Friday, October 21, 2016

Army Corps of Engineers prepares to protect Atwater Village from L.A. River

Sand will be used to create the barriers

Sand being trucked in to fill flood control barriers

ATWATER VILLAGE — The U.S. Army Corps of Engineers is scheduled to start installing temporary barriers along an approximately 3-mile stretch of the L.A. River this week. The intent is to raise the height of the channel and reduce the risk of flooding in the Atwater Village area during El Niño rains. Why are these barriers being placed on this stretch of the river? How long will it take to build? The Eastsider posed these and other questions to corps spokesman Jay Field.

Where along the river will the barriers be placed?
It begins in the north roughly at W. Broadway and continues roughly to the California 2 Freeway.

Why did this stretch of the river need extra protection?
Corps experts routinely evaluate flood risk management capabilities of the LA River as part of their winter storm inspections. In light of the likelihood of greater than average rainfall associated with El Niño weather conditions, further scrutiny of Corps structures and facilities was undertaken. The evaluation has indicated unacceptable levels of risk given anticipated rain fall events lasting through this spring. To address those elevated levels of risk, the Corps is implementing risk reduction measures which include placement of temporary protective barriers along the top of the riverbank.

Why is this section of the river more vulnerable than others?
It’s a matter of channel capacity. The original design capacity for that reach of the LA River was 78,000 cfs (cubic feet per second). Our evaluation showed the existing capacity averaging roughly 40,000 cfs due to vegetation growth. With the placement of the temporary protective barriers, we will restore capacity to an average of roughly 60,000 cfs.

Was the river close to overflowing in this section last week?
Not even close! During last week’s storm events, we observed water levels reaching only about one-third of the channel capacity.

How high is the current flood control channel?
Height varies with width in order to achieve the design flow conveyance capacity.

How high are the HESCO barriers?
The barriers we received come in two heights, 3-feet high and 4-feet high. They are 3 X 3, but come in sections of 15 linear feet (five 3 X 3 baskets connected together).

Are they filled with sand, gravel, etc?
They are filled with earthen material and, in our case, will be filled with sand.

How much does each hold?
Each 3 X 3 X 3 barrier holds approximately 27 cubic feet of material. The 3 X 3 X 4 barrier holds approximately 36 cubic feet.

Where will the barriers be placed? Will they be on both banks of the river?

The barrier will be placed immediately adjacent to the edge of the channel so as to minimize its footprint and impacts to the maintenance road. Mostly one bank, but there are a few spots where barriers will be placed on both banks.

When will the barrier be completed?
Temporary protective barrier installation should be complete within a month.

Have these kinds of barriers been used before in Southern California by the corps?
Our district has not used them before in Southern California, but the Corps has used them in the Midwest, in places like Fargo, N.D., and various locations along the Mississippi River.

Jonathan Straight

Army Corps sets up a staging area in North Atwater Village | Jonathan Vandiveer

Red line shows where protective barrier will be installed

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  1. And here we have the Army corps of engineers a day late and dollars short counting their chickens so close to their chest!!

  2. If anyone ever makes the suggestion that bike paths belong alongside our regions rivers they should be forced to be buried in the next flood control berm blocking the bike path or ride their bike in the Arroyo during a storm.

  3. I don’t understand why people are so angry and unintelligent on this topic. Obviously the army corps is not too late. The river has not gone over the banks and moving a lot of earth doesn’t actually take that long. Looks like they are being pre-emptive and cautious. Same thing with moving out the homeless folks. Thanks Army corps of engineers (federal money). Thanks city of LA. Good looking out!. As to the bike path… it is a cheap bit of landscaping that can be easily and relatively cheaply rebuilt. You may also notice that there are often sports fields and parks in flood planes. Same reason. No major property losses in the event of flooding . The river is a great place for a bike path. And like they said, they plan to restore it after the storms have past and we no longer need the berms. Please get your heads out of the sand and go easy on the metaphor mangling…..

    • Well said. The river has never overflowed and neither Atwater or EV have ever been flooded since the river was paved. This pre-cautionary effort is a good idea but it is only pre-cautionary. Otherwise, the original crew that paved the river to prevent flooding decades ago did a damn good job.

      • But now they have slowed the flow of the river, causing the water to back up and be deeper. The problem here is completely because of what has been done in the river bed there. The engineering to contain the water in the flood control channel (that’s what the river is) has been undermined. That’s why this has to be done.

        That’s why it didn’t overflow in the past, the engineering had the water flowing faster and shallower.. That safety will no longer be in place going forward unless the riverbed is cleared again. That whole area is a flood basin and was developed on the basis of the safety the flood control channel provided. But now that engineering has been undermined.

        • It is not a flood control channel. It is a river that we attempt to control.

          • Actually its a flood control channel. Little of the water in it is from the natural flow.There are multiple sewage treatment plants along the river that dump a load of fluid in there, and ALL the streets in the surrounding region empty all the water runoff from the storm drains into the river — that’s why it is so full of water when it rains, not because of the natural flow of water. The natural flow is just a little trickle of water.

  4. Wow I’m surprised how how hard this is to grasp. All rivers in the LA basin are seasonal. They flow sporadically during the rainy seasons and are mostly dry the rest of the year. Arroyo is a more accurate word. The fact that the LA River is not TOTALLY dry the rest of the year is because of the industrial runoff you describe, Tom. The topography flattens our around Atwater so the river wants to spread out in this area (aka flooding). The channel keeps the river narrow and controlled. When the channel is really full from rain in the area, OR up stream, as far north as about Canoga Park, that is natural flow. It’s not like the Mississippi that has such a huge drainage basin that it always runs. The LA river is a river.

    • The water that empties through storm drains are natural runoff. Before storm drains, the water found its own course into the river.

  5. Does anybody know if it’s still open to the public at this time? Thank you.

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