release water at a higher rate that could have overloaded the downstream watershed.

Buffer Against Downstream Flooding Worked

In other words, the policy worked. The seasonal lowering provided a buffer against downstream flooding. NOAA shows a double crest on the San Jacinto West Fork at US59 during the last two days that coincided with two waves of storms. At peak flow, the river came within about two feet of going out of its banks.

An additional foot of water released from Lake Conroe would have added two feet to Lake Houston and created flooding.

About a mile downstream at River Grove Park, the water was up, but still within its banks.

Despite torrential rains last night and early this morning, the West Fork remained in its banks. The river was up, but no homes flooded from the river.

Success: No Rivers or Streams Out of Banks

At this hour, neither NOAA, the SJRA, nor Harris County Flood Control, predicts any flooding from yesterday’s storms. In fact, all streams and bayous seem to be receding at this time. That’s one less thing to worry about as we clean up from the latest storm. The SJRA’s seasonal lowering DID help.

Remember, Lake Conroe is almost twice as big as Lake Houston (33 sq. mi. vs 18.5 sq. mi.). So one foot released there translates into almost two feet here. And two feet would likely have forced the San Jacinto out of its banks for the fifth time in a year.

Kudos to the SJRA board, the City of Houston, and the TCEQ for enabling this policy. That, in conjunction with the City’s pre-release policy for Lake Houston, have made a difference.

Posted by Bob Rehak on 5/5/2019

614 Days since Hurricane Harvey