Symposium Explores the Complexities of Sediment Management

September 29, 2011 § 8 Comments

1969. A conveyor belt transports sediment away from Big Tujunga Reservoir. (Los Angeles Public Library Images)

Last Tuesday (9/20), the Council for Watershed Health (formerly the Los Angeles & San Gabriel Rivers Watershed Council) hosted a creek-freaky event entitled Shifting Soil: Sediment Management Policies in Los Angeles. While I was fortunate enough to be in attendance, it has taken some time to digest all that was discussed and to place in context all of the remarks that were made. The following is my best attempt at a summary including a few thoughts on the topic. For further reading, have a gander at Mademoiselle Gramophone’s in depth coverage (including video and audio snippets) or visit the Council’s event archive for downloadable PDF files of each presentation. A friendly forewarning: this post is a lengthy one…

2011. Forty-two years after the first image was taken, an identical scene plays out in the foothills of Arcadia. This conveyor belt will transport sediment from Santa Anita Reservoir to a sediment placement site formerly occupied by the Arcadia Woodlands. (Tom Fauquher/Arcadia Patch)


Before diving into the detailed summary, a few general notes:

  • Symposium in context: While the ultimate catalyst for the event was almost certainly the Station Fire of 2009 (the largest L.A. County wildfire in recorded history at 160,557 acres and the reason so much sediment is now clogging debris basins and reservoirs), the subsequent related destruction of the Arcadia Woodlands this past January undoubtedly influenced the organization of the symposium as well.
  • Presentation order: As noted by a member in the audience during the Q&A session, the order of the presentations created a subtle yet palpable adversarial tone. Although the presentations were quite diverse and fairly well-balanced, a binary debate still managed to surface (perhaps not surprisingly). The seating arrangement of the panel discussion only added to the division, with the environmentally-minded folks seated conveniently on the left.
  • Resolution? Hope?: While the presentations and panel discussion were very informative, the event seemed to serve more as a jumping off point for future discussions rather than a consensus-building session. If you were to understand even a fraction of recent flood control and watershed management history, it might be easy to view the talks through a cynical lens, but there were actually a few moments of optimism to take away from the afternoon. Details below…



Pete Wohlgemuth (Geographer, USDA Forest Service, Pacific Southwest Research Station)

Offering up a very succinct presentation, Mr. Wohlgemuth put the region’s sediment management concerns in context, explaining that Southern California has some of the highest erosion rates in the world. Through a perfect storm of steep surrounding slopes (many of which are greater than the angle of repose), steep stream channel gradients, exposed soft sedimentary rock, poorly developed non-cohesive soils, volatile tectonic movement, high-intensity rainfall events, an ever-present threat of wildfires (which strip away protective vegetation and can cause soils to become hydrophobic), and a flood control network that does not allow sediment to pass through the engineered system, the region is burdened by a perpetual need for sediment management.


Gary Hildebrand (Assistant Deputy Director, Los Angeles County Flood Control District)

Likely the most anticipated presentation of the day, Mr. Hildebrand represents the agency charged with maintaining a majority of the flood control structures (formerly known as creeks and rivers) in the region. It was the Los Angeles County Flood Control District (LACFCD) who authorized the demolition of the Arcadia Woodlands so that the site could be used for sediment placement. Since the Arcadia Woodlands controversy, the LACFCD has received quite a bit of scrutiny from environmental groups, regulatory agencies and other concerned citizens regarding its sediment management methodologies. In response, the LACFCD has organized the Sediment Management Strategic Plan Task Force (who have met quarterly since January) to obtain input from a variety of stakeholders and community members. The department has also organized the smaller Sediment Management Advisory Working Group to “provide additional input and a broad perspective based on the members’ diverse experiences and key roles in the stakeholder community.” Three members of the latter group (Jeff Pratt, Tony Zampiello and Tim Brick) also presented at the symposium.

Mr. Hildebrand began by providing a concise description of the facilities controlled by LACFCD (14 dams, 162 debris basins, 26 sediment placement sites, 500 miles of open channel, etc.) and the history behind their construction and continued operation. He went on to explain that the department plans on removing a total of 87 million cubic yards of sediment from all facilities in the next 20 years and that the currently active sediment placement sites only have capacity for 11.6 million cubic yards. This mammoth discrepancy represents a nexus of sorts for the highly mechanized flood control systems of Los Angeles. It was encouraging to hear Mr. Hildebrand acknowledge that the current system is dated and could benefit from “re-structuring”. He maintained that most, if not all, options for sediment removal (conveyance, sluicing, trucking, piping, transporting via rail, etc.) and placement (active sediment placement sites, new sediment placement sites, abandoned quarry pits, beach replenishment, landfill cover, etc.) are currently on the table. While certain methods of removal and placement and more palatable than others, Mr. Hildebrand also referred to sediment as having value as a commodity, a welcome addition to the County’s rhetoric to say the least. Whether it was delivered through a veil of public relations/damage control or whether it was in fact genuine, it appears that the LACFCD has heard its constituents and is working toward developing a more sustainable approach to sediment management. The optimism I took away from the symposium stemmed from the final slide of Mr. Hildebrand’s presentation (shown below) which included the phrase “Restore/Mimic Natural Processes”.

A bit of hope courtesy of the Los Angeles County Flood Control District


L.B. Nye (Los Angeles Regional Water Quality Control Board)

A brief presentation on the history and role of the Regional Water Quality Control Board. Readers of this blog are likely familiar with most of the basic concepts of regulation as they pertain to issues of water. One notable topic was a discussion of the California Rapid Assessment Method (CRAM). This standardized tool for assessing the health of wetland and riparian habitats can be used to assess the performance of compensatory mitigation projects and restoration projects. This is how the RWQCB measures the success and/or compliance of habitat mitigation/restoration efforts required by the permit process for projects with any sort of environmental impact. Without the insight of actually performing a CRAM assessment myself, on the surface, the method appears to be a bit superficial in that results are based solely on observations made in a 1-3 hour time frame. It seems that a more measured, periodic observation over time would be more appropriate in judging the intricacies of habitat quality. The need for an affordable method is understandable but the results of such an assessment are only as good as the inputs.


Tomas Beauchamp (Chief, U.S. Army Corps of Engineers Operations Branch)

Around the Southwest: I admit, I must have been fading a bit at this point because I was quite distracted by the Corps’ red medieval castle logo and the emphatic “BUILDING STRONG… and taking care of people!” slogan. Another straightforward presentation about what facilities the Corps has built and continues to maintain. One interesting factoid came after a question from the audience regarding why the Corps maintains only some of the projects it has built and why it has handed over a majority of projects to local agencies for maintenance. Mr. Beauchamp explained that Congress ordered the Corps to maintain facilities built during a period of about a decade (sometime around the ’40s or ’50s) and that projects built before and after this brief interval would be handed over to local agencies upon completion.

Jeff Pratt (Director, County of Ventura Public Works Agency)

A View from Ventura County: Mr. Pratt offered up one of the more encouraging presentations of the day, his charming demeanor belying the stereotypical engineer persona. For a bit of telling pretext (and perhaps a bit of good PR), he explained that in 2003 the Ventura County Flood Control District changed its name to the Ventura County Watershed Protection District (VCWPD). The agency manages four distinct “zones” comprised of the Ventura River (zone 1), the Santa Clara River (zone 2), and the Calleguas Creek (zone 3) watersheds as well as coastal Malibu watersheds in the south and the Cuyama River watershed to the north (zone 4). Mr. Pratt explained that Ventura County’s sediment management challenges are far different than those of Los Angeles County due to the fact that a vast majority of Ventura’s waterways are unconfined by urban density and accompanying channelization. Sediment transport is commonplace in such systems as are flash floods, which constitute the primary challenges faced by the VCWPD. However, at the core of the agency, there appears to be an underlying appreciation for the immense value of the surrounding rivers and streams and a commitment to flood control efforts that keep the health of each respective watershed at the forefront.

Greg Woodside (Executive Director of Planning and Natural Resources, Orange County Water District)

A View from Orange County: Mr. Woodside focused his discussion on sediment management efforts in the Prado Basin and the Lower Santa Ana River. The build up of sediment behind Prado Dam has essentially starved the Lower Santa Ana River of sediment resulting in channel incising, riverbed armoring and coarsening (resulting in reduced percolation rates) and reduced beach replenishment at the coast. In response, the Orange County Water District (OCWD) has initiated the Prado Basin Sediment Management Demonstration Project. The project would remove sediment via dredging from the Prado Basin (primarily in areas where non-native vegetation dominates) and place it below the dam (through a sediment transport pipe) to allow for it to be transported downstream by high flows released from Prado Dam. The OCWD will use data collected from the project to assess long-term feasibility of re-establishing a natural sediment transport regime.


Tony Zampiello (Assistant Executive Officer of the Main San Gabriel Basin Watermaster)

Mr. Zampiello is the Assistant Executive Officer for the Main San Gabriel Basin Watermaster and Assistant Secretary/Treasurer for the Raymond Basin Management Board (effectively the Raymond Basin Watermaster). Both agencies were founded as the result of judgements that determined who had a right to extract water in each respective groundwater basin and the maximum annual amount of water allowed to be pumped by each producer. These agencies oversee the implementation of the provisions of basin-specific judgments and approve plans for storage of local and imported water within basin boundaries. In his presentation, Mr. Zampiello explained that groundwater contained in the Main San Gabriel Basin serves, on average, a total of 80% of the San Gabriel Valley’s water needs, a population of approximately 1.4 million people. The remaining water supply is supplemented via imported waters from the Colorado River (Metropolitan Water District) and/or the Feather River and Sacramento River Delta (State Water Project). Reservoirs and spreading grounds are critical facilities when it comes to basin recharge and sediment management activities can affect the amount of available water. For example, sluicing (the controlled flushing of sediment from reservoirs) can be detrimental to short-term groundwater conservation efforts, potentially leading to the need for increased amounts of imported waters. In short (or long considering this post!), sediment management activities have far reaching effects involving multiple parties. Most folks in the general public will never know of these various stakeholders but all are bound by the common perpetual need for water.

As an added bonus, Mr. Zampiello included photos of the current sediment removal and placement activities at the Arcadia Woodlands (see below).

Sediment excavation continues in earnest behind Santa Anita Dam. The sediment removed from this site will be placed on the former site of the Arcadia Woodlands. (image credit: Tony Zampiello)

When the Lower Sediment Placement Site adjacent to Santa Anita Wash (pictured) is full, crews will begin depositing sediment on the former site of the Arcadia Woodlands (aka the Middle Sediment Placement Site) just to the north. (image credit: Tony Zampiello)

Tim Brick (Managing Director of the Arroyo Seco Foundation)

Mr. Brick began his presentation with a potent “then-and-now” comparison, highlighting how Californians formerly burnt trash in backyard chimneys and used 7.5 gallon/flush toilets. While these practices have been abandoned in favor of more sustainable techniques, Brick argued that our views toward stormwater and sediment as waste products have not changed and that a paradigm shift in how we manage our watersheds is past due. After presenting a condensed history of the Arroyo Seco and the hydrological processes found in our region, he made his case for a thorough review of the current flood control system and a measured transition to a system defined by the restoration of natural processes and a greater respect for watershed resources.

Dr. Cheryl Swift (Professor of Biological Sciences at Whittier College)

Dr. Swift presented a succinct overview of the ecological function and value of our local riparian habitats. She described how riparian tree species have adapted to the ever-changing landscapes found in the volatile creek and river beds of Southern California. After co-evolving with flash floods, debris flows and suffocating sediment deposits for thousands of years, species such as willow, cottonwood, sycamore, and alder have developed the ability to re-sprout from buried trunks and branches. Such adaptations make these trees extremely resilient, a character trait that is to their benefit in a highly controlled human-altered system that requires major maintenance on a regular basis. According to Dr. Swift, however, what is not as resilient is the fauna that occupies this habitat. Because riparian forests have become so fragmented and disturbed in Southern California, the opportunities for riparian wildlife to migrate and/or regenerate after a disturbance has become extremely difficult if not unlikely. Her presentation underscored the need for a more integrated, sustainable approach to the way our watersheds are managed.

Lynette Kampe (Executive Director of the Theodore Payne Foundation)

Ms. Camp directs one of the most well-known and respected retail nurseries specializing in California native plants. She began her discussion by acknowledging that her involvement in the topic of sediment management came about as a result of a planned sediment placement site in La Tuna Canyon, just up the road from the nursery. She echoed Dr. Swift’s statements stressing the value of ecosystems as complete interconnected units as opposed to focusing attention on individual species. While it was not directly stated, her remarks undoubtedly referred to “compensatory mitigation” efforts that are required by regulatory processes as a trade-off for the destruction of habitat to make way for sediment placement (as in the case of the Arcadia Woodlands). As Kampe put it, “Simply replanting dominant species does not make an ecosystem.” She reiterated the many existent threats to local habitats and called for value-driven methods of sediment use such as for construction purposes, fill for decommissioned gravel pits, cover for landfills and beach replenishment.

1949. The beginning of the end for natural sediment transfer in Los Angeles. Channel construction along the Los Angeles River at Laurel Canyon Boulevard (Los Angeles Public Library Images)


All presenters present; Moderated by Nancy L.C. Steele (Executive Director, Council for Watershed Health)

After listening to such a variety of presentations, the panel discussion felt brief. A few interesting points emerged but constructive in depth dialogue among panel members remained a bit elusive. Dr. Cheryl Swift eloquently pointed out that the reservoirs, debris basins and flood control channels that were the focus of discussions throughout the day were in fact rivers and streams and that until they are perceived as such, a measurable change in how they are managed is unlikely. Another interesting and encouraging moment came from Gary Hildebrand in response to a question from the audience regarding the LACFCD’s commitment to a more sustainable path. He explained that the County’s plans at this point are two-fold: one path is focused on short-term sediment clearing efforts, which are an undeniably pressing issue, and the other path is centered around establishing a comprehensive long-term plan that will inevitably include the restoration of natural processes. He acknowledged that this would take time and that there would be a transition period, but hearing the County recognize that the status quo is an unsustainable path was worth the price of admission for this creek freak. If you have made it this far, I thank you a thousand times over. There are fundamental, ground-breaking changes on the horizon when it comes to watershed management in L.A. These are exciting times and we look forward to covering it all as it unfolds. We might even contribute a few ideas of our own along the way.

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§ 8 Responses to Symposium Explores the Complexities of Sediment Management

  • Thank you for writing about this and for your accuracy. As odd as it sounds, sediment removal/placement is the most important subject in the LA neighborhood-from mountains to beach. Devils Gate Dam will be the largest and first place for rennovated methods to be applied. It’s an important model at a time when old growth trees, water resources and the attendent cleansing synergistic ecosystems have become too valuable to be destroyed. There is a more delicate path.

    [“There are key issues of water-resource management, wildlife and vegetation – I’m talking trees and native plants and perhaps endangered species,” he said.]

    Pasadena Star News today:

  • Jessica Hall says:

    Josh, thank you for taking the time out to put together this great synopsis of the symposium.

  • nancysteele says:

    Even though, or perhaps because, I was the moderator, I must agree with your comment that the panel discussion “felt brief.” I would have liked to get the panelists interacting with each other and the audience more, but perhaps the day was too long or the audience too overwhelmed by all the information. In any event, thanks much for a very nice summary.

  • […] the Los Angeles and San Gabriel Rivers, that can really help us to postulate our way out of the sediment dilemma of debris dams and spoiled woodlands to floodplains and sediment transport, will bear new markings […]

  • Jackie says:

    Very nice synopsis of the complexities of proper sediment control. I really like the photos, especially the aerial (3rd photo down).

  • Ricky Grubb says:

    Dredging and transportation of sediment from streams and rivers has wiped out the Arroyo Toad in Sunland’s Big Tujunga river wash, where they were first described (discovered). The LACFCD refused to release any sand and gravel below the Big Tujunga Dam and instead spent $44 million taxpayers dollars to dredge and truck the sand and gravel through our community and deliver it to Vulcan Materials while avoiding any environmental over site.

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