kennadog
Dog On It!
Huge risk. And much of the delta habitat would be destroyed by the influx of salt water.
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- Thread starter Mike0476
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The biggest risk is to coastal towns and the delta area, especially the levee islands. Higher water levels would increase stress on the levees under static conditions and during floods or an earthquake would be even more devastating. Sacramento itself not *quite* as much, as it is at around elevation 25 or so. The increased problems for Sacramento would be from changing the number of storm events that could possibly cause river flooding that could overtop the levees, not necessarily from rising sea levels (except where those could cause rivers/delta area to drain more slowly and increase flood risk that way). I live at elevation 50±, so I (personally) am safe for quite a while.
RookieOfTheDay
Starter
Global warming, natural or man-made has nothing to do with it. The Sacramento and San Joaquin valleys are at risk from atmospheric river storms that derive copious amounts of moisture from the tropical Pacific. Such storms are otherwise called the "pineapple express”.
The most notable examples of this phenomena in modern times are the floods of February 1986 and January 1997. Those events were small compared to floods of 1861/1862, though.
From early December 1861 through January 1962 a 45 day rain event soaked the valley with 25+ inches of rain. Foothill locations received two to three times that amount. The resulting flooding was state wide. Downtown Sacramento as well as the majority of the central valley was underwater for months. Boat travel was literally the only means of transpiration in the valley. The water was said to be of a depth that only the tops of telegraph poles were visible. If there had been satellite pictures at the time, they would have shown a shallow lake that stretched from Bakersfield to Red Bluff and from the coast range to the Sierras.
Of course, this happened pre industrial revolution. Long before manmade atmospheric pollution was even an issue. I mention this because it’s gotten to the point where almost anything the weather does or could do is automatically blamed on global warming.
People need only to study a bit of climatic history to learn that the past is filled with extreme weather events that in many cases eclipse anything we’ve experienced in our life times.
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bajaden
Hall of Famer
I don't want to get into a global warming debate, but your absolutely right. And in my opinion, its a political football being used to make some industries and certain people wealthy. Nothing more than more goverment intrusion into our lives. And I'll leave it at that.
Everyone should read "Battling the Inland Sea" - a book discussing the history of flooding and levees in the Sacramento Valley. A very interesting book. The title refers to the multiple events (similar to the one Rookie is discussing) of flooding and how politics and land development (including mining in the foothills and mountains) impact the rivers and levees, etc.
And yes, the flooding used to take place back when only Native Americans were living here. Before "global warming" or "climate change" was a concern.
And yes, the flooding used to take place back when only Native Americans were living here. Before "global warming" or "climate change" was a concern.
To say the least. Yes flooding has been one of Sacramento area's issues for a very long time.
http://tsidebotham.blogspot.com/
Gary
All-Star
ehhhhhhhh.. I don't think the oceans are rising enough though.. The earth has cycles and we are not creating a cycle with greenhouse gasses..
OK, we are NOT going to delve into the politics and arguments of global warming. Just stating that now.
Section 101
All-Star
They would blow up the other side of the levee before letting it break on downtown.
bajaden
Hall of Famer
Source of facts please! The one's that prove that the ocean is rising, not the one proving that levees break. Levee's have been breaking for 200 years for a thousand different reasons, but mostly because of excessive rain and snow flooding the rivers. The levee's broke over 30 years ago in Marysville before anyone even mentioned global warming.
RookieOfTheDay
Starter
I don't know how people got the idea that Sacramento is at risk from rising sea levels. If the sea ever rose enough to inundate the delta and flood the valley, we'd all be screwed along with everyone else in the world living anywhere near the coast or near coastal rivers at low elevations.
bajaden
Hall of Famer
If you go back a 100 years, or even less, the valley used to flood regularly. It wasn't until they built all the levee's up and down the delta that we ended up with what we have today. Thats why a lot of the farm areas are called islands. They only exist because of the levee's that were built.
RookieOfTheDay
Starter
Very true. But it never flooded because of sea levels. That's the thing i don't get, is what would cause people to link rising sea levels with valley flooding. The sea would have to rise at least 15-20 feet, probably more for that to be a possibility. A sea level rise of that magnitude would be a world wide catastrophe. It's just a bit odd that anyone would make the jump from downtown flooding to sea level rise.
Yeah Sacramento flooding has only been a concern with what's happening up the hill and running into the Sacramento and American Rivers. The ocean levels are of little concern here.
Glenn
Hall of Famer
http://tidesandcurrents.noaa.gov/sltrends/sltrends.shtml
The upgoing arrows show where the ocean level is rising and I think these are stats averaged over 30-40 years. It is not catastrophic in California but in some areas it is bothersome. Why it goes down in other areas is beyond me. It just "IS" without any attribution to cause.
Levees 30 years ago broke at a rate of one per year according to a friend of mine who was the head of the Department of Water Resources. It is getting worse. Don't know why.
LPKingsFan
All-Star
LOL, this is like saying "I don't want to get political, but the Republicans are X,Y, and Z". Surprise surprise, a global warming debate has ensued.
Reminds me of when one of my moot court partners told a judge "with all due respect, your honor, but..." Needless to say, the judge did not feel respected
Section 101
All-Star
Uh wrong. The ocean tides change the level of the sacramento river and surrounding sloughs by over 5 feet each day.
No, it's still of little concern. Run off into the rivers and dam releases cause the levels to rise to flood danger levels. I know of no such danger coming from tidal influences.
Section 101
All-Star
Well if the river is full and it's low tide it will overflow at high tide.
kennadog
Dog On It!
Geez, sorry I started this. The central valley is thought to have been under the sea, thousands of years ago. The coastal range being pushed up eventually cut it off from the sea with only one outlet into SF bay. And before levees, much of the valley would be inundated every spring with the snow melt. That's what made the valley so very fertile.
However, many of the levees were built over a 100 years ago, primarily by Chinese labor. And they were built up with whatever materials were handy. These are not, in many cases, well-engineered levees.
Next to New Orleans, Sacramento is the second, most-threatened by flooding city. They estimate much of dowtown would be under 20feet of water. It has flooded before. There's an underground city downtown, from building up almost another story. Near the downtown shopping plaza and in other places, you can just see the tops of the old first floors of businesses.
I read something once about people (engineers?) coming to Sacramento from other cities that have flood protection issues. Apparently they were a bit stunned to see that Sacramento looks "up" to its rivers. The water is flowing by over our heads.
The central valley is thought to have been under the sea, thousands of years ago. The coastal range being pushed up eventually cut it off from the sea with only one outlet into SF bay. And before levees, much of the valley would be inundated every spring with the snow melt. That's what made the valley so very fertile.However, many of the levees were built over a 100 years ago, primarily by Chinese labor. And they were built up with whatever materials were handy. These are not, in many cases, well-engineered levees.
Next to New Orleans, Sacramento is the second, most-threatened by flooding city. They estimate much of dowtown would be under 20feet of water. It has flooded before. There's an underground city downtown, from building up almost another story. Near the downtown shopping plaza and in other places, you can just see the tops of the old first floors of businesses.
I read something once about people (engineers?) coming to Sacramento from other cities that have flood protection issues. Apparently they were a bit stunned to see that Sacramento looks "up" to its rivers. The water is flowing by over our heads.
Glenn
Hall of Famer
I think the original levees are just piles of "stuff" mainly dirt. Water can bubble through them and not even need to go over the top. In the Pocket Area, water can be seen trickling into the streets having traversed the trek from through the levee, bubbling into a backyard, and then draining into the streets. Pretty shakey. Fixing that almost means starting over and of course that can't be done.
The levees were typically placed by hydraulic dredging/fill placement. The (predominantly) silt and sand soils were dredged from the river bottom and placed along the river banks without compaction effort or consideration of soil composition. These levees are of poor quality and are prone to damage in earthquakes.
kennadog
Dog On It!
Hmmm....keep meaning to get flood insurance, even though its not "required" in my area. And buy that dinghy.
Section 101
All-Star
Beavers, squirrels, etc can dig holes/dens that cause leaks too.
One way the levee guys take care of them, according to the US Army Corps of Engineers guys I spoke with last year about the levees we were inspecting at the time.
http://www.rodenator.com/pests-controls-videos-rodenators
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