* MBM #4 1.08 inch elevation change explained...
MBM stands for Monitoring Benchmark. The map above shows all the MBMs that were installed in 2015 to monitor movement around the new GRP pipeline at the Panther Branch Fault. They're physically on the north side of Research Forest Drive near Cats Cradle, the water supply line for south county is on the south side of Research Forest Drive.
The Panther Branch fault is downthrown to the west - meaning the earth is moving down on the west side (that's unusual for a fault around here - that it's not downthrown to the east - and it creates an issue for floodwaters in that they become relatively trapped in the area west of Cats Cradle; like a bowl).
Homeowners that are in the bowl or whose homes straddle this fault (and others in The Woodlands) are particularly interested in seeing these numbers. Our elected leaders should be too.
MBM 4, or the bottom of the bowl, has always shown more subsidence than the other benchmarks and that was true this September too. 0.09 of a foot is the cumulative elevation drop that has occurred from September 2022 back to when the monuments were installed in March of 2015. 0.09 of a foot is 1.08 inches of movement. That's significant because the pipeline was only designed to withstand an inch of movement.
This updated slide above is from a 15-page powerpoint presentation, included below; the source of the data is the SJRA W2A Fault Monitoring data on the GRP division's website. (Use + to expand list of fault monitoring reports and see November 2022 and be sure to take in the chart on page 19 that shows accelerated subsidence after the summertime drought of 2022!)
This irreversible subsidence didn't just start when SJRA started measuring the effects of groundwater withdrawals, it's been adversely affecting 100s of homeowners in The Woodlands since they purchased their homes in the early 1990s.
It does happen slowly, so some newer homeowners perhaps aren't yet aware; folks that originally purchased their home in the 1990s are all-too aware of this faulting and seek to inform the entire community of this faulting activity; it affects all of us.
What can we do about it? Use more surface water, demand county-wide limitations on groundwater pumping, share our site with your neighbors. Thank you for informing yourself today, please share our site with others.
