By Paul Homewood
The ground around San Francisco Bay is sinking to meet the rising sea, another reason for Bay Area residents to worry about the impact of climate change on their region.
A new report suggests that sinking land, known as land subsidence, will increase the potential reach and damage of flooding in the Bay Area, submerging a larger portion of the region by the year 2100 than previously estimated.
Subsidence can be caused by groundwater pumping, which can act to “deflate” the ground above it or the gradual compacting of landfill — when lands are filled in an effort to create solid ground to build upon.
The authors of the report — Manoochehr Shirzaei, a professor at Arizona State University and Roland Bürgmann, a professor at University of California, Berkeley — have combined land elevation data with rising sea level projections. And they are now challenging the current flood threat projections as too conservative.
The authors hope that their new findings will help cities and agencies produce more accurate hazard maps, updating the extent of affected areas.
Under the new projections, San Francisco International Airport could see half of its runways submerged by the year 2100. Original estimates that did not include land subsidence were much lower. Other areas around the Bay that have been built on engineered landfill, like parts of Foster City and Treasure Island, are particularly vulnerable to the dual impact of subsidence and sea level rise.
Scientists have long tracked the effects of global warming on the planet’s water levels. A recent study of 25 years of satellite data pointed to climate change as a cause for the acceleration of rising sea levels, making previous estimates unreliable.
“It’s a very well-known problem, but we really don’t know how fast it’s going to be in the second half of the 21st century. This is a projection,” Dr. Shirzaei said.
Subsidence may be a very real problem, but sea level rise is not.
Sea levels at San Francisco have been rising records began in the 1850s, at an average rate of 1.96mm/yr:
The rate of rise has actually been decelerating since 1970, and the fastest rise occurred 1920 and 1970:
San Francisco airport is 13 ft above MSL on average, so at that rate it will be underwater in 2000 years time.
Meanwhile little seems to have changed since 1927.
San Francisco may have problems with subsidence, but this is an engineering problem, which cannot be solved with any number of wind farms.
via NOT A LOT OF PEOPLE KNOW THAT
March 9, 2018 at 06:15AM