The Barrier: Seeking Sustainable Sediment Management Solutions for Devil's Gate Dam by Nate Oakley

The Barrier: Seeking Sustainable Sediment Management Solutions for Devilâ&#x20AC;&#x2122;s Gate Dam A Senior Project presented to the Landscape Architecture Department of University of California Davis in partial fulfillment of the requirement for the degree of Bachelor of Science in Landscape Architecture.

Accepted and Approved by

Senior Project Advisor, Brett Milligan

Technical Advisor, Gregory Pasternack

Committee Member, David de la PeĂąa

Committee Member, Cory Parker

TABLE OF CONTENTS

ACKNOWLEDGMENTS

Prologue

I extend my sincerest gratitude to my adviser and professor for igniting my interest in reservoir sedimentation and dam removal. Thank you for your constant support and feedback along this short, yet extremely enlightening journey.

Acknowledgments List of Figures The Issue Abstract Sediment Defined

1 2 3 4 5

Introduction The Barrier Sediment Management Today Sustainable Sediment Management

6 8 9

Thank you to all of my committee members who have provided valuable insights, critiques and forward momentum. A special thank you to Tim Brick at the Arroyo Seco Foundation, for taking the time to sit down and answer my questions and for providing me with a wealth of information about the Arroyo Seco Watershed and Devilâ&#x20AC;&#x2122;s Gate Dam. To my friends and family, I could not have done this without your unwavering support.

Case Studies Reservoir Sedimentation Flood Plain Reclamation

10 18

Analysis

Design

Conclusion

Appendix

LIST OF FIGURES Cover – Devil’s Gate Dam and Reservoir; by author

0.1 – Sediment Visualization; 2015; by author; model by sketchup 3d warehouse 0.2 – Devil's Gate Dam; 2015; by author 0.3 – Hahamongna Watershed Park and reservoir; 2015; by author 0.4 – Alluvial sediment deposits and rider; 2015; by author 0.5 – Sediment excavation behind Devil's Gate Dam; 2014; lacanadaonline.com 0.6 – Nagle Dam Sediment Bypass diagram; 2014; hydroworld.com

2.19 – Desert Rose Golf Course flood; 2012; reviewjournal.com 2.20 – Las Vegas Wash drainage channel; 2012; reviewjournal.com 2.21 – Filsinger channel restoration; 2015; stantec.com/blog 2.22 – Filsinger channel; 2015; kitchener.ca 2.23 – Filsinger channel restored; 2015; stantec.com/blog 2.24 – South Platte River Confluence Park in flood; 2015; denverpost.com 2.25 – South Platte restoration; 2014; denverpost.com 2.26 – Confluence Park kayakers; 2015; Ed Andrieski 2.27 – Leith River channel project; 2015; otago.ac.nz 2.28 – Leith River channel project; 2015; otago.ac.nz

Case Studies 1.0 – Reservoir Sedimentation

Analysis 3.0

1.1 – Hahamongna Reservoir Aerial; 2012; nearmap.com 1.2 – Searsville Dam; 2015; news.stanford.edu/searsville 1.3 – Searsville Dam Sediment Map; 2015; news.stanford.edu/searsville 1.4 – San Clemente Dam Removal; 2014; sanclementedamremoval.org 1.5 – Barlin Dam; 2006,2007 ; Kondolf, G. Mathias 1.6 – Barlin Dam Sediment Filled; 2006,2007 ; Kondolf, G. Mathias, et. al. 1.7 – Barlin Dam Post-Failure; 2012 ; tushili.wordpress.com 1.8 – Xiaolangdi Dam Sediment Release (3 photos); 2012; dailymail.co.uk; reuters; AP 1.9 – Nagle Dam Sediment Bypass; 2015; google earth imagery 1.10 – Nunobiki Dam Sediment Bypass; 2015; google earth imagery 1.11 – Elwha Dam; 2008; commons.wikipedia.org 1.12 – Elwha Dam sediment flux; 2012; blog.seattletimes.nwsource.com

3.1 – Context Map; 2015; by author 3.2 – Urban Context Map; 2015; by author 3.3 – Urban Context Map; 2015; by author 3.4 – Conflagration, Inundation, Sedimentation timeline; 2015; Tim Brick; LAFCD; graphics by author 3.5 – Natural Forces Analysis; 2015; by author 3.6 – Infrastructural Analysis; 2015; by author 3.7 – Arroyo Seco channel and access map; 2015; by author 3.8 – Arroyo Seco natural channel; cityofpasadena.net 3.9 – Arroyo Seco box channel; flickr.com/lierne 3.10 – Arroyo Seco trapezoidal channel; panoramio.com/user/6318411 3.11 – Arroyo Seco trapezoidal channel and bike path; flickr.com/ubrayj02

Introduction

Case Studies 2.0 – Floodplain Reclamation 2.1 – South Platte River Confluence Park; 2015; nearmap.com 2.2 – Lowering the floodplains; 2011; ruimtevoorderivier.nl 2.3 – Dike relocation; 2011; ruimtevoorderivier.nl 2.4 – High Flow Channel; 2011; ruimtevoorderivier.nl 2.5 – Temporary water storage; 2011; ruimtevoorderivier.nl 2.6 – Deepening summer bed; 2011; ruimtevoorderivier.nl 2.7 – Dike strengthening; 2011; ruimtevoorderivier.nl 2.8 – Zuera bullring; 2002; publicspace.org 2.9 – Parque Fluvial trails; 2002; publicspace.org 2.10 – Gallegos aerial; 2002; publicspace.org 2.11 – Gallegos inundation maps; 2002; publicspace.org 2.12 – Emscher River revival; 2012; spiegel.de 2.13 – Emscher River channel; 2013; thefield.asla.org 2.14 – Emscher River retention plan; 2015; www.eglv.de 2.15 – LA River Restoration Plan – Taylor Yard; 2015; la.curbed.com 2.16 – Taylor Yard USACE Proposed Wetland; 2015; la.curbed.com 2.17 – LA River Restoration Masterplan - Chinatown Cornfields; 2011; inhabit.com 2.18 – Desert Rose Golf Course flood; 2012; reviewjournal.com

Design 4.0 4.1 – Design framework diagram; 2015; by author 4.2 – Design context map – focus areas; 2015; by author 4.3 – Design context map – Brookside; 2015; by author 4.4 – Brookside design map – Brookside; 2015; by author 4.5 – Brookside design strategies; 2015; by author 4.6 – Brookside framework flow diagram; 2015; by author 4.7– Brookside perspective; 2015; by author 4.8 – Lower Arroyo context map; 2015; by author 4.9 – Lower Arroyo design map; 2015; by author 4.10 – Lower Arroyo design strategies; 2015; by author 4.11 – Lower Arroyo framework flow diagram; 2015; by author 4.12 – Lower Arroyo perspective; 2015; by author 4.13 – South Pasadena context map; 2015; by author 4.14 – South Pasadena plan; 2015; by authorv 4.15 – South Pasadena strategies; 2015; by author 4.16 – Aerial Perspective - Brookside; 2015; by author

THE ISSUES

The Arroyo Seco is located in one of the most densely populated parts of the country. Two of the most significant alterations to the Arroyo Seco include the construction of Devil’s Gate Dam and the channelization of the lower Arroyo Seco. The Arroyo Seco is crossed and bounded by multiple-lane freeways. Parking areas and hardscape are now found in the former floodplain of the stream. Without significant human efforts to restore the watershed conditions in the Arroyo Seco are likely to worsen. -United States Army Corp of Engineers2011 Feasibility Scoping Meeting Documentation

Sediment: Defined and Visualized

ABSTRACT

his project will take a holistic approach in analyzing the ecological, infrastructural and cultural impacts of Devil’s Gate Dam and the channelized Arroyo Seco River, located in Pasadena, California. This analysis will aid in understanding current unsustainable and destructive sediment removal strategies deemed necessary for flood protection in a highly urbanized milieu.

The aim is to propose regenerative design planning strategies and design interventions that balance natural sediment delivery, water storage, flood control and habitat restoration. It is the author’s ultimate goal to supplement the current understanding of sustainable sediment management within an urban context, and in a landscape of aging flood-control infrastructure.

n his book, Sustainable Management of Sediment Resources, Philip Owens (Network, 2008) uses the European Sediment Network’s definition of sediment: ‘Sediment is suspended or deposited solids, of mineral as well as organic material, acting as a main component of a matrix which has been or is susceptible to being transported by water’ (p.2). Owens expands on this definition stating that these dynamic solids can be affected by more than water alone, “[and] indeed it can be argued that sediment movement by people, animals, machinery, etc. is relevant” (p.2).

PASADENA ROSE BOWL STADIUM - EMPTY

In the context of dams, this aforementioned susceptible matrix is carried by water in first-third order streams down the watershed and then becomes trapped behind man-made concrete holding cells. In the case of this project's dam, Devil’s Gate Dam, erosion is exacerbated by disturbance regimes and the storms that follow, creating an inevitable need to excavate and truck sediment from behind it. The diagram to the right shows an empty Rose Bowl stadium filled to the brim with 400,000 cubic yards of sediment, to give an idea of scale.

PASADENA ROSE BOWL STADIUM - FULL OF SEDIMENT

400,000 YD³ OF SEDIMENT

~16 YD³

30’

SEDAN 870’ 5’

15’ 700’

0.1 Sediment and Scale Visualization

The Barrier: Introduction

ver 2.4 million cubic yards of alluvial sediment sitting behind Devilâ&#x20AC;&#x2122;s Gate Dam in Pasadena California is slated to be excavated and trucked into nearby landfills to maintain reservoir capacity in the Hahamongna basin (Karlamangla, 2014). This will not be the first time an excavation at this scale has been completed. Since construction of the dam in 1920, four major conflagrations and several historic storm events have led to the erosional deposition of millions of cubic yards of sediment, which becomes trapped behind the 100 foot tall concrete gravity arch dam (L. A. C. F. C. District, 2014). The cyclical fire-storm-sedimentation event results in mandatory periodic sediment removal to prevent storm water from spilling over the dam. The most recent Station Fire in 2009 obliterated much of the vegetation within the Arroyo Seco watershed upstream of the Devilâ&#x20AC;&#x2122;s Gate Dam and has contributed the highest amount of erosional sediment in recent years. The Los Angeles County Flood Control District is now playing catch-up to remove as much debris as possible to maintain flood control levels within the Hahamongna reservoir. While on one hand the detritus is hindering the damâ&#x20AC;&#x2122;s ability to prevent flooding of a highly urbanized environment downstream, it is also creating acres of newly formed riparian habitat for wildlife in addition to new recreational

opportunities for the public. Pasadena locals are seeking to preserve as much of this new habitat as possible. Local nonprofits and even the city of Pasadena have criticized this removal plan positing that it will disrupt the ecology in the reservoir. The sustainability of transporting the removed sediment has also been called into question, as it would require hundreds of trucks making off-loading trips over a multi-year period (Kim, 2014).

0.2 (Left Page) Devil's Gate Dam 0.3 (Top) Hahamongna Watershed Park 0.4 (Bottom Right) Alluvial Sediment in Reservoir

Sediment Management Today

ediment management can involve a dance of different heavy machinery in varying landscape types be it a coast line or a high-traffic shipping channel. A myriad of different excavation, transportation and placement options exist for deposited material that must be managed. The International Association of Dredging Companies outlines the major phases of a dredging and excavation process as “dislodging of the in-situ material; raising of the dredged material to the surface; horizontal transport; and placement or further treatment” (IADC/CEDA, 2008). With respect to dams and reservoirs, sedimentation is dealt with by reducing the sediment flowing into the reservoir, flushing the in-situ material through the dam via sliding gates or other dam openings, or simply dredging it. Another option is sluicing which involves lowering reservoir water to pre-dam levels before storms and allowing initial storm flows to carry as much sediment as possible through the dam before allowing it to fill (McCully, 1996). Sluicing is the main method of sediment control at the Three Gorges Dam in China (Wang, n.d.), however, it should be noted that overall sediment delivery downstream has still been reduced by the dam (S. L. Yang, Zhang, & Xu, 2007). The overarching goal and practice has been to manage reservoirs to a point where sediment accumulates gradually

Sustainable Sediment Management

and is removed gradually subsequently relying on continual maintenance by future generations (Palmieri, Shah, & Dinar, 2001).

At larger scales, watershed management becomes an option in reservoir sedimentation management; managing lands above the reservoir by vegetating slopes and utilizing farming practices that lessen erosion (McCully, 1996). Not all of the previously mentioned management techniques are successful and sometimes the cost of implementation outweighs any benefit that a particular dam may be providing. These costs are becoming apparent around the world and in places that depend on them the most, like in the state of California.

hilip N. Owens, a professor of environmental science, describes an adaptive management framework in working toward sustainable sediment management. In his paper he calls for varied viewpoints from different disciplines and involvement of stakeholders in the research process. The process should allow for continual learning and adjustments based on constant monitoring at the river-basin scale and ultimately further investigation is needed to completely understand sustainable sediment management (Network, 2008).

Normal Flow Flood Weir

Siltation has also become a major issue in California’s current drought-stricken climate as more dams are being called for to increase water storage and existing reservoir’s capacities are shrinking due to sedimentation. In an article by California Magazine, the problem is becoming more apparent in current drought conditions as it is cited that about 1.7 million acre feet of sediment sits behind California’s dams with more flowing in each year. About 200 reservoirs are from a third to half full, and some dams are topped out completely (Martin, 2014).

Diversion Channel Flood Flow

Dam

G. Mathias Kondolf, professor at UC Berkeley, highlights sustainable sediment management techniques are numerous and for the most part not implemented. Some of these techniques include sediment bypasses around reservoirs, sluicing, drawdown flushing, and utilizing turbidity currents (Kondolf, Gao, & Annandale, 2014). More importantly, in taking scope of the complete picture of sedimentation management, the bigger issue is the sediment starved reaches below the installed dams. Kondolf mentions that sediment delivery is key in maintaining a riparian ecosystem and channel form. (Kondolf et al., 2014)

To counter-act the negative aspects of aging dams and siltation the concept of sustainable sediment management has manifested. 0.5 Sediment Removal behind Devil's Gate Dam

0.6 (Left) An example of sustainable sediment management - Nagle Dam Sediment Bypass Diagram

Case Studies: Reservoir Sedimentation

umerous dams throughout the world suffer from sedimentation management issues and are dealing with them in unique ways. Key dams that have or are experiencing abnormal amounts of sedimentation, as well as unique siltation management solutions which may inform design intervention, are identified in this section to serve as case studies for possible alternative solutions in dealing with reservoir sedimentation. The option of complete dam removal may not be feasible in the scope of this author’s project, nevertheless some case-studies of this type will be provided due to stakeholder exploration of alternative sediment management options, however this specific management option will need further exploration in future research.

1.1 Arroyo Seco Alluvial Deposits within Hahamongna Basin

Case Studies : Searsville Dam

earsville Dam is located in the San Francisquito Creek watershed in California. It was built in 1892 and acquired by Stanford University in 1919. Sedimentation has reduced the reservoir to less than 10 percent of its original water holding capacity and eliminated recreational activity that once existed behind the dam. Due to the anticipation of complete sedimentation of the dam’s reservoir, comprehensive reviews are being conducted of all possible options including sediment removal. The opposite of removal is also an option, letting the reservoir fill with sediment and transition to a forested wetland (Stanford University, 2014). The United States Army Corps of Engineers has flagged the Searsville dam as ‘high-hazard’, meaning that failing to manage the sediment behind it would result in economic, environmental and human damages (American Rivers, 2014).

1.2 (Top Left) Searsville Dam 1.3 (Bottom Right) Searsville Dam Sediment Map

Case Studies : San Clemente Dam

Case Studies : The Barlin Dam

Another California Dam dealing with the same issue of sediment accumulation is the San Clemente Dam in the Carmel Valley. California American Water, the company who owns the dam chose to not build a new dam or deal with sediment removal from the San Clemente Reservoir after 2.5 million cubic yards of debris built up within it reducing the reservoirs capacity to 5% of its original holding capacity (Fimrite, 2014) (Figure 2) .

The option of trucking dredged sediment out from behind the dam was deemed infeasible due to economic and environmental costs. The plan now is for complete removal of the dam, and it will be the largest dam in California that will have been removed to date (“Project Overview | San Clemente Dam Removal & Carmel River Reroute,” n.d.).

1.4 Excavators prepare for dam removal

he Barlin Dam, in Taiwan, was a 38 meter high sabo dam built in 1977 with an initial capacity close to 14 million cubic yards. Storage behind the dam was occupied with sediment by 2004 and the dam failed completely in 2007 during the WeiPa typhoon. (H. W. Wang & Kondolf, 2014). The dam was designed to control sedimentation and even built with an emergency “buffer” dam downstream to cushion impact from falling water. This emergency dam also failed. The resulting in-situ sediment released downstream after dam failures was in excess of 9 million cubic yards. The downstream reach aggraded over 18 feet and was captured in the reach before Ronghua Dam.(H. W. Wang & Kondolf, 2014)

1.5 (Top Left) Barlin Dam - 2006 1.6 (Top Right) Barlin Dam - 2007 1.7 (Bottom) Barlin Dam Post-Failure - 2007

Case Studies : Xiaolangdi Dam

NAGLE DAM

1.8 Xiaolangdi Dam Sediment Release

S AS YP )

(OP

The riverbed has been lowered by more than 2 meters since the dams construction, and large fish kills have been observed due to the high concentration of sediment being released into the river via sediment gates (Baiyinbaoligao, Xu Feng-ran, Chen Xing-ru, 2012) (“Apocalypse

EN DIM

This yearly sediment release has become an attraction for bystanders who are able to watch plumes of ejected sediment rise hundreds of feet high eventually splash down on the Yellow River (“Apocalypse Dam,” 2012). Over 39 million cubic yards are released from behind the dam each year which has created a unique cultural interest in an infrastructural process but, does not come without environmental consequences.

he Xiaolangdi Dam in Luoyang, China, impounds Yellow River. The river is considered to have one of the highest sediment loads in the world (however, this notion may be changing as anthropogenic use of the river increases) (River Inputs, 2001), which requires the Xiaolangdi dam to perform an annual ritual of “flushing” sediment through specially designed sluice tunnels toward the bottom of the dam (T. Yang et al., 2008).

Case Studies : Sustainable Sediment Management and Bypass Systems

Dam,” 2012).

RESERVOIR

SEDI

MEN

DIVERSION WEIR AND TUNNEL INLET

T BY

PASS

(CLO

SED)

n reservoirs where the water flow path makes a large bend, like the Nagl Dam in South Africa, sediment buildup is controlled through a bypass channel. During high flow events sediment is passed through an alternate route and released in front of the dam and once flows subside, water is allowed to flow into the reservoir. Mathias Kondolf , in his research cites that the Nagl Dam is in an ideal position (Kondolf, Gao, & Annandale, 2014). Kondolf goes on to cite numerous dams in Japan and Switzerland that have been able to install sediment bypass tunnels. One sediment tunnel has been operating successfully for over 100 years in the Nunobiki dam reservoir, near Kobe (Kondolf et al., 2014) (Sumi, Okano, & Yasufumi, 2004) .

RESERVOIR

NUNOBIKI DAM

1.9 (Top) Nagle Dam Sediment Bypass 1.10 (Bottom) Nunobiki Dam Sediment Bypass

Case Studies : Elwha Dam Removal and Sediment Flux

he removal of the Elwha Dam in Washington is part of the largest dam removal project in U.S. History and recent peer reviewed studies have been released demonstrating the flux of sediment that was once trapped behind the dam. One key finding cited by the USGS was how efficiently the river eroded and moved sediment from the former reservoir, more than 27 million cubic yards was eroded into the river during the first two years (â&#x20AC;&#x153;Silt, sediment and change,â&#x20AC;? 2015). An article written in for Environmental Health Perspectives, by Wendee Nicole, makes clear that the ejection of sediment immediately after dam removal may release some contaminants in the short term, but on a longer timeline habitat and ecosystems are restored. She goes on to state that as wildlife returns to the Elwha again, this dam removal project is being touted as a model for future dam removal projects (Nicole, 2012).

1.11 (Left Page) Elwha Dam pre-removal - 2006 1.12 (Right Page) Sediment flux following Elwha Dam removal

Case Studies: Flood Plain Reclamation

Case Studies: ruimte voor de rivier

he following section identifies relevant projects that involve river restoration and floodplain reclamation in urbanized environments. The author acknowledges that not all case studies provided match the environmental context that exists within the Arroyo Seco Watershed, but the ones chosen are most pertinent to informing this project’s framework and objectives. These case studies provide models, and inspiration for future reclamation projects in and along the Arroyo Seco.

s the reality of a changing climate threatens the low lying country of the Netherlands, greater flooding poses risk to life and property behind existing flood control infrastructure. To allow for greater discharge volume within the Rhine, the Minister of Infrastructure and the Environment is implementing strategies to allow more room for the river.

2.2 (Top Left) Lowering the floodplains 2.3 (Middle Left) Dike relocation 2.4 (Bottom Left) High Flow Channel

2.5 (Top Right)Temporary water storage 2.6 (Middle Right) Deepening summer bed 2.7 (Bottom Right) Dike strengthening

This method diverts from the business-as-usual strengthening of levees. The Room for the River plan does acknowledges that while the option of strengthening dikes would reduce flood risk it would “[…] result in even greater damage since more water would flood to the sunken land behind the dikes. A trend has to be broken if the Netherlands is to be a safe, comfortable and pleasant country for its inhabitants” (Programme Directorate “Room for the River,” 2015). The author acknowledges the river morphology and flow of the Rhine is much different from the Arroyo Seco, nevertheless strategies employed by the Dutch remain relevant to reclaiming floodplain and to general flood protection.

2.1 South Platte River - Confluence Park

Case Studies: Emscher Future Master Plan

Case Studies: Recuperación del Cauce y Riberas del Río Gállego

he highly dynamic River Gallego runs along the urban center of Zuera, Spain. For a time the town of Zuera had turned the Gallego into a dumping ground, and many of its banks were in disrepair nearest the town’s development. In 2001 the town’s connection to the river was restored.

2.8 The bullring located along the Rio Gallego is able to withstand inundation during high flow events

2.9 Parque Fluvial - trails

2.10 Aerial of Parque Fluvial the connecting link to urban development in Zuera

2.11 (Top) Inundation Maps of the Gallego before flood proof Parque Fluvial installation 2.11 (Bottom) Inundation maps post intervention

he Emscher in Germany, much like the Arroyo Seco, is encased in a trapezoidal channel, and shares the same inaccessible characteristic in some of its reaches. Studies were undertaken to determine how much room could be given to the Emscher if it was converted from sewage drainage channel to free-flowing river. It was found that dikes could be pushed back (one of the aforementioned Room for the River strategies) in some locations where feasible. Most of the channel will have some bank reinforcement at one end (Prominski et al., 2012). The future master plan also calls for in-channel retention basins to enhance ecological conditions as well as aid in smallscale flood control. Within the basins an initial meandering channel will be excavated with the knowledge that the river will once again find its own alignment (pg 259).

Trails and amenities were implemented that are able to withstand temporary high water levels (Aldayjover, 2001). The bullring in Zuera, for example, is submerged up to 1 meter during high water events, and allows townspeople to observe flood events up close (Prominski, Stokman, Zeller, Stimberg, & Voermanek, 2012). In addition to a newly added terraced park, the arena serves as a link between the higher point of the river with the lower portion (Guixer, 2002).

2.12 (Top) Emscher River revival 2.13 (Bottom Left)Emscher River - hazardous channel 2.14 (Bottom Right) Emscher River - retention bypass plan

Case Studies: Los Angeles River Restoration

Case Studies: Desert Rose Golf Course

he Los Angeles River Restoration plan, alternative 20, the boldest plan set forward by the United States Army Corp of Engineers has been put into play and the Corp is expected to decide whether to recommend that lawmakers approve federal funding for the project or not (â&#x20AC;&#x153;Los Angeles River restoration could cost city $1.2 billion,â&#x20AC;? n.d.) The restoration plan would create wetlands where large greyfields sit currently, and create terraced connections down to the river in several locations.

2.15 Taylor Yard along the Los Angeles River (Before)

The concrete channel condition of the LA River most closely matches the conditions of the channelized Arroyo Seco and is a relevant precedent to inform floodplain reclamation designs in this project. The Alternative 20 restoration plan calls for stream bed softening, restored wetlands, terraced access to the river, daylighting streams, and improving overall riparian habitat. (L. A. District, 2013).

2.17 Rendering - LA River Restoration Masterplan - Chinatown Cornfields

2.16 Rendering - conversion of Taylor Yard to wetland per USACE Alternative 20 restoration proposal (After)

devastating flood in 2012 at the Desert Rose Golf Course in East Las Vegas, Nevada, destroyed life and property. A stormwater channel flows through the golf course and overtopped causing the damage. The Flood Control District has begun retrofitting the course and channel to allow for greater flood capacity. The process involves lowering grade around the channel and widening it to accommodate more flows (Clark County Nevada, 2013). The project is expected to remove 1,700 homes and businesses from the flood zone, and reduce flood insurance rates in the area (Botkin, 2013). While the channel will remain in concrete, some portions will be covered with landscape and water will be conveyed via underground piping (Cruz, 2013). It is important to note that this sublandscape conveyance strategy used at Desert Rose Golf Course is similar to methods of restoration outlined in the recent USACE Arroyo Seco Feasibility Study and may be applicable to the Brookside Golf Course design area.

2.18 (Top Left) Desert Rose Golf Course 2012 flooding 2.19 (Top Right) Desert Rose Golf Course 2012 flooding 2.20 (Bottom) Las Vegas Wash drainage channel

Case Studies: Filsinger Park, Ontario

lose to 2 kilometers of concrete channel is being restored to natural stream at Filsinger Park in Ontario, Canada. The newly installed naturalized alignment is smaller than the original concrete channel, but was done so to allow occasional overtopping and temporary flooding of planted areas adjacent to cobble reinforced banks (Kitchener, 2015). The temporary flooding will allow new sediment to settle along banks to nourish new plantings and help cleanse water flowing toward Victoria Park lake The full restoration is expected in June, 2015 and community engagement has helped guide the design process. The firm behind the restoration, Stantec, mentions that local and reclaimed lumber was used as an in channel feature to help reduce erosion, add nutrients and provide new habitat for fish species. To date comments on the restoration have been positive (â&#x20AC;&#x153;Goodbye concrete, hello nature Stantec,â&#x20AC;? n.d.).

2.21 (Top Left) Filsinger Channel removal 2.22 (Top Right) Filsinger Channel preconstruction 2.23 (Bottom) Naturalized channel

Case Studies: South Platte River Restoration, Colorado

ver $24 million of riverfront project and reclamation projects are happening in Denver, Colorado, along the South Platte riverfront. From having riverfront amenities in the late 19th century to being turned into a dumping ground for toxic waste and chemicals, the South Platte was a less than ideal destination until major flooding in the 1960â&#x20AC;&#x2122;s catalyzed a river transformation movement (Peterson, 2014). One of the first projects in the restoration plan was Confluence Park, which boasts urban whitewater recreation reach supplemented with urban trails. The cost for the park was close to $2 million. Confluence Park is also designed to accept flooding. Referring to recent flooding in the park, The Urban Drainage and Flood Control District state that the park is expected to flood but, returns to usability shortly thereafter (Stanley, 2015)

2.24 (Top) South Platte - Confluence Park 2015 flooding 2.25 (Bottom Left) South Platte restoration 2.26 (Bottom Right) Confluence Park kayakers

Case Studies: Leith Flood Protection, New Zealand

Analysis

2.27 (Top) Leith River improvements at University of Otago 2.28 (Bottom) Leith River channel construction

LOS ANGELES COUNTY BOUNDARY

ARROYO SECO WATERSHED

he Leith River runs through the University of Otago in New Zealand and a major flood protection scheme was recently completed on the campus. The project saw the creation of terracing and steps that afford students and pedestrians direct access to the river channel on the west bank while the east bank remains a reinforced concrete wall (Otago, 2014). The project cost was over $5 million and was eagerly anticipated by students wishing to take photographs in front of the new riverfront terraces (Elder, 2014).

DEVIL’S GATE DAM

evil’s Gate Dam is located in Los Angeles County in the city of Pasadena, California. The dam sits 1.5 miles south of the base of the San Gabriel Mountains and impounds the Arroyo Seco River, a major tributary of the Los Angeles River (Hahamongna Watershed Park Advisory Committee, 2003). It is situated just north of the 210 highway overpass. The dam was installed by the Los Angeles County Flood Control District out of necessity for flood protection and water storage following the major flooding of Los Angeles in 1914 and 1916. Since its installation in 1920, four major conflagrations and numerous fires within the upper watershed have burned thousands of acres behind the dam. Following these fires are major storm events that form a cycle of fire-stormerosion-deposition behind the dam and within the reservoir (District, 2014) ( The tectonic uplift of the San Gabriel Mountains is a sediment generating machine with prolific steep slopes, many greater than 100%. These conditions can contribute to massive debris flows. These flows are summarized in a beach restoration study as having three distinct parts: first, local climate characterized by extended periods of below-average rainfall which causes accumulation over time of dry sediments in ravines and gullies; second, steep slopes enhance travel of dry sediments into ravines where it is stored until flooding releases it; third, removal of hillslope vegetation by wild fire and subsequent

reduction of interception of transportation (CDBW & Conservancy, 2002) Several infrastructural interventions are installed within and below the San Gabriel Mountains in order to manage the erosive slopes and provide flood control to communities that are in many cases built up to the base of the mountains. The first line of defense against sediment and debris flows is debris basins, which are designed to capture sediment and debris and allow water to pass through to flood control channels. Second, are large reservoirs and dams that help to maintain water delivered downstream. Third, are low friction concrete channelized riverbeds where free flowing rivers once ran wild. These concrete inverts are designed to move water through and out of the watershed as fast as possible to mitigate against any possible flood risk. All three of these infrastructural conditions occur within the Arroyo Seco Watershed where the Devil’s Gate Dam is located. Given future predictions of more infrequent, but intense storms and rising surface temperatures brought about by climate change, it is likely the cycles of fire-sedimentation-flood will increase in intensity.

3.1 (Left) Los Angeles County boundary and Arroyo Seco sub-watershed map

URBAN FLOW LINES

ARROYO SECO WATERSHED FLOW PATH AND CONTEXT

SAN GABRIEL MOUNTAINS

CO SE YO RO AR

ARROYO SECO WATERSHED

ER CONFLU RIV E

E NC

LES RIVE

LOS ANGELES

LOS ANGE

The flow path is unique in that urban development has been allowed to encroach along almost every part of the channel, making restoration a herculean task. According to a sediment transport analysis by Bureau Veritas, the lower watershed portion of the Arroyo is approximately 95%

PASADENA

he Arroyo Seco, a major tributary of the Los Angeles River, flows 9.5 miles beginning from Devil’s Gate Dam until it reaches the Los Angeles River confluence. It makes its journey through mostly concrete armored channels. The lower portion of the channel runs through the city of Pasadena, South Pasadena and Los Angeles. From the LA River confluence it is another 23 miles until the combined flows reach the Pacific Ocean at Long Beach.

’S GATE D VIL

urbanized (Bureau Veritas North America, 2013). Given this encroachment, the flood channel has been made to handle a large portion of storm water runoff from the aforementioned municipalities, making the channel a very precarious place during wet weather. Flows can rise travel horizontally quite rapidly. Those who are unfortunate enough to be caught in the channel during higher flow events can easily become stranded. During wet weather cars have swerved off adjacent streets and into the channel, stranding passengers in higher storm flows (ABC 7, 2008). For half of the year, however, the channel’s flow rate below the dam is nonexistent and less than 10 cubic feet per second 95% of the time (Seco, Sustainability, & Foundation, 2011).

Context: An urbanized watershed

PACIFIC OCEAN

3.2 (Right Page) Urban Context Map

RURAL SUBURBAN

LONG BEACH

URBAN

ARROYO SECO FLOW PATH

COASTAL EROSION CONCERN AREAS SEDIMENT STARVED BEACHES

A TUR VEN A UEN CH NB BEA SA NT O P R PIE

ES/

R HO

PASADENA CO

EA EB

ARROYO SECO WATERSHED

ER CONFLU RIV E

E NC

H EAC H EB T EAC A ST NB O O Y L L AN RRI SC CA OLA LEO H C NI

H EAC H YB EAC EB E O TY T T C A A N T T S GA OU NS AN RC ERS OO TOP OG CKE AG R O L CH L L L BU BEA NB WI ALI DA ITY M C / R ICE IDE VEN RFR H SU U EAC LIB EB A T A M ST LER EIL W CK DO

LOS ANGELES

T UN

PACIFIC OCEAN

N EDO

BEA

LONG BEACH

O RED

BEA

N OU

RA TOR

Y NT

3.3 (Right Page) Coastal Erosion Concern Areas

C BEA

LES RIVE

C BEA

LOS ANGE

EAC

YB ALA

’S GATE D VIL

he Arroyo Seco is impounded by the Devil’s Gate Dam and prevents a critical source of sediment delivery to nearby coastal beaches. The 2002 California Beach Restoration study lists the Devil’s Gate Dam as one of many dams that substantially reduce sediment flux to the oceans. Devil’s Gate Dam was responsible for holding back 120,000 cubic yards of sediment per year since its inception in 1919 through 1982. When total sediment production was totaled between all 14 coastal dams identified in the restoration study, over 273 million cubic yards of sediment was lost to dam reservoirs at an average impoundment rate of close to 6,000,000 cubic yards per year (CDBW & Conservancy, 2002). With the uncertain future climate change brings, flood resiliency along the coast line

is of paramount importance in protecting life and property. Wide beaches can be a critical defense mechanism against future sea level rise and inland flooding. With coastal dams impounding sediment, coastal resiliency can be weakened and “beaches can be expected to diminish in size if dams significantly reduce sediment supplies” (CDBW & Conservancy, 2002) (Willis & Griggs, 2003). Tragically, it has been demonstrated that anthropogenic effects have increased the rate of erosion, yet less and less of this sediment is reaching the ocean (Syvitski, Vo, Kettner, & Green, 2005).

SAN GABRIEL MOUNTAINS

BEA

Context: Coastal Sediment Flux

TE STA

JEC

ARROYO SECO FLOW PATH

FSI

R SU

P SET

FFS

CLI

N GTO

CONFLAGRATION, INUNDATION AND SEDIMENTATION

1914 FLOOD

1916 FLOOD

1934 FLOOD

1938 50 YEAR STORM

1943 FLOOD

FLOODING IN THE ARROYO SECO CAUSES DAMAGE TO PROPERTY AND CLAIMS 43 LIVES. TEMPORARY WALLS ARE CONSTRUCTED

MAJOR FLOODING IN ARROYO SECO LEADS TO DAM EASEMENT GRANTED BY CITY OF PASADENA

2 MINUTES AFTER MIDNIGHT ON NEW YEARS DAY A 20 FOOT WALL OF OF WATER, MUD AND ROCK TEAR THROUGH SAN GABRIEL MOUNTAINS VALLEY FLOOR.

A MARCH STORM WITH RAINFALL INTENSITY GREATER THAN A 50 YEAR STORM EVENT DEPOSITS OVER 1.7 MCY OF SEDIMENT INTO THE RESERVOIR.

FLOODING CONTRIBUTES 500,000 CY OF SEDIMENT TO RESERVOIR AND DAMAGES ARROYO SECO CHANNEL.

DEVIL’S GATE DAM

1971-83 STORMS

1969 50 YR. STORM JANUARY STORM DROPS HEAVY RAINS TRIGGERING LANDSLIDES AND FLOODS. SEDIMENT DEPOSITED IN RESERVOIR CLOGS ALL THREE DAM VALVES.

RAINFALL INTENSITY 50 YEAR STORM

4.5

DEBRIS BASINS WITHIN ARROYO SECO WATERSHED

5 TIMELINE

4.5

STORMS DURING THIS PERIOD CONTRIBUTE OVER 2.2 MCY OF SEDIMENT TO RESERVOIR

4.31 4.19

DEVIL’S GATE DAM

3.9

3.89

3.5 3.38 0 0.5 1

Miles 4

3.39

3.29 3.23

3.17 3.05

1920 DEVIL’S GATE DAM COMPLETED

1935 CHANNELIZATION

LA COUNTY FLOOD CONTROL DISTRICT COMPLETES ITS FIRST DAM FOR FLOOD CONTROL AND WATER CONSERVATION

THE WORKS PROGRESS ADMINISTRATION BEGINS CHANNELIZING THE ARROYO SECO RIVER AS PART OF THE ARROYO SECO PARKWAY.

3.08

2.99

3.02

2.99

1942 BROWN CANYON BARRIER COMPLETED

2.5

2.79

UNITED STATES FOREST SERVICE BUILDS FLOOD PROTECTION DAM 3.5 MILES NORTH OF DEVIL’S GATE DAM IN THE UPPER ARROYO SECO WATERSHED.

1959 WOODWARDIA FIRE

1966 CLOUDBURST FIRE

1.3 MCY CAPACITY REMAINING

OIR BOTT

RESERV

0.98

DEVIL’S GATE DAM

0.76

0.5

1915

1920

NT A

IME

SED

N LATIO UMU

IM ER T

1925

1930

1935

900,000 CY

800,000 CY

700,000 CY

600,000 CY

500,000 CY

400,000 CY

300,000 CY

200,000 CY

100,000 CY

1940

1945

1950

1955

TOTAL REMOVED

A MAJORITY OF THE ENTIRE UNDEVELOPED WATERSHED WAS DENUDED BY THE LARGEST FIRE IN L.A. HISTORY

1.5

SLUICED

+ 1,040.5’

SEDIMENT EXCAVATED SEDIMENT SLUICED

7 MCY CAPACITY

2009 STATION FIRE

TOTALS

27 ACRES OF WATERSHED BURNED ABOVE DEVIL’S GATE DAM DEPOSITS ADDITIONAL 900,000 CY OF SEDIMENT INTO RESERVOIR.

WOODWARDIA FIRE BURNS 1/3 OF WATERSHED ABOVE DAM LEADING TO THE CONTRIBUTION OF 900,000 CY OF SEDIMENT DEPOSITED INTO THE RESERVOIR.

2.5

ENT LEVE

T SEDIM

CURREN

DEVIL’S GATE DAM

EXCAVATED

1.5

2.83

MCY 2009 - 1.3 T SINCE OM SEDIMEN ATION FIRE OIR BOTT E-ST PR SE RE RV 2.8 MCY

DEVIL’S GATE DAM

3,550 ACRES ABOVE THE DAM IS BURNED AND 800,000 CY OF SEDIMENT IS DEPOSITED IN THE HAHAMONGNA BASIN.

E ULATION OVER TIM

SEDIMENT ACCUM

2.77

2.79

2.68

1934 BROWN MOUNTAIN FIRE

2.87

2.84 2.64

2.95

2.92

VERY HIGH FIRE HAZARD SEVERITY ZONES

SEDIMENT ACCUMULATION (MCY)

3.62

3.5

1960

1965

1970

1975

1980

2,205,426 MCY

5,925,772 MCY

8,131,198 MCY

1985

1990

1995

2000

0.5

2005

2010

water flow

DEVIL’S GATE DAM + SPILLWAY

sediment placement site

beach replenishing

+1230’

landfill cover

construction material

ARROYO SECO CHANNEL TYPOLOGIES

trash fence

+1075’ perforated outlet tower

tectonic uplift

conflagaration + denuding

excavation + transport

CALIFORNIA

habitat re-generation

LOS ANGELES

DEBRIS BASINS, TYP. valley terminus

sediment flow

orographic precipitation

LOS ANGELES

FLOOD AND MUDFLOW DEFENSE INFRASTRUCTURE

accumulation

erosion + debris flow + deposition

ARROYO SECO WATERSHED

LOS ANGELES BASIN SEDIMENTATION ENGINE

parapet

bottom of basin

ess

acc

d roa

/ da

+1040’

cre

reservoir

spillway ports

+980’

spillway

+940’ +986’ slide + sluice gate outlets

34º

los angeles river confluence

+700’

+500’

33º 3.5 Natural Forces Analysis

3.6 Infrastructural Analysis

LOS ANGELES

ARROYO SECO WATERSHED

3.7 Channel Types and location aerial

3.8 (Top) Natural Section - Arroyo Seco Channel 3.9 (Top Middle) Arroyo Seco - Concrete Box Channel

.5 MILES

DEVIL’S GATE DAM

2.4 MILES 9.5 mi

4.6 MILES

INACCESSIBLE OFF-CHANNEL TRAIL / NO IN CHANNEL ACCESS IN-CHANNEL TRAIL ACCESS

CHANNEL TYPOLOGIES + ACCESS AERIAL PERSPECTIVE

2 MILES 3.10 (Bottom Middle) - Arroyo Seco - Trapezoidal Channel at Brookside Golf course 3.11 (Bottom) Trapezoidal Channel with bike trail

A natural sediment flux would replenish beaches, nourish and recharge nascent riparian habitat, afford new and innovative revenue streams, and bring forth new recreational opportunities for residents of municipalities along the Arroyo Seco riverfront. Three reaches are identified in the proposed floodplain reclamation framework based on an USACE Arroyo Seco restoration feasibility study and earlier restoration efforts by CDM Smith. These areas include the Brookside Park area, Lower Arroyo Seco Park, and the South Pasadena Island extending into the Los Angeles Reach.

STRATEGIES

This design framework envisions regenerative toolkit strategies that enhance watershed flood resiliency, groundwater recharge, in-channel sediment management and habitat restoration. The ultimate goal of implementing strategies under this framework is a partial to complete removal of the Devil’s Gate Dam in order to facilitate natural sediment flux to the LA River and coastal beaches.

SAN GABRIEL MOUNTAINS

CATALYZE

SUSTAINABLE SEDIMENT MANAGEMENT

DIFFUSE

FORTIFY

SLOW STORM PEAK FLOW

RECHARGE

NATURALIZED YET SECURE CHANNEL ALIGNMENT

EMERGENCY FLOOD BYPASS LOCAL SEDIMENT RE-USE WIDEN CHANNEL

LOS ANGELES

RECLAMATION FRAMEWORK

GREEN INFRASTRUCTURE

DEVIL’S GATE DAM

BROOKSIDE

INCREASE PERMEABLE SURFACES

EMERGENCY FLOOD PROTECTION INFRASTRUCTURE

WATER COLLECTION + STORAGE

RESILIENT INFRASTRUCTURE

REGENERATIVE USE OF EXCESS SEDIMENT GIVEN HIGHLY EROSIONAL FORCES WITHIN WATERSHED

RESTORE NATURAL SEDIMENT FLUX

MOVE TOWARD A NATURAL HYDROGRAPH AND WIDEN CHANNEL TO CREATE SAFE AND HABITABLE FLOWS

PROTECT EXISTING DEVELOPMENT FROM FLASH FLOODING AND DEBRIS FLOWS

MOVE TOWARD A NATURAL HYDROGRAPH AND WIDEN CHANNEL TO CREATE SAFE AND HABITABLE FLOWS

ALLOW FOR INCREASED WATER STORAGE DURING HIGH FLOW EVENTS

LOWER ARROYO SECO

SOUTH PASADENA ISLAND

MOVE TOWARD A NATURAL HYDROGRAPH AND REDUCE STORMWATER RUN OFF INTO ARROYO SECO

REDUCE FLASH FLOOD OCCURRENCE WHILE LESSENING DEPENDENCE ON RESERVOIR WATER STORAGE

CONFLUENCE PARKWAY

REDUCE NEEDED RESERVOIR CAPACITY AND EVENTUAL REMOVAL OF DEVIL’S GATE DAM

LA RIVER CONFLUENCE

4.1 Design Framework flowchart

ARROYO SECO WATERSHED

4.2 Aerial map - design focus areas

RE-CHARGE AQUIFER

NEAR-TERM GOAL

he short term sediment management solution behind Devil’s Gate Dam of excavation and trucking of sediment to placement sites is unsustainable, and destructive to what little habitat exists on the developed portion of the Arroyo Seco watershed.

LONG -TERM GOAL

Specific toolkit strategies under the floodplain reclamation framework will be identified and explained in each intervention area. These interventions are envisioned happening on a 50+ year timeline, and are to serve as planning guidelines and to catalyze dialogue regarding the pertinent need to develop a more sustainable sediment management manifested through a restored riparian corridor in a highly urbanized context.

ULTIMATE GOAL

Design Framework

DESIGN CONTEXT AERIAL PERSPECTIVE

EXISTING CONDITIONS - BROOKSIDE

lmost immediately downstream from the Devilâ&#x20AC;&#x2122;s Gate Dam, the Arroyo Seco enters a concrete channel which runs through Brookside Golf Course and past the Rose Bowl Stadium. The reclamation framework calls for lowering the grade of the Brookside Golf Course, and removing the concrete channel flowing through it. Once removed the channel can initially be re-graded to match a meandering river alignment type D (Figure 4.16). Over time, natural sediment flow through the Arroyo Seco would be allowed to create new channel alignments and bank reinforcement can be implemented in the future, much like the Filsinger Park restored channel in Ontario, if a more stable alignment is desired. Ultimately the golf course would allow for flooding during rare high flow events, similar to the Desert Rose Golf Course in Neveda.

To make up for lost parking, recharging framework calls for elevated parking garages with green roofs and water harvesting systems. The green roofs would reduce impervious surface area while simultaneously allowing for water storage and programmatic events. Before entering the South Pasadena area, the Brookside Park play fields are retrofitted with retention strips for water infiltration in times of high rain fall, allowing even more aquifer recharge.

REC. FIELD

FR EE W AY

PLAN

(as pictured) or simply graded to allow infiltration after storm events while still allowing for recreation during dry times. Adaptive management flood gates can be installed at exit and entrance points to both basins.

21 0

Planning Framework: Brookside

ROSE BOWL

T AVE.

ROSEMON

PARKING LOTS

To increase capacity further within the golf course, the fortification framework calls for modular flood protection walls that are variable in height, placed along reinforced banks around the golf courseâ&#x20AC;&#x2122;s perimeter. With advanced warning systems in place, this modular wall could be erected quickly for extra storage within the Brookside Golf Course area. Downstream of the park near the Rose Bowl, two of the large parking lots are converted to flood detention and retention basins respectively. The retention basin could be converted into wetland habitat

BROOKSIDE PARK

CHANNELIZED ARROYO SECO

WEST

DR.

BROOKSIDE GOLFCOURSE

4.3 (Right Page) Context Map - Brookside

1:12000

BROOKSIDE PLAN

4.4 (Left Page) Brookside Plan View 4.5 (Right Page) Design Strategies

RECHARGE ELEVAT

F L O O DP

LAI

DIFFUSE NE

L S IN U O SI T Y

-RETROFIT WASHINGTON BLVD. TO WITHSTAND FLOODING -SMALLER BRIDGES TO THE SOUTHERN PORTION OF THE SITE TO BE EVALUATED FOR POTENTIAL RETROFITS AS NEEDED

-REMOVE EXISTING CONCRETE CHANNEL AND RE-GRADE NEW CHANNEL TYPE C -ALLOW FOR FUTURE DYNAMIC CHANNEL ALIGNMENT OR REINFORCE BANKS TO STABILIZE

FLO OD

P TIN

REINFORCE DB A

S NK

FL O O D P AR

R O FIT

GA R A G ES

-PARKING GARAGES CAN BE OUTFITTED WITH WATER COLLECTION CISTERNS

E R ET

O OF

- INSTALL ELEVATED GREEN ROOF PARKING GARAGES IN 4 EXISTING ROSE BOWL PACKING LOTS

RE STOR

IDG

GR EE

FORTIFY

O L F CO U RS E

-INSTALL REINFORCED BANKS ALONG GOLF COURSE PERIMETER WITH ACCESSIBLE RECREATION TRAILS P RO

-LOWER GRADE OF GOLFCOURSE TO ALLOW FOR TEMPORARY FLOODING DURING HIGH FLOW EVENTS

BYPASS

WE T S

TIO

FL O OD

- BROOKSIDE PARK BORDERED WITH RETENTION BASIN CELLS ALLOWING EXCESS STORMWATER TO SLOWLY INFILTRATE AND RECHARGE AQUIFER

EASU RES

-FLOODWALL FOOTINGS INSTALLED AROUND GOLF COURSE PERIMETER FOR EMERGENCY FLOOD WALL PROTECTION

1:12000

-RECREATIONAL FIELD AND PARKING LOT ALONG ARROYO BLVD. CONVERTED INTO FLOOD BYPASSES DURING STORM EVENTS

BROOKSIDE

FRAMEWORK FLOW DIAGRAM + PERSPECTIVE

spillway

NATURALIZED SINUOUS CHANNEL + FLOOD ACCEPTING GOLF COURSE infiltration

water flow

sediment flow

infiltration + recharge

WETLAND BYPASS

infiltration + recharge

orographic precipitation

Devilâ&#x20AC;&#x2122;s Gate Dam

wa te

r fl

EMERGENCY MODULAR FLOOD WALLS

SOFT BOTTOM REINFORCED CHANNEL

dim

t fl

precipitation

infiltration + recharge

precipitation

infiltration + recharge

precipitation

PERMEABLE LOTS + STORAGE TANKS

4.6 Brookside Design Framework Flow Diagram

4.7 Brookside Perspective

Planning Framework: Lower Arroyo Park

EXISTING CONDITIONS - LOWER ARROYO PARK areas will aid in reducing peak flow rates through the channel and make it more suitable for recreation and wildlife.

rom Brookside to the Lower Arroyo Seco Park in Pasadena, the channel will be converted to a natural bottom with a type C profile (Figure 4.16), sheet piling reinforcements with in-channel access. This channel is similar to a design option outlined by the USACE in their ecosystem restoration feasibility study (USACE, 2015). The channel form changes within the park from type C + type D (Figure 4.16), as the western bank becomes habitat-friendly, sloped at 3:1 while the eastern edge remains sheet-pile reinforced.

NATURALIZED ARROYO SECO

GE C OLORADO ST. BRID

210 FREEWAY

S. ARR OYO BL VD.

V FAEL A SAN RA

LA CASITA DEL ARROYO

GRAND

RECREATIONAL NODES

AVE.

Upon entering Lower Arroyo Park, bankful width briefly increases to allow slowing of flow and dropout of sediment material into a sediment trap. This trap is placed adjacent to two nodes that can utilize trapped sediment for low-impact glassware production via electrical melt and bio-masonry, production of building material without use of heat. These nodes can be interactive, and house smaller incubator hubs within them for expanded programmatic and revenue generating opportunities within the park. Existing recreational facilities and structures are to remain. Bordering residential zones that slope toward the channel and drain run-off into it, are to be retrofitted with green infrastructure; sunken stormwater planters parellel to the road, to allow for water retention and aquifer recharge. Allowing more infiltration in adjacent developed

WAY

REE

F 134

A LOM

DGE

BRI

CHANNELIZED ARROYO SECO

4.8 (Right Page) Context Map - Lower Arroyo Park

1:12000

LOWER ARROYO PARK

CATALYZE

PLAN

S E DI ME

F L O O DP

L AI

DIFFUSE

C TU R

R CE

REINFO

-INSTALL CHANNEL TYPES A AND B TO ALLOW EXISTING RECREATIONAL NODES TO REMAIN WHILE SUPPLEMENTING CHANNEL WILDLIFE CORRIDOR

INF

-RETROFIT EXISTING STREETS WITH GREEN INFRASTRUCTURE SUCH AS SUNKEN STORMWATER PLANTERS FOR THE PURPOSE OF SLOWING RUN-OFF TO THE ARROYO SECO, INCREASING FILTRATION AND GROUNDWATER SUPPLY.

-REINFORCE BANKS TO KEEP CHANNEL ALIGNMENT FOR PREDICTIVE SANDBARS

-REMOVE CONCRETE CHANNEL

G R EE N

-RETROFIT CHANNEL BRIDGE NEAR CASTING POND IF NEEDED OR CONSIDER FLOATING BRIDGE

IN U O S I T Y

-ELECTRIC MELT FURNACE FOR LOCAL GLASSWARE MANUFACTURING

EL S

-RETROFIT LA LOMA BRIDGE TO WITHSTAND TEMPORARY FLOODING AND HIGH FLOW EVENTS

S E DI ME

R O FI T

N ODE

-SMALL SCALE SEDIMENT PRODUCTION NODE ERECTED IN SLOW FLOW ZONE DOWNSTREAM OF COLORADO ST. BRIDGE

R E STO R

RECHARGE

TIO N

E R ET

IDG

4.9 (Left Page) Lower Arroyo Park Plan 4.10 (Right Page) Design Strategies

FORTIFY

TIO N N ODE

-SMALL SCALE SEDIMENT PRODUCTION NODE ERECTED IN SLOW FLOW ZONE -NO EMISSION BIO-MASONRY PRODUCTION HUB FOR LOCAL BUILDING MATERIAL SYNTHESIZING

-INSTALL SHEET-PILE BANK PROTECTION ON EASTERN CHANNEL BANK WITH ACCESSIBLE TRAILS -WESTERN BANK TO BE SLOPED 3:1 AND HABITAT FRIENDLY

1:12000

LOWER ARROYO SECO

FRAMEWORK FLOW DIAGRAM + PERSPECTIVE

GREEN INFRASTRUCTURE

NATURALIZED SINUOUS CHANNEL

pile re

inforc

ed ban

infiltration + recharge

sheet

slowed + filtered runoff via green streets

local sale + re-use

SEDIMENT CAPTURE + PRODUCTION HUBS

local sale + re-use

water flow

sediment flow

Devil’s Gate Dam

GREEN INFRASTRUCTURE

infiltration + recharge

RETROFITTED FLOODPLAIN BRIDGE

slowed + filtered runoff via green streets

4.11 Lower Arroyo Design Framework Flow Diagram

wa te

r fl

dim

t fl

to s

outh

pas

ade

isla

4.12 Lower Arroyo Perspective

EXISTING CONDITIONS + SOUTH PASADENA ISLAND

Planning Framework: South Pasadena Island

ramework for the South Pasadena Island reach includes retaining existing site green space, but allowing for flooding within Lower Arroyo Parks and restoring channel sinuosity. Channel type B is called for and type C where type B is infeasible (Figure 4.16). Fortification framework calls for floodable park infrastructure and detention borders along outer park perimeters. Low flow channels are with a type A channel alignment are installed in some parks in addition with terraced access to the Arroyo. Floodable park amenities can include seat walls, tables and terraces.

CHANNELIZED ARROYO SECO

LOWER ARROYO PARK

GRAND

AVE.

SAN PASCUAL STABLES

Y EWA

RE 110 F

On a longer timeline it where feasible, the historic 110 freeway can be retrofitted to allow channel and animal migration via conversion to floodplain causeway similar to the Yolo Causeway near Davis, California. Reclamation of flood plain along this reach can be maximized by re-zoning residential blocks for wetland or open space. If re-zoning or buyback is not possible, retrofitting with green streets and increasing permeability within the adjacent developed areas will further enhance future flows through the Arroyo Seco and increase channel habitability and safety.

ARROYO SECO GOLF COURSE

ARROYO SECO IN CHANNEL BIKE PATH IL

T RA LIGH

S. PASADENA NATURE PARK

HERMON DOG PARK

Two sediment production sand bars are included within this analyzed reach to allow for even more minimally intrusive in-channel sediment management.

AY W K R

O OY RR

4.13 (Right Page) Context Map - South Pasadena Island

AY ARKW CO P

SE OYO / ARR

AY EW

O EC

1:12000

0 11

SOUTH PASADENA ISLAND

CATALYZE

PLAN

S E DI ME

F L O O DP

LAI

DIFFUSE C HA

RECHARGE

GR E

TR U C TU R E

N ODE

R O FI T

RATION

TIO N

E R ET

ST O

IDG

4.14 (Left Page) South Pasadena Island Plan 4.15 (Right Page) Design Strategies

PR OD

FORTIFY

2 1

-ALLOW EXISTING RECREATIONAL NODES TO REMAIN WHILE SUPPLEMENTING CHANNEL WILDLIFE CORRIDOR

PR UC

TIO N N ODE

-INSTALL SHEET-PILE BANK PROTECTION ON EASTERN CHANNEL BANK WITH ACCESSIBLE TRAILS -WESTERN BANK TO BE SLOPED 3:1 AND HABITAT FRIENDLY

IC 1

- ZO

F IT

TR O

H IS T O R

R E CL A I

-SMALL SCALE SEDIMENT PRODUCTION NODE ERECTED IN SLOW FLOW ZONE NEAR RE-LOCATED SAN PASCUAL STABLES

FLO O

DP A

-REINFORCE BANKS TO KEEP CHANNEL ALIGNMENT FOR PREDICTIVE SANDBARS NEAR SEDIMENT PRODUCTION HUBS (#1 AND #2)

S E DI ME

1:12000

-INSTALL CHANNEL TYPES A AND B WHERE HIGHWAY RETROFIT IS INFEASIBLE.

-RETROFIT EXISTING STREETS WITH GREEN INFRASTRUCTURE SUCH AS SUNKEN STORMWATER PLANTERS FOR THE PURPOSE OF SLOWING RUN-OFF TO THE ARROYO SECO, INCREASING FILTRATION AND GROUNDWATER SUPPLY.

R CE

-ELECTRIC MELT FURNACE FOR LOCAL GLASSWARE MANUFACTURING

REINFO

-REMOVE CONCRETE CHANNEL

-RETROFIT EAST WEST BRIDGES TO BE FLOODPLAIN COMPATIBLE

-SMALL SCALE SEDIMENT PRODUCTION NODE ERECTED IN SLOW FLOW ZONE NEAR RE-LOCATED SAN PASCUAL STABLES AND HERMON PARK

-NO EMISSION BIO-MASONRY HUB FOR BUILDING MATERIAL PRODUCTION -WHERE FEASIBLE THE EXISTING 110 FREEWAY IS CONVERTED INTO AN ELEVATED BYPASS TO ALLOW FOR EXPANDED CHANNEL MIGRATION AND AN EAST-WEST WILDLIFE CORRIDOR

-ADD FLOOD PROOF PARK FURNISHINGS AND ALLOW FOR FLOOD WATER INFILTRATION IN EXISTING PARKS: HERMON PARK, SOUTH PASADENA NATURE PARK, AND LOWER ARROYO PARK.

-RE-ZONE BLOCKS FOR FUTURE USE AS WETLAND HABITAT OR OPEN SPACE TO MAXIMIZE ROOM FOR ARROYO SECO AND WILDLIFE CORRIDORS. -CONVERT ARROYO SECO GOLF COURSE TO AN OPEN SPACE PARK TO ALLOW ROOM FOR CHANNEL MEANDERS AND ADDITIONAL RECREATIONAL CHANNELS

LOS ANGELES

ARROYO SECO WATERSHED

A Restored Channel and Sediment Flow

TYPE A

his design framework envisions a completely restored soft bottom Arroyo Seco with increased channel access throughout the entire corridor. Bank typologies vary and may need reinforcement depending on the level of development adjacent to bankful elevation. Sediment flux is restored and if emergency debris flows should occur, 3 sediment collection nodes occur along the channel to allow in-channel excavation and immediate onsite use and production. An adaptive management outlook is assumed as the channel becomes more dynamic and areas of aggradation manifest.

TYPE B

TYPE C

TYPE D

INACCESSIBLE OFF-CHANNEL TRAIL / NO IN CHANNEL ACCESS IN-CHANNEL TRAIL ACCESS

4.16 (Right Page) Context Map - South Pasadena Island

PROPOSED CHANNEL TYPOLOGIES + ACCESS AERIAL PERSPECTIVE

APPENDIX CONCLUSION

he problem of reservoir sedimentation behind Devil’s Gate Dam may be solved temporarily by excavation, but the highly erosive San Gabriel Mountains and intensive urbanized watershed call for long-term sustainable solutions to both sediment management and flood mitigation. Early settlement within the Arroyo Seco Watershed was plagued by extreme flooding, and today it is plagued by destruction of natural habitat and impervious surfaces. Solutions to these issues should strike a balance between flood resiliency, and ecosystem resiliency.

ABC 7. (2008). Two women saved by swiftwater rescue teams after car careened off freeway | abc7.com. Retrieved June 2, 2015, from http://abc7.com/ archive/5918489/ Aldayjover. (2001). Aldayjover Landscape Recovery. Retrieved May 30, 2015, from http://www.aldayjover.com/index.php?option=com_ articulo&idcategoria=17&idarticulo=256&lang=en American Rivers. (2014). America’s Most Endangered Rivers for 2014 | San Francisquito Creek | American Rivers. Retrieved February 6, 2015, from http:// www.americanrivers.org/endangered-rivers/2014-report/san-francisquitocreek/ Apocalypse Dam. (2012). Retrieved March 13, 2015, from http://www.dailymail. co.uk/sciencetech/article-2170185/Apocalypse-Dam-Chinas-giant-manwaterfall-floodgates-opened-send-millions-tons-silt-downstream.html

Materials, 159, 499–504. doi:10.1016/j.jhazmat.2008.02.046 Clark County Nevada. (2013). Las Vegas Wash and Desert Rose Golf Project. Retrieved June 4, 2015, from http://www.lvwashproject.com/wp-content/ uploads/2013/06/LV_Wash_PublicMeeting_brochure_6-26-13.pdf County, L. O. S. A., & District, F. C. (2014). Devil ’ s Gate Reservoir Sediment Removal and Management Project Final Environmental Impact Report ( FEIR ). Cruz, Y. (2013). Flooding forces renovations at Desert Rose Golf Course | Las Vegas Review-Journal. Retrieved June 3, 2015, from http://www.reviewjournal.com/ view/sunrise/flooding-forces-renovations-desert-rose-golf-course District, L. A. (2013). Los Angeles River Ecosystem Restoration Feasibility Study DRAFT – APPENDIX A DESIGN, 1(August). District, L. A. C. F. C. (2014). Summary of Devil’s Gate Dam.

As more and more dams are removed along the Pacific Coast, examples of restored rivers and unrestricted sediment flux are becoming the norm. The option of a future removal of Devil’s Gate Dam should not be taken off the table as a solution to sustainable sediment management. Reservoir sedimentation is in need of creative solutions so long as the desire for increased density and urban development continues in the Los Angeles Basin. The LA River Restoration is gaining traction and its momentum can spur a restoration of the Arroyo Seco. A restored Arroyo Seco, paired with scaled back development along the riverfront, and green infrastructure retrofits may reduce the need for a dam that will require incessant maintenance for the foreseeable future. More research is needed and true collaboration between architects, engineers, planners, and stakeholders could allow for creative solutions for restoring watershed health while allowing smart growth in the Arroyo Seco.

Baish, S. K., David, S. D., & Graf, W. L. (2002). Removing Dams. Environment: Science and Policy for Sustainable Development, 44(February 2015), 20–31. doi:10.1080/00139150209605779 Baiyinbaoligao, Xu Feng-ran, Chen Xing-ru, C. W. (2012). Impact of sediment flushing of Xiaolangdi Reservoir on downstream fish. Journal of Hydraulic Engineering, 43(10). Boom, T. (2014). Dam-notching project costs balloon - News. Retrieved March 11, 2015, from http://www.mailtribune.com/article/20140925/News/140929788 Botkin, B. (2013). Desert Rose Golf Course to close for major flood control project | Las Vegas Review-Journal. Retrieved June 4, 2015, from http://www. reviewjournal.com/news/las-vegas/desert-rose-golf-course-close-major-floodcontrol-project Bureau Veritas North America, I. (2013). Sediment Transport Capacity Analysis Final Detailed Sediment Transport Capacity Analysis for the Arroyo Seco Channel. Cardina, S. (2015). Group eyes lawsuit aimed at Devil’s Gate sediment removal plan. Retrieved February 20, 2015, from http://www.lacanadaonline.com/ news/tn-vsl-me-group-eyes-lawsuit-aimed-at-devils-gate-sediment-removalplan-20150114,0,7152690.story

Elder, V. (2014). Leith works good but too slow | Otago Daily Times Online News : Otago, South Island, New Zealand & International News. Retrieved June 3, 2015, from http://www.odt.co.nz/news/dunedin/324082/leith-works-good-tooslow Fimrite, P. (2014). Carmel River diverted to demolish San Clemente Dam - SFGate. Retrieved February 6, 2015, from http://www.sfgate.com/science/article/ Carmel-River-diverted-to-demolish-San-Clemente-Dam-5956979.php Gold, L. (2014). Final environmental report released for Devil’s Gate Reservoir Sediment Removal Project. Retrieved February 1, 2015, from http://www. dailynews.com/environment-and-nature/20141021/final-environmental-reportreleased-for-devils-gate-reservoir-sediment-removal-project Goodbye concrete, hello nature - Stantec. (n.d.). Retrieved June 3, 2015, from http://www.stantec.com/blog/2015/goodbye-concrete-hello-nature.html#. VW5yUs9VhBe Graf, W. L. (2005). Geomorphology and American dams: The scientific, social, and economic context. Geomorphology, 71, 3–26. doi:10.1016/j. geomorph.2004.05.005 Guixer, M. O. i. (2002). public space: Recuperación del Cauce y Riberas del Río

CDBW, & Conservancy, C. S. C. (2002). California beach restoration study, (January), 280.

Gállego: Zuera (Spain), 2001. Retrieved May 29, 2015, from http://www.publicspace. org/en/works/b009-recuperacion-del-cauce-y-riberas-del-rio-gallego

Chiang, K. Y., Chien, K. L., & Hwang, S. J. (2008). Study on the characteristics of building bricks produced from reservoir sediment. Journal of Hazardous

Hahamongna Watershed Park Advisory Committe. (2003). Hahamongna Watershed Park Master Plan.

Morris, G., & Fan, J. (1997). Reservoir Sedimentation Handbook. McGraw-Hill Professional.

San Clemente Dam Removal | Photos. (2008). Retrieved March 6, 2015, from http:// www.sanclementedamremoval.org/?page_id=1095

Huang, C., Pan, J. R., Sun, K. D., & Liaw, C. T. (2001). Reuse of water treatment plant sludge and dam sediment in brick-making. Water Science and Technology, 44, 273–277.

Network, E. S. (2008). Sustainable Management of Sediment Resources. (P. N. Owens, Ed.) (First.). Amsterdam: Elsevier.

Seco, A., Sustainability, W., & Foundation, A. S. (2011). Final Arroyo Seco Watershed Assessment.

Nicole, W. (2012). EHP – Lessons of the Elwha River: Managing Health Hazards during Dam Removal. Retrieved May 30, 2015, from http://ehp.niehs.nih. gov/120-a430/

Seco, A., & Team, S. (2012). Preliminary Habitat Assessment of Southwest Hahamongna.

IADC/CEDA. (2008). Environmental Aspects of Dredging. (R. N. Bray, Ed.). Taylor & Francis. Jenkin, P. (2011). Ventura River Ecosystem: Next steps - Notching? Retrieved March 11, 2015, from http://www.venturariver.org/2011/02/next-steps-notching.html

No Big Dig Lawsuit to Save Hahamongna. (2015). Retrieved February 20, 2015, from https://www.indiegogo.com/projects/no-big-dig-the-lawsuit-to-savehahamongna

Karlamangla, S. (2014). L.A. County supervisors OK debris clearance for Devil’s Gate Dam - LA Times. Retrieved February 3, 2015, from http://www.latimes. com/local/countygovernment/la-me-1113-devils-gate-2-20141113-story.html

Otago, U. of. (2014). Leith scheme flood protection confers greater river access , Otago Bulletin Board, University of Otago, New Zealand. Retrieved June 4, 2015, from http://www.otago.ac.nz/otagobulletin/news/otago064182.html

Kim, J. (2014). Environmentalists to sue county over Devil’s Gate Dam sediment. Retrieved February 1, 2015, from http://www.scpr.org/news/2014/12/09/48575/ environmentalists-to-sue-county-over-devil-s-gate/

Palmieri, a, Shah, F., & Dinar, a. (2001). Economics of reservoir sedimentation and sustainable management of dams. Journal of Environmental Management, 61(September 2000), 149–163. doi:10.1006/jema.2000.0392

Kitchener, C. of. (2015). City of Kitchener. Retrieved June 4, 2015, from https:// www.kitchener.ca/en/livinginkitchener/Filsinger-Park-Naturalization-Project. asp?hdnContent=

Peterson, E. (2014). From What River? to River Vision: South Platte Getting $25

Kondolf, G., Gao, Y., & Annandale, G. (2014). Sustainable sediment management in reservoirs and regulated rivers: Experiences from five continents. Earth’ S Future, 2, 256–280. doi:10.1002/2013EF000184.of LACDPW. (2014a). Devil’s Gate Reservoir Sediment Removal and Management Project Approval and Certification of FEIR. LACDPW. (2014b). Final EIR Devil’s Gate Reservoir Sediment Removal and Management Project Los Angeles County, California - Section 4. LAMountains. (n.d.). Hahamongna Watershed Park. Retrieved February 6, 2015, from http://www.lamountains.com/parks.asp?parkid=643 Los Angeles River restoration could cost city $1.2 billion. (n.d.). Retrieved May 30, 2015, from http://www.visaliatimesdelta.com/story/news/2015/03/26/losangeles-river-restoration-cost-city-billion/70492186/ Martin, M. (2014). No Joy in Mudville: Amid Drought, California’s Reservoirs are Clogged with Gunk | California Magazine. Retrieved February 3, 2015, from http://alumni.berkeley.edu/california-magazine/just-in/2014-06-09/no-joymudville-amid-drought-californias-reservoirs-are McCully, P. (1996). Silenced Rivers. Zed Books.

Million Upgrade. Retrieved June 4, 2015, from http://www.confluence-denver.com/ features/south_platte_river_vision_091014.aspx Programme Directorate “Room for the River.” (2015). Room for the River Programme. Retrieved May 29, 2015, from http://www.ruimtevoorderivier.nl/ english/room-for-the-river-programme/ Project Overview | San Clemente Dam Removal & Carmel River Reroute. (n.d.). Retrieved February 6, 2015, from http://www.sanclementedamremoval. org/?page_id=60 Prominski, M., Stokman, A., Zeller, S., Stimberg, D., & Voermanek, H. (2012). River. Space.Design. Ramadan, M. O., Fouad, H. a, & Hassanain, A. M. (2008). Reuse of Water Treatment Plant Sludge in Brick Manufacturing. Journal of Applied Sciences, 4(10), 1223–1229. River Inputs. (2001). See also. Encyclopedia of Ocean Sciences, 2419–2427. doi:10.1006/rwos.2001.0074 Rogers, P. (2013). California’s biggest dam removal project in history begins in Carmel Valley - San Jose Mercury News. Retrieved March 11, 2015, from http://www.mercurynews.com/ci_23508105/californias-biggest-dam-removalproject-history-begins-carmel

Wang, H. W., & Kondolf, G. M. (2014). Upstream sediment-control dams: Five decades of experience in the rapidly eroding dahan river basin, Taiwan. Journal of the American Water Resources Association, 50(3), 735–747. doi:10.1111/jawr.12141 Wang, Z. (n.d.). Management of the Three Gorges Dam.

Sediment Working Group. (2014). Pasadena Sediment Working Group Recommendations A Sustainable Sediment.

Willis, C. M., & Griggs, G. B. (2003). Reductions in Fluvial Sediment Discharge by Coastal Dams in California and Implications for Beach Sustainability. The Journal of Geology, 111(2), 167–182. doi:10.1086/345922

Sheng, J., & Wilson, J. P. (2009). Watershed urbanization and changing flood behavior across the Los Angeles metropolitan region. Natural Hazards, 48, 41–57. doi:10.1007/s11069-008-9241-7

Yang, S. L., Zhang, J., & Xu, X. J. (2007). Influence of the Three Gorges Dam on downstream delivery of sediment and its environmental implications, Yangtze River. Geophysical Research Letters, 34(May), 1–5. doi:10.1029/2007GL029472

Silt, sediment and change. (2015). Retrieved May 30, 2015, from http://www. peninsuladailynews.com/article/20150218/NEWS/302189985

Yang, T., Zhang, Q., Chen, Y. D., Tao, X., Xu, C., & Chen, X. (2008). A spatial assessment of hydrologic alteration caused by dam construction in the middle and lower Yellow River, China. HYDROLOGICAL PROCESSES, 22(18), 3829–3843. doi:10.1002/hyp

Snyder, N. P., Rubin, D. M., Alpers, C. N., Childs, J. R., Curtis, J. a., Flint, L. E., & Wright, S. a. (2004). Estimating accumulation rates and physical properties of sediment behind a dam: Englebright Lake, Yuba River, northern California. Water Resources Research, 40, 1–19. doi:10.1029/2004WR003279 Stanford University. (2014). Searsville Dam FAQs | Stanford University. Retrieved February 6, 2015, from http://news.stanford.edu/searsville/faqs Stanley, D. (2015). Confluence Park water flowing 10 times the normal rate - 7NEWS Denver TheDenverChannel.com. Retrieved June 4, 2015, from http://www. thedenverchannel.com/news/front-range/denver/confluence-park-waterflowing-10-times-the-normal-rate Sumi, T., Okano, M., & Yasufumi, T. (2004). Reservoir sedimentation management with bypass tunnels in Japan. Proceedings of the Ninth International Symposium on River Sedimentation October 18 – 21, 2004, Yichang, China, 1036–1043. Syvitski, J. P. M., Vo, C. J., Kettner, A. J., & Green, P. (2005). Impact of Humans on the Flux of Terrestrial Sediment to the Global Coastal Ocean. Science, 2(663). U. S. Geological Survey. (2004). Should Englebright Dam Be Removed. Ucar, A. (2014). Is the First Steelhead Trout in Decades Really Back at Malibu Lagoon? - Los Angeles | Los Angeles News and Events | LA Weekly. Retrieved February 27, 2015, from http://www.laweekly.com/news/is-the-first-steelheadtrout-in-decades-really-back-at-malibu-lagoon-4757393 USACE. (2015). Arroyo Seco Ecosystem Restoration Integrated Feasibility Study.