Dustin Mulvaney Profile picture
Jan 14, 2023 29 tweets 14 min read Read on X
The Power of the San Lorenzo River.. a short history.
Spanish settlers met the power of the river soon after the Portola Expedition and occupation. They built their 12th mission in 1791 along the river bank on rich fertile soil. After heavy damage from two floods in two years, they relocated the mission to an overlooking hill.
The new site they built above the river on Mission Hill is believed to be the location of Aulintak, a village of the Awaswas - speaking Uypi Tribe who lived with the river for thousands of years - today they are represented by the Amah Mutsun Tribal Band. nebraskapress.unl.edu/nebraska/97814…
There are accounts of major San Lorenzo River floods in 1847 and 1852, but the first documented in local newspapers is from the Great Flood of 1862.

Letter from Santa Cruz, January 14, 1862.

“The San Lorenzo rose higher than ever before known.” ImageImageImageImage
Flood of 1869 - “The foot bridge across the San Lorenzo River is gone. Great fears are entertained for the safety of the new bridge on the same stream, near Santa Cruz” Image
Flood of 1871 - “The San Lorenzo rose far above the highest mark of 1862, washing over the bulkhead and flooding the lower portions of the city.” Image
1871 flood “The massive bridge over the California Powder Works was swept away and entirely destroyed.”

Powder works was built on land bought from paper mill destroyed in 1862. They used the power of the river to make explosive powder from guano for California’s mining industry. Image
Same 1871 storm, San Lorenzo Bridge in part destroyed, “about 240 feet of the bridge was carried away.”

An article from the Santa Cruz Weekly Sentinel says 23.5 inches of rain fell in 16 days in December 1871. ImageImageImage
Flood of 1888 - “a large amount of driftwood came down the San Lorenzo River this morning and struck the bridge of the South Pacific Coast Railroad, the force of which added to high water, sweeping the bridge out of line four feet, making it impassible.” twitter.com/i/web/status/1… Image
1890 flood, again - “the river reached the highest point ever known.”

“20 feet of the upper bridge across the San Lorenzo River gave way, rendering the bridge impassible.. 100 feet of the railroad bridge on the Southern pacific, at the mouth of the river, fell into the water. twitter.com/i/web/status/1… Image
1906 “San Lorenzo quickly converted from peaceful stream into torrent.”

January floods swept away Loma Prieta lumber Co.’s mill at Hinckley Creek stranding 11 workers overnight; Late March rain contributed to a mudslide at the mill site after April 1906 SF earthquake, killing 9. ImageImageImage
1907 Flood - Five Bridges of Boulder Creek Destroyed.. Bridges of Santa Cruz also menaced. Image
*Boulder Creek had some rough years 1904 to 1907. Curious how this wildfire, which burned for 14 months, and settler clear-cutting and grazing practices at the time contributed to the flooding and flood damage in 1907. #SantaCruzMountains
Businesses and residents had long sought flood control, and after storms there would be renewed interest.
In 1909, there was a push in the city for a bulkhead along the San Lorenzo river to be built by the railroads in exchange for track; this editorial “property holders, think!” emphasized how destruction to the watershed from deforestation was making flood risk worse. ImageImage
But it wasn’t built, no funding.. so there were floods again in 1911, 1913, 1914, 1926.. Image
December 28, 1931, San Lorenzo overflows banks for first time in 18 years. Image
*This 1931 storm was the first storm to shake the cement ship #SSPaloAlto. It moved in three feet that year. See 2023: ImageImageImage
San Lorenzo on Worst Rampage of Century, February 1940. Image
February 1940 floods destroyed six of the nine bridges on Zayante Creek, a San Lorenzo tributary just upstream of big trees, and destroyed newly constructed cement bridges on Scott Creek and Liddell Creek. ImageImage
March 1940, San Lorenzo threatens again. Image
Garfield St lowlands were evacuated several times in 1940 from raging San Lorenzo floods. City commissioned a report on flood control that year and Federal govt funded flood control surveys. Garfield St would’ve been to right in 12/31/22 photo, flow in photo ~6k cfs @ bigtrees. ImageImageImageImage
February 1941, Raging San Lorenzo Sweeps Through Santa Cruz. Image
Proposals to reduce flood risk included removing a six acre island from the river mouth, building dams up the San Lorenzo gorge and further upstream, and building a wall along the river. ImageImageImage
Flood of 1952 saw log jams as big trees gage hit a record at the time of 24,000 cfs. Image
The deadly 1955 flood flowed at an astonishing 30,400 cubic foot per second plus 8,100 cfs in Branciforte Creek. The confluence of those creeks was called the triangle of death. Downtown flooded in ten feet of water and nine died, including two inside their home on Garfield St. ImageImage
By 1958 the Army Corps committed to building levees.. the island was removed and the river straightened. Loch Lomond dam was built on Newell Creek, completed in 1960, and there was a proposal to dam Zayante.
The river height at big trees on the San Lorenzo was highest in 1982 than any other time on record, (though river at Ocean St was higher in 1955), but the levies held through the city. *The disaster from the 1982 storms would be the Love Creek Slide. pubs.er.usgs.gov/publication/pp…
Levees transformed the river. Big flows in 1996, 2006, 2017, 2022, 2023 stayed in channel through the city. The river is less prone to damage or injury, but the river also no longer supports the Coho and steelhead populations it once did.

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More from @DustinMulvaney

Sep 13, 2023
Written testimony..
Verbal testimony today.. mine starts ~ 51:00. naturalresources.house.gov/uploadedfiles/…
youtube.com/live/6JpHxVFmw…
My testimony in a nutshell is that public policy on critical minerals should (1) Promote more circular economy approaches to the critical minerals challenge,
(2) Develop robust take back and collection systems and recycling of electronics and electronically equipment…
Read 5 tweets
Aug 23, 2023
Today we released our permitting reform report! #JustTransition #EnergyJustice 🧵
The report aims to unpack what many folks are lumping into the permitting reform debate, identifying forces that are slowing decarbonization and electrification, and centering environmental justice principles and policy.
The first thing about “permitting reform” is the phrase is used to talk about very different things. I just listened to a podcast about interconnection queues and issues slowing those private contracts and both professionals kept calling for interconnection “permitting reform”! Image
Read 13 tweets
Jul 19, 2023
Another day, another chase. #otter841 🦦 Image
🦦🦦🦦🦦
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🦦 🦦
🦦🦦
🦦
Today’s chase involved a diver-operated Wilson trap. Image
Read 7 tweets
Jul 18, 2023
Otter 841 surfin’ today. Image
There were four other sea otters watching her today. Image
@CaliforniaDFW tried to float her towards the boat, but she jumped off every time any where close.


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Read 8 tweets
Mar 16, 2023
A Brief History of the Pajaro River, my latest, at California Local. californialocal.com/localnews/sant…
The Pajaro Valley has some of the most productive and valuable farmland in the world. Strawberry fields generate almost $100,000 per acre.
The Pajaro Valley is also an environmental justice community, disproportionately burdened by pollution, particularly the Monterey County side of the river. experience.arcgis.com/experience/11d…
Read 4 tweets
Mar 11, 2023
The Pajaro River in the news today is the second largest watershed on the central coast of California, at 1,340 square miles.
It’s in the news because a major levee failure inundated the town of Pajaro in the middle of the night.
The river is the boundary between Santa Cruz and Monterey counties, and Santa Clara and San Benito counties, draining a few more counties; so has long been politically fragmented. It’s a case study in conflict over shared river basins, riparian political conflict.
Read 14 tweets

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