Fact Sheet

Los Angeles River Frequently Asked Questions

Los Angeles District
Published Sept. 20, 2017

Los Angeles River Frequently Asked Questions




What are the Corps’ various roles operating the LAR?

The Corps has several roles in operating, maintaining, and regulating the LAR, as well as managing Federal lands. Under the LACDA project, the Corps operates and maintains several dams and portions of the LA River channel and tributaries. Land behind dams (referred to as basins) is managed by the Corps for flood risk management and compatible purposes, and any proposals for use must be approved by the Corps in conjunction with lessees such as the City of LA or MRCA. Under the Section 408 program, anyone wishing to alter or modify a completed Corps project (such as LACDA) must apply for a permit to ensure the activity does not impair the project function. For temporary uses such as special events or filming in the river channel, a Corps permit or review to ensure compatibility with flood risk management must be obtained. Under the Section 404 program, the Corps regulates discharges of dredged and fill materials within waters of the United States.


Why is the project designed with a low capacity given the location?

The current Los Angeles County Drainage Area (LACDA) project authorized design capacities were established based upon 1930/1940s design conditions.  Urbanization since that time as well as limited resources have reduced the capacity of the channel to address the amount of runoff currently experienced.  Hesco barriers offer an interim risk reduction measure that is necessary until design capacity can be restored.


What are the functions of HESCO barriers and why are they lining parts of the River? 

HESCO barriers are a proactive interim risk reduction measure put into place to reduce flood risk in preparation for the anticipated 2015/2016 El Niño storm season.  The HESCO barriers were strategically placed to reduce risk in areas adjacent to areas of the Glendale Narrows section of the Los Angeles River (LAR).


What is the estimated monetary amount in damages and population at risk in the affected area?

It is estimated that a 25-year storm event could cause as much as $85 million in property damages, and place as many as 1,718 residents at risk of flooding.


What properties are at risk?

Properties within the floodplain. To name a few:

  • Portions of Griffith Park, including Wilson & Harding Golf Course, Crystal Springs Picnic Area and Griffith Park Recreation Center
  • North Atwater Park
  • Glenhurst Park
  • Los Feliz Golf Course
  • Recreation and equestrian trails along the river.
  • Parking lots for commercial, industrial and public properties, including a used car dealership
  • Segments of the Interstate 5 freeway
  • Of particular concern is potential inundation of Interstate 5, which has average annual daily traffic counts of approximately 250,000 vehicles.
  • Residential properties


When will the HESCO barriers be removed? 


The Corps understands the HESCO barriers have changed the visual dynamic of recreational opportunities along the levee walls.  Due to the reduced ability of the channel to contain flood waters and the limited funding available to the Corps to remove and replace the HESCO barriers, portions of the originally installed barrier will remain in place for the time being.  As funding allows, the Corps will engage in activities to increase the channel’s ability to contain flood water, such as non-native vegetation removal and sediment removal.


What work has the District done to restore capacity to the LAR along the Glendale Narrows?

The District is pursuing aggressive measures to restore conveyance capacity within the Los Angeles River.  More specifically, the District is prioritizing areas that are the most heavily populated by removing sediment and non-native vegetation.

Reach 6A-6B (Ripple Pl to Roseview Ave) The District has completed the removal of 12,192 cubic yards of non-native vegetation and 3,048 cubic yards of trash and debris within reaches 5C, 6A, and 6B (Clearwater St through Riverdale Ave) approximately 66 acres which started in September 2016 through March 2017. Recurring vegetation management is critical to maintaining advancements made against the proliferation of Arundo Donax and Arundo regrowth.


Why is the Corps removing vegetation and/or sediment from the channel?  

Vegetation and sediment within the River channel can inhibit the channel’s capacity to convey floodwaters. The channel is designed to be maintained free of vegetation and sediment to avoid impacts to flood conveyance and channel structures.  However, lack of funds for maintenance has resulted in substantial sediment buildup and vegetation growing within the channel.  Due to limited funds available to maintain vegetation in the channel, the Corps has focused on removing non-native vegetation using both herbicide and mechanical means. 


How does the Corps manage non-native vegetation?  

In early 2016, a team of District subject matter experts quantified the amount of non-native vegetation in various reaches of the LAR from Griffith Park to the Arroyo Seco Confluence to prioritize maintenance of those areas with the largest strands of contiguous non-native vegetation and those areas that most severely constrict storm/flood flows.  These areas were deemed the highest priority areas and were addressed in early FY 16 and continue to be addressed through FY 18 and future years. 

The non-native vegetated areas are cut and sprayed with herbicide by hand to minimize the overall impact to waters, habitat and wildlife.  The most pervasive non-native species is Arundo (giant reed), which is known to require several years of repeated follow-up to ensure that removal is permanent.  While initial cutting and spraying occurred and continues to occur, we foresee that follow-up spraying and occasional cutting of regrowth will be needed for up to a 7-year period. The Corps is looking at revised processes or procedures that have been recommended by the public to evaluate the efficacy and the financial cost of implementing these and other approaches.


What structural repair work has the District successfully completed to the LAR along the Glendale Narrows?

Reach 4D (Rigali Ave to Los Feliz Blvd)


An assessment of the current condition of the LAR has revealed that significant portions of the levee grouted-stone toe protection and some of the ascending grouted stone slopes have been damaged by previous runoff events over the past several years. Erosion associated with these events has, at isolated locations, caused undermining of the grouted-stone toe protection and local undermining of the ascending grouted-stone slope protection. The observed damage includes collapse features, ten to twenty-foot wide scour holes and collapse cracking, displacement and rotation of grouted stone toe protection. The measure for repair as defined by the Project Delivery Team includes removal of the damaged portion of grouted stone toe protection and constructing a replacement based on the as-built plans.


  • Approximately 350 ft in length and 58 ft width of levee wall and toe has been repaired on the left bank (east bank)
  • Approximately 250 ft in length and 58 ft width of levee wall and toe has been repaired on the right bank (west bank)
  • 20 ft of HESCO barriers were opened up to allow for access ramp construction into the river bed. Barriers have been restored.
  • Approximately 3,000 square feet of vegetation and sediment has been removed to facilitate the dewatering process.

Starting in Summer 2017 to completion in Fall 2017, this project was a success with minimal run-in construction problems. The District did not receive any negative inputs from the community about the construction work repairing the river’s structural integrity of the channel toe and levee wall. Although this project was a great success, there are some concerns about the access right of way which the District is working closely with the City of Los Angeles to resolve.


What work does the District have planned for the upcoming years to decrease flood risk in the LAR along portions of the Glendale Narrows?

Subject to the availability of funds, the District’s tentative plans for FY 18 include:

Reach 2A (Justin Ave to Grandview Ave): estimated to start Fall 2017, completion of March 2018

  • Estimating the removal of 4,000 cubic yards of sediment, rhizome/root ball, and vegetation, and 26 mixture between *common/non-native trees and 56 stumps within a 2.5 acre area

 *  Common native trees that are within 15ft of the channel toe and/or compromising structural integrity.

Reach 4A (Brazil St to Colorado St): estimated to start September 2017, completion of March 2018

  • Estimating the removal of 1200 cubic yards of trash and vegetation in a 2 acre area
  • Estimating the removal of 20 cubic yards of sediment debris and 10 cubic yards of concrete debris
  • Mixture between 44 *common/non-native trees
  • 480 cubic yards of trash and vegetation (vegetation management) will be performed in a 10 month follow up period

 *  Common native trees that are within 15ft of the channel toe and/or compromising structural integrity.

Reach 4B (Colorado St to Sequoia St): estimated to start September 2017, completion of March 2018

  • Estimating the removal of 1800 cubic yards of trash and vegetation in a 3 acre area
  • Estimating the removal of 20 cubic yards of sediment debris and 10 cubic yards of concrete debris
  • 480 cubic yards of trash and vegetation (vegetation management) will performed in a 9 month follow up period

Reach 5C (Fletcher Dr to Ripple Pl): estimated to start October 2018, completion of January 2019

  • Estimating the removal of 25,000 – 40,000 cubic yards of sediment


What is the District doing in regards to maintenance and repairs to the HESCO barriers?

HESCO initial maintenance consisting of structural repairs, vegetation management, and graffiti abatement is scheduled for the first week of September 2017 performed by the District’s O&M Section.  After the completion of initial maintenance, ongoing maintenance to remove graffiti, manage vegetation regrowth and ensure structural integrity will occur routinely.  


What herbicides are used in maintenance of vegetation?   

For aquatic environments, the Corps applies Roundup Custom, which is an EPA- and DOD- approved aquatic herbicide manufactured by Monsanto.  The herbicide is applied through backpack sprayers on a monthly basis to non-native vegetation in channel areas where vegetation cutting/removal has occurred.  Information about this product is available at the manufacturer’s website:  www.monsantoito.com

Glyphosate, the active ingredient in this herbicide and others, works by interfering with a plant's protein production system and disrupting metabolic functions, particularly energy use and growth.  It is systemic in action, transferred through the plant’s vascular system from the tissues that absorb it to all parts of the plant. Current studies indicate that glyphosate does not increase the appreciable risk for cancer, mutations, nerve damage or birth defects. In fact, the U.S. EPA, based on long-term toxicological tests, has classified glyphosate as Category E for evidence of non-carcinogenicity in humans—the most favorable cancer rating for pesticide active ingredients and one that few other products meet.  Roundup Custom falls into the least toxic category, with its oral and dermal LD50s of >5,000 mg/kg. Studies on mammals, fish and birds indicate that glyphosate does not bio accumulate in the food chain. Glyphosate is highly water-soluble and is rapidly eliminated from the body. Test results show it has not been found to accumulate in test species, even after repeated exposure. Roundup Custom and glyphosate have low acute toxicity to aquatic organisms. The toxicity and exposure is sufficiently low that there is no significant risk of unreasonable adverse effects to aquatic organisms under normal use conditions (including the Corps’ application technique).


Why do we use herbicide to manage vegetation in the river channel? 

The use of herbicide to control invasive species is widely practiced by federal (National Park Service, Forest Service), state (Caltrans), and non-profit (TNC) land management agencies.  The Corps uses the best available science to determine proper treatment mixes and treatment times for each invasive species controlled with herbicide.  The Corps only uses herbicides in a manner consistent with the product labeling and only uses products approved by the U.S. EPA and California Department of Pesticide Regulation.  To assure products are applied in the safest manner for both the members of the community and the environment, only applicators operating under a valid State of California applicator license are allowed to apply herbicide on Corps owned or maintained properties. 


What recreation opportunities exist within the river channel? 

Recreation is allowed seasonally in a small portion of the LAR channel managed by the MRCA in cooperation with the Corps.  For information about the recreational opportunities, please visit www.lariverrecreation.org. Due to safety concerns, the Corps discourages public access to all other portions of the Flood Control Channel.


Is the Corps responsible for any of the parks along the river channel? 

The Corps does not operate or maintain any of the pocket parks along the LAR.  These parks are maintained by the City of Los Angeles and the various communities in which the parks are located.


Who is responsible for maintaining the bike path along the river? 

The Corps does not own or operate the bike path along the LAR.  The bike path is owned and operated by the City of Los Angeles Department of Transportation.  For information about bike path closures and maintenance issues, please visit http://bike.lacity.org


Why is the bike path subject to intermittent closures?    

The bike path is partially located on the Corps O&M road for the LAR.  The bike path in these areas is governed by a tri-party agreement which prioritizes the needs of LAR for flood risk management, as the O&M road is the main and in some cases only route for the Corps to conduct maintenance. Because Corps funding hasn’t kept up with O&M requirements, the public may not be accustomed to these closures, but the Corps has a compelling need to conduct maintenance activities to reduce flood risk to the surrounding community. 

The Los Angeles Department of Transportation is the agency with responsibility for the operation and maintenance of the bike path.  They are the subject matter experts that determine detours when closures are necessary.  As such, the Corps notifies LA DOT of the need for closures and LA DOT then develops the messaging and detour routes available to the public.  Once Corps work is completed, LA DOT then determines when the bike path is ready to be re-opened.


Who’s responsible for notifying the public regarding bike path closures?   

Bike paths along the LAR are operated and managed by the City of Los Angeles, Department of Transportation (LA DOT).  The Corps issues a closure notice to LA DOT.  LA DOT notifies the public of the closures and possible detour and alternate routes.     


How does the Corps assist the homeless in the river channel? 

The Corps has limited funding and policing authority to assist the homeless population living within the LAR Channel.  The Corps routinely coordinates with local law enforcement and city administrations who work with local advocacy groups to assist the homeless population in finding alternate residences outside of the river channel.


Can the Corps assist in dealing with the homeless encampments located in the LAR and in the basins that the Corps operates and maintains?  

The Corps’ primary responsibility is for operation and maintenance of the flood risk management purpose. Addressing homeless encampments is generally a local responsibility, but the Corps works with local agencies, including law enforcement, on these issues. The Corps is willing to provide assistance in removing homeless encampment debris in the LAR when funding and resources permit.  Often the issue is a challenging one to manage because these communities are often mobile and accustomed to moving upstream or downstream.  Once removal activities occur, the encampments often reestablish shortly thereafter.  We rely on LAPD to relocate the communities and secure personal belongings.  Once these measures are in place, the Corps must comply with applicable environmental laws and regulations as well as balance resource constraints to determine how best we can assist.  We do work closely with LAPD HOPE task force and others to maximize limited resources and to place public safety first.


My home abuts the river channel, how close to the channel walls (appurtenance) can I plant trees or construct a structure? 

The Corps requires a setback of approximately 15 feet from the channel or levee wall or appurtenance to protect structural integrity.  Contact the Corps at AMoperations.Branch@usace.army.mil before planting trees or planning to construct any type of structure within 15 feet of the Right-of-Way of the channel/levee wall or appurtenance to ensure that your activities will not compromise the integrity of the channel system.  The property owner should review their property deeds and maps and ensure that the channel easement is maintained clear of obstacles, structures, and planted trees.


Where can people get more information?  

There are several avenues to obtain information on the LAR.  In August of 2016, the Corps launched the LACDA Project website, which is available at: http://www.spl.usace.army.mil/Missions/Operations/


In addition, the Corps frequently posts updates regarding updates and documents on its social media platforms:

Facebook: www.facebook.com/LosAngelesDistrictUSACE

Twitter: twitter.com/LADistrictUSACE

Questions/Concerns related to:

Corps operations may be e-mailed to: AMOperations.Branch@usace.army.mil

Recreation, filming, land use, etc. may be e-mailed to AMCivilWorks.Branch@usace.army.mil


The appearance of external hyperlinks does not constitute endorsement by the U.S. Army of this Web site or the information, products, or services contained therein. For other than authorized activities such as military exchanges and MWR sites, the U.S. Army does not exercise any editorial control over the information you may find at these locations. Such links are provided consistent with the stated purpose of this Web site.