While San Luis Obispo County is no stranger to extreme flooding, the rainstorm on January 9th of this year caused millions of dollars in damage to public infrastructure in the region.
There are past notable storm events and how they’ve shaped how City and County officials - prepare for the next big rainfall.
For some residents, it was an eye-opening event.
Though it's known there have been major floods on the Central Coast, Matt Horn with the City of San Luis Obispo says records are a bit scattered.
"People who have lived here for 20, 30 years probably haven't seen an event like what happened on January 9th," said Horn. “Perhaps the general public doesn't have a good understanding of our watershed and how frequently it does flood. Our best information right now - we’ve had large rain events in 1969, 1973, 1982, and then 1995."
Thomas Kessler with the San Luis Obispo County History Center explains the significance of the flooding in 1969. “The first one that was ever titled a 100 year flood was in January of 1969,” said Kessler.
City records and photos from 1969 show the massive damage across San Luis Obispo County.
“There was about 8 inches of rain over the course of 2 days," said Kessler. "There was one weather gauge in downtown SLO that measured two inches in half an hour.”
Kessler continues to describe the impacts saying, “Mudslides, the Salinas River topped it’s banks, downtown SLO had some very serious flooding as well. It caused millions of dollars in damage. It was one of the first times we were declared a federal disaster area. ”
Here is a snapshot of January 1969 rain totals (in inches) in San Luis Obispo and Santa Barbara counties, according to the National Weather Service.
Four years later - another devastating storm hit. ”73 was really just concentrated on the City of SLO,” said Kessler.
Here is a snapshot of January 1973 rain totals (in inches) in San Luis Obispo and Santa Barbara counties, according to the National Weather Service.
The next notable flood event we are highlighting here is in March of 1995. ” The '95 flood was notable for a couple of different reasons. It's the most recent one and it's the most regulated one that's occurred," said Horn. "And so we had very good inventory of the damage that occurred and then we had an action plan afterwards.”
Here is a snapshot of March 1995 rain totals (in inches) in San Luis Obispo and Santa Barbara counties, according to the National Weather Service.
Freddy Otte is a Biologist for the City of San Luis Obispo. He pointed out the limitations of the San Luis Obispo creek and its capacity and said, “typically in a natural system a creek is going to meander back and forth it has the ability to move. It doesn’t have the ability here just because of the legacy walls we have around Mission Plaza.”
Pre-winter surveys and vegetation management are just a couple of tools the City uses each year to help mitigate flooding and maximize the amount of water creeks can hold.
Though, if the rain falls hard or long enough, like it did in January, there are just some areas more likely to flood no matter what measures are taken.
“We had a couple of storm events beforehand so the ground was saturated so now with that big storm coming through on January 9th - the ground wasn’t able to absorb as much water as it could have earlier in the season. So here again - we had a lot more runoff coming into the creek - which caused that peak flow to come through early in the morning of January 9th,” said Otte.
Water managers expect significant flooding every 25 to 30 years - the goal is to learn from each situation and get better at handling it.
After the 1995 flood, the Waterway Management Plan was born to identify key projects and create maintenance schedule to mitigate flooding in our area.
“That was certified in 2003," said Otte. "So the City is working with the County of SLO to update that document to make it contemporary climate predictions and models. New projects that we’ve identified especially from these recent storms."
Horn said, projects are ongoing. “We're continually replacing pipes and upgrading drainage inlets. We're removing silt from the creeks, managing vegetation, and then we're also looking to implement larger flood control projects like the Mid-Higuera Bypass Project, which will increase the capacity of San Luis Creek.
The 9-million dollar project aims to increase capacity downstream of the Marsh Street Bridge. Construction is expected to begin next year.