What is subsidence and how it's measured
Introduction
Our homes, roads and businesses are structurally supported by the groundwater aquifers below us, so excessive groundwater use causes sinking. Areas of South Montgomery County have already sunk 1’ in the past 20 years activating faulting and reducing the ability of rainwater to drain. New rules are being proposed which will INCREASE the amount of groundwater being used and so increase sinking.
What is subsidence
Subsidence is the sinking of a wide area of ground. Its usually not noticeable since it’s gradual - with all of the ground in an area sinking at similar rates (i.e. no sinkholes, potholes, etc). Instead, the entire elevation in an area is being lowered.
Montgomery County has sunk an average of ¾ foot since 2001.
How is subsidence measured
Subsidence is measured by 1) stations that allow the ground surface to move relative to a stationary rod anchored deep in the ground, and 2) by GPS stations that measure distances to satellites. In Montgomery County we have a total of 14 subsidence monitoring stations and the data they collect is available at: https://hgsubsidence.org/