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Will this be 12th flood in 90 years?

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POSTED February 16, 2017 1:19 a.m.

High stakes behind-the-scenes jockeying has been underway for the past two days as South County officials scramble to get the state bureaucracy to take steps to avoid rural Manteca and Lathrop from dealing with levee failure along the San Joaquin River for the 12th time since 1927.
State Senator Cathleen  Galgiani, D-Patterson,  joined the fray Wednesday.
Galgiani’s Chief of Staff Bob Alvarez said the senator has “been in contact with the governor’s office and is trying to monitor the very fast moving situation. And she is sharing all of the saved articles from the 1997 flood with staff and the administration to remind them of what the community faced then and could potential face at this moment.”
The real fear is that the series of three storms expected to hit starting today in the higher elevation will start sending more snow melt into reservoirs at or near capacity that are part of the San Joaquin River watershed.
Apparently no one took notes in Sacramento the last time in 1997 when the eerily same reservoir and massive snowpack followed by rain in the higher elevation led to 70 square miles being flooded south of Manteca, 800 buildings were damaged and losses hit $100 million.
Many in Lathrop voluntarily evacuated while Weston Ranch driveways were filled with loaded U-Hauls and Ryder trucks with families ready to flee as a levee failure at Lathrop would give them eight hours max to get out of Dodge.
Don Pedro Reservoir is where it was at in 1997. New Melones Reservoir — that in a post mortem interview state officials said came within 24 hours of being breached if the Bureau of Reclamation hadn’t finally given into local pressure to increase releases — is barely releasing water this time around as it is at only 56 percent capacity.
While that may sound like good news, it is being negated by a sober reality. For the first time since 1927 Manteca-Lathrop is without the safety valve that prevented catastrophic levee breaks that prevented water from rolling into Lathrop and parts of southwest Manteca.
That safety valve is Stewart Tract. After breaks happened on the east side that protects rural Manteca and Lathrop proper, levees then failed on Stewart Tract flooding  the 4,800 acres with as much as 10 feet of water. That took a lot of pressure off the levees where the river curves before it passes under Interstate 5 and the Mossdale bridge.
Today, Stewart Tract is fortified by arguably the strongest levees in the country — 300-foot wide super levees put in place to protect the River Islands at Lathrop planned community.
The levees will not fail. They are as bullet proof as you can get.
Meanwhile on the east side of the river is the rag-tag levees of Reclamation District 17.
There is a misunderstanding by many that when the Army Corps made repairs after the 1997 floods and a smaller localized failure in 2011 that all 11 miles of levees were strengthened. Federal law prohibits that from happening. Instead only the segments that failed were fixed and they were restored to the level of protection they were at before the failures.
The levees south of Manteca are over a century-old. From the confluence with the Stanislaus River near the Airport Way bridge to the split with the Old River Channel just west of Interstate 5 is where all run-off from the San Joaquin River watershed passes in order to reach the Delta.
Eleven times since 1927 those levees have failed.
Back a number of years the late Alex Hildebrand — an engineer by trade and a farmer by choice — lived in an elevated home on the river side of the levee near Hays Road where he formed.
A former president of the Sierra Club, Hildebrand spent his life immersed in California water issues as well as being an astute student of state water politics.
He had the ear of water experts in Sacramento who respected his insight and on target projections of water policy outcomes.
Of the many conversations with Hildebrand about water that stuck with me, none was as chilling as his prediction when conditionings mimicking 1997 surfaced again and the 300-foot wide levees protecting River Islands were in place. His bottom line: There would be more breaks, more often on the Manteca side of the San Joaquin River. That’s because water — for nearly 150 years passing between Vernalis and Mossdale during heavy flows — has been doing what water has done since the beginning of time by taking the path of least resistance.
River Islands has taken Stewart Tract out of play as a safety valve.
The decision by the state not to kick up releases earlier may have already sealed the fate of south Manteca for the 12th time since 1927.
If it has, the real question will be whether levees near Mossdale will protect the rest of Lathrop and if the dry levee south of Woodard Avenue will hold.

To contact Dennis Wyatt, email dwyatt@mantecabulletin.com

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